Study On Preparation And Electrochemical Performance Of Oxide Solid Electrolyte Li₇La₃Zr₂O₁₂

In recent years,with the country's strong support for the development of the new energy industry,lithium-ion batteries have been rapidly developed,and the application fields are also increasing.Currently widely used liquid lithium-ion batteries use organic liquid electrolytes,which poses a potential safety hazard for leakage and flammability.Therefore,the solid-state battery using an inorganic solid electrolyte can well solve the safety problem of the current liquid battery.The main reason is that the all-solid-state lithium-ion battery has its good thermal stability and safety and high energy density.The key material for the development of solid-state batteries is the development of solid electrolytes with excellent performance.In the development system of solid electrolytes,Li₇La₃Zr₂O₁₂?LLZO?has a high room temperature lithium ion conductivity(¹0^-4S/cm),a wide electrochemical window?>5V?,and is chemically stable at room temperature.The advantages such as good contact have become one of the most promising solid electrolytes.Therefore,this article studies the garnet type oxide solid electrolyte LLZO,and in order to better prepare the LLZO solid electrolyte with excellent performance,this article uses microwave sintering method and solid phase sintering method to optimize the LLZO sintering process,respectively,to prepare a cube with excellent performance Phase solid electrolyte LLZO.LLZO solid electrolyte materials with high purity were prepared at low temperature?1150??using microwave sintering technology.The effects of different sintering temperature?1000?¹230??and different holding time?1⁶h?on the synthesis of LLZO were studied.Influence of phase,microstructure and ionic conductivity.The experimental results show that at 1000 ^oC,the microwave-sintered LLZO phase is tetragonal and the lithium ion conductivity is low.When the temperature is 1100^oC,the phase is a mixture of tetragonal phase and cubic phase.At1150^oC¹200^oC,it is a high-purity cubic phase LLZO with high ion conductivity.When the temperature is 1230^oC,it is a mixture of tetragonal phase and cubic phase.When the holding time is shorter than 1² h,it is a mixture of tetragonal phase and cubic phase,and the ion conductivity is low.When the holding time is 4 hours,the sample has the highest ionic conductivity of 3.1×10^-4S/cm,and the holding time is 6 hours,and the lithium ion conductivity decreases.Therefore,the best heat preservation time of microwave sintering LLZO is about 4h,and the suitable sintering temperature is1150?¹200?.The process of sintering LLZO solid electrolyte materials by traditional solid-phase method was optimized,and the effects of different sample green thickness on the phase,microstructure and lithium ion conductivity of LLZO solid electrolyte were studied.Using magnesium oxide crucible instead of alumina crucible for sample sintering reduces the problem of"aluminum pollution"caused by high temperature sintering of alumina crucible,and at the same time improves the sintering system andprepares LLZO solid electrolytic sheets with different thicknesses.When the thickness of the sample is 1.8mm².3mm,the specific surface area is large,and the phase is the cubic phase LLZO with low crystallinity.When the thickness of the sample is increased to 2.5mm,the pure phase is the LLZO of the cubic phase,and the ion conductivity at this time is the highest,which is 3.35×10^-4S/cm.When the thickness of the sample is2.9⁴.0mm,the specific surface area is small,the phase is a mixed phase of cubic phase and tetragonal phase,and the ion conductivity is low.Therefore,the thickness suitable for sintering the LLZO electrolyte sheet is about 2.5 mm.