Study On The Preparation And Properties Of Some Composite Plastic Electrolyte

Lithium battery is widely used in all kinds of electronic devices and electric vehicles because of its high theoretical specific capacity,wide electrochemical window and long cycle life.However,the traditional lithium battery used organic solvent and lithium salt as electrolyte;film of polyolefin as a separator.The safety problems of lithium battery were caused owning to volatile,flammable of the electrolyte and shrinkage of the diaphragm.The polymer lithium battery has been greatly concerned because of its good flexibility,no leakage,high thermal stability,and good stability toward to the metal lithium.In view of the above advantages of polymer electrolyte,three different kinds of plastic composite polymer electrolytes were prepared from the structure and design to substitute the traditional electrolyte.Specific research programs and results are as follows:1、The composite plastic crystal polymer electrolyte(MB-PCPE)is prepared by an ultraviolet irradiation(UV-curing)process.The MB-PCPE is composed of Trimethylolpropane propoxylate triacrylate(TPPTA),polyvinylidene fluoride-co-hexafluoropropylene(PVDF-HFP)(acting as the mechanical skeleton),solid plasticizer succinonitrile(SN as ion transport channel),lithium bis-trifluoromethanesulphonimide(LiTFSI as lithium salt)and aluminum oxide(Al2O3 as filler).Experimental results show that mechanical bending of MB-PCPE is more than 200 times.The ionic conductivity of MB-PCPE may reach1.03 ×10-3S cm-1at room temperature and the electrochemical stability window is up to 5.2 V(vs.Li/Li+).Furthermore,the MB-PCPE shows outstanding interfacial stability toward lithium metal electrodes.The LiFePO4/Li cell assembled with MB-PCPE reveals excel ent cycling performance and rate capability.2、Silicon dioxide(SiO2)were synthesized by sol-gel reaction of Triethoxymethylsilane in an aqueous solution.The new type of composite plastic crystal polymer electrolyte is composed of a UV(ultraviolet)-crosslinked the mixture of Trimethylolpropane propoxylate triacrylate(TPPTA)and SiO2.Experimental results show that the as-prepared CLPC-CPE shows no obvious weight loss until up to 230℃ and outstanding interfacial stability toward lithium metal electrodes.The ionic conductivity of CLPC-CPE may reach 7.02×10-4 S cm-1at room temperature and the electrochemical stability window of CLPC-CPE is above 4.7V(vs.Li/Li+).The LiFePO4/Li cell assembled with CLPC-CPE presents superior cyclic stability and rate capability.The LiFePO4/Li cell assembled with CLPC-CPE may deliver a discharge capacity of 154.4mAh g-1after 100 charge-discharge cycles and 112.7mAh g-1at the rate of 2C.3、Different ratio of plastic crystal polymer electrolyte were synthesized in situ cross-linked the functionalized ionic liquids with polyimide(PI)as the self-supporting membrane.Research imply the composite plastic crystal polymer electrolyte shows no obvious weight loss until up to 300℃.The ionic conductivity and electrochemical stability window of composite plastic crystal polymer electrolyte is 9.95×10-4 S cm-1 and 5.4V respectively.The LiFePO4/Li cell and LiFePO4/LTO cell assembled with plastic crystal polymer electrolyte show good cycle stability.