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Ionics

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ISSN (Print) 1862-0760 - ISSN (Online) 0947-7047
Published by Springer-Verlag

[2216 journals]

Sn and SnO₂-graphene composites as anode materials for lithium-ion batteries
- Abstract: Abstract Sn and SnO2-graphene composites were synthesized using hydrothermal process, followed by annealing in Ar/H2 atmosphere, and characterized using x-ray diffraction, scanning electron microscopy, and transition electron microscopy. The results indicated that the polycrystalline metallic Sn forms nanospheres with a diameter of 100 ∼ 300 nm, while the SnO2 nanoparticles are much smaller with a size below 15 nm, which adsorb tightly on the surface of graphene sheets. The Sn and SnO2-gaphene composites showed good electrochemical performance. After 55 charging/discharging cycles, the capacity remains above 440 mAh/g at a cycling rate of 400 mA/g and the coulombic efficiency is 99.1 %. The good electrochemical properties of the composites are partially contributed to the graphene component with good mechanical flexibility and electrical conductivity, which is an excellent carbon matrix for dispersing the Sn and SnO2 nanostructures and provides the electron transport pathways as well.
  PubDate: 2013-05-10
Solvothermal synthesis of mesoporous NiCo₂O₄ spinel oxide nanostructure for high-performance electrochemical capacitor electrode
- Abstract: Abstract NiCo2O4 nanostructure was successfully synthesized via a d-glucose-assisted solvothermal process. Spinel-type cubic phase and mesoporous microstructure of the sample for different calcination temperatures were confirmed by X-ray diffraction and transmission electron microscopy. Typical pseudocapacitance feature of the NiCo2O4 treated at different temperatures was then evaluated in aqueous 6 M KOH electrolyte solution. Electrochemical measurements showed that the spinel nickel cobaltite nanostructure heated at 300 °C exhibits maximum specific capacitances of 524 F g−1 at 0.5 A g−1 and 419 F g−1 at 10 A g−1 with excellent cycle stability and only ~9 % of capacitance loss after 2,500 cycles. This demonstrates the potential application of the material for supercapacitors. The attractive pseudocapacitive performance of NiCo2O4 is mainly attributed to the redox contribution of the Ni and Co metal species, high surface area, and their desired mesoporous nanostructure.
  PubDate: 2013-05-09
The across-plane conductivity and microstructure of SrZr_0.95Y_0.05O_3 − δ thin films
- Abstract: Abstract The across-plane electrical conductivity of the proton-conducting SrZr0.95Y0.05O3 − δ thin films fabricated by chemical solution deposition on single-crystalline ZrO2 doped by 10 mol% of Y2O3 (YSZ) substrates was investigated using impedance spectroscopy. The average grain size of the films was found to increase considerably with thermal treatment. This change in grain size has a strong effect on the electrical behavior of films. Our results show that the electrochemical performance of the cell is strongly affected by the potential difference at the film/substrate interface. Coarse-grain film microstructure was proved to be preferable for the reduction of both the film resistance and interfacial barrier.
  PubDate: 2013-05-09
Phosphazene groups modified sulfur composites as active cathode materials for rechargeable lithium/sulfur batteries
- Abstract: Abstract A novel phosphazene groups modified sulfur composites cathode [triphosphazene sulfide composite (PS) or nitroaniline–triphosphazene disulfide composite (NPS)] which can give good affinity with electrolytes was prepared. Their chemical structures were identified by FTIR and XRD analysis. SEM analysis showed PS and NPS had a denser and rougher surface structure than elemental sulfur, with many tiny pores on the surface. Contact angles measurement showed that PS had a hydrophilic surface, which exhibited better affinity of ether solvent. When used as a cathode material in lithium–sulfur batteries, its initial discharge capacity was 1,109 mAh/g for NPS, 784 mAh/g for PS. Discharge capacity of NPS was higher than charge capacity, which implied nitroanilino base on sulfur particles involving in generation of polysulfides.
  PubDate: 2013-05-09
Novel layered perovskite GdBaCuFeO_5+x as a potential cathode for proton-conducting solid oxide fuel cells
- Abstract: Abstract A layered perovskite GdBaCuFeO5+x (GBCuF) was developed as a cathode material for intermediate-temperature solid oxide fuel cells based on a proton-conducting electrolyte of stable BaZr0.1Ce0.7Y0.2O3−δ (BZCY). The X-ray diffraction results showed that GBCuF was chemically compatible with BZCY after co-fired at 1,000 °C for 10 h. The thermal expansion coefficient of GBCuF, which showed a reasonably reduced value (15.1 × 10−6 K−1), was much closer to that of BZCY than the cobalt-containing conductor. The button cells of Ni–BZCY/BZCY/GBCuF were fabricated and tested from 500 to 700 °C with humidified H2 (∼3 % H2O) as a fuel and ambient oxygen as the oxidant. A high open-circuit potential of 1.04 V, maximum power density of 414 mW cm−2, and a low electrode polarization resistance of 0.21 Ω cm2 were achieved at 700 °C, with calculated activation energy (E a) of 128 kJ mol−1 for the GBCuF cathode. The experimental results indicated that the layered perovskite GBCuF is a good candidate for cathode material.
  PubDate: 2013-05-04
Ex situ FTIR spectroscopy study of LiVPO₄F as cathode material for lithium-ion batteries
- Abstract: Abstract The LiVPO4F as cathode material for lithium-ion batteries was synthesized through two steps of solid-state reactions and investigated by ex situ Fourier transform infrared (FTIR) spectroscopy for the initial charge and discharge cycle. The characterization of the effect on the structure of the LiVPO4F in the process of lithium-ion insertion/extraction at a molecular level by ex situ FTIR spectroscopy is helpful for the mechanism research for lithium-ion insertion/extraction and the improvement of the performance of lithium-ion batteries. In the process of the initial cycle, new bands of VPO4F appear in the charge and the featured bands of LiVPO4F reappear in the discharge. In this paper, ex situ FTIR spectra indicates that the structure of the LiVPO4F in the process of lithium-ion insertion/extraction is almost not affected, which clearly states that the LiVPO4F possesses stable structure as cathode material. Consequently, the LiVPO4F might be expected as a potential cathode replacement for commercial lithium-ion batteries.
  PubDate: 2013-05-01
Physical and electrochemical characterizations of Ni-SiO₂ nanocomposite coatings
- Abstract: Abstract Advances in materials performance often require the development of composite system. In the present investigation, SiO2-reinforced nickel composite coatings were deposited on a mild steel substrate using direct current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of the Ni and Ni-SiO2 nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of SiO2 particles in the Ni nanocomposite coating on the microhardness and corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon oxide particles were obtained. The preferred growth process of the nickel matrix in crystallographic directions <111>, <200> and <220> is strongly influenced by SiO2 nanoparticles. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~23 nm for electrodeposited nickel and ~21 nm for Ni-SiO2 nanocomposite coatings. The crystallite structure was fcc for electrodeposited nickel and Ni-SiO2 nanocomposite coatings. The incorporation of SiO2 particles into the Ni matrices was found to improve corrosion resistance of pure Ni coatings. The corrosion potential (E corr) in the case of Ni-SiO2 nanocomposite coatings had shown a negative shift, confirming the cathodic protective nature of the coating. The Ni-SiO2 composite coatings have exhibited significantly improved microhardness (615 HV) compared to pure nickel coatings (265 HV)
  PubDate: 2013-05-01
Synthesis and electrochemical characterization of InSn₄ and InSn₄/C as new anode materials for lithium-ion batteries
- Abstract: Abstract The InSn4 intermetallic powders are synthesized via carbothermal reduction route from In2O3 and SnO2. The reaction possibility is estimated by thermodynamic calculation. Pure InSn4 intermetallic powders with spherical morphology can be obtained at 900 °C in flowing nitrogen. The micro-sized InSn4 particle is actually composed of a large number of nano-sized grains with polycrystalline and loose structure. The synthesized InSn4 shows high reversible specific capacity (ca. 500 mAhg−1) and a good cycling performance as an anode material for lithium-ion batteries. Coating InSn4 with carbon can increase the reversible specific capacity and improve significantly the rate capability. The InSn4/C composite displays a stable specific capacity of ca. 600 mAhg−1. In consideration of the simple and moderate synthesis route and the mass productive feature, the InSn4/C composite is a promising anode material for lithium-ion batteries.
  PubDate: 2013-05-01
Conductivity and thermal stability of proton-conducting electrolytes at confined geometry of polymeric gel
- Abstract: Abstract The proton-conducting gel electrolytes based on poly(methyl methacrylate) (PMMA) doped by acid solutions in aprotic solvents were synthesized and discussed in this work. The gel conductivity as a function on concentrations of acid and polymer as well as of molecular mass of PMMA has been analyzed. The thermal stability of electrolytes was estimated and discussed. Extreme dependence of the conductivity on concentration is found to be for the gel (at a concentration of PMMA from 5 to 15 wt.%). The increase of electrical conductivity in the concentration range from 5 to 10 wt.% of PMMA with an increase in viscosity of the system is discussed as an indication of an involvement of the polymer matrix in increasing the mobility of the charge carriers in frame of Grotthuss mechanism.
  PubDate: 2013-05-01
Improvement of a novel anode material TeO₂ by chlorine doping
- Abstract: Abstract A simple and versatile method for the preparation of chlorine-doped TeO2 was developed via thermal decomposition of Te6O11Cl2 in situ. Te6O11Cl2 was prepared with TeCl4 and ethanol as reagents, while TeO2 was fabricated with water as a solvent. The morphology, surface, and electrochemical performances of the obtained materials were systematically studied. It was found that chlorine-doped TeO2 demonstrated the highest cycling efficiency and stability than Te6O11Cl2 and TeO2. The presence of Te–Cl bond is expected to contribute to the reversible capacity and Li inserting process.
  PubDate: 2013-05-01
A polymer electrolyte based on poly(vinylidene fluoride-hexafluoropylene)/hydroxypropyl methyl cellulose blending for lithium-ion battery
- Abstract: Abstract A polymer electrolyte based on the blending of poly(vinylidene fluoride-hexafluoropylene) (PVDF-HFP) and hydroxypropyl methyl cellulose (HPMC) was prepared for the first time. The structure and performance of the gel polymer electrolyte were characterized and measured by X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, electrochemical impedance spectroscopy, linear sweep voltammetry, and by a charge/discharge test. The results show that the gel polymer electrolyte has the best performance when PVDF-HFP/HPMC ratio (w/w) is 4:1. At room temperature, the ionic conductivity can reach 0.38 × 10−3 S cm−1, the electrochemical stable window is up to 5.0 V (vs. Li/Li+), and the half cell of Li/GPE/LiMn2O4 shows high-discharge-specific capacity and good cycling performance.
  PubDate: 2013-05-01
Surface coating of LiMn₂O₄ spinel via in situ hydrolysis route: effect of the solution
- Abstract: Abstract Thin SiO2 shell consisting of nano-SiO2 particles can be deposited on to LiMn2O4 through the facile hydrolysis of tetraethoxysilane (TEOS) as a solution in either methanol or ethanol. The structure and surface morphologies of the modified and pristine materials were characterized by means of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The choice of solvent (methanol vs. ethanol) for TEOS hydrolysis has a profound effect on the physical and electrochemical properties of the resultant SiO2-coated LiMn2O4. Coated LiMn2O4 demonstrated an improved cycling ability compared to the uncoated counterpart. Moreover, samples coated using a TEOS–methanol solution showed better cycling ability in extended potential windows and at an elevated temperature than that coated using ethanol.
  PubDate: 2013-05-01
Erratum to: Part II: Effect of high energy proton beam fluence on the electrical studies of lithium gallium phosphate glass electrolyte doped with selenium ions
- PubDate: 2013-05-01
Effect of ethylene carbonate concentration on structural and electrical properties of PEO–PMMA polymer blends
- Abstract: Abstract Polyethylene oxide–polymethyl methacrylate (PEO–PMMA) polymer blend electrolyte system complexed with silver salt having different ethylene carbonate (EC) concentrations was prepared using solution cast technique. Complex formation and change in structural and microstructural properties have been studied by X-ray diffraction, Fourier transform infrared, and scanning electron microscopy analysis. The thermal properties of polymer films have been examined by the differential scanning calorimetry technique. Addition of plasticizer is observed to lower melting temperature. Electrical response of polymer films has been measured as a function of EC concentration and temperature using complex impedance spectroscopy. Complex impedance data are used to analyze the conductivity, permittivity, and modulus formalism to understand the conduction mechanism. The temperature dependence of electrical conductivity of polymer electrolytes shows a sudden rise at the melting temperature of PEO.
  PubDate: 2013-05-01
Combined effect of nanochitosan and succinonitrile on structural, mechanical, thermal, and electrochemical properties of plasticized nanocomposite polymer electrolytes (PNCPE) for lithium batteries
- Abstract: Abstract A sequence of novel plasticized polymer nanocomposite electrolyte systems based on polyethylene oxide (PEO) as polymer host, LiCF3SO3 as salt, and a variety of concentrations of nanochitosan as inert filler, succinonitrile as a solid non-ionic plasticizer has been prepared. The prepared membranes were subjected to X-ray diffraction, FT-IR, tensile strength, morphological studies, thermal analysis, AC ionic conductivity measurement, and interfacial analyses. The combined effect of succinonitrile and nanochitosan on the electrochemical properties of polymer electrolytes has been studied, and it was confirmed that the ionic conductivity is significantly increased. The maximum ionic conductivity of the plasticized nanocomposite polymer electrolytes are found to be in the range of 10−2.8 S/cm. Besides, the interfacial stability also shows a significant improvement. The tensile measurement and thermal analysis results illustrate that the electrolytes based on that polymer host possess good mechanical and thermal stabilities.
  PubDate: 2013-05-01
The determination of Li⁺ mobility in solid electrolyte Li_1.3Al_0.1Zn_0.1Ti_1.8P₃O₁₂ in view of ionic diffusivity and conductivity
- Abstract: Abstract Nasicon-type solid electrolyte Li1.3Al0.1Zn0.1Ti1.8P3O12 was prepared by citric acid-assisted acrylamide polymerisation gel method. X-ray diffraction pattern showed that the introduction of Zn2+ in the parent matrix Li1+x Al x Ti2−x P3O12 made it easier to get high-purity rhombohedral structure (space group $ R\overline 3 C $ ) Li1.3Al0.1Zn0.1Ti1.8P3O12 without the evidence of impurity secondary phase. The Li+ kinetics were investigated by complex impedance in bulk pellet and ionic conductivity in battery-type composite cathode, respectively. Grain-interior resistance measured by galvanostatic intermittent titration technique, potential step chronoamperometry, and AC impedance spectroscopy at 20 °C varies in the range 1.2–1.95 × 10−4 S cm−1, which is in good agreement with that obtained by complex impedance method 1.5 × 10−4 S cm−1.
  PubDate: 2013-05-01
Part II: Effect of high energy proton beam fluence on the electrical studies of lithium gallium phosphate glass electrolyte doped with selenium ions
- Abstract: Abstract A series of glass samples, according to the formula (100 − x) (0.5Li2O − 0.2Ga2O3 − 0.3P2O5) + xSeO2 (x = 0, 2, 4, 6, 8, 10) and 12 mol.%, labeled as LGPS x (x is the mole percent of SeO2), were synthesized through melt quenching technique. All the LGPS x samples were irradiated by a high energy proton (H+) beam of 3 MeV at fluence of 1014, 5 × 1014, and 10 × 1014 ions/cm2. FTIR and Raman spectra indicated that SeO2 acts either as a glass modifier (SeO 3 2− ) or a glass former (SeO 4 2− ), as the dose rate of beam fluence changes. The bulk conductivity of the highest conducting sample LGPS10 irradiated at a beam fluence of 5 × 1014 ions/cm2 was determined as 5.87 × 10−04 S/cm at 303 K. The super curve in the normalized spectra of electrical modulus at different temperatures confirms that the LGPS samples follow the temperature-independent, frequency-dependent relaxation time before and after irradiation.
  PubDate: 2013-05-01
Plastic separators with improved properties for portable power device applications
- Abstract: Abstract We report a novel clay-intercalated polymer nanocomposites (PNC) having very high ionic conductivity (~10−3 S cm−1) and improved stability properties. The suitability of the PNC films for subsequent use as a separator component in energy storage devices has been explored in terms of desirable voltage (~4.3 V), thermal (~290 °C) and mechanical (~55 MPa) stability, and ion transport (t ion, ~0.99) properties. Intercalation of (polyacrylonitrile (PAN)8LiPF6 complex into nanometric channels of organophilic clay has been confirmed by X-ray diffraction analysis. These observations agree well with transmission electron microscopy results. Impedance spectroscopy indicated bulk electrical conduction in the high-frequency region followed by electrode polarization effects at lower frequencies. The latter effect is clearly noticed in the admittance plots. Estimated value of ionic conductivity and stability is invariably higher in PNCs compared with clay-free polymer–salt complex film. The feasibility of ionic conduction in the PNC separators has been explained in terms of hopping mechanism. The optimized PNC film may be expected to serve the dual purpose of electrolyte as well as separator in portable energy storage/conversion devices.
  PubDate: 2013-05-01
Synthesis and characterization of Li₄Ti₅O₁₂/graphene composite as anode material with enhanced electrochemical performance
- Abstract: Abstract The use of graphene as a conductive additive to enhance the rate capability and cycle stability of Li4Ti5O12 electrode material has been demonstrated. Li4Ti5O12 and its composite with graphene (1.86 wt%) are prepared by ball milling and simple chemical method, respectively. Among the as-synthesized composites, Li4Ti5O12 particles uniformly clung to the graphene sheets. When used as an electrode material for lithium ion battery, the composite presents excellent rate performance and high cyclic stability. It is found that the composite displayed high-rate capacity of 118.7 mAh g−1 at 20 C. Furthermore, the composite exhibits good cycle stability, retaining over 96 % of its initial capacity after 50 cycles at 10 C. The excellent electrochemical performance is attributed to a decrease in the charge-transfer resistance.
  PubDate: 2013-05-01
The DC bias function of electrical characterization of PVA inducted nickel chloride composite film
- Abstract: Abstract The synthesis of nickel chloride (NiCl2)-mixed with polyvinyl alcohol films of 15–20 μm in thickness has been carried by solution blending technique. The dielectric properties of the films have been measured in the frequency range of 20 Hz to 1 MHz under a positive bias potential in the range from 0 to 40 V. Improved electric characterization was demonstrated due to ionic incorporation of NiCl2. The low-frequency polarization was based on the Maxwell–Wagner interfacial model. Hence, this composite film may suggest as suitable electronic polar medium for versatile low-frequency applications.
  PubDate: 2013-04-27