| Polymer lithium-ion batteries have been extensively studied in recent years forapplications in various electrochemical devices, such as cellular phones, smart creditcards, laptop computers and chemical sensors, due to their excellent thermal andmechanical stability, flexibility and Safety. Despite extensive researches on lithiumpolymer conductors, the conductivity of pure solid electrolytes (with no liquid) isinsufficient for practical application at room temperature. Most of the recent studieshave been focused on the gel polymer electrolytes in which the liquid electrolyte hasbeen immobilized by incorporating into the polymer matrix because their ionicconductivity can reach 10-3S cm-1 at ambient temperature.With the aim to develop polymer membrane with high conductivity andmechanical stability for lithium-ion batteries, this work attempted to synthesize apolymer,poly-methyl metacrylate-vinyl acetate (PMMA-Vac) by emulsion polymeri-zetion with methyl metacrylate (MMA) and vinyl acetate (Vac) as monomers. Withthis polymer, polymer membrane and polymer electrolyte were prepared on the baseof polyethylene (PE) membrane with a dip coating and phase inversion method. ThePE can give mechanical integrity to the electrolyte system and offers enhanced safetyby exhibiting thermal shutdown under condition of severe abuse. While gellablepolymer was coated on PE, it could encapsulate and hold electrolyte.Performances of the synthesized polymer and prepared polymer membrane andelectrolyte were studied with FTIR, DSC/TG, SEM, GPC and battery charging anddischarge experiments. Following results were obtained:1 It is found from FTIR that PMMA-Vac was formed by breaking the doublebonds of monomers. PMMA-Vac can be easily dispersed in mixed carbonates to forma gel. The polymer has best transformation rate of 97.49% and better performancewhen the rate of MMA:Vac is 9:1, Cross-linked reagent can improve porous structure of membrane, which is good for electrolyte absorptivity and supports transfer pathsfor Li+, so the polymer membrane has electrolyte absorption of 2000% and betterconductivity. The polymer membrane has better performance when the solvent isDMF in contract of acetone, The ion conductance is 1.85×10-3s×cm-1.The bestcontent of PMMA-Vac for polymer membrane is 2% for practical application.Polymer membrane can be stable up to 380℃. The conductivity of the polymerelectrolyte at room temperature is 1.85×10-3s×cm-1. With the polymer electrolyte asthe gel polymer electrolyte (GPE) of battery, the battery shows its good cyclicstability and high rate discharge performance.2. Polymer membranes were prepared by mixing PMMA-Vac and PVDF, PTFE,PVP-VA64 with different solvent. It is found the polymer membrane has betterelectrolyte absorption for DMF as solvent. The polymer membrane mixed with PTFEis not fit for lithium-ion battery for its crispation.The polymer membrane mixed withPVDF has lower electrolyte absorption than PMMA-Vac membrane, The polymermembrane mixed with PVP-VA64 has excellent electrolyte retainability and good heatstability, The cells consisting GPE mixed with PMMA-Vac and PVP-VA64 showedgood cycling characteristics and rate capacities.The discharge capacity of the batterybased on LiMn2O4/ PMMA-Vac+PVP-VA64 polymer electrolyte/C retains 80.3%after 100 cycles.
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