Properties Of Liquid Crystal Modified Aramid Fiber Reinforced PEO Based Solid Polymer Electrolyte

All-solid-state lithium-ion battery with high safety and high energy density is considered to be the ideal energy storage device for the next generation,Solid electrolyte,as the key component,can fundamentally solve the safety problems existing in the current liquid electrolyte.Poly(ethylene oxide)(PEO)is an ideal matrix for solid polymer electrolytes due to its high dielectric constant.But PEO segments have high crystallinity at room temperature.PEO-based polymer electrolyte with liquid crystal modified aramid fiber as reinforcing phase was designed to increase the amorphous area of PEO.Liquid crystal monomer 4-4-dihydroxy-α,α’-dimethylbianonitrile(DDBA)and BY monomer containing sulfonic acid group(SO32-)were grafted onto aramid fiber by interfacial polymerization to obtain two reinforcing phases DF and DBF.DF/PEO electrolyte and DBF/PEO electrolyte were prepared by mixing DF and DBF into PEO matrix.The effects of DF and DBF doping on the physicochemical and electrical properties of electrolytes were investigated.The synthesized DF and DBF were characterized by infrared spectroscopy,DSC and TGA.DDBA and BY were successfully grafted onto aramid fibers with lower thermal stability.The optimal addition amount of LiTFSI was determined as 10 wt.%.When 10 wt.%LiTFSI was added,the ionic conductivity was 9.21×10-6 S·cm-1(25℃),the ionic migration number was 0.24,and the crystallinity was 40.6%.In the DF/PEO system,when the DF content was 2 wt.%,the crystallinity decreased(Xc=34.4%),the ionic conductivity at room temperature(25℃)was 1.98×10-5 S·cm-1,the initial decomposition voltage was 4.7 V,and the ion migration number was 0.3.In the DBF/PEO system,when the DBF content was 4 wt.%,the relative crystallinity was 25.7%,the ionic conductivity at room temperature(25℃)was 2.1 ×10-5 S·cm-1,the ionic migration number was 0.34,and the initial decomposition voltage was 5 V.The ion transport in the electrolyte follows Arrhenius model.The blending of DF and DBF as reinforcements with PEO helps to improve the ionic conductivity and ionic migration number of electrolyte at room temperature.DBF further inhibits crystallization due to the interaction of SO32-groups with PEO segments and lithium salts,and the amorphous area increases more.Therefore,DBF can be used as an effective strategy to improve the electrical properties of SPE.The PMMA-DBF/PEO electrolyte was prepared by mixing methyl methacrylate(PMMA)in DBF/PEO into an in-depth study,and PMMA had basically no effect on the thermal and electrochemical stability of the DBF/PEO electrolyte,but the ion mobility number was slightly increased from 0.34 to 0.38 when the PMMA doping amount was 3 wt.%.