Effect of various electrophoretically deposited nano‐silica contents on the properties of poly(vinylidene fluoride‐co‐hexafluoropropylene)‐based electrospun polymer electrolytes

Poly(vinylidene fluoride‐co‐hexafluoropropylene) (P(VDF‐HFP)) based composite polymer electrolyte (CPE) membranes were successfully prepared by electrospinning followed by electrophoretic deposition processes, and desirable polymer electrolytes were obtained after being activated in liquid electrolytes. The physicochemical properties of the CPEs with different electrophoretically deposited nano‐SiO₂ contents were investigated by SEM, XRD, TGA, linear sweep voltammetry and electrochemical impedance spectroscopy measurements. When the ratio of electrophoretically deposited nano‐SiO₂ to P(VDF‐HFP) is up to 4 wt%, the results show that the CPE membrane presents a very uniform surface with abundant interconnected micropores and possesses excellent mechanical tensile strength with high thermal and electrochemical stability; the ionic conductivity at room temperature can reach 3.361 mS cm^?1 and the reciprocal temperature dependence of the ionic conductivity follows a Vogel ? Tamman ? Fulcher relationship. The interfacial resistance of the assembled Li/CPE/Li simulated cell can rapidly increase to a steady value of about 950 Ω from the initial value of about 700 Ω at 30 °C during 15 days' storage. The battery performance test suggests that the CPE also shows excellent compatible properties with commercial LiCoO₂ and graphite materials. © 2015 Society of Chemical Industry     

Preparation of monodispersed ZrO2 nanoparticles and their applications in poly[(vinylidene fluoride)‐co‐hexafluoropropylene]‐based composite polymer electrolytes

To improve the electrochemical performance of pure poly[(vinylidene fluoride)‐co‐hexafluoropropylene] (P(VDF‐HFP))‐based gel polymer electrolytes, different amounts of monodispersed ZrO₂ nanoparticles were introduced to fabricate P(VDF‐HFP)/ZrO₂ composite polymer electrolytes (CPEs) using the phase inversion method and activated processes, in which the monodispersed ZrO₂ nanoparticles were synthesized by an easy route without any chelating agents or surfactants, and confirmed using scanning electron microscopy, particle size distribution measurement and X‐ray diffraction. The characterization results show that the as‐fabricated CPE membranes present not only an abundant porous structure, but also an improved mechanical strength. In particular, sample CPE‐5 presents the best properties when the doped content of the monodispersed ZrO₂ nanoparticles reaches 5 wt% in the polymer matrix, in which the liquid uptake and ionic conductivity at room temperature are about 192.4% and 3.926 mS cm^?1, and the electrochemical working window and thermal decomposition temperature can increase to 5.1 V and 420 °C, respectively. Moreover, an assembled LiCoO₂/CPE‐5/Li coin cell can deliver excellent rate and cycling performance, in which the discharge specific capacity of the cell can show about 83.95% capacity retention at 2.0 C after 85 cycles. © 2018 Society of Chemical Industry     

A novel PEO-based composite polymer electrolyte with absorptive glass mat for Li-ion batteries

A novel PEO (polyethylene oxide)-based composite polymer electrolyte (CPE) using absorptive glass mat (AGM) as filler was prepared and characterized. Scanning electronic micrograph (SEM) images showed that the addition of Li salt and modified AGM may improve the surface morphology of CPE. The results of Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeters (DSC) indicated that the inclusion of LiClO₄ salt and the addition of AGM filler can reduce the crystallinity of PEO. It was concluded that the addition of AGM plays two roles in PEO-based CPEs, namely, interruption of the PEO recrystallization and reinforcement of CPEs, accordingly enhancing room temperature ionic conductivity of CPEs and improving its mechanical strength and electrochemical stability at high temperatures.     

Composite polymer electrolyte based on (PEO)6:NaPO3 dispersed with BaTiO3

BACKGROUND: Polymer electrolytes have attracted considerable attention as regards portable solid‐state electrochemical device applications. The present investigation is focused on the characterization of a new Na⁺ ion conducting polymer electrolyte (PEO)₆:NaPO₃ dispersed with 3–10 wt% BaTiO₃ (0.7 µm) fillers. The composite polymer electrolytes (CPEs) were prepared by a solution‐casting method and characterized using various physical measurement techniques. RESULTS: Differential scanning calorimetry results indicate a maximum reduction in the degree of crystallinity of the polymer from 62.6% for uncomplexed poly(ethylene oxide) (PEO) to 27.6% for the CPE with 6 wt% BaTiO₃. This substantiates an enhancement in the amorphous phase of the polymer inferred from X‐ray diffraction and optical micrographs. The CPE dispersed with 6 wt% BaTiO₃ is found to be the best composition exhibiting a maximum ionic conductivity of 1.2 × 10^?6 S cm^?1 at 345 K with cationic transport number (t) of 0.33. CONCLUSIONS: An enhancement in the ionic conductivity of about two orders of magnitude is achieved for the composite electrolytes when compared to filler‐free solid polymer electrolyte. Correlation of the temperature‐dependent conductivity, activation energy for ion migration and transport number enables an understanding of the role played by the fillers in conduction characteristics of the CPEs. Copyright © 2007 Society of Chemical Industry     

Preparation and physicochemical performances of poly[(vinylidene fluoride)‐co‐hexafluoropropylene]‐based composite polymer electrolytes doped with modified carbon nanotubes

Modified carbon nanotubes (m‐CNTs) were successfully prepared by the interactions between nitric and sulfuric acids and CNTs, which was confirmed using Fourier transform infrared spectroscopy. Poly[(vinylidene fluoride)‐co‐hexafluoropropylene]‐based composite polymer electrolyte (CPE) membranes doped with various amounts of m‐CNTs were prepared by phase inversion method. The desired CPEs were obtained by soaking the liquid electrolytes for 30 min. The physicochemical and electrochemical properties of the CPE membranes were investigated using scanning electron microscopy, X‐ray diffraction, thermogravimetry, electrochemical impedance spectroscopy and linear sweep voltammetry. The results show that the CPE membranes doped with 2.2 wt% m‐CNTs possess the smoothest surface and the highest decomposition temperature about 450 °C. Obviously, adding an appropriate amount of m‐CNTs into the polymer matrix can decrease the crystallinity and enhance the ionic conductivity; the temperature dependence of ionic conductivity follows the Arrhenius relation and the ionic conductivity at room temperature is up to 4.9 mS cm^?1. The interfacial resistance can reach a stable value of about 415 Ω cm^?2 after 10 days storage. The excellent rate and cycle performances with an electrochemical working window up to 5.4 V ensure that the CPEs doped with 2.2 wt% m‐CNTs can be considered as potential candidates as polymer electrolyte for lithium ion batteries. © 2013 Society of Chemical Industry     

Preparation and performance study on P(St‐MMA)‐SiO2 doped P(VDF‐HFP) based composite polymer electrolyte

The organic–inorganic hybrid material poly(styrene‐methyl methacrylate)‐silica (P(St‐MMA )‐SiO₂) was successfully prepared by in situ polymerization confirmed by Fourier transform infrared spectroscopy and was employed to fabricate poly(vinylidene fluoride‐hexafluoropropylene) (P(VDF‐HFP )) based composite polymer electrolyte (CPE ) membrane. Desirable CPEs can be obtained by immersing the CPE membranes into 1.0 mol L^?1 LiPF₆‐EC /DMC /EMC (LiPF₆ ethylene carbonate + dimethyl carbonate + ethylmethyl carbonate) liquid electrolyte for about 0.5 h for activation. The corresponding physicochemical properties were characterized by SEM , XRD , electrochemical impedance spectroscopy and charge–discharge cycle testing measurements. The results indicate that the as‐prepared CPEs have excellent properties when the mass ratio of the hybrid P(St‐MMA )‐SiO ₂ particles to polymer matrix P(VDF‐HFP ) reaches 1:10, at which point the SEM analyses show that the as‐prepared P(St‐MMA )‐SiO ₂ particles are uniformly dispersed in the membrane and the CPE membrane presents a homogeneous surface with abundant interconnected micropores. The XRD results show that there may exist interaction forces between the P(St‐MMA )‐SiO ₂ particles and the polymer matrix, which can obviously decrease the crystallinity of the composite membrane. Moreover, the ionic conductivity at room temperature and the electrochemical working window of the CPE membrane can reach 3.146 mS cm^?1 and 4.7 V, respectively. The assembled LiCoO₂/CPE /Li coin cell with the CPE presents excellent charge–discharge and C ‐rate performance, which indicates that P(St‐MMA )‐SiO ₂ hybrid material is a promising additive for the P(VDF‐HFP ) based CPE of the lithium ion battery. © 2016 Society of Chemical Industry     

Study on performances of ZSM-5 doped P(VDF-HFP) based composite polymer electrolyte prepared by steam bath technique

Several novel kinds of poly (vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) based composite polymer electrolyte (CPE) membranes doped with ZSM-5 (Zeolite sieve of molecular porosity) were fabricated by steam bath technique. The desirable CPE membranes were further prepared by immersing them into the liquid electrolyte solution of 1.0?M LiPF₆-ethylene carbonate /dimethyl carbonate/ethylmethyl carbonate (v/v/v:1/1/1) for 1?h to be activated at room temperature. Physical and chemical properties of the as-prepared CPEs are studied by scanning electron microscope, Fourier transform infrared, thermogravimetry and differential scanning calorimetry and electrochemical methods. The results showed that the thermal and electrochemical stabilities of the CPEs can be reached to 350?°C and 5?V, respectively. Reciprocal temperature dependence of corresponding ionic conductivity follows Vogel?CTamman?CFulcher relation, and ionic conductivity at ambient temperature can be up to 5.1?mS?cm^?1. The fabricated Li/CPEs/LiCoO₂ coin cells with the CPE membranes prepared by steam bath technique can achieve a high discharge capacity about 144.97?mAh?g^?1 at 0.1?C. At 1.0?C, the capacity can be kept to 89.84?% of that at 0.1 C for the cell. After 26 cycles, the cell prepared with these CPE membranes can keep 97.5?% of its initial discharge capacity. These excellent physicochemical and battery properties indicate that these novel CPEs can be potentially used as electrolyte in lithium ion polymer battery.     

Physicochemical properties of poly(ethylene oxide)-based composite polymer electrolytes with a silane-modified mesoporous silica SBA-15

Mesoporous silica SBA-15 was surface-modified by γ-glycidoxypropyltrimethoxy silane (GPTMS), and novel poly(ethylene oxide) (PEO)-based composite polymer electrolytes (CPE) using the silane-modified SBA-15 (SBA-15-GPTMS) as filler were prepared and characterized. The results of the low-angle X-ray diffraction (XRD) patterns and Fourier-transform infrared (FT-IR) spectroscopy indicated that GPTMS has been successfully attached to the surface of SBA-15 with a high degree of mesoscopic hexagonal pore structure. The incorporation of SBA-15-GPTMS in the PEO-LiClO₄ matrix effectively reduced the PEO crystallinity and obviously improved the conductivity and electrochemical stability of the CPEs. The CPE with 10 wt.% SBA-15-GPTMS provided the highest conductivity among all the tested CPEs, about 2-3 orders of magnitude higher than that of the PEO-LiClO₄ matrix below the melting temperature of PEO. The reasons that the CPEs using SBA-15-GPTMS as filler showed higher conductivity than that with SBA-15 were discussed.     

Comb polymer electrolytes

Summary Three comb polymers(CP) with oligo-oxyethylene side chains of the type-O(CH₂CH₂O)_nCH₃ were prepared from methyl vinyl ether/maleic anhydride alternating copolymer. Homogeneous amorphous polymer electrolytes were made from CP and LiCF₃SO₃ or LiClO₄ by solvent-casting method, and their conductivities were measured as a function of temperature and salt concentration. The conductivity which displayed non-Arrhenius behaviour was analyzed using the Vogel-Tammann-Fulcher equation. The conductivity maximum appears at lower salt concentration when CP has longer side chains. XPS was used to study the cation-polymer interaction.     

Effect of the addition of hydrophobic clay on the electrochemical property of polyacrylonitrile/LiClO4 polymer electrolytes for lithium battery

In this study, an organoclay, ALA-MMT, was prepared by the ionic exchange reaction of montmorillonite (MMT) with 12-aminododecanoic acid (ALA). ALA-MMT was then used as a filler to prepare a series of composite polymer electrolytes based on polyacrylonitrile (PAN) and LiClO₄. The effect of the addition of ALA-MMT on the properties of the composite polymer electrolytes (CPEs) was investigated by XRD, FT-IR, DSC, tensile strength, AC impedance, and cyclic voltammetry measurements. It was found that the ALA-MMT particles were well dispersed in the CPEs. Owing to the incorporation of ALA-MMT, a higher fraction of the free anions was obtained, indicating that the lithium salt dissolved in the PAN matrix more effectively for the CPE than in the PAN/LiClO₄ polymer electrolyte. Moreover, the glass-transition temperature was reduced, benefiting the ion transport. The best ionic conductivity at room temperature was obtained from the CPE with 7 wt% of the modified clay and 0.6 M LiClO₄ per PAN repeat unit (CPE-7) and was more than seven times higher than that from the corresponding PAN/LiClO₄ polymer electrolyte (CPE-0). The mechanical property and the cation transference number, t₊, of CPE-7 are largely increased compared to that of CPE-0. Besides, the CPEs were electrochemically stabilized up to 4.75 V and the corresponding cell exhibited excellent electrochemical stability and cyclability over the potential range between 0 V and 4.0 V vs. Li/Li⁺.     

Poly(ethylene oxide)/clay nanocomposites for solid polymer electrolyte applications

Poly(ethylene oxide) (PEO)/clay nanocomposites were prepared using a solution intercalation method. The organoclay (Nanocore I30E) used for nanocomposite synthesis was basically an octadecylammonium salt of montmorillonite clay prepared using an ion exchange method. Nanocomposite‐based solid polymer electrolytes were prepared using LiBF₄. The nanocomposite structures were characterised using wide‐angle X‐ray diffraction. The crystallisation behaviour and thermal properties were studied using differential scanning calorimetry. It was found that the crystallinity of the composite electrolytes decreases with increasing clay concentration up to 7.5 wt% and then increases with a further increase in clay concentration. The trend is different from that observed in PEO/clay nanocomposites without lithium salt where the crystallinity gradually decreases with increasing clay concentration. The solid polymer electrolyte samples were evaluated using an alternating current impedance analyser. A considerable increase in room temperature conductivity was observed at the optimum clay concentration. The conductivity decreases beyond the optimum clay concentration. Copyright © 2007 Society of Chemical Industry     

Preparation and performance analysis of barium titanate incorporated in corn starch‐based polymer electrolytes for electric double layer capacitor application

Polymer electrolyte membranes composing of corn starch as host polymer, lithium perchlorate (LiClO₄) as salt, and barium titanate (BaTiO₃) as composite filler are prepared using solution casting technique. Ionic conductivity is enhanced on addition of BaTiO₃ by reducing the crystallinity and increasing the amorphous phase content of the polymer electrolyte. The highest ionic conductivity of 1.28 × 10^?2 S cm^?1 is obtained for 10 wt % BaTiO₃ filler in corn starch‐LiClO₄ polymer electrolytes at 75°C. Glass transition temperature (T_g) of polymer electrolytes decreases as the amount of BaTiO₃ filler is increased, as observed in differential scanning calorimetry analysis. Scanning electron microscopy and thermogravimetric analysis are employed to characterize surface morphological and thermal properties of BaTiO₃‐based composite polymer electrolytes. The electrochemical properties of the electric double‐layer capacitor fabricating using the highest ionic conductivity polymer electrolytes is investigated using cyclic voltammetry and charge‐discharge analysis. The discharge capacitance obtained is 16.22 F g^?1. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43275.     

Effect on properties of PVDF-HFP based composite polymer electrolyte doped with nano-SiO2

Various kinds of nano-SiO₂ using different catalysts were obtained and characterized by scanning electron microscope (SEM) technique. The results showed that the nano-SiO₂ using NH₃·H₂O as catalyst presented the best morphology. Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based composite polymer electrolyte (CPE) membranes doped with different contents of nano-SiO₂ were prepared by phase inversion method. The as-prepared CPE membranes were immersed into 1.0 M LiPF₆-EC/DMC/EMC electrolytes for 0.5 h to be activated. The physicochemical and electrochemical properties of the CPEs were characterized by SEM, X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) techniques. The results indicate that the CPEs doped with 10 % nano-SiO₂ exhibit the best performance. SEM micrographs showed that the CPE membranes have uniform surface with abundant interconnected micro-pores, and the uptake ratio was up to 104.4 wt%. EIS and LSV analysis also showed that the ionic conductivity at room temperature and electrochemical stability window of the modified membrane can reach 3.372 mS cm^?1 and 4.7 V, respectively. The interfacial resistance R _i was 670 Ω cm^?2 in the first day, then increased to a stable value of about 850 Ω cm^?2 in 10 days storage at room temperature. The Li/As-fabricated CPEs/LiCoO₂ cell also showed good charge–discharge performance, which suggested that the prepared CPE membranes can be used as potential electrolytes for lithium ion batteries.     

Free volume‐related microstructural properties of lithium perchlorate/sodium alginate polymer composites

The effect of salt (LiClO₄) on free volume‐related microstructural, optical, and dielectric properties of lithium perchlorate (LiClO₄)‐doped sodium alginate (NaC₆H₇O₆)_n solid polymer electrolyte were studied using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), UV–Visible, dielectric measurements, and positron annihilation lifetime spectroscopy (PALS) techniques. The FTIR study reveal that the LiClO₄ interact with the O H groups of sodium alginate (NaAlg) and forms charge transfer complex (CTC). These formed CTC within the composite film affect the optical property of the polymer composite, which was reflected from UV–Visible study. The free volume was probed by the PALS technique, which uses the o‐Ps pickup lifetime τ _3, as an indication of local electron density and mean free volume radius. The o‐Ps pickup intensity I₃, reflects the probability of o‐Ps formation. The o‐Ps components τ₃ and I₃ increases with salt concentration, which shows microstructural modifications due to the decrease in the crystallinity of the NaAlg as observed from XRD studies. Therefore, electrical studies on the doped NaAlg reveal that the ionic movement in the composites is mainly due to the segmental motion of the polymer backbone. So, the complex formation due to doping affects the free volume‐related microstructure and hence the dielectric properties including the AC conductivity of the polymer composites. POLYM. COMPOS., 35:1267–1274, 2014. © 2013 Society of Plastics Engineers     

Composite polymer electrolytes based on electrospun thermoplastic polyurethane membrane and polyethylene oxide for all‐solid‐state lithium batteries

To improve the electrochemical properties and enhance the mechanical strength of solid polymer electrolytes, series of composite polymer electrolytes (CPEs) were fabricated with hybrids of thermoplastic polyurethane (TPU) electrospun membrane, polyethylene oxide (PEO), SiO₂ nanoparticles and lithium bis(trifluoromethane)sulfonamide (LiTFSI). The structure and properties of the CPEs were confirmed by SEM, XRD, DSC, TGA, electrochemical impedance spectroscopy and linear sweep voltammetry. The TPU electrospun membrane as the skeleton can improve the mechanical properties of the CPEs. In addition, SiO₂ particles can suppress the crystallization of PEO. The results show that the TPU‐electrospun‐membrane‐supported PEO electrolyte with 5 wt% SiO₂ and 20 wt% LiTFSI (TPU/PEO‐5%SiO₂‐20%Li) presents an ionic conductivity of 6.1 × 10^?4 S cm^?1 at 60 °C with a high tensile strength of 25.6 MPa. The battery using TPU/PEO‐5%SiO₂‐20%Li as solid electrolyte and LiFePO₄ as cathode shows an attractive discharge capacity of 152, 150, 121, 75, 55 and 26 mA h g^?1 at C‐rates of 0.2C, 0.5C, 1C, 2C, 3C and 5C, respectively. The discharge capacity of the cell remains 110 mA h g^?1 after 100 cycles at 1C at 60 °C (with a capacity retention of 91%). All the results indicate that this CPE can be applied to all‐solid‐state rechargeable lithium batteries. © 2018 Society of Chemical Industry     

1H NMR,thermal, and conductivity studies on PVAc based gel polymer electrolytes

The lithium‐ion conducting gel polymer electrolytes (GPE), PVAc‐DMF‐LiClO₄ of various compositions have been prepared by solution casting technique. ¹H NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer‐ and plasticizer‐salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer‐salt complex. DSC measurements show a decrease in T_g with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO₄ gel polymer electrolytes has been found to be in the range of (30–60°C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 × 10^?7 and 4.1 × 10^?4 S cm^?1 at 303 K depending on the concentration of DMF (10–20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and characterization of SrBi4Ti4O15ferroelectric filler based composite polymer electrolytes for lithium ion batteries

Composite polymer electrolytes (CPEs) based on poly (ethylene oxide) (PEO) (Mol.Wt ∼6×10⁵) complexed with LiN(CF₃SO₂)₂ lithium salt and SrBi₄Ti₄O₁₅ ferroelectric ceramic filler have been prepared as films. Citrate gel technique and conventional solid state technique were employed for the synthesis of the ferroelectric fillers in order to study the effect of particle size of the filler on ionic conductivity of the polymer electrolyte. Characterization techniques such as X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM) and temperature dependant DC conductivity studies were taken for the prepared polymer composite electrolytes. The broadening of DTA endotherms on addition of ceramic fillers to the polymer salt complex indicated the reduction in crystallinity. An enhancement in conductivity was observed with the addition of SrBi₄Ti₄O₁₅ as filler to the (PEO)₈-LiN(CF₃SO₂)₂ polymer salt complexes. Among the investigated samples (PEO)₈-LiN(CF₃SO₂)₂ +10 wt% SrBi₄Ti₄O₁₅ (citrate gel) polymer composite exhibits a maximum conductivity.     

Composite polymer electrolytes based on the low crosslinked copolymer of linear and hyperbranched polyurethanes

Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO₄ were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO₄ reached its maximum conductivity, 1.51 × 10^?5 S cm^?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007     

Characterization of solid polymer electrolytes based on poly(trimethylenecarbonate) and lithium tetrafluoroborate

The results of an investigation of a polymer electrolyte system based on the poly(trimethylene carbonate) host matrix, designated as p(TMC), with lithium tetrafluoroborate guest salt are described in this presentation. Electrolytes with lithium salt compositions with n between 3 and 80 (where n represents the number of (OCOCH₂CH₂CH₂O) units per lithium ion) were prepared by co-dissolution of salt and polymer in anhydrous tetrahydrofuran. The homogeneous solutions obtained by this procedure were evaporated, within a preparative glovebox and under a dry argon atmosphere, to form thin films of electrolyte.The solvent-free electrolyte films produced were obtained as very flexible, transparent, completely amorphous films and were characterized by measurements of total ionic conductivity, cyclic voltammetry, differential scanning calorimetry and thermogravimetry.     

Lithium difluoro(oxalate)borate‐based novel nanocomposite polymer electrolytes for lithium ion batteries

BACKROUND: HF formation and poor thermal stability found in commercial lithium ion batteries comprising LiPF₆ (and other salts) have hampered the replacement of LiPF₆. Therefore, a new kind of electrolyte salt is necessary to replace the one commercially available. RESULTS: A novel lithium difluoro(oxalate)borate (LiDFOB)‐based nanocomposite polymer electrolyte has been prepared in a matrix of poly[(vinylidene fluoride)‐co‐(hexafluoropropylene)] (PVdF‐HFP). The electrolyte contains ethylene carbonate and diethyl carbonate as plasticizers and nanoparticulate Sb₂O₃ as a filler. Membranes obtained by a solution casting technique were characterized by AC impedance, thermogravimetry and tensile strength measurements and morphological studies. Membranes with 5 wt% Sb₂O₃ exhibit a room‐temperature conductivity of 0.298 mS cm^?1, and are thermally stable up to ca 130 °C. Furthermore, the nanocomposite membranes show a 125% increase in mechanical stability as compared to filler‐free membranes. The structural change from α to β phases was confirmed by Raman studies. CONCLUSION: One of the important advantages of using LiDFOB lies in its bulkier DFOB anion, which also acts as solid plasticizer, thus improving the basic requirements of the electrolyte, such as mechanical and thermal stabilities, as well ionic conductivity and with a lower filler content. The overcharge tolerance of LiDFOB salt at higher temperature is also to be noted, because of the oxalate moieties. Preliminary investigations confirmed the possibility of using Sb₂O₃ nanoparticle‐filled membranes in industry in the near future. Copyright © 2008 Society of Chemical Industry