An investigation on PAN-PVC-LiTFSI based polymer electrolytes system

Polymer-salt complex with poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) as host polymers blended with lithium bis-(trifluoro methanesulfonyl)imide, LiTFSI [LiN(CF₃SO₂)₂] as dopant salt were prepared in the form of thin film. Fourier transform infrared (FTIR) studies show the evidence of the complexation between PVC, PAN and LiTFSI. Ionic conductivity studies reveal that polymer electrolyte with 30 wt.% LiTFSI has the highest ionic conductivity of 4.39 × 10^− 4 S/cm at room temperature. The polymer electrolytes are also found to be stable up to 315 °C before they decompose. Thermal stability of the polymer electrolytes was also found to increase with increase in salt content. This was proven through thermogravimetric studies.     

RETRACTED ARTICLE: Polymer electrolytes: characteristics and peculiarities

Polymer electrolytes are an important component of many electrochemical devices. This paper reviews state-of-the-art of the electrochemical and physical properties of polymer electrolytes. This review mainly encompasses the properties of different salts, solvents, and polymer hosts, which are encaged in liquid electrolytes. The additions of filler in polymer electrolytes result in composite polymer electrolytes, having high mechanical integrity and ionic conductivity, that are ideal electrolyte for these applications. The next generation state-of-the-art room-temperature ionic liquids based electrolytes, which are far superior to corresponding nonionic solvent-based electrolytes, are also discussed. An erratum to this article can be found at     

Blended lithium ion conducting polymer electrolytes based on boroxine polymers

A new series of blended polymer electrolytes based on a boroxine polymer (BP) with poly(ethylene oxide) (PEO), an ethylene oxide–propylene oxide copolymer or poly(methyl methacrylate) were prepared. Good room temperature mechanical properties were exhibited by electrolytes containing in excess of 30% PEO. Cationic transference number measurements indicated that a slight improvement in lithium ion conductivity could be achieved by using a mixture of LiCF₃SO₃ and LiN(CF₃SO₂)₂ as the electrolyte salt. Electrolytes incorporating significant proportions of BP exhibited reduced lithium–polymer electrolyte interfacial resistance.     

A study on the blending effect of polyvinyledene fluoride in the ionic transport mechanism of plasticized polyvinyl chloride + lithium perchlorate gel polymer electrolytes

The gel polymer electrolytes composed of the blend of polyvinylchloride (PVC) and polyvinylidene fluoride (PVdF) as host polymers, the mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO₄ as a salt was studied. An attempt was made to investigate the effect of PVdF in the plasticized PVC + LiClO₄ system in three blend ratios. The differential scanning calorimetry study confirms the formation of polymer–salt complex and miscibility of the PVC and PVdF. The X-ray diffraction results of plasticized PVC (S1, S2, S3) and PVdF-blended films (S4, S5, S6) were compared, in that an increase in PVC concentration decreases the degree of crystallinity for S1 and S3, respectively, but drastically increases for PVC (S2). The increase in PVC content has not accounted in the conductivity studies also noted. However, the blending effect of PVdF showed decreases in crystallinity homogeneously for (S6 > S5 > S4), which were reflected in ionic conductivity measurements. The surface morphology of the films were also studied by scanning electron microscope, and it corroborates the same. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Investigation on PVDF-HFP microporous membranes prepared by TIPS process and their application as polymer electrolytes for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) microporous membranes were prepared via thermally induced phase separation (TIPS) process. Then they were immersed in a liquid electrolyte to form polymer electrolytes. The effects of polymer content in casting solution on the morphology, crystallinity, and porosity of the membranes were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and a mercury porosimeter, respectively. Ionic conductivity, lithium-ion transference number, and electrochemical stability window of corresponding polymer electrolytes were characterized by AC impedance spectroscopy, DC polarization/AC impedance combination method, and linear sweep voltammetry, respectively. The results showed that spherulites and “net-shaped” structure coexisted for the membranes. Polymer content had no effect on crystal structure of the membranes. The maximum transference number was 0.55. The temperature dependence of ionic conductivity followed the Vogel–Tammann–Fulcher (VTF) relation. The maximum ionic conductivity was 2.93 × 10⁻³ Scm⁻¹ at 20 °C. Electrochemical stability window was stable up to 4.7 V (vs. Li⁺/Li).     

Solid polymer electrolytes based on poly(lithium carboxylate) salts

The ionic conductivity, lithium ion transference number, electrochemical stability, and thermal property of solid polymer electrolytes composed of poly(ethylene oxide) (PEO) and poly(lithium carboxylate)s, (poly(lithium acrylate) (Poly(Li-A)) or poly(lithium fumarate) (Poly(Li-F)), with and without BF₃·OEt₂ were investigated. The ionic conductivities of all solid polymer electrolytes were enhanced by one to two orders of magnitude with addition of BF₃·OEt₂ because the dissociation of lithium ion and carboxylate anion was promoted by the complexation with BF₃. The lithium ion transference number in the solid polymer electrolytes based on poly(lithium carboxylate)s showed relatively high values of 0.41–0.70, due to the suppression of the transport of counter anion by the use of a polymeric anion. The solid polymer electrolytes with addition of BF₃·OEt₂ showed good electrochemical stability.     

Ionic conduction in plasticized PVC/PAN blend polymer electrolytes

Blended polymer electrolytes with poly(vinyl chloride) (PVC)–poly(acrylonitrile) (PAN) were prepared with different plasticizer concentrations and constant lithium perchlorate (LiClO₄) ratio by the solution-casting technique. The structure and complexation of the prepared films were studied by X-ray diffraction and Fourier transform infrared spectroscopy. The effect of the plasticizer on the ionic conduction in these electrolytes was investigated using alternating current impedance measurement and discussed. The temperature-dependant ionic conductivity was carried out in the range 302–373 K. The prepared films were also examined by thermogravimetry/differential thermal analysis to determine their thermal stability.     

Recent progress in solid oxide and lithium ion conducting electrolytes research

Recent material developments of fast solid oxide and lithium ion conductors are reviewed. Special emphasis is placed on the correlation between the composition, structure, and electrical transport properties of perovskite-type, perovskite-related, and other inorganic crystalline materials in terms of the required functional properties for practical applications, such as fuel or hydrolysis cells and batteries. The discussed materials include Sr- and Mg-doped LaGaO₃, Ba₂In₂O₅, Bi₄V₂O₁₁, RE-doped CeO₂, (Li,La,)TiO₃, Li₃La₃La₃Nb₂O₁₂ (M=Nb, Ta), and Na super-ionic conductor-type phosphate. Critical problems with regard to the development of practically useful devices are discussed.     

Preparation and electrical characterization of (PVC + KBrO3) polymer electrolytes for solid state battery applications

This paper presents results of studies on dc electrical conductivity and transference number measurements on potassium bromate (KBrO₃) complexed polyvinyl chloride (PVC) films prepared by solution cast technique. Temperature dependence of dc electrical conductivity and transference number data indicated the dominance of ion type charge transport in these specimens. The magnitude of conductivity increased with increase in concentration of the salt and temperature. Using this (PVC + KBrO₃) electrolyte, solid-state electrochemical cells were fabricated, and their discharge profiles were studied under a constant load of 100 kΩ. Several cell profiles such as open circuit voltage, short circuit current, power density, and energy density associated with these cells were evaluated and were reported. The features of complexation of the electrolytes were studied by X-ray diffraction and Fourier transform infrared spectroscopy. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

High-pressure conductivity studies of blends of poly(p-phenylene)s with oxyethylene side-chains and lithium salts

High-pressure electrical conductivity studies have been carried out with poly(p-phenylene)s with oxyethylene side-chains (PPP(EO)_x/y), which were blended with LiCF₃SO₃. Measurements were performed at pressures up to 280 MPa and at different temperatures. The influences of salt concentration, side-chain length, temperature, and plasticizer content on the relative conductance and activation volume are investigated. The temperature-dependent conductivity of the sample is non-Arrhenius and exhibits Williams–Landel–Ferry (WLF) behavior. The logarithm of relative conductance for PPP(EO)_x/y/LiCF₃SO₃ decreases almost linearly with increasing pressure but increases with salt concentration and side-chain length. As temperature increases, the activation volume becomes smaller but remains positive for PPP(EO)_x/y/LiCF₃SO₃. At higher salt concentrations and longer side-chain lengths, a smaller activation volume for the ion motion is found. These results can be interpreted such that PPP(EO)_x/y/LiCF₃SO₃ behaves like a true polymer electrolyte where ion transport is mediated by segmental motions of the EO side-chains. The addition of tetraethylene glycol dimethyl ether (TEGDME) as a plasticizer increases the activation volume but reduces the conductance.     

In-situ synchrotron X-ray absorption studies of LiMn0.25Fe0.75PO4 as a cathode material for lithium ion batteries

Recently, lithium bi-metal phosphates (LiM′M″PO₄) have been synthesized for use as cathode materials in order to increase cell voltages and electrical performances. In this work, we have substituted Mn²⁺ at the 4c site of LiFePO₄ to prepare the lithium bi-metal phosphate LiMn_0.25Fe_0.75PO₄ and have found that it greatly enhances the cell voltage. At a 0.05 C discharge rate, the cell capacity was about 153 mAhg^− 1 and the average working voltage rose to 3.53 V due to the Mn substitution. However, the capacity and working voltage both decrease as the discharge rate increases. By in-situ metal K-edge absorption analysis, it reveals that the substituted metal Mn²⁺ does not work completely at a higher discharge rate, due to poor electrical conductivity and a serious Jahn–Teller effect.     

Investigations on the effect of complexation of NaF salt with polymer blend (PEO/PVP) electrolytes on ionic conductivity and optical energy band gaps

Sodium ion conducting polymer blend electrolyte films, based on polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP) complexed with NaF salt, were prepared using solution casting technique. The complexation of the salt with the polymer blend was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy. Electrical conductivity of the films was measured with impedance analyzer in the frequency range of 1 Hz to 1 MHz and in the temperature range of 303-348 K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. UV-vis absorption spectra in wavelength region of 200-800 nm were used to evaluate the optical properties like direct and indirect optical energy band gaps, optical absorption edge. The optical band gaps decreased with the increase in Na⁺ ion concentration. This suggests that NaF, as a dopant, is a good choice to improve the electrical properties of PEO/PVP polymer blend electrolytes.     

An electrochemical investigation of Li intercalation in the sol-gel LiMn2O4 spinel oxide

An alternative approach for obtaining the LiMn₂O₄ spinel phase is provided by the use of the sol-gel method in aqueous solution. The main electrochemical properties of the sol-gel LiMn₂O₄ phase are reported. In addition to chronopotentiometric and voltammetric experiments, the kinetics of the electrochemical insertion–extraction of lithium in Li_xMn₂O₄ (0.25<x<1) has been investigated using ac impedance spectroscopy. The strong variation of the chemical diffusion coefficient D_Li vs x, in the range 10⁻⁸–10⁻¹¹ cm² s⁻¹ (D_Li is found to be maximum for x=0.55) is critically discussed.     

Electrical and electrochemical properties of glass-ceramic electrolytes in the systems Li2S-P2S5-P2S3 and Li2S-P2S5-P2O5

Electrical and electrochemical properties of the 70Li₂S·(30 − x)P₂S₅·xP₂S₃ and the 70Li₂S·(30 − x)P₂S₅·xP₂O₅ (mol%) glass-ceramics prepared by the mechanical milling technique were investigated. Glass-ceramics with 1 mol% P₂S₃ and 3 mol% P₂O₅ showed the highest conductivity of 5.4 × 10^− 3 S cm^− 1 and 4.6 × 10^− 3 S cm^− 1, respectively. Moreover, these glass-ceramics showed higher electrochemical stability than the 70Li₂S·30P₂S₅ (mol%) glass-ceramic. From the XRD patterns of the obtained glass-ceramics, trivalent phosphorus and oxygen were incorporated into the Li₇P₃S₁₁ crystal. We therefore presume that the Li₇P₃S₁₁ analogous crystals, which were formed by incorporating trivalent phosphorus and oxygen into the Li₇P₃S₁₁ crystal, improve the electrical and electrochemical properties of the glass-ceramics. An all-solid-state cell using the 70Li₂S·29P₂S₅·1P₂S₃ (mol%) glass-ceramic as solid electrolyte operated under the high current density of 12.7 mA cm^− 2 at the high temperature of 100 °C. The cell showed an excellent cyclability of over 700 cycles without capacity loss.     

Synthesis and characterization of lithium manganese oxides with core-shell Li4Mn5O12@Li2MnO3 structure as lithium battery electrode materials

By a facile LiNO₃ flux method, lithium manganese oxide composites (xLi₄Mn₅O₁₂? yLi₂MnO₃) were synthesized using a hierarchical organization precursor of manganese dioxide. Li₄Mn₅O₁₂ and Li₂MnO₃ have spinel and rocksalt structures, respectively. The lithiation and structural transformation from the precursor to the composites occurred topotactically from exterior toward interior in the precursor particle with the increase of reaction time, and the composites had core-shell spinel@rocksalt structures in addition to the original hierarchical core-shell organization. The electrochemical measurements at 50 °C after 50 cycles confirmed that a typical spinel@rocksalt cathode had higher capacity retention (87.1%) than that with the composition close to the stoichiometric spinel (64.6%), indicating the Li₂MnO₃ shell can improve cycling stability for the composite electrode at elevated temperature.     

Improved performance of porous LiFePO4/C as lithium battery cathode processed by high energy milling comparison with conventional ball milling

Porous LiFePO₄ is synthesized and coated with amorphous carbon by using high energy nano-mill (HENM) processed solid-state reaction method. FeCl₃ (38%) containing water solution which is originated from pickling of steel scrap (waste liquid) is used as a source material in this study. The result indicates that LiFePO₄ powders are well coated with the amorphous carbon. HENM process successfully produces the porous LiFePO₄ with homogeneously distributed pores and a well networked carbon web, which delivers an enhanced electrochemical rate capability. HENM process is incorporated as an effective route for reducing particle size, distributing particle homogeneously and averting agglomeration of particles of precursor in this study. X-ray diffraction, scanning electron microscopy with elemental mapping, transmission electron microscopy with selected area (electron) diffraction, Raman spectroscopy, cyclic voltammetry, and galvanostatic charge/discharge are employed to characterize the final product. Electrochemical measurement shows that the synthesized LiFePO₄/C composite cathode delivers an initial discharge capacity of 161 mAhg⁻¹ at 0.1C-rate between 4.2 and 2.5 V. Remarkably, the cathode delivers 101.9 mAhg⁻¹ at high charge/discharge rate (10 C).     

锂离子电池SnSb/C复合负极材料的热碳还原法制备及电化学性能研究

采用高温还原技术,以SnO2,SbO3为原料,分别以葡萄糖、中间相碳微球(MCMB)作为还原剂,制备了两种结构的SnSb/C复合材料,并对比了它们的形貌和电化学性能.采用X射线衍射技术、拉曼技术、扫描电子显微镜技术对材料的结构和形貌进行了表征,并且通过测试恒电流充放电曲线、循环伏安曲线和交流阻抗谱分析了材料的电化学性能.实验结果表明:葡萄糖作为还原剂时,形成以合金颗粒为内核,絮状碳壳均匀包裹的微米球状结构,首次放电比容量为793.379 mA·h·g-1,循环50周后仍维持在449.987 mA·h·g-1;而以MCMB作为还原剂时,形成合金颗粒与MCMB混合共存并部分包覆的结构,首次放电比容量为1164.938 mA·h·g-1,50周后的比容量仅有290.807 mA·h·g-1.