Preparation And Performance Of Li_1.5Al_0.5Ge_1.5?PO₄?₃ Solid-state Electrolyte

Compared with traditional liquid electrolytes,solid electrolytes have many advantages such as high temperature resistance,corrosion resistance,high specific energy and great safety.Therefore,it has become one of the important directions in this field to study solid electrolytes with high ionic conductivity,great chemical stability and wide temperature range.In all kinds of solid electrolytes?sulfide solid electrolyte,oxide solid electrolyte and polymer electrolyte,etc.?,the oxide solid electrolyte has the advantages of good air stability and wide voltage window,which has a broad application prospect in all-solid-state lithium-ion batteries.Among them,the NASICON-type solid electrolyte Li_1.5Al_0.5Ge_1.5?PO₄?₃?LAGP?is considered as one of the most promising oxide solid electrolytes,but the ionic conductivity at room temperature is only 10^-4-10^-5S/cm.In order to prepare LAGP solid electrolyte that can be used in all-solid-state lithium-ion batteries,LAGP solid electrolyte powder and sheet were prepared by using non-volatile raw materials through optimizing the preparation process of LAGP.For further improving the ionic conductivity of LAGP,the effects of different heat treatment temperature,time and different additives?Li F,B₂O₃,Li PO₃?on the ionic conductivity,relative density,micromorphology and crystal phase of LAGP were studied.Besides,based on the theory of vertical array structure,the composite electrolyte with vertical array structure was prepared and studied.Meanwhile,the interface and assembly problems of solid electrolyte applied in all-solid-state lithium-ion batteries were analyzed.The specific research contents are as follows:1.Based on the current preparation process of LAGP solid electrolyte,the powder and sheet of LAGP without obvious secondary phases were prepared by using non-volatile metaphosphate,aiming at the problem that the volatile raw material would affect the consistency of the phase of LAGP.In order to further improve the room temperature ionic conductivity of LAGP,the effects of heat treatment temperature,time and different additives?Li F,B₂O₃,Li PO₃?on LAGP ionic conductivity,crystal phase and micromorphology were studied.In addition,the rapid crystallization of LAGP solid electrolyte by laser sintering was studied,and the influence of laser power and other parameters on LAGP microstructure was also analyzed.2.Based on the theory of vertical array structure and ion transport,the composite solid electrolyte with vertical array structure was designed and prepared.In order to solve the matching problem between electrode and electrolyte,lithium iron phosphate?Li Fe PO₄?anode sheet was prepared.By doping Sn O in Te O₂-Zn O-Li₂O system to produce Te element,the potential of its application in Li-Te battery was analyzed.In addition,the cyclic voltammetry and other electrochemical properties of the solid-state lithium-ion battery assembled by the composite solid electrolyte,lithium sheet and Li Fe PO₄ were studied,and the interface and assembly problems of LAGP solid electrolyte in the solid-state lithium-ion battery were analyzed.