Preparation And Optimization Of Composite Solid Electrolyte Based On Li_6.75La₃Zr_1.75Ta_0.25O₁₂ Oxide Polymer

Due to the significant safety problems of liquid lithium-ion batteries,and with the rise of the electric vehicle industry,the safety of lithium-ion batteries is becoming more and more important.The main induced factor is the electrolyte in liquid lithium-ion batteries,which will be liquid.The replacement of the electrolyte with a solid electrolyte can solve the safety problem of the lithium ion battery and reduce the safety hazard.Among many solid electrolytes,the garnet crystal structure of lithium lanthanum zirconium oxide(Li_6.75La₃Zr_1.75Ta_0.25O₁₂,LLZTO)has excellent electrochemical stability and ionic conductivity as a solid electrolyte,and it is related to polyvinylidene fluoride.The composite polymer solid electrolyte composed of poly(vinylidene fluoride?PVDF?is an important research hotspot in recent years and an important part of promoting the industrialization of solid lithium ion batteries.However,at this stage,the LLZTO prepared by the literature reports that the LLZTO is produced in small batches in the laboratory.The high-volume production process of LLZTO still needs to be further explored on the basis of laboratory preparation,and the LLZTO and PVDF are mixed in the N-class A pyrrolidone solution.It will cause gel discoloration of PVDF slurry,which will lead to a large amount of raw material cost waste in industrial production.In the electrochemical performance of solid electrolyte,the ionic conductivity of the composite polymer solid electrolyte will decrease,ultimately affecting the performance of the battery.Therefore,the work of this paper mainly focuses on the preparation of high-volume LLZTO powder and the modification of LLZTO powder.The Al-doped and Ta-doped LLZTO powders are prepared by solid-phase sintering method,and the powder sintering process is completed.The sintering temperature,sintering time,lithium source selection,and lithium source ratio were systematically studied.The reasonable preparation scheme of LLZTO suitable for industrial production was explored with less impurity content and purer reactants.So the work of this paper is mainly about mass LLZTO powder preparation and modification of these two aspects,through the solid phase sintering,the preparation of Al doping and Ta LLZTO powder,and heat preservation time of powder sintering process,lithium source selection,the ratio of lithium source aspect system of comparative research,the preparation of the impurity content is less,more pure LLZTO reactants.Based on the problem of reaction gel discoloration between LLZTO powder and PVDF slurry,the LLZTO powder was modified by coupling agent coating,binder replacement and anhydrous ethanol centrifugal washing.The LLZTO powder before and after modification was applied to the preparation of composite polymer solid electrolyte membrane and solid lithium ion battery.The effects of LLZTO powder modification on the ionic conductivity of LLZTO ceramic sheet,the film-forming property and ionic conductivity of composite polymer solid electrolyte film,and the electrochemical properties of solid lithium ion battery were investigated.The results show that coupling agent coating,binder replacement and anhydrous ethanol centrifugal washing of LLZTO powder can indeed solve the problem of gel discoloration of LLZTO powder and PVDF slurry,and improve the film-forming property of composite polymer solid electrolyte film.However,coupling agent coating can reduce the ionic conductivity of solid electrolyte membrane and affect the efficiency and capacity of solid lithium ion battery.Although the replacement of binder does not reduce the ionic conductivity of the solid electrolyte film,it will affect the electrochemical performance of the battery.However,centrifugal washing with anhydrous ethanol can improve the ionic conductivity of LLZTO ceramic sheet and its solid electrolyte film,and improve the electrochemical performance of solid lithium ion battery.