Studies On Preparation And Properties Of Garnet-type Solid Electrolyte Li₇La₃Zr₂O₁₂

This thesis focuses on the synthesis of high-quality LLZO ceramics using a variety of methods.The solid-state synthetic process was explored and optimized,including the powder processing,sintering schedule and the effects of sintering aids on the phase,morphology and electrochemical performance of the ceramic electrolyte.The hydrothermal method and sol-gel method were also studied to synthesize the LLZO powder,and the influences of solvent and calcination temperature were explored.The main conclusions are as follows:In the solid-state synthesis,the synthetic process was optimized through the exploration of Li source,ball milling time,sintering temperature,holding time,sintering aid content and other factors.The optimized conditions for the solid-state synthesis of LLZO ceramics are as following:Li OH as Li source,ball milling for 12 h,6%Li OH as the sintering aid,sintering at 1200°C for 5 h.The obtained LLZO exhibits an ion conductivity of 6.23×10^-4 S/cm.In the sol-gel synthesis,the calcination schedule was explored in detail,and it was found that the cubic phase LLZO can be synthesized with the condition of 12% excessive Li at low temperature.For example,calcination at 700°C for 36 h,800°C for 24 h,etc.LLZO powders were synthesized by the hydrothermal method using water or water+ethanol as solvents,and the experimental results show that the solvents can significantly affect the phase and microstructure of the product.water/ethanol solvent benefits the formation of pure LLZO phase.Based on the results in this thesis,the synthetic process of LLZO ceramic is optimized,which can provide an experimental guide for the synthesis of high-quality LLZO ceramic.