Preparation And Electrochemical Performance Of Inorganic Nanoparticle-Reinforced PEO-based Composite Electrolyte

Solid state electrolyte is an effective means to solve the flammability,explosion and other safety hazards of lithium-ion batteries.Among them,PEO based solid polymer electrolyte is considered as the first choice to replace traditional liquid electrolyte because of its small interfacial impedance,simple structure,easy preparation and safe application.However,PEO polymer based solid electrolytes have low room temperature ionic mobility and poor mechanical properties.Herein,the preparation and properties of inorganic particle reinforced PEO polymer based solid electrolyte were studied.Lewis acid-base interaction and the size effect of ultrafine nanoparticles can effectively reduce the proportion of crystalline region in PEO system,promoting the movement of PEO polymer segments.What's more,extra lithium ion transport channels are formed by using the lithium affinity of active particles and the lithium sites in the active particles.The main research contents are as follows:1.The single-crystal ZnO nanoparticles(?60 nm)was prepared by one-step solvothermal method and used as inert inorganic fillers.The proportion of crystalline area in the PEO system was effectively reduced,and the ionic mobility of polymer electrolyte was improved.Compared with commercial grade ZnO(?200 nm),the mechanical strength and high temperature stability of composite electrolyte are improved significantly by ultrafine ZnO single crystal particles due to their size effect.In addition,ZnO nanoparticles can significantly reduce the crystallinity of PEO.With 20 wt%ZnO,the ionic mobility of the polymer electrolyte reaches the highest,witch is 1.2×10-5 S·cm-1 under room temperature.In addition,the electrochemical window of polymer electrolyte is increased to 5.2 V.When used with LiFePO4 cathode,the initial discharge capacity of the material is 164 mAh/g,and the capacity retention rate is 96.3%after 120 cycles.2.Li4Ti5O12 active nanoparticles were prepared by evaporation induced self-assembly method,and PEO solid electrolyte with active nanoparticles was further prepared.While decreasing the crystallinity of PEO,Li4Ti5O12 can provide additional lithium ion transport channels and improve the overall ion conductivity.Compared with ultrafine ZnO inert nanoparticles,Li4Ti5O12 active nanoparticles can improve the performance of polymer electrolyte more significantly.The room temperature ionic mobility can reach 5.2×10-4 S·cm-1.The initial discharge capacity of the LFP battery is 168 mAh/g,and the capacity retention rate is 98.3%after 150 cycles.