Preparation And Study Of Polycarbonate Based Solid Electrolyte

At present,organic liquid electrolyte is widely used in commercial lithium-ion batteries,and there are inflammable and explosive safety problems.Replacing organic electrolyte with solid electrolyte is an effective way to solve the safety problems of lithium batteries.Polymer solid electrolyte has attracted more and more attention because of its good interface compatibility and easy processing.Polycarbonate polymers containing carbonyl（C=O）electron-absorbing groups have lower HOMO levels and wider intrinsic electrochemical Windows.Therefore,polycarbonate electrolytes are more promising to be used in high voltage lithium batteriesIn this paper,a polycarbonate based polymer electrolyte was prepared by free radical polymerization from the point of view of designing high pressure stable polymer electrolyte.On this basis,inorganic filler vinyl silica（V-SiO₂）was added as a crosslinking agent to participate in polymer copolymerization to further improve the electrochemical performance of the electrolyte.The details are as follows:（1）PVEC-TFEMA polymer electrolyte was prepared by free radical copolymerization using vinyl ethyl carbonate and trifluoroethyl methacrylate as polymeric monomers.The electrochemical window was 4.8V and the ionic conductivity reached 8.8×10-5 S cm^-1 at 55^oC.Li/PVEC-TFEMA/Li Fe PO₄ and Li/PVEC-TFEMA/Li Fe Mn PO₄ showed good battery cycle performance.After100 cycles of charging and discharging at 0.1 C,the remaining specific discharge capacity is 154 m Ah g^-1 and 127 m Ah g^-1,capacity retention rates are92%and 76%,respectively.（2）Vinyltriethoxy-silane was hydrolyzed to prepare vinyl-silica particles containing active functional groups（V-SiO₂）,which were introduced into the polymer matrix as crosslinking agent,and a three-dimensional crosslinked composite polymer electrolyte was generated.The influence of the content of V-SiO₂ on the structure and electrochemical performance of polymer electrolyte was explored.When the content of V-SiO₂was 5wt%,the ionic conductivity of the composite electrolyte PVEC-TFEMA/5%SiO₂ was the highest(1.37×10^-4 S cm^-1,55^oC).Li/PVEC-TFEMA/5%SiO₂/Li Fe Mn PO₄ battery stable 100 cycles at 55^oC,0.2 C rate of capacity retention rate of 85%,remaining capacity of 140m Ah g^-1.