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Advanced Energy Materials
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Hybrid journal (It can contain Open Access articles)
ISSN (Online) 1614-6840
Published by John Wiley and Sons

[1583 journals]

Self-Doped, n-Type Perylene Diimide Derivatives as Electron Transporting
Layers for High-Efficiency Polymer Solar Cells
- Authors: Zhenfeng Wang; Nannan Zheng, Wenqiang Zhang, He Yan, Zengqi Xie, Yuguang Ma, Fei Huang, Yong Cao
  Abstract: Perylene diimide (PDI) with high electron affinities are promising candidates for applications in polymer solar cells (PSCs). In addition, the strength of π-deficient backbones and end-groups in an n-type self-dopable system strongly affects the formed end-group-induced electronic interactions. Herein, a series of amine/ammonium functionalized PDIs with excellent alcohol solubility are synthesized and employed as electron transporting layers (ETLs) in PSCs. The electron transfer properties of the resulting PDIs are dramatically tuned by different end-groups and π-deficient backbones. Notably, electron transfer is observed directly in solution in self-doped PDIs for the first time. A significantly enhanced power conversion efficiency of 10.06% is achieved, when applying the PDIs as ETLs in PTB7-Th:PC71BM-based PSCs. These results demonstrate the potential of n-type organic semiconductors with stable n-type doping capability and facile solution processibility for future applications of energy transition devices.Serials self-doped perylene diimides (PDIs) are investigated and applied as electron transporting layer in high-efficiency polymer solar cells. Variations of both the π-deficient PDI cores and the electron-donating amine/ammonium end-groups induce electronic interactions between them in different intensity, which facilitates the management of the electron transfer properties for applications in organic electronics.
  PubDate: 2017-04-25T07:21:13.125163-05:
  DOI: 10.1002/aenm.201700232
Cu, Co-Embedded N-Enriched Mesoporous Carbon for Efficient Oxygen
Reduction and Hydrogen Evolution Reactions
- Authors: Min Kuang; Qihao Wang, Peng Han, Gengfeng Zheng
  Abstract: Rational synthesis of hybrid, earth-abundant materials with efficient electrocatalytic functionalities are critical for sustainable energy applications. Copper is theoretically proposed to exhibit high reduction capability close to Pt, but its high diffusion behavior at elevated fabrication temperatures limits its homogeneous incorporation with carbon. Here, a Cu, Co-embedded nitrogen-enriched mesoporous carbon framework (CuCo@NC) is developed using, a facile Cu-confined thermal conversion strategy of zeolitic imidazolate frameworks (ZIF-67) pre-grown on Cu(OH)2 nanowires. Cu ions formed below 450 °C are homogeneously confined within the pores of ZIF-67 to avoid self-aggregation, while the existence of CuN bonds further increases the nitrogen content in carbon frameworks derived from ZIF-67 at higher pyrolysis temperatures. This CuCo@NC electrocatalyst provides abundant active sites, high nitrogen doping, strong synergetic coupling, and improved mass transfer, thus significantly boosting electrocatalytic performances in oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). A high half-wave potential (0.884 V vs reversible hydrogen potential, RHE) and a large diffusion-limited current density are achieved for ORR, comparable to or exceeding the best reported earth-abundant ORR electrocatalysts. In addition, a low overpotential (145 mV vs RHE) at 10 mA cm−2 is demonstrated for HER, further suggesting its great potential as an efficient electrocatalyst for sustainable energy applications.A bi-metallic (Cu and Co) embedded, N-doped mesoporous carbon framework is developed as an oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) electrocatalyst, by a Cu-confined thermal conversion strategy of Cu(OH)2 nanowires and ZIF-67 polyhedrons. This hybrid electrocatalyst presents abundant bi-metallic electrocatalytic active sites, high nitrogen doping level, strong synergetic coupling, and excellent mass transfer, thus significantly boosting electrocatalytic ORR and HER performances.
  PubDate: 2017-04-25T07:16:50.269078-05:
  DOI: 10.1002/aenm.201700193
Ultrafine Metal Nanoparticles/N-Doped Porous Carbon Hybrids Coated on
Carbon Fibers as Flexible and Binder-Free Water Splitting Catalysts
- Authors: Yongqi Zhang; Xinhui Xia, Xun Cao, Bowei Zhang, Nguyen Huy Tiep, Haiyong He, Shi Chen, Yizhong Huang, Hong Jin Fan
  Abstract: By employing in situ reduction of metal precursor and metal-assisted carbon etching process, this study achieves a series of ultrafine transition metal-based nanoparticles (Ni–Fe, Ni–Mo) embedded in N-doped carbon, which are found efficient catalysts for electrolytic water splitting. The as-prepared hybrid materials demonstrate outstanding catalytic activities as non-noble metal electrodes rendered by the synergistic effect of bimetal elements and N-dopants, the improved electrical conductivity, and hydrophilism. Ni/Mo2C@N-doped porous carbon (NiMo-polyvinylpyrrolidone (PVP)) and NiFe@N-doped carbon (NiFe-PVP) produce low overpotentials of 130 and 297 mV at a current density of 10 mA cm−2 as catalysts for hydrogen evolution reaction and oxygen evolution reaction, respectively. In addition, these binder-free electrodes show long-term stability. Overall water splitting is also demonstrated based on the couple of NiMo-PVP NiFe-PVP catalyzer. This represents a simple and effective synthesis method toward a new type of nanometal–carbon hybrid electrodes.A new way for metal–carbon composite: Ultrafine transition metal-based nanoparticles (Ni-Fe, Ni-Mo) embedded in N-doped carbon by employing in situ reduction of metal precursor and metal-assisted carbon etching process. They are applied as efficient hydrogen evolution reaction and oxygen evolution reaction catalysts for water splitting.
  PubDate: 2017-04-25T07:16:45.036398-05:
  DOI: 10.1002/aenm.201700220
An Improved Li–SeS2 Battery with High Energy Density and Long Cycle
Life
- Authors: Zhen Li; Jintao Zhang, Hao Bin Wu, Xiong Wen (David) Lou
  Abstract: Selenium–sulfur solid solutions are a class of potential cathode materials for high energy batteries, since they have higher theoretical capacities than selenium and improved conductivity over sulfur. Here, a high-performance cathode material by confining 70 wt% of SeS2 in a highly ordered mesoporous carbon (CMK-3) framework with a polydopamine (PDA) protection sheath for novel Li–Se/S batteries is reported. With a relatively high SeS2 mass loading of 2.6–3 mg cm−2, the CMK-3/SeS2@PDA cathode exhibits a high capacity of >1200 mA h g−1 at 0.2 A g−1, excellent C-rate capability of 535 mA h g−1 at 5 A g−1, and prolonged life over 500 cycles. Benefitting from the unique advantages of SeS2 and the rationally designed host framework, this new cathode material demonstrates a feasible strategy to overcome the bottlenecks of current Li–S systems for high energy density rechargeable batteries.A high-performance cathode material is synthesized by confining SeS2 in a highly ordered mesoporous carbon framework with a polydopamine protection sheath for Li–SeS2 batteries. This new cathode material might overcome the bottlenecks of current Li–S systems for high energy density rechargeable batteries.
  PubDate: 2017-04-25T07:16:33.379696-05:
  DOI: 10.1002/aenm.201700281
Metal-Nanowire-Electrode-Based Perovskite Solar Cells: Challenging Issues
and New Opportunities
- Authors: Jihoon Ahn; Hyewon Hwang, Sunho Jeong, Jooho Moon
  Abstract: Recently, organometal halide perovskite (OMHP)-based solar cells have been regarded as one of the most promising technologies in the research field of renewable energy applications. Along with successful demonstrations of high power conversion efficiencies (PCEs), various characteristic strategies for fabricating functional OMHP-based solar cells have been exploited to facilitate both their practical applicability and industrial suitability. As a part of such efforts, unconventional transparent conductive electrodes have been suggested based on the implementation of metal nanowires (MeNWs), which possess both high transparency and low sheet resistance, in order to replace traditional counterparts such as costly, limitedly-flexible vacuum-deposited conductive metal oxides. This allows for the facile fabrication of solution-processable, low-cost, highly flexible, high-performance solar cell devices. In this review, the recent progress on OMHP solar cells integrated with MeNW-network electrodes is investigated and the challenges associated with the integration of MeNW-network electrodes are comprehensively addressed with the suggestion of possible solutions for resolving the critical issues.Integration between metal nanowire network-based electrodes and perovskite solar cells enables diversification of fabrication processes and functionalities of perovskite solar cells. High-performance, semi-transparent, and flexible perovskite solar cells with metal nanowires are expected to be fabricated without resorting to vacuum processes. The challenging issues facing the integration are also investigated.
  PubDate: 2017-04-25T02:00:58.042604-05:
  DOI: 10.1002/aenm.201602751
Excellent Comprehensive Performance of Na-Based Layered Oxide Benefiting
from the Synergetic Contributions of Multimetal Ions
- Authors: Hu-Rong Yao; Peng-Fei Wang, Yi Wang, Xiqian Yu, Ya-Xia Yin, Yu-Guo Guo
  Abstract: Na-ion batteries are promising for large-scale energy storage applications, but few cathode materials can be practically used because of the significant difficulty in synthesizing an electrode material with superior comprehensive performance. Herein, an effective strategy based on synergetic contributions of rationally selected metal ions is applied to design layered oxides with excellent electrochemical performances. The power of this strategy is demonstrated by the superior properties of as-obtained NaFe0.45Co0.5Mg0.05O2 with 139.9 mA h g−1 of reversible capacity, 3.1 V of average voltage, 96.6% of initial Coulombic efficiency, and 73.9 mA h g−1 of capacity at 10 C rate, which benefit from the synergetic effect of Fe3+ (high redox potential), Co3+ (good kinetics), and inactive Mg2+ with compatible radii (stabilizing structure). Moreover, it is clarified that the superior property is not the simple superposition of performance for layered oxides with single metal ions. With the assistance of density functional theory calculations, it is evidenced that the wide capacity range (>70%) of prismatic Na+-occupied sites during sodiation/desodiation is responsible for its high rate performance. This rational strategy of designing high-performance cathodes based on the synergetic effect of various metal ions might be a powerful step forward in the development of new Na-ion-insertion cathodes.An effective strategy based on the synergetic contributions of metal ions in transition metal layers is proposed to design high-performance layered oxides for Na-ion batteries. The as-obtained NaFe0.45Co0.5Mg0.05O2 shows superior comprehensive performance benefiting from the synergetic effect of Fe3+ with high redox potential, Co3+ with good kinetics, and inactive Mg2+ with compatible radii stabilizing structure.
  PubDate: 2017-04-24T07:42:51.362805-05:
  DOI: 10.1002/aenm.201700189
Electrospun NaVPO4F/C Nanofibers as Self-Standing Cathode Material for
Ultralong Cycle Life Na-Ion Batteries
- Authors: Ting Jin; Yongchang Liu, Yang Li, Kangzhe Cao, Xiaojun Wang, Lifang Jiao
  Abstract: NaVPO4F has received a great deal of attention as cathode material for Na-ion batteries due to its high theoretical capacity (143 mA h g−1), high voltage platform, and structural stability. Novel NaVPO4F/C nanofibers are successfully prepared via a feasible electrospinning method and subsequent heat treatment as self-standing cathode for Na-ion batteries. Based on the morphological and microstructural characterization, it can be seen that the NaVPO4F/C nanofibers are smooth and continuous with NaVPO4F nanoparticles (≈6 nm) embedded in porous carbon matrix. For Na-storage, this electrode exhibits extraordinary electrochemical performance: a high capacity (126.3 mA h g−1 at 1 C), a superior rate capability (61.2 mA h g−1 at 50 C), and ultralong cyclability (96.5% capacity retention after 1000 cycles at 2 C). 1D NaVPO4F/C nanofibers that interlink into 3D conductive network improve the conductivity of NaVPO4F, and effectively restrain the aggregation of NaVPO4F particles during charge/discharge process, leading to the high performance.NaVPO4F/C nanofibers are synthesized with NaVPO4F nanoparticles (≈6 nm) embedded in porous carbon matrix via an electrospinning method. For Na-storage, NaVPO4F/C nanofibers exhibit extraordinary electrochemical performance: a high capacity (126.3 mA h g−1 at 1 C), a superior rate capability (61.2 mA h g−1 at 50 C), and ultralong cyclability (96.5% capacity retention after 1000 cycles at 2 C).
  PubDate: 2017-04-24T07:36:37.3418-05:00
  DOI: 10.1002/aenm.201700087
One-to-One Comparison of Graphite-Blended Negative Electrodes Using
Silicon Nanolayer-Embedded Graphite versus Commercial Benchmarking
Materials for High-Energy Lithium-Ion Batteries
- Authors: Sujong Chae; Namhyung Kim, Jiyoung Ma, Jaephil Cho, Minseong Ko
  Abstract: While existing carbonaceous anodes for lithium–ion batteries (LIBs) are approaching a practical capacitive limit, Si has been extensively examined as a potential alternative because it shows exceptional gravimetric capacity (3579 mA h g−1) and abundance. However, the actual implementation of Si anodes is impeded by difficulties in electrode calendering processes and requirements for excessive binding and conductive agents, arising from the brittleness, large volume expansion (>300%), and low electrical conductivity (1.56 × 10−3 S m−1) of Si. In one rational approach to using Si in high-energy LIBs, mixing Si-based materials with graphite has attracted attention as a feasible alternative for next-generation anodes. In this study, graphite-blended electrodes with Si nanolayer-embedded graphite/carbon (G/SGC) are demonstrated and detailed one-to-one comparisons of these electrodes with industrially developed benchmarking samples are performed under the industrial electrode density (>1.6 g cc−1), areal capacity (>3 mA h cm−2), and a small amount of binder (3 wt%) in a slurry. Because of the favorable compatibility between SGC and conventional graphite, and the well-established structural features of SGC, great potential is envisioned. Since this feasible study utilizes realistic test methods and criteria, the rigorous benchmarking comparison presents a comprehensive understanding for developing and characterizing Si-based anodes for practicable high-energy LIBs.Comparing the industrially developed benchmarking samples with synthesized Si nanolayer-embedded graphite/carbon hybrids in the graphite-blended electrode, Si nanolayer-embedded graphite/carbon exhibits the highest coulombic efficiency (CE 89.7%) at the first cycle, and cycling stabilization (CE >99.5%) is achieved after only second cycle, even with the least electrode volume expansion. This benchmarking comparison presents concrete guidelines and a comprehensive understanding of the implementation of Si anodes.
  PubDate: 2017-04-24T02:06:19.690727-05:
  DOI: 10.1002/aenm.201700071
Large-Sized Few-Layer Graphene Enables an Ultrafast and Long-Life
Aluminum-Ion Battery
- Authors: Leyuan Zhang; Liang Chen, Hao Luo, Xufeng Zhou, Zhaoping Liu
  Abstract: To develop high-power and high-energy batteries with a long life remains a great challenge, even combining the benefits of metal (fast kinetics and high capacity) and carbon materials (robust structure). Among them, Al-ion batteries based on aluminum anode and graphite carbon cathode have gained lots of interests as one of the most promising technologies. Here, it is demonstrated that the size of graphitic material in ab plane and c direction plays an important role in anion intercalation chemistry. Sharply decreasing the size of vertical dimension (c direction) strongly facilitates the kinetics and charge transfer of anions (de)intercalation. On the other hand, increasing the size of horizontal dimension (ab plane) contributes to improving the flexibility of graphitic materials, which results in raising the cycling stability. Meanwhile, chloroaluminate anions are reversibly intercalated into the interlayer of graphite materials, leading to the staging behaviors. In the end, an ultrafast Al-ion battery with exceptional long life is achieved based on large-sized few-layer graphene as a cathode and aluminum metal as an anode.An ultrafast and long-life aluminum-ion battery is achieved using large-sized few-layer graphene and Al-metal. It retains 90% discharging capacity at 4800 mA g−1 and exhibits no capacity fading over 4500 cycles. Moreover, the size effect plays an important role in rate capability and cycling stability and a staging intercalation chemistry is also addressed during AlCl4− insertion/extraction.
  PubDate: 2017-04-21T07:35:26.887329-05:
  DOI: 10.1002/aenm.201700034
Ultrafine MoO2-Carbon Microstructures Enable Ultralong-Life Power-Type
Sodium Ion Storage by Enhanced Pseudocapacitance
- Authors: Changtai Zhao; Chang Yu, Mengdi Zhang, Huawei Huang, Shaofeng Li, Xiaotong Han, Zhibin Liu, Juan Yang, Wei Xiao, Jianneng Liang, Xueliang Sun, Jieshan Qiu
  Abstract: The achievement of the superior rate capability and cycling stability is always the pursuit of sodium-ion batteries (SIBs). However, it is mainly restricted by the sluggish reaction kinetics and large volume change of SIBs during the discharge/charge process. This study reports a facile and scalable strategy to fabricate hierarchical architectures where TiO2 nanotube clusters are coated with the composites of ultrafine MoO2 nanoparticles embedded in carbon matrix (TiO2@MoO2-C), and demonstrates the superior electrochemical performance as the anode material for SIBs. The ultrafine MoO2 nanoparticles and the unique nanorod structure of TiO2@MoO2-C help to decrease the Na+ diffusion length and to accommodate the accompanying volume expansion. The good integration of MoO2 nanoparticles into carbon matrix and the cable core role of TiO2 nanotube clusters enable the rapid electron transfer during discharge/charge process. Benefiting from these structure merits, the as-made TiO2@MoO2-C can deliver an excellent cycling stability up to 10 000 cycles even at a high current density of 10 A g−1. Additionally, it exhibits superior rate capacities of 110 and 76 mA h g−1 at high current densities of 10 and 20 A g−1, respectively, which is mainly attributed to the high capacitance contribution.High-rate and long-life sodium storage is achieved by using a nanorod-shaped core–shell architecture functionalized with the ultrafine MoO2 nanoparticles. This is evident from the ultralong cycle life of up to 10 000 cycles and the ultrahigh-rate capability of ≈13.7 s for full charge, which is due to the enhanced pseudocapacitance behavior.
  PubDate: 2017-04-21T07:18:15.934332-05:
  DOI: 10.1002/aenm.201602880
Four-Terminal Perovskite/Silicon Multijunction Solar Modules
- Authors: Manoj Jaysankar; Weiming Qiu, Maarten van Eerden, Tom Aernouts, Robert Gehlhaar, Maarten Debucquoy, Ulrich W. Paetzold, Jef Poortmans
  Abstract: Multijunction solar cells employing perovskite and crystalline-silicon (c-Si) light absorbers bear the exciting potential to surpass the efficiency limit of market-leading single-junction c-Si solar cells. However, scaling up this technology and maintaining high efficiency over large areas are challenging as evidenced by the small-area perovskite/c-Si multijunction solar cells reported so far. In this work, a scalable four-terminal multijunction solar module design employing a 4 cm2 semitransparent methylammonium lead triiodide perovskite solar module stacked on top of an interdigitated back contact c-Si solar cell of identical area is demonstrated. With a combination of optimized transparent electrodes and efficient module design, the perovskite/c-Si multijunction solar modules exhibit power conversion efficiencies of 22.6% on 0.13 cm2 and 20.2% on 4 cm2 aperture area. Furthermore, a detailed optoelectronic loss analysis along with strategies to enhance the performance is discussed.A high-efficient large-area scalable perovskite/silicon four-terminal multijunction solar module is presented. The four-terminal perovskite/silicon multijunction photovoltaic devices are scaled up from a 0.13 cm2 cell-on-cell configuration to a 4 cm2 module-on-cell configuration while maintaining high efficiency. By using efficient solar module design and optimized electrodes, the scalability of four-terminal perovskite/silicon multijunction photovoltaics is demonstrated.
  PubDate: 2017-04-21T07:18:09.784264-05:
  DOI: 10.1002/aenm.201602807
Open-Structured V2O5·nH2O Nanoflakes as Highly Reversible Cathode
Material for Monovalent and Multivalent Intercalation Batteries
- Authors: Huali Wang; Xuanxuan Bi, Ying Bai, Chuan Wu, Sichen Gu, Shi Chen, Feng Wu, Khalil Amine, Jun Lu
  Abstract: The high-capacity cathode material V2O5·nH2O has attracted considerable attention for metal ion batteries due to the multielectron redox reaction during electrochemical processes. It has an expanded layer structure, which can host large ions or multivalent ions. However, structural instability and poor electronic and ionic conductivities greatly handicap its application. Here, in cell tests, self-assembly V2O5·nH2O nanoflakes shows excellent electrochemical performance with either monovalent or multivalent cation intercalation. They are directly grown on a 3D conductive stainless steel mesh substrate via a simple and green hydrothermal method. Well-layered nanoflakes are obtained after heat treatment at 300 °C (V2O5·0.3H2O). Nanoflakes with ultrathin flower petals deliver a stable capacity of 250 mA h g−1 in a Li-ion cell, 110 mA h g−1 in a Na-ion cell, and 80 mA h g−1 in an Al-ion cell in their respective potential ranges (2.0–4.0 V for Li and Na-ion batteries and 0.1–2.5 V for Al-ion battery) after 100 cycles.A binder-free V2O5·nH2O nanoflake cathode, prepared by a simple hydrothermal method, shows decent cyclability and capacity retention for Li+, Na+, and Al3+ insertion/deinsertion. Water molecules in the oxide network lead to a good ion mobility because of the electrostatic shielding effect. The water-deficient V2O5·0.3H2O shows fast kinetics benefiting from the large interlayer spacing and its 3D open structure.
  PubDate: 2017-04-21T01:47:48.546842-05:
  DOI: 10.1002/aenm.201602720
Tuning Energy Levels without Negatively Affecting Morphology: A Promising
Approach to Achieving Optimal Energetic Match and Efficient Nonfullerene
Polymer Solar Cells
- Authors: Jianquan Zhang; Kui Jiang, Guofang Yang, Tingxuan Ma, Jing Liu, Zhengke Li, Joshua Yuk Lin Lai, Wei Ma, He Yan
  Abstract: One advantage of nonfullerene polymer solar cells (PSCs) is that they can yield high open-circuit voltage (VOC) despite their relatively low optical bandgaps. To maximize the VOC of PSCs, it is important to fine-tune the energy level offset between the donor and acceptor materials, but in a way not negatively affecting the morphology of the donor:acceptor (D:A) blends. Here, an effective material design rationale based on a family of D–A1–D–A2 terthiophene (T3) donor polymers is reported, which allows for the effective tuning of energy levels but without any negative impacts on the morphology of the blend. Based on a T3 donor unit combined with difluorobenzothiadiazole (ffBT) and difluorobenzoxadiazole (ffBX) acceptor units, three donor polymers are developed with highly similar morphological properties. This is particularly surprising considering that the corresponding quaterthiophene polymers based on ffBT and ffBX exhibit dramatic differences in their solubility and morphological properties. With the fine-tuning of energy levels, the T3 polymers yield nonfullerene PSCs with a high efficiency of 9.0% for one case and with a remarkably low energy loss (0.53 V) for another polymer. This work will facilitate the development of efficient nonfullerene PSCs with optimal energy levels and favorable morphology properties.A terthiophene-based donor polymer PffBTBX-T3 with the D–A1–D–A2 structure is demonstrated and compared with the other two D–A-type polymers PffBT-T3 and PffBX-T3. While the energy levels of three polymers are fine-tuned, their optical and morphological properties are not dramatically changed. The optimal energetic match and well-controlled morphology enable 9.0% efficient nonfullerene devices based on PffBTBX-T3 and ITIC-Th.
  PubDate: 2017-04-21T01:47:14.19706-05:0
  DOI: 10.1002/aenm.201602119
Suppressing Energy Loss due to Triplet Exciton Formation in Organic Solar
Cells: The Role of Chemical Structures and Molecular Packing
- Authors: Xian-Kai Chen; Tonghui Wang, Jean-Luc Brédas
  Abstract: In the most efficient solar cells based on blends of a conjugated polymer (electron donor) and a fullerene derivative (electron acceptor),ultrafast formation of charge-transfer (CT) electronic states at the donor-acceptor interfaces and efficient separation of these CT states into free charges, lead to internal quantum efficiencies near 100%. However, there occur substantial energy losses due to the non-radiative recombinations of the charges, mediated by the loweset-energy (singlet and triplet) CT states; for example, such recombinations can lead to the formation of triplet excited electronic states on the polymer chains, which do not generate free charges. This issue remains a major factor limiting the power conversion efficiencies (PCE) of these devices. The recombination rates are, however, difficult to quantify experimentally. To shed light on these issues, here, an integrated multi-scale theoretical approach that combines molecular dynamics simulations with quantum chemistry calculations is employed in order to establish the relationships among chemical structures, molecular packing, and non-radiative recombination losses mediated by the lowest-energy charge-transfer states.In many polymer–fullerene bulk heterojunction solar cells, triplet exciton formation on the polymer chains has been identified as a major energy loss channel. Here, an integrated multiscale theoretical approach is used to establish detailed relationships among chemical structures, molecular packing, and nonradiative recombination loss mediated by the lowest-energy charge-transfer states with either singlet or triplet spin character.
  PubDate: 2017-04-21T01:41:58.398268-05:
  DOI: 10.1002/aenm.201602713
Stable and Highly Efficient PbS Quantum Dot Tandem Solar Cells Employing a
Rationally Designed Recombination Layer
- Authors: Guozheng Shi; Yongjie Wang, Zeke Liu, Lu Han, Jie Liu, Yakun Wang, Kunyuan Lu, Si Chen, Xufeng Ling, Yong Li, Si Cheng, Wanli Ma
  Abstract: This study reports the fabrication of stable, high-performance, simple structured tandem solar cells based on PbS colloidal quantum dots (CQDs) under ambient air. This study also reveals detailed device engineering to deposit each functional layer in the subcells at low temperature to avoid damage to the PbS CQDs and meanwhile makes the fabrication process compatible to flexible plastic substrate. Two efficient recombination layers (RLs) are rationally designed to connect the two subcells in series. The use of solution-processed RL with an organic PEDOT:PSS (poly(3,4-ethylenedioxythiophene): polystyrene sulfonate) interlayer leads to the fabrication of the tandem devices in solution process. The use of robust inorganic RL containing an ultrathin Au interlayer results in more efficient device performance and remarkably improved device lifetime. The optimal PbS CQDs tandem cells based on inorganic RL demonstrate a high power conversion efficiency approaching 9%. This efficiency is more than two times higher than the previous record of 4.2%, which has been kept for more than five years. The remarkable stability, high performance, and low-temperature processing of these tandem devices may provide insight into the commercialization of flexible and large-area CQDs tandem solar cells in the near future.Air-stable PbS colloidal quantum dot (CQD) tandem solar cells with a power conversion efficiency approaching 9% and a recorded-high open-circuit voltage of 1.13 V are demonstrated. By rationally designing the recombination layers, air stable, solution-processed, highly efficient CQD tandem devices with simplified structure are successfully realized.
  PubDate: 2017-04-21T01:41:46.536538-05:
  DOI: 10.1002/aenm.201602667
Distinctive Supercapacitive Properties of Copper and Copper Oxide
Nanocrystals Sharing a Similar Colloidal Synthetic Route
- Authors: Songhao Wu; Weiqiang Lv, Tianyu Lei, Yidong Han, Xian Jian, Min Deng, Gaolong Zhu, Mingzhen Liu, Jie Xiong, James H. Dickerson, Weidong He
  Abstract: CuO and Cu2O are non-noble transition metal oxide supercapacitive materials with high theoretical specific capacitances above 1800 F g−1. In this work, by adjusting organic additives of a colloidal system, Cu, Cu2O, and CuO are grown in situ on nickel foam. CuO exhibits a specific capacitance of 1355 F g−1 at 2 A g−1 in 3 m KOH, a value well above those of Cu and Cu2O (
  PubDate: 2017-04-21T01:41:06.398276-05:
  DOI: 10.1002/aenm.201700105
Efficient Perovskite Solar Cells Based on a Solution Processable
Nickel(II) Phthalocyanine and Vanadium Oxide Integrated Hole Transport
Layer
- Authors: Ming Cheng; Yuanyuan Li, Majid Safdari, Cheng Chen, Peng Liu, Lars Kloo, Licheng Sun
  Abstract: An organic–inorganic integrated hole transport layer (HTL) composed of the solution-processable nickel phthalocyanine (NiPc) abbreviated NiPc-(OBu)8 and vanadium(V) oxide (V2O5) is successfully incorporated into structured mesoporous perovskite solar cells (PSCs). The optimized PSCs show the highest stabilized power conversion efficiency of up to 16.8% and good stability under dark ambient conditions. These results highlight the potential application of organic–inorganic integrated HTLs in PSCs.A perovskite solar cell containing a NiPc-(OBu)8 and V2O5 based organic–inorganic integrated hole transport layer is reported. It achieves a power conversion efficiency of 17.6%.
  PubDate: 2017-04-20T08:22:16.794607-05:
  DOI: 10.1002/aenm.201602556
Thieno[3,4-c]Pyrrole-4,6-Dione-Based Polymer Acceptors for High
Open-Circuit Voltage All-Polymer Solar Cells
- Authors: Shengjian Liu; Xin Song, Simil Thomas, Zhipeng Kan, Federico Cruciani, Frédéric Laquai, Jean-Luc Bredas, Pierre M. Beaujuge
  Abstract: While polymer acceptors are promising fullerene alternatives in the fabrication of efficient bulk heterojunction (BHJ) solar cells, the range of efficient material systems relevant to the “all-polymer” BHJ concept remains narrow, and currently limits the perspectives to meet the 10% efficiency threshold in all-polymer solar cells. This report examines two polymer acceptor analogs composed of thieno[3,4-c]pyrrole-4,6-dione (TPD) and 3,4-difluorothiophene ([2F]T) motifs, and their BHJ solar cell performance pattern with a low-bandgap polymer donor commonly used with fullerenes (PBDT-TS1; taken as a model system). In this material set, the introduction of a third electron-deficient motif, namely 2,1,3-benzothiadiazole (BT), is shown to (i) significantly narrow the optical gap (Eopt) of the corresponding polymer (by ≈0.2 eV) and (ii) improve the electron mobility of the polymer by over two orders of magnitude in BHJ solar cells. In turn, the narrow-gap P2TPDBT[2F]T analog (Eopt = 1.7 eV) used as fullerene alternative yields high open-circuit voltages (VOC) of ≈1.0 V, notable short-circuit current values (JSC) of ≈11.0 mA cm−2, and power conversion efficiencies (PCEs) nearing 5% in all-polymer BHJ solar cells. P2TPDBT[2F]T paves the way to a new, promising class of polymer acceptor candidates.Alternating π-conjugated polymers composed of electron-deficient thieno[3,4-c]pyrrole-4,6-dione (TPD) and 3,4-difluorothiophene ([2F]T) motifs are proving relevant as fullerene alternatives for “all-polymer” bulk heterojunction (BHJ) solar cells. When a third electron-deficient motif, namely 2,1,3-benzothiadiazole (BT), is inserted in the main chain, the corresponding polymer (P2TPDBT[2F]T) yields a twofold increase in BHJ device efficiency.
  PubDate: 2017-04-20T08:11:47.168751-05:
  DOI: 10.1002/aenm.201602574
A Printable Organic Electron Transport Layer for
Low-Temperature-Processed, Hysteresis-Free, and Stable Planar Perovskite
Solar Cells
- Authors: Jinho Lee; Junghwan Kim, Chang-Lyoul Lee, Geunjin Kim, Tae Kyun Kim, Hyungcheol Back, Suhyun Jung, Kilho Yu, Soonil Hong, Seongyu Lee, Seok Kim, Soyeong Jeong, Hongkyu Kang, Kwanghee Lee
  Abstract: Despite recent breakthroughs in power conversion efficiencies (PCEs), which have resulted in PCEs exceeding 22%, perovskite solar cells (PSCs) still face serious drawbacks in terms of their printability, reliability, and stability. The most efficient PSC architecture, which is based on titanium dioxide as an electron transport layer, requires an extremely high-temperature sintering process (≈500 °C), reveals hysterical discrepancies in the device measurement, and suffers from performance degradation under light illumination. These drawbacks hamper the practical development of PSCs fabricated via a printing process on flexible plastic substrates. Herein, an innovative method to fabricate low-temperature-processed, hysteresis-free, and stable PSCs with a large area up to 1 cm2 is demonstrated using a versatile organic nanocomposite that combines an electron acceptor and a surface modifier. This nanocomposite forms an ideal, self-organized electron transport layer (ETL) via a spontaneous vertical phase separation, which leads to hysteresis-free, planar heterojunction PSCs with stabilized PCEs of over 18%. In addition, the organic nanocomposite concept is successfully applied to the printing process, resulting in a PCE of over 17% in PSCs with printed ETLs.An innovative method for achieving printable planar heterojunction perovskite solar cells (PSCs) is demonstrated using self-assembled organic nanocomposites of fullerene derivatives and cationic polyelectrolytes as the electron transport layer. Highly reliable and stable PSCs with low-temperature solution-processable organic nanocomposites exhibit stabilized power conversion efficiencies exceeding 18%.
  PubDate: 2017-04-20T08:11:11.765335-05:
  DOI: 10.1002/aenm.201700226
Contents: (Adv. Energy Mater. 8/2017)
- PubDate: 2017-04-19T05:43:14.306284-05:
  DOI: 10.1002/aenm.201770041
Lithium-Ion Batteries: Multiscale Morphological and Electrical
Characterization of Charge Transport Limitations to the Power Performance
of Positive Electrode Blends for Lithium-Ion Batteries (Adv. Energy Mater.
8/2017)
- Authors: Nicolas Besnard; Aurélien Etiemble, Thierry Douillard, Olivier Dubrunfaut, Pierre Tran-Van, Laurent Gautier, Sylvain Franger, Jean-Claude Badot, Eric Maire, Bernard Lestriez
  Abstract: A better understanding of the charge transport (ions and electrons) kinetics limitations through the electrode is required to improve the Li-ion battery's energy and power density in view of electrical cars deployment. In article number 1602239, Bernard Lestriez and co-workers connect for the first time the parameters describing the microstructure of electrodes with both measurements of their transport properties and their electrochemical performance.
  PubDate: 2017-04-19T05:43:13.015985-05:
  DOI: 10.1002/aenm.201770043
Masthead: (Adv. Energy Mater. 8/2017)
- PubDate: 2017-04-19T05:43:10.481408-05:
  DOI: 10.1002/aenm.201770042
Rechargeable Batteries: Nanoporous Hybrid Electrolytes for High-Energy
Batteries Based on Reactive Metal Anodes (Adv. Energy Mater. 8/2017)
- Authors: Zhengyuan Tu; Michael J. Zachman, Snehashis Choudhury, Shuya Wei, Lin Ma, Yuan Yang, Lena F. Kourkoutis, Lynden A. Archer
  Abstract: Stable lithium metal batteries are achieved utilizing hybrid electrolytes in which a liquid is infused into the pores of a nanoporous solid. At moderate salt concentrations, the Debye screening length is large and a selective cation transport is observed. At higher salt concentrations, nanopores are effective in limiting lithium nucleate sizes to below critical values required for unstable dendritic growth. This is reported by Lynden A. Archer and co-workers in article number 1602367.
  PubDate: 2017-04-19T05:43:08.935983-05:
  DOI: 10.1002/aenm.201770039
Lithium-Sulfur Batteries: Fabrication of N-doped Graphene–Carbon
Nanotube Hybrids from Prussian Blue for Lithium–Sulfur Batteries (Adv.
Energy Mater. 8/2017)
- Authors: Dawei Su; Michael Cortie, Guoxiu Wang
  Abstract: In article number 1602014, Guoxiu Wang and co-workers report the preparation of an innovative Fe3C@nitrogen-doped graphene-carbon nanotube (Fe3C@N-GE-CNTs) hybrid material by a one-step pyrolysis process for sulphur storage in lithium-sulfur batteries. Lithium-sulfur batteries made with these cathodes demonstrate outstanding electrochemical performances. This strategy could open a new avenue for high performance lithium-sulfur batteries.
  PubDate: 2017-04-19T05:43:08.473616-05:
  DOI: 10.1002/aenm.201770040
Advances in Quantum-Confined Perovskite Nanocrystals for Optoelectronics
- Authors: Lakshminarayana Polavarapu; Bert Nickel, Jochen Feldmann, Alexander S. Urban
  Abstract: Metal halide perovskites have emerged as a promising new class of layered semiconductor material for light-emitting and photovoltaic applications owing to their outstanding optical and optoelectronic properties. In nanocrystalline form, these layered perovskites exhibit extremely high photoluminescence quantum yields (PLQYs) and show quantum confinement effects analogous to conventional semiconductors when their dimensions are reduced to sizes comparable to their respective exciton Bohr radii. The reduction in size leads to strongly blueshifted photoluminescence and large exciton binding energies up to several hundreds of meV. This not only makes them interesting for optoelectronic devices, but also enables complex architectures based on cascaded energy transfer. Here, an overview of the current state-of-the-art of quantum confinement effects in perovskite nanocrystals is provided, with a focus on synthetic strategies and resulting optical properties, characterization methods, and emerging applications.Metal halide perovskites have emerged as a promising new class of material for light-emitting and photovoltaic applications owing to their outstanding optical and optoelectronic properties. This research news provides an overview of the current state-of-the-art of quantum-confinement effects in perovskite nanocrystals, with a focus on synthetic strategies and resulting optical properties, characterization methods, and emerging applications.
  PubDate: 2017-04-10T08:21:46.040689-05:
  DOI: 10.1002/aenm.201700267
A Conductive Molecular Framework Derived Li2S/N,P-Codoped Carbon Cathode
for Advanced Lithium–Sulfur Batteries
- Authors: Jun Zhang; Ye Shi, Yu Ding, Lele Peng, Wenkui Zhang, Guihua Yu
  Abstract: Li2S is one of the most promising cathode materials for Li-ion batteries because of its high theoretical capacity and compatibility with Li-metal-free anode materials. However, the poor conductivity and electrochemical reactivity lead to low initial capacity and severe capacity decay. In this communication, a nitrogen and phosphorus codoped carbon (N,P–C) framework derived from phytic acid doped polyaniline hydrogel is designed to support Li2S nanoparticles as a binder-free cathode for Li–S battery. The porous 3D architecture of N and P codoped carbon provides continuous electron pathways and hierarchically porous channels for Li ion transport. Phosphorus doping can also suppress the shuttle effect through strong interaction between sulfur and the carbon framework, resulting in high Coulombic efficiency. Meanwhile, P doping in the carbon framework plays an important role in improving the reaction kinetics, as it may help catalyze the redox reactions of sulfur species to reduce electrochemical polarization, and enhance the ionic conductivity of Li2S. As a result, the Li2S/N,P–C composite electrode delivers a stable capacity of 700 mA h g−1 with average Coulombic efficiency of 99.4% over 100 cycles at 0.1C and an areal capacity as high as 2 mA h cm−2 at 0.5C.Nitrogen and phosphorus codoped carbon framework with Li2S nanoparticles impregnated is designed as a high-performance binder-free cathode for Li–S batteries. The porous 3D architecture facilitates fast ion and electron transport to each Li2S nanoparticle, improving the utilization of active material and rate capability.
  PubDate: 2017-04-10T08:21:34.891254-05:
  DOI: 10.1002/aenm.201602876
Rubidium Multication Perovskite with Optimized Bandgap for
Perovskite-Silicon Tandem with over 26% Efficiency
- Authors: The Duong; YiLiang Wu, Heping Shen, Jun Peng, Xiao Fu, Daniel Jacobs, Er-Chien Wang, Teng Choon Kho, Kean Chern Fong, Matthew Stocks, Evan Franklin, Andrew Blakers, Ngwe Zin, Keith McIntosh, Wei Li, Yi-Bing Cheng, Thomas P. White, Klaus Weber, Kylie Catchpole
  Abstract: Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4%. The study shows the beneficial effect of Rb in improving the crystallinity and suppressing defect migration in the perovskite material. The light stability of the cells examined under continuous illumination of 12 h is improved upon the addition of Cs and Rb. After several cycles of 12 h light–dark, the cell retains 90% of its initial efficiency. In parallel, sputtered transparent conducting oxide thin films are developed to be used as both rear and front transparent contacts on quartz substrate with less than 5% parasitic absorption of near infrared wavelengths. Using these developments, semi-transparent perovskite cells are fabricated with steady state efficiency of up to 16.0% and excellent average transparency of ≈84% between 720 and 1100 nm. In a tandem configuration using a 23.9% silicon cell, 26.4% efficiency (10.4% from the silicon cell) in a mechanically stacked tandem configuration is demonstrated which is very close to the current record for a single junction silicon cell of 26.6%.Rubidium doping improves the crystallinity and suppresses the defect migration in the 1.73 eV bandgap perovskite, which lead to improvement in cell performance and light stability. Semi-transparent perovskite cell with efficiency of 16% and average transparency of 84% between 720 and 1100 nm is fabricated. By combining with 23.9% silicon cell, efficiency of 26.4% for four terminal tandem is obtained.
  PubDate: 2017-04-04T02:00:02.952754-05:
  DOI: 10.1002/aenm.201700228
A High-Performance D–A Copolymer Based on
Dithieno[3,2-b:2′,3′-d]Pyridin-5(4H)-One Unit Compatible with
Fullerene and Nonfullerene Acceptors in Solar Cells
- Authors: Mingwei An; Fangyuan Xie, Xinjian Geng, Jianqi Zhang, Jiaxing Jiang, Zhongli Lei, Dan He, Zuo Xiao, Liming Ding
  Abstract: Development of high-performance donor–acceptor (D–A) copolymers is vital in the research of polymer solar cells (PSCs). In this work, a low-bandgap D–A copolymer based on dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one unit (DTP), PDTP4TFBT, is developed and used as the donor material for PSCs with PC71BM or ITIC as the acceptor. PDTP4TFBT:PC71BM and PDTP4TFBT:ITIC solar cells give power conversion efficiencies (PCEs) up to 8.75% and 7.58%, respectively. 1,8-Diiodooctane affects film morphology and device performance for fullerene and nonfullerene solar cells. It inhibits the active materials from forming large domains and improves PCE for PDTP4TFBT:PC71BM cells, while it promotes the aggregation and deteriorates performance for PDTP4TFBT:ITIC cells. The ternary-blend cells based on PDTP4TFBT:PC71BM:ITIC (1:1.2:0.3) give a decent PCE of 9.20%.A low-bandgap D–A copolymer based on dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one unit, PDTP4TFBT, is developed and used as the donor material for polymer solar cells. PDTP4TFBT is among a few D–A copolymers that can deliver >7% power conversion efficiencies (PCEs) in both fullerene and nonfullerene solar cells. Ternary-blend solar cells based on PDTP4TFBT, PC71BM, and ITIC give a PCE of 9.20%.
  PubDate: 2017-04-03T08:40:37.416153-05:
  DOI: 10.1002/aenm.201602509
Addressing Toxicity of Lead: Progress and Applications of Low-Toxic Metal
Halide Perovskites and Their Derivatives
- Authors: Miaoqiang Lyu; Jung-Ho Yun, Peng Chen, Mengmeng Hao, Lianzhou Wang
  Abstract: Metal halide perovskites have been brought to the forefront of research focus in solution-processable photovoltaics, with the device efficiency swiftly surging to over 22% over the past few years. The state-of-the-art metal halide perovskites that have been intensively investigated include toxic lead, which potentially hampers their commercialization process. To address this toxicity issue, intensive recent research effort has been devoted to developing low-toxic metal halide perovskites and their derivatives for photovoltaic applications. Herein, the recent research progress achieved so far in addressing the toxicity issue of lead halide perovskites in photovoltaics is summarized. By comparing the merits and drawbacks of different low-toxic metal halide systems, the current challenges and opportunities in the photovoltaic field are highlighted. Potential low-toxic metal halide perovskites and their derivatives are also discussed from the perspective of theoretical calculations. Furthermore, promising applications of low-toxic metal halide perovskites beyond the photovoltaic sector are briefly discussed.Recent progress in low toxic metal halide perovskites/derivatives is reviewed with a main focus on photovoltaic applications. The merits and drawbacks of the emerging alternatives in replacement of the state-of-the-art lead halide perovskites are discussed and their future challenges and research opportunities in both photovoltaics and other potential applications are highlighted.
  PubDate: 2017-03-29T01:50:50.532106-05:
  DOI: 10.1002/aenm.201602512
Trends in Aluminium-Based Intercalation Batteries
- Authors: Filip Ambroz; Thomas J. Macdonald, Thomas Nann
  Abstract: Over the last decade, optimizing energy storage has become significantly important in the field of energy conversion and sustainability. As a result of immense progress in the field, cost-effective and high performance batteries are imperative to meeting the future demand of sustainability. Currently, the best performing batteries are lithium-ion based, but limited lithium (Li) resources make research into alternatives essential. In recent years, the performance of aluminium-ion batteries has improved remarkably in all battery-relevant metrics, which renders them a promising alternative. Compared with monovalent Li-ion batteries, aluminium (Al) cations can carry three positive charges, which could result in higher energy densities. This review describes recent developments in Al-based cathode materials. The major goal of this review is to highlight strengths and weaknesses of various different approaches and provide guidelines for future research.Is there a life after lithium' The most promising alternative to lithium-ion batteries is aluminium. However, the current performance of aluminium-ion batteries is not suitable for large scale application yet. This review article provides a critical overview of the current state-or-the-art in aluminium-ion batteries.
  PubDate: 2017-03-23T02:15:44.96619-05:0
  DOI: 10.1002/aenm.201602093
Structure of Organometal Halide Perovskite Films as Determined with
Grazing-Incidence X-Ray Scattering Methods
- Authors: Johannes Schlipf; Peter Müller-Buschbaum
  Abstract: Grazing-incidence X-ray scattering (GIXS) methods have proven to be a valuable asset for investigating the morphology of thin films at different length scales. Consequently, GIXS has been applied to the fast-progressing field of organometal halide perovskites. This exciting class of materials has propelled research in the areas of cheap and sustainable photovoltaics, light emitting devices, and optoelectronics in general. Especially, perovskite solar cells (PSC) have seen a remarkable rise in power conversion efficiencies, crossing the 20% mark after only five years of research. This research news outlines GIXS studies focusing on the most challenging research topics in the perovskite field today: Current–voltage hysteresis, device reproducibility, and long-term stability of PSC are inherently linked to perovskite film morphology. On the other hand, film formation depends on the choice of precursors and processing parameters; understanding their interdependence opens possibilities to tailor film morphologies. Owing to their tunability and moisture resistance, 2D perovskites have recently attracted attention. Examples of GIXS studies with different measurement and data analysis techniques are presented, highlighting especially in-situ investigations on the many kinetic processes involved. Thus, an overview on the toolbox of GIXS techniques is linked to the specific needs of research into organometal halide perovskite optoelectronics.Grazing-incidence X-ray scattering is a powerful tool for investigating the morphology of hybrid perovskite thin films. This research news covers a broad range of grazing-incidence small- and wide-angle X-ray scattering studies and sheds light on the remarkable possibilities these methods offer for understanding film morphology, film formation, crystallization, and degradation mechanisms when combined with advanced data treatment.
  PubDate: 2017-03-20T05:26:37.420242-05:
  DOI: 10.1002/aenm.201700131
Mechanistic Evolution of Aprotic Lithium-Oxygen Batteries
- Authors: Fujun Li; Jun Chen
  Abstract: Aprotic lithium-oxygen (Li-O2) batteries have attracted much attention in recent years. Considerable efforts have been devoted to understand the reaction mechanisms and improving battery performance. Here, various reaction mechanisms at the cathode are discussed, including the direct electrochemical formation and decomposition of Li2O2 and LiOH and the redox mediator (RM) assisted reactions in both the discharging and charging processes. Formation of Li2O2 in discharging processes is related to the electrolyte solvent property, and its following decomposition proceeds stepwise with the intermediate of Li2–xO2. Low overpotentials have been reported in LiOH-involved discharging and charging processes, and it can alleviate the instability of carbon against Li2O2 and provide new insights into the design of practical Li-air batteries. RMs are promising for Li-O2 batteries, and the prerequisites in addition to the redox potentials should be taken into account. Perspectives on the development of Li-O2 batteries are provided. The future deployment of Li-O2 batteries relies on the continuous efforts of all the scientists around the world.Reaction mechanisms of Li-O2 batteries, including electrochemical formation and decomposition of Li2O2 and LiOH, and reactions of redox mediators during discharge and charge, are discussed in this review paper, as well as future perspectives.
  PubDate: 2017-03-20T05:26:29.421684-05:
  DOI: 10.1002/aenm.201602934
High-Performance and Stable All-Polymer Solar Cells Using Donor and
Acceptor Polymers with Complementary Absorption
- Authors: Zhaojun Li; Wei Zhang, Xiaofeng Xu, Zewdneh Genene, Dario Di Carlo Rasi, Wendimagegn Mammo, Arkady Yartsev, M. R. Andersson, René A. J. Janssen, Ergang Wang
  Abstract: To explore the advantages of emerging all-polymer solar cells (all-PSCs), growing efforts have been devoted to developing matched donor and acceptor polymers to outperform fullerene-based PSCs. In this work, a detailed characterization and comparison of all-PSCs using a set of donor and acceptor polymers with both conventional and inverted device structures is performed. A simple method to quantify the actual composition and light harvesting contributions from the individual donor and acceptor is described. Detailed study on the exciton dissociation and charge recombination is carried out by a set of measurements to understand the photocurrent loss. It is unraveled that fine-tuned crystallinity of the acceptor, matched donor and acceptor with complementary absorption and desired energy levels, and device architecture engineering can synergistically boost the performance of all-PSCs. As expected, the PBDTTS-FTAZ:PNDI-T10 all-PSC attains a high and stable power conversion efficiency of 6.9% without obvious efficiency decay in 60 d. This work demonstrates that PNDI-T10 can be a potential alternative acceptor polymer to the widely used acceptor N2200 for high-performance and stable all-PSCs.High-performance and stable all-polymer solar cells (all-PSCs) are realized by incorporating a pair of donor and acceptor polymers with complementary absorption. The high power conversion efficiency of 6.9% retains 90% for 60 d, which highlights the promising future of all-PSCs.
  PubDate: 2017-03-20T05:26:15.506911-05:
  DOI: 10.1002/aenm.201602722
Carbon Anode Materials for Advanced Sodium-Ion Batteries
- Authors: Hongshuai Hou; Xiaoqing Qiu, Weifeng Wei, Yun Zhang, Xiaobo Ji
  Abstract: The ever-increasing demand of lithium-ion batteries (LIBs) caused by the rapid development of various electronics and electric vehicles will be hindered by the limited lithium resource. Thus sodium-ion batteries (SIBs) have been considered as a promising potential alternative for LIBs owing to the abundant sodium resource and similar electrochemical performances. In recent years, significant achievements regarding anode materials which restricted the development of SIBs in the past decades have been attained. Significantly, the sodium storage feasibility of carbon materials with abundant resource, low cost, nontoxicity and high safety has been confirmed, and extensive investigation have demonstrated that the carbonaceous materials can become promising electrode candidates for SIBs. In this review, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized. Additionally, the critical issues, challenges and perspectives are provided to further understand the carbonaceous anode materials.Carbon materials have been considered as promising anode candidate for sodium-ion batteries (SIBs) due to their unique merits. Tremendous efforts have been made to exploit appropriate carbon materials and unveil the corresponding sodium storage mechanism. Here, recent progress, challenges, and prospects of carbon anode materials for SIBs are presented.
  PubDate: 2017-03-17T07:56:29.975602-05:
  DOI: 10.1002/aenm.201602898
Solving Key Challenges in Battery Research Using In Situ Synchrotron and
Neutron Techniques
- Authors: Qinfen Gu; Justin A. Kimpton, Helen E. A. Brand, Zhiyang Wang, Shulei Chou
  Abstract: Understanding the electrochemical reaction mechanisms and kinetics in batteries is the key challenge for developing breakthroughs with new or existing electrode materials. X-rays and neutrons are excellent probes for studying atomic structure changes and phase evolution in battery materials during charge and discharge. Synchrotron X-ray powder diffraction (SXPD), with its high angular resolution and beam intensity, allows fast scattering and diffraction data collection to record crystalline structure changes that occur on short time-scales. Neutron powder diffraction (NPD) provides complementary information that is sensitive to different structural details during charge/discharge. More recently X-ray absorption spectroscopy (XAS) has been used to identify the oxidation states of transition metal ions present in new cathode compositions at different stages of battery cycling. Using in-house designed battery cells, electrodes or other cell components can be subjected to conditions designed to mimic their real operating conditions. It is preferable to investigate battery materials in operation to identify any critical intermediate stages during charge/discharge rather than using ex situ methods to analyse dismantled batteries. Examples and combinations of SXPD, XAS, and NPD measurements, which have been used to investigate lithium ion batteries and sodium ion batteries, are described and reviewed in this contribution.Understanding the electrochemical reaction mechanisms and kinetics is the key challenge for developing breakthroughs with new or existing battery electrode materials. Novel in situ cells combined with synchrotron and neutron techniques reveal structural details which correlate with the electrochemical performance of individual battery cell compositions and improve the understanding of electrochemical performance across the field.
  PubDate: 2017-03-17T07:56:03.998331-05:
  DOI: 10.1002/aenm.201602831
Inkjet Printed Large Area Multifunctional Smart Windows
- Authors: Guofa Cai; Peter Darmawan, Xing Cheng, Pooi See Lee
  Abstract: Multifunctional smart windows are successfully fabricated by assembling inkjet printed CeO2/TiO2 and WO3/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) films as the anode and cathode, respectively. Large optical modulation (more than 70% at 633 nm), fast switching (12.7/15.8 s), high coloration efficiency (108.9 cm2 C−1), and excellent bistability are achieved by the assembled smart windows. The multifunctional smart window not only can be used as typical electrochromic window, which can change its color to dynamically control the solar radiation transmittance through windows or protect privacy during the day, but also can be used as energy-storage device simultaneously. The designed smart window releases the stored energy to light the bulbs and power other electronic devices at night while its color gradually reverts to transparent state. Moreover, the level of stored energy can be monitored via the visually detectable reversible color variation of the window. The fascinating multifunctional smart windows exhibit promising features for a wide range of applications in buildings, airplanes, automobiles, etc.Multifunctional smart windows are successfully fabricated, which can be used not only as typical electrochromic window but also as energy-storage device simultaneously. The smart window changes its color to dynamically control the solar radiation transmittance through windows or protect privacy during the day. Then, it releases the stored energy to light the bulbs and power other electronic devices at night.
  PubDate: 2017-03-17T07:55:59.951788-05:
  DOI: 10.1002/aenm.201602598
Pushing the Energy Output and Cyclability of Sodium Hybrid Capacitors at
High Power to New Limits
- Authors: Ranjith Thangavel; Brindha Moorthy, Do Kyung Kim, Yun-Sung Lee
  Abstract: Hybrid capacitors, especially sodium hybrid capacitors (NHCs), have continued to gain importance and are extensively studied based on their excellent potential to serve as advanced devices for fulfilling high energy and high power requirements at a low cost. To achieve remarkable performance in hybrid capacitors, the two electrodes employed must be superior with enhanced charge storage capability and fast kinetics. In this study, a new sodium hybrid capacitor system with a sodium super ionic conductor NaTi2(PO4)3 grown on graphene nanosheets as an intercalation electrode and 2D graphene nanosheets as an adsorption electrode is reported for the first time. This new system delivers a high energy density of ≈80 W h kg−1 and a high specific power of 8 kW kg−1. An ultralow performance fading of ≈0.13% per 1000 cycles (90%–75 000 cycles) outperforms previously reported sodium ion capacitors. The enhanced charge transfer kinetics and reduced interfacial resistance at high current rates deliver a high specific energy without compromising the high specific power along with high durability, and thereby bridge batteries and capacitors. This new research on kinetically enhanced NHCs can be a trendsetter for the development of advanced energy storage devices requiring high energy—high power.A high performing sodium hybrid capacitor is fabricated utilizing graphene nanosheets as high power adsorption electrode and graphene/NaTi2(PO4)3 as a high energy intercalation electrode. High energy retention at high power along with excellent stability of 90% after 75 000 cycles with a lowest ever energy loss of ≈0.13% per 1000 cycles is documented.
  PubDate: 2017-03-17T07:55:52.166231-05:
  DOI: 10.1002/aenm.201602654
Bifunctional Oxygen Electrocatalysis through Chemical Bonding of
Transition Metal Chalcogenides on Conductive Carbons
- Authors: Anand P. Tiwari; Doyoung Kim, Yongshin Kim, Hyoyoung Lee
  Abstract: Improving the electrochemical performance of both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been of great interest in emerging renewable energy technologies. This study reports an advanced bifunctional hybrid electrocatalyst for both ORR and OER, which is composed of tungsten disulphide (WS2) and carbon nanotube (CNT) connected via tungsten carbide (WC) bonding. WS2 sheets on the surface of CNTs provide catalytic active sites for electrocatalytic activity while the CNTs act as conduction channels and provide a large surface area. Moreover, the newly formed WC crystalline structure provides an easy path for electron transfer by spin coupling and helps to solve stability issues to enable excellent electrocatalytic activity. In addition, it is found that four to five layers of WS2 sheets on the surface of CNTs produce excellent catalytic activity toward both ORR and OER, which is comparable to noble metals (Pt, RuO2, etc.). These findings show the many advantages enabled by designing highly active, durable, and cost-effective ORR and OER electrocatalysts.An advanced bifunctional hybrid electrocatalyst is developed for both oxygen reduction reaction and oxygen evolution reaction, which is composed of tungsten disulphide (WS2) and carbon nanotube (CNT) connected via tungsten carbide bonding. WS2 sheets on the surface of CNTs provide catalytic active sites for electrocatalytic activity while the CNTs act as conduction channels and provide a large surface area.
  PubDate: 2017-03-17T07:55:45.393125-05:
  DOI: 10.1002/aenm.201602217
Self-Encapsulating Thermostable and Air-Resilient Semitransparent
Perovskite Solar Cells
- Authors: J. Zhao; K. O. Brinkmann, T. Hu, N. Pourdavoud, T. Becker, T. Gahlmann, R. Heiderhoff, A. Polywka, P. Görrn, Y. Chen, B. Cheng, T. Riedl
  Abstract: Semitransparent perovskite solar cells (PSCs) are of interest for application in tandem solar cells and building-integrated photovoltaics. Unfortunately, several perovskites decompose when exposed to moisture or elevated temperatures. Concomitantly, metal electrodes can be degraded by the corrosive decomposition products of the perovskite. This is even the more problematic for semitransparent PSCs, in which the semitransparent top electrode is based on ultrathin metal films. Here, we demonstrate outstandingly robust PSCs with semitransparent top electrodes, where an ultrathin Ag layer is sandwiched between SnOx grown by low-temperature atomic layer deposition. The SnOx forms an electrically conductive permeation barrier, which protects both the perovskite and the ultrathin silver electrode against the detrimental impact of moisture. At the same time, the SnOx cladding layer underneath the ultra-thin Ag layer shields the metal against corrosive halide compounds leaking out of the perovskite. Our semitransparent PSCs show an efficiency higher than 11% along with about 70% average transmittance in the near-infrared region (λ> 800 nm) and an average transmittance of 29% for λ = 400–900 nm. The devices reveal an astonishing stability over more than 4500 hours regardless if they are exposed to ambient atmosphere or to elevated temperatures.SnOx/Ag/SnOx-based semitransparent electrodes are used to prepare self-encapsulated semitransparent perovskite solar cells, in which the SnOx grown by atomic layer deposition serves as a permeation barrier. The semitransparent cells show an efficiency of 11.8% and 29% average transmittance between 400 and 900 nm, realizing an outstanding stability over more than 4500 h in ambient air and at elevated temperatures.
  PubDate: 2017-03-17T07:55:39.120887-05:
  DOI: 10.1002/aenm.201602599
Hierarchically Structured 3D Integrated Electrodes by Galvanic Replacement
Reaction for Highly Efficient Water Splitting
- Authors: Jianying Wang; Lvlv Ji, Shangshang Zuo, Zuofeng Chen
  Abstract: A NiFe-based integrated electrode is fabricated by the spontaneous galvanic replacement reaction on an iron foam. Driven by the different electrochemical potentials between Ni and Fe, the dissolution of surface Fe occurs with electroless plating of Ni on iron foam with no need to access instrumentation and input energy. A facile cyclic voltammetry treatment is subsequently applied to convert the metallic NiFe to NiFeOx. A series of analytical methods indicates formation of a NiFeOx film of nanosheets on the iron foam surface. This hierarchically structured three dimensional electrode displays high activity and durability against water oxidation. In 1 m KOH, a current density of 1000 mA cm−2 is achieved at an overpotential of only 300 mV. This method is readily extended to fabricate CoFe or NiCoFe-based integrated electrodes for water oxidation. Phosphorization of the bimetallic oxide (NiFeOx) generates the bimetallic phosphide (NiFe-P), which can act as an excellent electrocatalyst for hydrogen production in 1 m KOH. An alkaline electrolyzer is constructed using NiFeOx and NiFe-P coated iron foams as anode and cathode, which can realize overall water splitting with a current density of 100 mA cm−2 at an overpotential of 630 mV.By the spontaneous galvanic replacement reaction, the low-cost iron foam is used as an ideal 3D electrode substrate for fabrication of integrated bimetallic or even trimetallic electrocatalysts for both oxygen and hydrogen evolution reactions, which offers significant advantages of simplicity and zero energy consumption. An alkaline electrolyzer combining both electrode materials is constructed to realize efficient overall water splitting.
  PubDate: 2017-03-17T07:50:38.376195-05:
  DOI: 10.1002/aenm.201700107
3D Synergistically Active Carbon Nanofibers for Improved Oxygen Evolution
- Authors: Yun Pei Zhu; Yu Jing, Anthony Vasileff, Thomas Heine, Shi-Zhang Qiao
  Abstract: Developing earth-abundant and active electrocatalysts for the oxygen evolution reaction (OER) as replacements for conventional noble metal catalysts is of scientific and technological importance for achieving cost-effective and efficient conversion and storage of renewable energy. However, most of the promising candidates thus far are exclusively metal-based catalysts, which are disadvantaged by relatively restricted electron mobility, corrosion susceptibility, and detrimental environmental influences. Herein, hierarchically porous nitrogen (N) and phosphorus (P) codoped carbon nanofibers directly grown on conductive carbon paper are prepared through an electrochemically induced polymerization process in the presence of aniline monomer and phosphonic acid. The resultant material exhibits robust stability (little activity attenuation after 12 h continuous operation) and high activity with low overpotential (310 mV at 10 mA cm−2) toward electrocatalytic oxygen production, with performance comparable to that of the precious iridium oxide (IrO2) benchmark. Experimental measurements reveal that dual doping of N and P can result in an increased active surface area and abundant active sites in comparison with the single doped and pristine carbon counterparts, and density functional theory calculations indicate that N and P dopants can coactivate the adjacent C atoms, inducing synergistically enhanced activity toward OER.3D carbon electrocatalysts: highly porous nitrogen and phosphorus codoped carbon nanofibers, prepared through the pyrolysis of polyaniline synthesized in the presence of phosphonic acid, are rationally designed to show outstanding electrocatalytic oxygen evolution performance. Electrochemical measurements in combination with density functional theory simulations reveal a synergistic effect from the dual-doped heteroatoms in boosting electrochemical activity.
  PubDate: 2017-03-17T07:50:32.676957-05:
  DOI: 10.1002/aenm.201602928
Surface Layering and Supersaturation for Top-Down Nanostructural
Development during Spin Coating of Polymer/Fullerene Thin Films
- Authors: Wei-Ru Wu; Chun-Jen Su, Wei-Tsung Chuang, Yen-Chih Huang, Po-Wei Yang, Po-Chang Lin, Chun-Yu Chen, Tsung-Yu Yang, An-Chung Su, Kung-Hwa Wei, Chih-Ming Liu, U-Ser Jeng
  Abstract: This study provides new evidence on a long postulated mechanism of phase separation in a polymer/fullerene mixture during spin coating for controlled nanodomains of oriented crystallization and heterojunctions that favor applications in polymer solar cells (PSCs). The simultaneous nanoscale phase separation and crystallization during spin coating of the mixture are traced using in situ grazing-incidence small- and wide-angle X-ray scattering. Combined with the complimentary results from time-resolved optical reflectance spectroscopy, transient stratification of the liquid film during the transition from the flow- to evaporation-dominated stage of spin coating is disclosed; the vertical liquid–liquid phase separation incubates a supersaturated skin layer where fullerene aggregation and polymer crystallization occur and develop concomitantly. Shortly after the transition, the near-surface structural development is largely pinned, leaving the solvent-rich bottom layer to diminish via solvent diffusion and evaporation through the thickened skin layer that finally condenses into the spin-coated film upon solvent depletion. The shear-enhanced surface layering and supersaturation for the surface-down nanostructural development are unexpected in all the existing structural models for PSCs. The mechanistic understanding of coupled vertical phase separation and local nanosegregation provides new insights and alternative strategy to the morphology control of spin-cast PSC active layers in particular and various solution-processed polymeric films in general.Surface layering and supersaturation over transition of the flow- to evaporation-dominance of the spin coating of a polymer/fullerene mixture lead to surface-down structural development of coupled vertical liquid–liquid phase separation and local nanosegregation/crystallization. A segregated upper layer enriched with nanostructures transforms into the final spin-coated film, after solvent depletes from the bottom layer.
  PubDate: 2017-03-16T09:35:55.240379-05:
  DOI: 10.1002/aenm.201601842
3D Printable Ceramic–Polymer Electrolytes for Flexible High-Performance
Li-Ion Batteries with Enhanced Thermal Stability
- Authors: Aaron J. Blake; Ryan R. Kohlmeyer, James O. Hardin, Eric A. Carmona, Benji Maruyama, John Daniel Berrigan, Hong Huang, Michael F. Durstock
  Abstract: This study establishes an approach to 3D print Li-ion battery electrolytes with controlled porosity using a dry phase inversion method. This ink formulation utilizes poly(vinyldene fluoride) in a mixture of N-methyl-2-pyrrolidone (good solvent) and glycerol (weak nonsolvent) to generate porosity during a simple drying step. When a nanosized Al2O3 filler is included in the ink, uniform sub-micrometer pore formation is attained. In other words, no additional processing steps such as coagulation baths, stretching, or etching are required for full functionality of the electrolyte, which makes it a viable candidate to enable completely additively manufactured Li-ion batteries. Compared to commercial polyolefin separators, these electrolytes demonstrate comparable high rate electrochemical performance (e.g., 5 C), but possess better wetting characteristics and enhanced thermal stability. Additionally, this dry phase inversion method can be extended to printable composite electrodes, yielding enhanced flexibility and electrochemical performance over electrodes prepared with only good solvent. Finally, sequentially printing this electrolyte ink over a composite electrode via a direct write extrusion technique has been demonstrated while maintaining expected functionality in both layers. These ink formulations are an enabling step toward completely printed batteries and can allow direct integration of a flexible power source in restricted device areas or on nonplanar surfaces.A 3D printable Li-ion battery electrolyte with desirable thermal stability, wettability, and electrochemical properties is demonstrated based upon a dry phase inversion technique. The unique characteristics of the electrolyte ink enable the ability to directly deposit this material over an electrode, yielding a high-performance printed electrode membrane assembly.
  PubDate: 2017-03-16T09:31:34.79605-05:0
  DOI: 10.1002/aenm.201602920
Soft Carbon as Anode for High-Performance Sodium-Based Dual Ion Full
Battery
- Authors: Ling Fan; Qian Liu, Suhua Chen, Zhi Xu, Bingan Lu
  Abstract: Sodium-based dual ion full batteries (NDIBs) are reported with soft carbon as anode and graphite as cathode for the first time. The NDIBs operate at high discharge voltage plateau of 3.58 V, with superior discharge capacity of 103 mA h g−1, excellent rate performance, and long-term cycling stability over 800 cycles with capacity retention of 81.8%. The mechanism of Na+ and PF6− insertion/desertion during the charging/discharging processes is proposed and discussed in detail, with the support of various spectroscopies.Sodium-based dual ion full batteries (NDIBs) are reported with soft carbon as anode and graphite as cathode for the first time. The NDIBs deliver high discharge voltage plateau of 3.58 V, superior discharge capacity of 103 mA h g−1, excellent rate performance, and long-term cycling stability over 800 cycles with capacity retention of 81.8%.
  PubDate: 2017-03-16T03:01:22.528701-05:
  DOI: 10.1002/aenm.201602778
Stabilization of Li Metal Anode in DMSO-Based Electrolytes via
Optimization of Salt–Solvent Coordination for Li–O2 Batteries
- Authors: Bin Liu; Wu Xu, Pengfei Yan, Sun Tai Kim, Mark H. Engelhard, Xiuliang Sun, Donghai Mei, Jaephil Cho, Chong-Min Wang, Ji-Guang Zhang
  Abstract: The conventional electrolyte of 1 m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethyl sulfoxide (DMSO) is unstable against the Li metal anode and therefore cannot be used directly in practical Li–O2 batteries. Here, we demonstrate that a highly concentrated electrolyte based on LiTFSI in DMSO (with a molar ratio of 1:3) can greatly improve the stability of the Li metal anode against DMSO and significantly improve the cycling stability of Li–O2 batteries. This highly concentrated electrolyte contains no free DMSO solvent molecules, but only complexes of (TFSI−)aLi+(DMSO)b (where a + b = 4), and thus enhances their stability with Li metal anodes. In addition, such salt–solvent complexes have higher Gibbs activation energy barriers than the free DMSO solvent molecules, indicating improved stability of the electrolyte against the attack of superoxide radical anions. Therefore, the stability of this highly concentrated electrolyte at both Li metal anodes and carbon-based air electrodes has been greatly enhanced, resulting in improved cycling performance of Li–O2 batteries. The fundamental stability of the electrolyte in the absence of free-solvent against the chemical and electrochemical reactions can also be used to enhance the stability of other electrochemical systems.Concentrated dimethyl sulfoxide (DMSO)-based electrolyte with optimized salt–solvent coordination can greatly promote stabilization of Li metal, as well as minimize electrolyte decomposition in lithium–oxygen batteries because of the highly stable TFSI−Li+(DMSO)3 complex in concentrated electrolyte, i.e., lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)–3DMSO. This study points to new approach on the stable operation of Li–O2 batteries.
  PubDate: 2017-03-08T07:05:44.906947-05:
  DOI: 10.1002/aenm.201602605
Unveiling the Dynamic Processes in Hybrid Lead Bromide Perovskite
Nanoparticle Thin Film Devices
- Authors: Bianka M. D. Puscher; Meltem F. Aygüler, Pablo Docampo, Rubén D. Costa
  Abstract: Hybrid and all-inorganic perovskite (PK) materials are a promising next generation of semiconducting materials due to their outstanding light-harvesting features, as well as their color-tunablility and efficient luminescent properties that lead to highly efficient photovoltaic and lighting devices. Bulk PK films are both ionic and electronic conductors under the presence of an externally applied electric field. In this work, the internal ion motion behavior is demonstrated within PK nanoparticles in thin-film devices by means of different long-time poling scheme assays and both static and dynamic electrochemical impedance spectroscopy measurements. In particular, the existence of a dynamic device behavior is related to the migration and rearrangement of different ionic species upon applying different driving schemes. The latter resembles the well-known signatures of the ionic motion in light-emitting electrochemical cells (LECs), that is, (i) the formation of electrical double layers due to the ionic distribution at the electrodes' interfaces, (ii) the growth of the doped regions once the charge injection is effective, and (iii) the subsequent formation of a non-doped region in the bulk of the device. Hence, this comprehensive study opens up an alternative route toward understanding the dynamics inside hybrid perovskite materials based on the large body of knowledge of LECs.The effect of the ion motion on the mechanism of hybrid perovskite nanoparticles (PK NP) devices is investigated by static and dynamic electrochemical impedance spectroscopy and different poling schemes. Overall, these studies suggest that the electrical behavior of the PK NP devices resemble that of light-emitting electrochemical cells.
  PubDate: 2017-03-08T07:05:32.170624-05:
  DOI: 10.1002/aenm.201602283
Roll-to-Roll Printed Large-Area All-Polymer Solar Cells with 5% Efficiency
Based on a Low Crystallinity Conjugated Polymer Blend
- Authors: Xiaodan Gu; Yan Zhou, Kevin Gu, Tadanori Kurosawa, Yikun Guo, Yunke Li, Haoran Lin, Bob C. Schroeder, Hongping Yan, Francisco Molina-Lopez, Christopher J. Tassone, Cheng Wang, Stefan C. B. Mannsfeld, He Yan, Dahui Zhao, Michael F. Toney, Zhenan Bao
  Abstract: The challenge of continuous printing in high-efficiency large-area organic solar cells is a key limiting factor for their widespread adoption. A materials design concept for achieving large-area, solution-coated all-polymer bulk heterojunction solar cells with stable phase separation morphology between the donor and acceptor is presented. The key concept lies in inhibiting strong crystallization of donor and acceptor polymers, thus forming intermixed, low crystallinity, and mostly amorphous blends. Based on experiments using donors and acceptors with different degree of crystallinity, the results show that microphase separated donor and acceptor domain sizes are inversely proportional to the crystallinity of the conjugated polymers. This methodology of using low crystallinity donors and acceptors has the added benefit of forming a consistent and robust morphology that is insensitive to different processing conditions, allowing one to easily scale up the printing process from a small-scale solution shearing coater to a large-scale continuous roll-to-roll (R2R) printer. Large-area all-polymer solar cells are continuously roll-to-roll slot die printed with power conversion efficiencies of 5%, with combined cell area up to 10 cm2. This is among the highest efficiencies realized with R2R-coated active layer organic materials on flexible substrate.The morphology formation of different all-polymer solar cells during the coating process is investigated and that a low crystalline donor and acceptor polymer blend has stable morphology between the various coating methods is identified. Large-area all-polymer solar cells are continuously roll-to-roll slot die printed with power conversion efficiencies of 5%, with combined cell area up to 10 cm2.
  PubDate: 2017-03-07T08:05:48.019266-05:
  DOI: 10.1002/aenm.201602742
Achieving High Pseudocapacitance of 2D Titanium Carbide (MXene) by Cation
Intercalation and Surface Modification
- Authors: Jian Li; Xiaotao Yuan, Cong Lin, Yanquan Yang, Le Xu, Xin Du, Jinglin Xie, Jianhua Lin, Junliang Sun
  Abstract: Supercapacitors attract great interest because of the increasing and urgent demand for environment-friendly high-power energy sources. Ti3C2, a member of MXene family, is a promising electrode material for supercapacitors owing to its excellent chemical and physical properties. However, the highest gravimetric capacitance of the MXene-based electrodes is still relatively low (245 F g−1) and the key challenge to improve this is to exploit more pseudocapacitance by increasing the active site concentration. Here, a method to significantly improve the gravimetric capacitance of Ti3C2Tx MXenes by cation intercalation and surface modification is reported. After K+ intercalation and terminal groups (OH−/F−) removing , the intercalation pseudocapacitance is three times higher than the pristine MXene, and MXene sheets exhibit a significant enhancement (about 211% of the origin) in the gravimetric capacitance (517 F g−1 at a discharge rate of 1 A g−1). Moreover, the as-prepared electrodes show above 99% retention over 10 000 cycles. This improved electrochemical performance is attributed to the large interlayer voids of Ti3C2 and lowest terminated surface group concentration. This study demonstrates a new strategy applicable to other MXenes (Ti2CTx, Nb2CTx, etc.) in maximizing their potential applications in energy storage.Cation intercalation and surface modification are new strategies in maximizing the potential applications of MXene in energy storage. After K+ intercalation and terminal groups (OH−/F−) removing, the intercalation-pseudocapacitance of Ti3C2 MXene is three times higher than pristine MXene and exhibits a significant enhancement in the gravimetric capacitance and energy density. The as-prepared electrodes show above 99% retention over 10 000 cycles.
  PubDate: 2017-03-06T07:45:44.696613-05:
  DOI: 10.1002/aenm.201602725
Hybrid Photoconductive Cathode Interlayer Materials Composed of Perylene
Bisimide Photosensitizers and Zinc Oxide for High Performance Polymer
Solar Cells
- Authors: Zengqi Xie; Frank Würthner
  Abstract: Hybrid photoconductive materials based on zinc oxide (ZnO) doped with perylene bisimide (PBI) dye molecules have emerged as new promising cathode interlayer materials for inverted polymer solar cells (i-PSCs). Such interlayers show increased conductivity under light irradiation (working condition of i-PSCs) due to enhanced electron mobility and carrier density, enabling high performance devices at interlayer thickness of up to 100 nm. Such increased interlayer thickness is desired for roll-to-roll processing techniques to facilitate mass production of photovoltaic modules.Hybrid photoconductive cathode interlayers based on zinc oxide doped with perylene bisimide dye molecules show increased conductivity under light irradiation due to enhanced electron mobility and carrier density, enabling high performance polymer solar cells at interlayer thickness of up to 100 nm, which is desired for roll-to-roll processing techniques to facilitate mass production of photovoltaic modules.
  PubDate: 2017-03-06T07:45:32.651659-05:
  DOI: 10.1002/aenm.201602573
Progress in Tandem Solar Cells Based on Hybrid Organic–Inorganic
Perovskites
- Authors: Bo Chen; Xiaopeng Zheng, Yang Bai, Nitin P. Padture, Jinsong Huang
  Abstract: Owing to their high efficiency, low-cost solution-processability, and tunable bandgap, perovskite solar cells (PSCs) made of hybrid organic-inorganic perovskite (HOIP) thin films are promising top-cell candidates for integration with bottom-cells based on Si or other low-bandgap solar-cell materials to boost the power conversion efficiency (PCE) beyond the Shockley-Quiesser (S-Q) limit. In this review, recent progress in such tandem solar cells based on the emerging PSCs is summarized and reviewed critically. Notable achievements for different tandem solar cell configurations including mechanically-stacked, optical coupling, and monolithically-integrated with PSCs as top-cells are described in detail. Highly-efficient semitransparent PSC top-cells with high transmittance in near-infrared (NIR) region are critical for tandem solar cells. Different types of transparent electrodes with high transmittance and low sheet-resistance for PSCs are reviewed, which presents a grand challenge for PSCs. The strategies to obtain wide-bandgap PSCs with good photo-stability are discussed. The PCE reduction due to reflection loss, parasitic absorption, electrical loss, and current mismatch are analyzed to provide better understanding of the performance of PSC-based tandem solar cells.Recent progress in the research and development PSCs-based tandem solar cells is reviewed. Different architectures, such as monolithically-integrated, mechanically-stacked, and optically-coupled tandems are discussed. The development of transparent electrodes and wide bandgap PSCs are presented. The power losses in the tandem solar cells are analyzed.
  PubDate: 2017-03-06T07:40:52.001289-05:
  DOI: 10.1002/aenm.201602400
Organic Gelators as Growth Control Agents for Stable and Reproducible
Hybrid Perovskite-Based Solar Cells
- Authors: Sofia Masi; Aurora Rizzo, Rahim Munir, Andrea Listorti, Antonella Giuri, Carola Esposito Corcione, Neil D. Treat, Giuseppe Gigli, Aram Amassian, Natalie Stingelin, Silvia Colella
  Abstract: Low-molecular-weight organic gelators are widely used to influence the solidification of polymers, with applications ranging from packaging items, food containers to organic electronic devices, including organic photovoltaics. Here, this concept is extended to hybrid halide perovskite-based materials. In situ time-resolved grazing incidence wide-angle X-ray scattering measurements performed during spin coating reveal that organic gelators beneficially influence the nucleation and growth of the perovskite precursor phase. This can be exploited for the fabrication of planar n-i-p heterojunction devices with MAPbI3 (MA = CH3NH3+) that display a performance that not only is enhanced by ≈25% compared to solar cells where the active layer is produced without the use of a gelator but that also features a higher stability to moisture and a reduced hysteresis. Most importantly, the presented approach is straightforward and simple, and it provides a general method to render the film formation of hybrid perovskites more reliable and robust, analogous to the control that is afforded by these additives in the processing of commodity “plastics.”Organic gelators, widely used in the processing of commodity “plastics,” are applied to hybrid halide perovskites solidification. They are shown to beneficially influence the nucleation and growth of the perovskite sol–gel precursor phase, leading to a material characterized by a higher stability to moisture and a reduced hysteresis in planar n-i-p heterojunction solar cells.
  PubDate: 2017-03-03T13:51:36.888581-05:
  DOI: 10.1002/aenm.201602600
Direct Evidence of Ion Diffusion for the Silver-Electrode-Induced Thermal
Degradation of Inverted Perovskite Solar Cells
- Authors: Jiangwei Li; Qingshun Dong, Nan Li, Liduo Wang
  Abstract: Perovskite solar cells (PSCs) have recently demonstrated high efficiencies of over 22%, but the thermal stability is still a major challenge for commercialization. In this work, the thermal degradation process of the inverted structured PSCs induced by the silver electrode is thoroughly investigated. Elemental depth profiles indicate that iodide and methylammonium ions diffuse through the electron-trasnporting layer and accumulate at the Ag inner surface. The driving force of forming AgI then facilitates the ions extraction. Variations on the morphology and current mapping of the MAPbI3 thin films upon thermal treatment reveal that the loss of ions occurs at the grain boundaries and leads to the reconstruction of grain domains. Consequently, the deteriorated MAPbI3 thin film, the poor electron extraction, and the generation of AgI barrier result in the degradation of efficiencies. These direct evidences provide in-depth understanding of the effect of thermal stress on the devices, offering both experimental support and theoretical guidance for the improvement on the thermal stability of the inverted PSCs.Silver-electrode-induced thermal degradation of the inverted perovskite solar cells is investigated with direct evidences. The diffusion of iodide and methylamine ions is directly observed in the elemental depth profile during thermal treatment only when the Ag electrode is introduced. The loss of ions leads to the reconstruction of the grain boundaries and forming thick PbI2 gaps between crystal grains.
  PubDate: 2017-03-03T08:25:55.48831-05:0
  DOI: 10.1002/aenm.201602922
Ultrasensitive Iron-Triggered Nanosized Fe–CoOOH Integrated with
Graphene for Highly Efficient Oxygen Evolution
- Authors: Xiaotong Han; Chang Yu, Si Zhou, Changtai Zhao, Huawei Huang, Juan Yang, Zhibin Liu, Jijun Zhao, Jieshan Qiu
  Abstract: Effectively active oxygen evolution reaction (OER) electrocatalysts are highly desired for water splitting. Herein, the design and fabrication of nanometer-sized Fe-modulated CoOOH nanoparticles by a novel conversion tailoring strategy is reported for the first time and these nanoparticles are assembled on graphene matrix to construct 2D nanohybrids (FeCoOOH/G) with ultrasmall particles and finely modulated local electronic structure of Co cations. The Fe components are capable of tailoring and converting the micrometer-sized sheets into nanometer-sized particles, indicative of ultrasensitive Fe-triggered behavior. The as-made FeCoOOH/G features highly exposed edge active sites, well-defined porous structure, and finely modulated electron structure, together with effectively interconnected conducting networks endowed by graphene. Density functional theory calculations have revealed that the Fe dopants in the FeCoOOH nanoparticles have an enhanced adsorption capability toward the oxygenated intermediates involved in OER process, thus facilitating the whole catalytic reactions. Benefiting from these integrated characteristics, the as-made FeCoOOH/G nanohybrids as an oxygen evolution electrocatalyst can deliver a low overpotential of 330 mV at 10 mA cm−2 and excellent electrochemical durability in alkaline medium. This strategy provides an effective, durable, and nonprecious-metal electrocatalyst for water splitting.Ultrasensitive iron-triggered nanosized FeCoOOH nanoparticles are integrated on graphene surface by a novel and simple conversion tailoring strategy, producing the hybrids with rich active sites, distinct pore structure, and numerous channels together with interconnected conducting networks. The FeCoOOH/G hybrids can deliver a low overpotential of 330 mV at 10 mA cm−2 and excellent durability as an oxygen evolution electrocatalyst.
  PubDate: 2017-03-03T08:20:47.2713-05:00
  DOI: 10.1002/aenm.201602148
Perovskite Solar Cells on the Way to Their Radiative Efficiency Limit –
Insights Into a Success Story of High Open-Circuit Voltage and Low
Recombination
- Authors: Wolfgang Tress
  Abstract: Inorganic-organic lead-halide perovskite solar cells have reached efficiencies above 22% within a few years of research. Achieved photovoltages of>1.2 V are outstanding for a material with a bandgap of 1.6 eV – in particular considering that it is solution processed. Such values demand for low non-radiative recombination rates and come along with high luminescence yields when the solar cell is operated as a light emitting diode. This progress report summarizes the developments on material composition and device architecture, which allowed for such high photovoltages. It critically assesses the term “lifetime”, the theories and experiments behind it, and the different recombination mechanisms present. It attempts to condense reported explanations for the extraordinary optoelectronic properties of the material. Amongst those are an outstanding defect tolerance due to antibonding valence states and the capability of bandgap tuning, which might make the dream of low-cost highly efficient solution-processed thin film solar cells come true. Beyond that, the presence of photon recycling will open new opportunities for photonic device design.Perovskite solar cells show exceptionally high photovoltages. This progress report discusses the current understanding of the main material properties that are responsible for the high electronic quality of the metal-halide perovskites. Amongst them is a pronounced defect tolerance, which facilitates low non-radiative recombination rates and high luminescence yields.
  PubDate: 2017-03-03T08:20:39.493206-05:
  DOI: 10.1002/aenm.201602358
Charge Transfer Processes in OPV Materials as Revealed by EPR Spectroscopy
- Authors: Jens Niklas; Oleg G. Poluektov
  Abstract: Understanding charge separation and charge transport at a molecular level is crucial for improving the efficiency of organic photovoltaic (OPV) cells. Under illumination of Bulk Heterojunction (BHJ) blends of polymers and fullerenes, various paramagnetic species are formed including polymer and fullerene radicals, radical pairs, and photoexcited triplet states. Light-induced Electron Paramagnetic Resonance (EPR) spectroscopy is ideally suited to study these states in BHJ due to its selectivity in probing the paramagnetic intermediates. Advanced techniques like pulsed EPR and ENDOR spectroscopy allow the determination of hyperfine coupling tensors, while high-frequency EPR allows the EPR signals of the individual species to be resolved and their g-tensors to be determined. The magnetic resonance parameters of the various polymer donors reveal details about the delocalization of the positive polaron which is important for the efficient charge separation in BHJ systems. Time-resolved EPR can contribute to the study of the dynamics of charge separation, charge transfer and recombination in BHJ by probing the unique spectral signatures of charge transfer and triplet states. EPR also has the potential to allow characterization of intermediates and products of BHJ degradation.Light-induced EPR spectroscopy is ideally suited to study charge separated states in BHJ since it selectively probes the paramagnetic charge carriers and excited states. This review focusses on the application of advanced EPR techniques to characterize the electronic structure of positive and negative polarons as well as dynamics of spin-dependent charge separation and charge recombination processes in organic photovoltaic materials.
  PubDate: 2017-03-03T08:15:50.091893-05:
  DOI: 10.1002/aenm.201602226
Elucidating the Irreversible Mechanism and Voltage Hysteresis in
Conversion Reaction for High-Energy Sodium–Metal Sulfide Batteries
- Authors: Jiajun Wang; Liguang Wang, Christopher Eng, Jun Wang
  Abstract: Irreversible electrochemical behavior and large voltage hysteresis are commonly observed in battery materials, in particular for materials reacting through conversion reaction, resulting in undesirable round-trip energy loss and low coulombic efficiency. Seeking solutions to these challenges relies on the understanding of the underlying mechanism and physical origins. Here, this study combines in operando 2D transmission X-ray microscopy with X-ray absorption near edge structure, 3D tomography, and galvanostatic intermittent titration techniques to uncover the conversion reaction in sodium–metal sulfide batteries, a promising high-energy battery system. This study shows a high irreversible electrochemistry process predominately occurs at first cycle, which can be largely linked to Na ion trapping during the first desodiation process and large interfacial ion mobility resistance. Subsequently, phase transformation evolution and electrochemical reaction show good reversibility at multiple discharge/charge cycles due to materials' microstructural change and equilibrium. The origin of large hysteresis between discharge and charge is investigated and it can be attributed to multiple factors including ion mobility resistance at the two-phase interface, intrinsic slow sodium ion diffusion kinetics, and irreversibility as well as ohmic voltage drop and overpotential. This study expects that such understandings will help pave the way for engineering design and optimization of materials microstructure for future-generation batteries.Combining in operando synchrotron hard X-ray microscopy with X-ray absorption technique, the irreversible mechanism and large voltage hysteresis in conversion reaction for sodium–metal sulfide batteries is comprehensively elucidated, potentially guiding us in optimization and design of advanced materials with improved performance.
  PubDate: 2017-03-03T08:15:36.717223-05:
  DOI: 10.1002/aenm.201602706
Infrared Regulating Smart Window Based on Organic Materials
- Authors: Hitesh Khandelwal; Albertus P. H. J. Schenning, Michael G. Debije
  Abstract: Windows are vital elements in the built environment that have a large impact on the energy consumption in indoor spaces, affecting heating and cooling and artificial lighting requirements. Moreover, they play an important role in sustaining human health and well-being. In this review, we discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or transmitting excess solar energy (infrared radiation) in such a way that comfortable indoor temperatures can be maintained throughout the year. Moreover, we place emphasis on windows that maintain transparency in the visible region so that additional energy is not required to retain natural illumination. We discuss a number of ways to fabricate windows which remain as permanent infrared control elements throughout the year as well as windows which can alter transmission properties in presence of external stimuli like electric fields, temperature and incident light intensity. We also show the potential impact of these windows on energy saving in different climate conditions.In this review, smart windows are discussed which reflect excess of solar energy (infrared radiations) in summer and allow entrance into the building during winter, without interfering with visible light, to save significant amounts of energy in heating, cooling and lighting.
  PubDate: 2017-03-02T04:35:39.688349-05:
  DOI: 10.1002/aenm.201602209
High Efficiency Ternary Nonfullerene Polymer Solar Cells with Two Polymer
Donors and an Organic Semiconductor Acceptor
- Authors: Lian Zhong; Liang Gao, Haijun Bin, Qin Hu, Zhi-Guo Zhang, Feng Liu, Thomas P. Russell, Zhanjun Zhang, Yongfang Li
  Abstract: A ternary nonfullerene polymer solar cell with a high efficiency of 9.70% is realized by using an n-type organic semiconductor ITIC acceptor and two polymer donors of medium bandgap polymer J51 and narrow bandgap polymer PTB7-Th with the polymer weight ratio of 0.8:0.2.
  PubDate: 2017-02-24T02:15:56.644319-05:
  DOI: 10.1002/aenm.201602215
Incorporation of Counter Ions in Organic Molecules: New Strategy in
Developing Dopant-Free Hole Transport Materials for Efficient Mixed-Ion
Perovskite Solar Cells
- Authors: Jinbao Zhang; Bo Xu, Li Yang, Alba Mingorance, Changqing Ruan, Yong Hua, Linqin Wang, Nick Vlachopoulos, Mónica Lira-Cantú, Gerrit Boschloo, Anders Hagfeldt, Licheng Sun, Erik M. J. Johansson
  Abstract: Hole transport matertial (HTM) as charge selective layer in perovskite solar cells (PSCs) plays an important role in achieving high power conversion efficiency (PCE). It is known that the dopants and additives are necessary in the HTM in order to improve the hole conductivity of the HTM as well as to obtain high efficiency in PSCs, but the additives can potentially induce device instability and poor device reproducibility. In this work a new strategy to design dopant-free HTMs has been presented by modifying the HTM to include charged moieties which are accompanied with counter ions. The device based on this ionic HTM X44 dos not need any additional doping and the device shows an impressive PCE of 16.2%. Detailed characterization suggests that the incorporated counter ions in X44 can significantly affect the hole conductivity and the homogeneity of the formed HTM thin film. The superior photovoltaic performance for X44 is attributed to both efficient hole transport and effective interfacial hole transfer in the solar cell device. This work provides important insights as regards the future design of new and efficient dopant free HTMs for photovotaics or other optoelectronic applications.A new strategy to design dopant-free hole transport materials (HTMs) by modifying the organic molecule to include charged moieties that are accompanied by counter ions is investigated. The introduced counter ions are highly beneficial for improving the conductivity of the HTM and the perovskite solar cell devices based on the designed ionic HTM show impressive power conversion efficiency of more than 16%.
  PubDate: 2017-02-21T10:42:02.567703-05:
  DOI: 10.1002/aenm.201602736
Toward Enhanced Electronic and Ionic Conductivity in Olivine LiCoPO4 Thin
Film Electrode Material for 5 V Lithium Batteries: Effect of LiCo2P3O10
Impurity Phase
- Authors: Gennady Cherkashinin; Sankaramangalam Ulhas Sharath, Wolfram Jaegermann
  Abstract: Controlled off-stoichiometry is induced in 5 V olivine LiCoPO4 battery electrode material to overcome its insulating properties through the incorporation of lithium cobalt tripolyphosphate. An excellent electrochemical activity is achieved in this tailored carbon-free material. The electronic structure of the polyanionic compound, the Co2+/Co3+ redox energy, and quantification of the inductive effect are provided.
  PubDate: 2017-02-21T09:42:15.224347-05:
  DOI: 10.1002/aenm.201602321
Improving Perovskite Solar Cells: Insights From a Validated Device Model
- Authors: Tejas S. Sherkar; Cristina Momblona, Lidón Gil-Escrig, Henk J. Bolink, L. Jan Anton Koster
  Abstract: To improve the efficiency of existing perovskite solar cells (PSCs), a detailed understanding of the underlying device physics during their operation is essential. Here, a device model has been developed and validated that describes the operation of PSCs and quantitatively explains the role of contacts, the electron and hole transport layers, charge generation, drift and diffusion of charge carriers and recombination. The simulation to the experimental data of vacuum-deposited CH3NH3PbI3 solar cells over multiple thicknesses has been fit and the device behavior under different operating conditions has been studied to delineate the influence of the external bias, charge-carrier mobilities, energetic barriers for charge injection/extraction and, different recombination channels on the solar cell performance. By doing so, a unique set of material parameters and physical processes that describe these solar cells is identified. Trap-assisted recombination at material interfaces is the dominant recombination channel limiting device performance and passivation of traps increases the power conversion efficiency (PCE) of these devices by 40%. Finally, guidelines to increase their performance have been issued and it is shown that a PCE beyond 25% is within reach.A numerical model is developed and validated that describes the operation of perovskite solar cells and quantitatively explains the role of contacts, the charge transport layers, charge generation, drift and diffusion of carriers and recombination. By doing so, a unique set of material parameters and physical processes is identified that describes these solar cells. To increase their performance, some guidelines are issued.
  PubDate: 2017-02-21T09:42:00.898728-05:
  DOI: 10.1002/aenm.201602432
Recent Advances in Perovskite Oxides as Electrode Materials for Nonaqueous
Lithium–Oxygen Batteries
- Authors: Peng Tan; Meilin Liu, Zongping Shao, Meng Ni
  Abstract: Lithium–oxygen batteries are considered the next-generation power sources for many applications. The commercialization of this technology, however, is hindered by a variety of technical hurdles, including low obtainable capacity, poor energy efficiency, and limited cycle life of the electrodes, especially the cathode (or oxygen) electrode. During the last decade, tremendous efforts have been devoted to the development of new cathode materials. Among them, perovskite oxides have attracted much attention due to the extraordinary tunability of their compositions, structures, and functionalities (e.g., high electrical conductivities and catalytic activities), demonstrating the potential to achieve superior battery performance. This article focuses on the recent advances of perovskite oxides as the electrode materials in nonaqueous lithium–oxygen batteries. The electrochemical mechanisms of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the surface of perovskite oxides are first summarized. Then, the effect of nanostructure and morphology on ORR and OER activities is reviewed, from nanoparticles to hierarchical porous structures. Moreover, perovskite-oxide-based composite electrodes are discussed, highlighting the enhancement in electrical conductivities, catalytic activities, and durability under realistic operating conditions. Finally, the remaining challenges and new directions for achieving rational design of perovskite oxides for nonaqueous lithium–oxygen batteries are outlined and discussed.Perovskite oxides as the electrode materials in nonaqueous lithium–oxygen batteries are reviewed. Future research directions of perovskite oxides should focus on the understanding of electrochemical mechanisms during the oxygen reduction and evolution processes, the structure design from nanoparticles to hierarchical porous structures, and the composite incorporation with improved electrical conductivities, catalytic activities, and structural merits.
  PubDate: 2017-02-20T11:45:59.212527-05:
  DOI: 10.1002/aenm.201602674
Recent Advances of Mn-Rich LiFe1-yMnyPO4 (0.5 ≤ y < 1.0) Cathode
Materials for High Energy Density Lithium Ion Batteries
- Authors: Yuanfu Deng; Chunxiang Yang, Kaixiang Zou, Xusong Qin, Zhenxia Zhao, Guohua Chen
  Abstract: LiMnPO4 (LMP) is one of the most potential candidates for high energy density (≈700 W h kg−1) lithium ion batteries (LIBs). However, the intrinsically low electronic conductivity and lithium ion diffusion coefficient of LMP result in its low performance. To overcome these challenges, it is an effective approach to prepare nanometer-sized Fe-doping LMP (LFMP) materials through optimization of the preparation routes. Moreover, surface coating can improve the ionic and electronic conductivity, and decrease the interfacial side reactions between the nanometer particles and electrolyte. Thus, a uniform surface coating will lead to a significant enhancement of the electrochemical performance of LFMP. Currently, considerable efforts have been devoted to improving the electrochemical performance of LiFe1-yMnyPO4 (0.5 ≤ y < 1.0) and some important progresses have been achieved. Here, a general overview of the structural features, typical electrochemical behavior, delithiation/lithiation mechanisms, and thermodynamic properties of LiFe1-yMnyPO4-based materials is presented. The recent developments achieved in improvement of the electrochemical performances of LiFe1-yMnyPO4-based materials are summarized, including selecting the synthetic methods, nanostructuring, surface coating, optimizing Fe/Mn ratios and particle morphologies, cation/anion doping, and rational designing of LFMP-based full cells. Finally, the critical issues at present and future development of LiFe1-yMnyPO4-based materials are discussed.Mn-rich LiFe1-yMnyPO4 (0.5 ≤ y < 1.0) materials are among the most promising cathode materials for next generation of high-energy-density lithium ion batteries. The recent advances of the development of LiFe1-yMnyPO4, especially on the studies of synthesis strategies, structural features, delithiation/lithiation mechanisms, thermodynamic properties, as well as some aspects for future exploration are outlined in this review.
  PubDate: 2017-02-20T08:26:09.788382-05:
  DOI: 10.1002/aenm.201601958
Chlorine-Enabled Electron Doping in Solution-Synthesized SnSe
Thermoelectric Nanomaterials
- Authors: Guang Han; Srinivas R. Popuri, Heather F. Greer, Lourdes F. Llin, Jan-Willem G. Bos, Wuzong Zhou, Douglas J. Paul, Hervé Ménard, Andrew R. Knox, Andrea Montecucco, Jonathan Siviter, Elena A. Man, Wen-guang Li, Manosh C. Paul, Min Gao, Tracy Sweet, Robert Freer, Feridoon Azough, Hasan Baig, Tapas K. Mallick, Duncan H. Gregory
  Abstract: An aqueous solution method is developed for the facile synthesis of Cl-containing SnSe nanoparticles in 10 g quantities per batch. The particle size and Cl concentration of the nanoparticles can be efficiently tuned as a function of reaction duration. Hot pressing produces n-type Cl-doped SnSe nanostructured compacts with thermoelectric power factors optimized via control of Cl dopant concentration. This approach, combining an energy-efficient solution synthesis with hot pressing, provides a simple, rapid, and low-cost route to high performance n-type SnSe thermoelectric materials.An aqueous solution method is developed for the scalable synthesis of Cl-containing SnSe nanoparticles with tuneable particle size and Cl concentration. Hot pressing produces n-type Cl-doped SnSe nanostructured compacts with thermoelectric power factors optimized via control of Cl dopant concentration.
  PubDate: 2017-02-20T08:25:35.557587-05:
  DOI: 10.1002/aenm.201602328
Atomic Modulation of FeCo–Nitrogen–Carbon Bifunctional Oxygen
Electrodes for Rechargeable and Flexible All-Solid-State Zinc–Air
Battery
- Authors: Chang-Yuan Su; Hui Cheng, Wei Li, Zhao-Qing Liu, Nan Li, Zhufeng Hou, Fu-Quan Bai, Hong-Xing Zhang, Tian-Yi Ma
  Abstract: Rational design and exploration of robust and low-cost bifunctional oxygen reduction/evolution electrocatalysts are greatly desired for metal–air batteries. Herein, a novel high-performance oxygen electrode catalyst is developed based on bimetal FeCo nanoparticles encapsulated in in situ grown nitrogen-doped graphitic carbon nanotubes with bamboo-like structure. The obtained catalyst exhibits a positive half-wave potential of 0.92 V (vs the reversible hydrogen electrode, RHE) for oxygen reduction reaction, and a low operating potential of 1.73 V to achieve a 10 mA cm−2 current density for oxygen evolution reaction. The reversible oxygen electrode index is 0.81 V, surpassing that of most highly active bifunctional catalysts reported to date. By combining experimental and simulation studies, a strong synergetic coupling between FeCo alloy and N-doped carbon nanotubes is proposed in producing a favorable local coordination environment and electronic structure, which affords the pyridinic N-rich catalyst surface promoting the reversible oxygen reactions. Impressively, the assembled zinc–air batteries using liquid electrolytes and the all-solid-state batteries with the synthesized bifunctional catalyst as the air electrode demonstrate superior charging–discharging performance, long lifetime, and high flexibility, holding great potential in practical implementation of new-generation powerful rechargeable batteries with portable or even wearable characteristic.Bamboo-like FeCo alloy encapsulated in nitrogen-doped carbon nanotubes exhibits superior catalytic oxygen reduction and oxygen evolution performance than that of noble metal benchmarks, which benefits from the nitrogen-rich and defect-rich catalyst surface. The all-solid-state zinc–air batteries equipped by the synthesized materials show low charging/discharging overpotentials, long lifetime, and high flexibility, suitable for practical application.
  PubDate: 2017-02-20T08:20:55.940474-05:
  DOI: 10.1002/aenm.201602420
Nanoporous Hybrid Electrolytes for High-Energy Batteries Based on Reactive
Metal Anodes
- Authors: Zhengyuan Tu; Michael J. Zachman, Snehashis Choudhury, Shuya Wei, Lin Ma, Yuan Yang, Lena F. Kourkoutis, Lynden A. Archer
  Abstract: Successful strategies for stabilizing electrodeposition of reactive metals, including lithium, sodium, and aluminum are a requirement for safe, high-energy electrochemical storage technologies that utilize these metals as anodes. Unstable deposition produces high-surface area dendritic structures at the anode/electrolyte interface, which causes premature cell failure by complex physical and chemical processes that have presented formidable barriers to progress. Here, it is reported that hybrid electrolytes created by infusing conventional liquid electrolytes into nanoporous membranes provide exceptional ability to stabilize Li. Electrochemical cells based on γ-Al2O3 ceramics with pore diameters below a cut-off value above 200 nm exhibit long-term stability even at a current density of 3 mA cm−2. The effect is not limited to ceramics; similar large enhancements in stability are observed for polypropylene membranes with less monodisperse pores below 450 nm. These findings are critically assessed using theories for ion rectification and electrodeposition reactions in porous solids and show that the source of stable electrodeposition in nanoporous electrolytes is fundamental.Constraining electrodeposition of liquid electrolytes in charged nanoporous membranes increases lithium-ion transference number and stabilizes electrodeposition of lithium in rechargeable batteries.
  PubDate: 2017-01-06T08:01:29.268612-05:
  DOI: 10.1002/aenm.201602367