Comparison among the performance of LiBOB,LiDFOB and LiFAP impregnated polyvinylidenefluoride-hexafluoropropylene nanocomposite membranes by phase inversion for lithium batteries

This paper describes the physico-chemical and electrochemical properties of polyvinylidenefluoride-hexafluoropropylene (PVdF-HFP) membranes (GPM) prepared by phase inversion technique. Nanocomposite polymer membranes (NCPM) are also prepared by the same technique using AlO(OH)_n nanoparticles. The prepared GPM and NCPM are gelled with liquid electrolyte containing three different salts namely, lithium bis(oxalate)borate, lithium fluoroalkylphosphate and lithium difluoro(oxalato)borate. Prepared membranes were subjected to various physico-chemical characterizations likely, mechanical stability, ionic conductivity, morphological studies, surface area and thermal analysis. Electrochemical chemical properties of membranes are evaluated in half-cell configurations (Li/NCPM or GPM/LiFePO₄) at room temperature conditions. Galvanostatic cycling profiles clearly indicates the improved performance of chelato borate based anions i.e. BOB and DFOB when compared to fluoroalkyl group (FAP).     

Organosilicon functionalized quaternary ammonium ionic liquids as electrolytes for lithium-ion batteries

Organosilicon-functionalized quaternary ammonium ionic liquids (ILs) with oligo(ethylene oxide) substituent are designed and synthesized. Such properties as viscosity, conductivity, and thermal/electrochemical stability of these ILs are characterized. These ILs are miscible with the commercial carbonate electrolyte (EC: DEC?=?1:1(w/w), 1 M LiPF₆) and are used as cosolvents to form hybrid electrolytes in proportions up to 30 vol%. By using such hybrid electrolytes, the LiFePO₄/Li half cells exhibit no deterioration in specific capacity and cyclability, and the graphite/Li half cells show improved compatibility in the presence of lithium oxalyldifluoroborate. These hybrid electrolytes exhibit less flammability compared with the commercial baseline electrolyte, and thus improved safety for use in lithium-ion batteries.     

A novel and shortcut method to prepare ionic liquid gel polymer electrolyte membranes for lithium-ion battery

The ionic liquid polymer electrolyte (IL-PE) membrane is prepared by ultraviolet (UV) cross-linking technology with polyurethane acrylate (PUA), methyl methacrylate (MMA), ionic liquid (Py₁₃TFSI), lithium salt (LiTFSI), ethylene glycol dimethacrylate (EGDMA), and benzoyl peroxide (BPO). N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py₁₃TFSI) ionic liquid is synthesized by mixing N-methyl-N-propyl pyrrolidinium bromide (Py₁₃Br) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The addition of Py₁₃TFSI to polymer electrolyte membranes leads to network structures by the chain cross-linking. The resultant electrolyte membranes display the room temperature ionic conductivity of 1.37 × 10^?3 S cm^?1 and the lithium ions transference number of 0.22. The electrochemical stability window of IL-PE is about 4.8 V (vs. Li⁺/Li), indicating sufficient electrochemical stability. The interfacial resistances between the IL-PE and the electrodes have the less change after 10 cycles than before 10 cycles. IL-PE has better compatibility with the LiFePO₄ electrode and the Li electrode after 10 cycles. The first discharge performance of Li/IL-PE/LiFePO₄ half-cell shows a capacity of 151.9 mAh g^?1 and coulombic efficiency of 87.9%. The discharge capacity is 131.9 mAh g^?1 with 95.5% coulombic efficiency after 80 cycles. Therefore, the battery using the IL-PE exhibits a good cycle and rate performance.     

A study on LiBOB-based nanocomposite gel polymer electrolytes (NCGPE) for Lithium-ion batteries

Lithium bis(oxalato)borate (LiBOB) salt-based nanocomposite gel polymer blend electrolyte (PVdF/PVC) membranes have been prepared by solution casting technique for various concentrations of TiO₂. The effect of anatase structure of nanosized titanium dioxide in the plasticized PVC/PVdF + LiBOB matrix has been observed in the 2:1 salt filler ratio in the impedance measurements that the conductivity is increased one order of magnitude higher than the filler-free electrolyte (1:0 salt:filler ratio). The phase morphology of this electrolyte membrane represents the appearance of the free volume sites for ionic migration.     

Electrical and electrochemical properties of poly (methyl methacrylate) based nanocomposite gel electrolytes dispersed with dedoped (insulating) polyaniline nanofibers

In this work, we have investigated the effect of dedoped (insulating) polyaniline (PAni) nanofibers on the electrical and electrochemical properties of poly(methyl methacrylate) (PMMA)-based gel electrolytes. PAni nanofibers have been synthesized using interfacial polymerization technique. By analysis of X-ray diffraction (XRD) and impedance spectroscopy results, it has been demonstrated that the incorporation of dedoped PAni nanofibers up to a moderate concentration (4 wt%) to PMMA–(PC?+?DEC)–LiClO₄ gel polymer electrolyte system significantly enhances the ionic conductivity of the electrolyte system, which can be attributed to the inhibition of polymer chain reorganization upon dispersion of high aspect ratio nanofibers in PMMA matrix resulting in reduction in polymer crystallinity, which gives rise to an increase in ionic conductivity. At higher concentration, dedoped nanofibers appear to get phase separated and form insulating clusters, which impede ionic transport. The phase separation phenomena at higher fraction of nanofibers are confirmed by XRD. Studies on electrochemical behavior reveal that electrochemical potential window increases with the increase of nanofibers loading.     

Characterization of PEO/PVP/GO nanocomposite solid polymer electrolyte membranes: microstructural,thermo-mechanical,and conductivity properties

Poly (ethylene oxide) (PEO)/polyvinylpyrrolidone (PVP) blended nanocomposite polymers, incorporating graphene oxide (GO) nano-sheets and embedded with NaIO₄ salt, were prepared using solution casting technique. The as-prepared nanocomposite electrolyte membranes were characterized by SEM, TEM, XRD, and Raman vibrational spectroscopic techniques to confirm the dispersion of GO nano-sheets and to understand the synergistic properties of GO/polymer interactions as a function of GO nano-sheets concentration. GO fillers incorporated electrolyte membranes demonstrated distinctive surface morphology composed of circular-shaped protuberances of different dimensions. The decrease of Raman intensity ratio (I_D/I_G) and in-plane crystallite size (L_a) values of the nanocomposites suggested the good dispersion and confinement of the GO nano-sheets. The optical properties of blend electrolyte films were studied as a function of GO filler concentration using optical absorption and diffuse reflectance spectra. In reference to PEO/PVP/NaIO₄, the resultant PEO/PVP/NaIO₄/GO (0.4% in weight) electrolyte membrane demonstrated both an increase in tensile strength of ca. 42% and in Young’s modulus of ca. 40%, improvements coupled with a maximum fractured elongation of 3%. Through impedance spectroscopy analysis, the role of the GO nano-sheets onto the room temperature conductivity properties of the prepared electrolyte membranes has been probed.     

Study on ionic conductivity and dielectric properties of PEO-based solid nanocomposite polymer electrolytes

The ionic conductivity and dielectric properties of the solid nanocomposite polymer electrolytes formed by dispersing a low particle-sized TiO₂ ceramic filler in a poly (ethylene oxide) (PEO)-AgNO₃ matrix are presented and discussed. The solid nanocomposite polymer electrolytes are prepared by hot press method. The optimum conducting solid polymer electrolyte of polymer PEO and salt AgNO₃ is used as host matrix and TiO₂ as filler. From the filler concentration-dependent conductivity study, the maximum ionic conductivity at room temperature is obtained for 10 wt% of TiO₂. The real part of impedance (Z′) and imaginary part of impedance (Z″) are analyzed using an LCR meter. The dielectric properties of the highest conducting solid polymer electrolyte are analyzed using dielectric permittivity (ε′), dielectric loss (ε″), loss tangent (tan δ), real part of the electric modulus (M′), and imaginary part of the electric modulus (M″). It is observed that the dielectric constant (ε′) increases sharply towards the lower frequencies due to the electrode polarization effect. The maxima of the loss tangent (tan δ) shift towards higher frequencies with increasing temperature. The peaks observed in the imaginary part of the electric modulus (M″) due to conductivity relaxation shows that the material is ionic conductor. The enhancement in ionic conductivity is observed when nanosized TiO₂ is added into the solid polymer electrolyte.     

A piperidinium-based ester-functionalized ionic liquid as electrolytes in Li/LiFePO<Subscript>4</Subscript> batteries

A new functionalized ionic liquid (IL) based on cyclic quaternary ammonium cations with ester group and bis(trifluoromethanesulfonyl)imide ([TFSI]^?) anion, namely, N-methyl-N-methoxycarbonylpiperidinium bis(trifluoromethanesulfonyl)imide ([MMOCPip][TFSI]), was synthesized and characterized. Physical and electrochemical properties, including Li-ion transference number, ionic conductivity, and electrochemical stability, were investigated. The electrochemical window of [MMOCPip][TFSI] was 6 V, which was wide enough to be used as a common electrolyte material. The Li-ion transference number of this IL electrolyte containing 0.1 M LiTFSI was 0.56. The half-cell tests indicated that the [MMOCPip][TFSI] obviously improved the cyclability of a Li/LiFePO₄ cell. For the Li/LiFePO₄ half-cells, after 20 cycles at room temperature at 0.1 C, the discharge capacity was 109.7 mAh g^?1 with 98.7% capacity retention in the [MMOCPip][TFSI]/0.1 M LiTFSI electrolyte. The good electrochemical performance demonstrated that the [MMOCPip][TFSI] could be used as electrolyte for lithium-ion batteries.     

Impedance and dielectric studies of nanocomposite polymer electrolyte systems using MMT and ferroelectric fillers

Impedance and dielectric properties of nanocomposite polymer electrolyte systems modified with nano size MMT and ferroelectric fillers have been investigated for varying lithium to oxygen ratios. The changes in the structural properties of the electrolyte samples were characterized by X-ray diffraction (XRD) and differential scanning calorimetric (DSC) technique. The ion transport number estimated by DC polarization technique is found to be between 0.86 and 0.95. The bulk conductivities of nanocomposite polymer electrolyte films were studied using impedance spectroscopic technique. The impedance plot shows high frequency semicircle, due to the bulk effect of sample and maximum ionic conductivity of 2.15 × 10⁻⁴ Scm⁻¹ was observed for (PEO)₄LiCBSM at 323 K with lithium to oxygen ratio 1: 4. The complex impedance data was used to evaluate ionic conductivity and dielectric relaxation process, to understand the ion transport mechanism in these systems.

     

Combined effect of nanochitosan and succinonitrile on structural, mechanical, thermal, and electrochemical properties of plasticized nanocomposite polymer electrolytes (PNCPE) for lithium batteries

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.     

Preparation and Characterization of Poly(Vinyl Alcohol) (PVA)/SiO2, PVA/Sulfosuccinic Acid (SSA) and PVA/SiO2/SSA Membranes: A Comparative Study

Abstract

New organic–inorganic nanocomposites based on PVA, SiO₂ and SSA were prepared in a single step using a solution casting method, with the aim to improve the thermomechanical properties and ionic conductivity of PVA membranes. The structure, morphology, and properties of these membranes were characterized by Raman spectroscopy, small- and wide-angle X-ray scattering (SAXS/WAXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), water uptake (Wu) measurements and ionic conductivity measurements. The SAXS/WAXS analysis showed that the silica deposited in the form of small nanoparticles (～ 10?nm) in the PVA composites and it also revealed an appreciable crystallinity of pristine PVA membrane and PVA/SiO₂ membranes (decreasing with increasing silica loading), and an amorphous structure of PVA/SSA and PVA/SSA/SiO₂ membranes with high SSA loadings. The thermal and mechanical stability of the nanocomposite membranes increased with the increasing silica loading, and silica also decreased the water uptake of membranes. As expected, the ionic conductivity increased with increasing content of the SSA crosslinker, which is a donor of the hydrophilic sulfonic groups. Some of the PVA/SSA/SiO₂ membranes had a good balance between stability in aqueous environment (water uptake), thermomechanical stability and ionic conductivity and could be potential candidates for proton exchange membranes (PEM) in fuel cells.     

Preparation of nano-sized functional materials using laser ablation in liquids

We propose a convenient technique applicable for investigations of various functions of nanoparticles produced by laser ablation in liquids. It was demonstrated that nanoparticles of anatase-TiO₂, a electrode material for lithium secondary batteries, produced by laser ablation in acetone could be efficiently deposited on a substrate by using an electrophoresis technique. Analysis of the electrochemical properties of nanoparticles become much more facile with those deposited nanoparticles than with dispersed nanoparticles. In addition, it was demonstrated that comparison of the electrochemical properties between nanoparticles and microparticles were possible by means of this technique.     

A polymer electrolyte based on poly(vinylidene fluoride-hexafluoropylene)/hydroxypropyl methyl cellulose blending for lithium-ion battery

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.     

Electrochemical performance of plasticized PEO-LiTf complex-based composite gel polymer electrolytes with the addition of barium titanate

Gel electrolytes and solid electrolytes have been reported as a potential element to slow down the polysulfide shuttle by reducing its mobility in the electrolytes. The preparation of sulfur-conductive polymer composites, or sulfur-carbon composites, has been reported as softening the impact of the shuttle effects. Unlike Li-ion batteries so far, no electrolyte is found to be optimal for Li–S batteries at all conditions. Taking into account all these factors, in the present study, an attempt has been made to develop solid polymer electrolytes in conjunction with non-aqueous liquid electrolytes along with inert fillers for Li–S batteries. Poly-ethylene oxide (PEO)-based composite gel polymer electrolytes (CGPE) comprising a combination of plasticizers, namely 1,3-dioxolane (DIOX)/tetraethylene glycol dimethylether (TEGDME) and a lithium salt (LiTf) with the addition of ceramic filler, barium titanate (BaTiO₃) have been prepared using a simple solution casting technique in an argon atmosphere. The as-prepared polymer electrolyte films were subjected to SEM, ionic conductivity, TG/DTA, and FTIR analyses. A symmetric cell composed of Li/CGPE/Li was assembled, and the variation of interfacial resistance as a function of time was also measured. The ionic conductivity was found to be increased as a function of temperature. The lithium transference number (Li_t ⁺) was measured, and the value was calculated as 0.7 which is sufficient for battery applications. The electrochemical stability window of the sample was studied by linear sweep voltammetry, and the polymer electrolyte film was found to be stable up to 5.7 V. The TG/DTA analysis reveals that this CGPE is thermally stable up to 350 °C. The compatibility studies exhibited that CGPE has better interracial properties with lithium metal anode. The interaction between the PEO and salt has been identified by an FTIR analysis.     

A piperidinium-based ionic liquid electrolyte to enhance the electrochemical properties of LiFePO<Subscript>4</Subscript> battery

A piperidinium-based ionic liquid, N-methylpiperidinium-N-acetate bis(trifluoromethylsulfonyl)imide ([MMEPip][TFSI]), was synthesized and used as an additive to the electrolyte of LiFePO₄ battery. The electrochemical performance of the electrolytes based on different contents of [MMEPip][TFSI] has been investigated. It was found that the [MMEPip][TFSI] significantly improved the high-rate performance and cyclability of the LiFePO₄ cells. In the optimized electrolyte with 3 wt% [MMEPip][TFSI], 70 % capacity can be retained with an increase in rate to 3.5 C, which was 8 % higher than that of electrolyte without [MMEPip][TFSI]. For the Li/LiFePO₄ half-cells, after 100 cycles at 0.1 C, the discharge capacity retention was 78 % in the electrolyte without ionic liquid. However, in the electrolyte with 3 wt% [MMEPip][TFSI], it displayed a high capacity retention of 91 %. The good electrochemical performances indicated that the [MMEPip][TFSI] additive would positively enhance the electrochemical performance of LiFePO₄ battery.     

Effect of zinc salt on transport,structural, and thermal properties of PEG-based polymer electrolytes for battery application

Solid polymer polyethylene glycol (PEG)-based electrolytes composed with zinc acetate Zn(CH₃COO)₂ have been prepared by using solution blending. We proposed a scheme of PEG–zinc acetate for battery application. The structure confirmation was done by using X-ray diffraction studies detecting the phase variation. The thermal properties demonstrate the optimization of melting point (T _m) as a function of loading zinc acetate. The impedance analysis reveals that the role of ionic conductivity depends on the controlled concentration of Zn(CH₃COO)₂. Optimum ionic conductivity σ?~?1.55?×?10^?6 S?cm^?1 at room temperature (303 K) was observed for 70:30 composition. The linear variation in log σ vs 1000/T plot is based on the Arrhenius-type thermally activated process. The simultaneous discharge profile was confirmed by the solid-state electrochemical cell. Hence, the PEG–zinc acetate composition was suggested for polymer electrolyte battery application.     

Thermally activated ionic conduction and local structure in solid LiPON thin films

Compact lithium phosphorous oxynitride (LiPON) thin films, as a solid-state electrolyte for all solid-state Li batteries and electrochromic (EC) devices, with the high ratio of the triply coordinated –N< (N_t) over the doubly coordinated –N= (N_d) structural units was deposited by a conventional reactive RF magnetron sputtering of a Li₃PO₄ target at a low pure N₂ pressure. The effect of heat treatment from 200 to 500 °C on the ionic conductivity and local structure of LiPON thin films were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) core level analysis. A dramatical improvement of ionic conductivity from 1.1 to 3.28 μS/cm and microstructure changes were happened on the LiPON thin films while annealed for 1 h at 300 °C, which was linked to structural differences with a highest ratio of –N< over –N= structural units. The work proves that a proper heat treatment on LiPON thin film can effectively improve its ionic conductivity and change its microstructure.     

Poly (ethylene oxide) (PEO)-based,sodium ion-conducting‚ solid polymer electrolyte films,dispersed with Al<Subscript>2</Subscript>O<Subscript>3</Subscript> filler,for applications in sodium ion cells

The studies on solid polymer electrolyte (SPE) films with high ionic conductivity suitable for the realization of all solid-state Na-ion cells? form the focal theme of the work presented in this paper. The SPE films are obtained by the solution casting technique using the blend solution of poly (ethylene oxide) (PEO) with ethylene carbonate (EC) and propylene carbonate (PC) and complexed with sodium nitrate. Structural and thermal studies of SPE films are done by XRD, FTIR spectroscopy, and TGA techniques. Surface morphology of the films is studied using the FESEM. The ionic conductivity of SPE films is determined from the electrochemical impedance spectroscopy studies. For the SPE film with 16 wt% of NaNO₃ used for reacting with the polymer blend of PEO with EC and PC, the ionic conductivity obtained is around 1.08 × 10^?5 S cm^?1. Addition of the Al₂O₃ as the filler material is found to enhance the ionic conductivity of the SPE films. The studies on the Al₂O₃ modified SPE film show an ionic conductivity of 1.86 × 10^–4 S cm^?1, which is one order higher than that of the SPE films without the filler content. For the SPE film dispersed with 8 wt% of Al₂O₃, the total ion transport number observed is around 0.9895, which is quite impressive from the perspective of the applications in electrochemical energy storage devices. From the cyclic voltammetry studies, a wide electrochemical stability window up to 4 V is observed, which further emphasizes the commendable electrochemical behavior of these SPE films.     

Effect of nanochitosan on electrochemical, interfacial and thermal properties of composite solid polymer electrolytes

PEO-based solid polymer electrolyte films with various concentrations of nanochitosan as filler and LiCF₃SO₃ as salt were prepared by membrane hot-press technique. Nanochitosan was prepared from chitosan by conventional chemical cure method. The prepared composite membranes were characterized by FT-IR, XRD, thermal, SEM, AFM analyses, electrochemical impedance spectroscopy, cyclic voltammetry and compatibility studies. The ionic conductivity and thermal stability of the polymer membranes were enhanced significantly by addition of nanofiller. The compatibility studies reveal that filler incorporated membrane is better compatible with lithium interface than filler free electrolyte.     

Microstructural studies of bulk and thin film GDC

Ceria rare earth solid solutions are known as solid electrolyte with potential application in oxygen sensors and solid oxide fuel cells. We report the preparation of gadolinia-doped ceria, Ce_0.90Gd_0.10O_1.95, by the conventional solid-state reaction method and the preparation of thin films from a sintered pellet of gadolinia-doped ceria by the pulsed laser deposition technique. The effect of process conditions, such as substrate temperature, oxygen partial pressure, and laser energy on microstructural properties of these films are examined using powder X-ray diffraction, scanning electron microscopy, atomic force microscopy, and Raman spectroscopy.