Structure Design And Mechanism Research Of Lithiumair Battery Electrolyte Based On Li₇La₃Zr₂O₁₂

Solid-state lithium-air batteries have always been considered as the research hotspots in the field of lithium based batteries due to their high theoretical energy density and high safety and reliability.At present,the key issues that need to be resolved for the lithium-air batteries include: the actual discharge capacity of the battery is low,the internal resistance of the battery is large,and stable and cycle ability is unsatisfactory.The key to solve these problems is to develop electrolyte materials with high electrical conductivity,high mechanical strength and easy processing.Solid-state electrolytes have attracted much attention due to their excellent mechanical strength,which can effectively suppress lithium dendrites,but there are several shortcomings such as insufficient conductivity and high interface resistance when contacting with electrodes.This thesis takes GARNET solid ceramic electrolyte Li₇La₃Zr₂O₁₂?LLZO?and its cation-doped subspecies as the research object,systematically studied its performance as an electrolyte host material and polymer electrolyte additive,including the two types of electrolyte Preparation process,structural characteristics and electrochemical performance,as well as the comprehensive performance of lithium-air batteries based on these two types of electrolytes.In this thesis,the solid-phase synthesis method was used to prepare LLZO,Al-doped Li_6.9A_l?0.1?La₃Zr₂O₁₂?LALZO?and Ta-doped Li_6.4La₃Zr_1.4Ta_0.6O₁₂?LLZTO?.The physical phase and structural characteristics for the samples were determined and it was used to confirm the optimal preparation conditions.The optimized powder is further pressed and sintered to prepare a dense electrolyte ceramic sheet,which is then evenly cut,polished and cleaned,and a three-dimensional porous structure is constructed on the surface through an acid etching process.Finally active material is coated onto the inner surface of the porous skeleton through an impregnation and carbonization process.After that,an integrated electrolyte-air electrode structure is built,which is then used to assemble the typical lithium-air batteries to test the charge and discharge performance.And the testing results shows that the acid etching treatment technology can substantially reduce the resistance of the electrolyte sheet,and greatly increase the amount of surface active material adhesion,and thus significantly improve the discharge capacity of the battery.This thesis also prepares a ternary chemical cross-linked polymer electrolyte based on polymer PEO,cross-linking agent PEGDA and DVB,in which the LLZO powder is added and served as an active agent,the main research content includes:?1?the optimized ratio of LLZO active agent and?2?the cross-linking degree.The experimental results show that the hardness of PEO increases after the cross-linking operation,but the ionic conductivity will decrease rapidly,and reducing the degree of cross-linking can alleviate this trend.In addition,LLZO additives can improve the ionic conductivity of the cross-linked polymer system,through changing the structure of the polymer layer.Furthermore the electrolyte can suppress the lithium dendrites and improve the battery cycle-life.