Preparation Of Li₇La₃Zr₂O₁₂Garnet Electrolyte By Tape-casting And Study On Negative Interface Modification

The energy density of currently commercialized organic-liquid electrolyte lithium-ion batteries has reached a bottleneck,and the safety issues that have always been concerned are also a major factor restricting their rapid development.Solid-state batteries have incomparable advantages over traditional lithium-ion batteries in terms of energy density and safety.The current types of solid electrolytes are mainly divided into polymer and inorganic solid electrolyte materials.Among them,the garnet-type inorganic solid electrolyte material represented by Li₇La₃Zr₂O₁₂（LLZO）has attracted wide attention in recent years.It has the advantages of high ionic conductivity at room temperature and good interface compatibility with lithium metal.Therefore,it is recognized as the most promising solid electrolyte materials,but there are two major problems in the process of its commercialization that have been restricting its development.First,the current main preparation method of LLZO is difficult to achieve large-scale preparation;on the other hand,the interface problem that has always plagued the development of solid-state batteries is also affected the development of its commercialization.Regarding the above two major issues,this study mainly focused on the large-scale preparation of LLZO solid-state electrolyte sheets and the modification of the lithium anode interface.The LLZO solid electrolyte sheet is prepared by the tape casting that can be prepared on a large scale.In this study,the various components of the slurry are studied.The study found that the use of 0.5%triethanolamine as a dispersant achieves the lowest The viscosity of the slurry;when PVB is used as the binder and the plasticizer is mixed and the content of both is 1:1,a smooth and easy-to-separate cast blank is obtained;on the basis of ensuring good blank properties,The solid content is 40-45%to obtain relatively dense cast blanks.The thermogravimetric test analysis shows that the sample obtained when the debinding temperature is 650℃and the heating rate is 0.2℃/min,the surface is smooth without obvious cracks,blisters,etc.Finally,comparing the sintering effects of the buried firing method and the pressure firing method,the buried firing method is determined to be the most ideal.The final sintering system is to adopt the buried sintering method,reach 1100℃after 2400 minutes of heating,and keep the temperature for 6hours.In view of the interface problem of the negative electrode caused by the presence of lithium-phobic Li₂CO₃,the interface is modified,and the prepared Mxene two-dimensional material is used for in-situ conversion reaction at high temperature,and it is converted into LiTiO₂/Li₂TiO₃ mixture with good lithophilicity in situ.molten lithium and solid electrolyte sheet have achieved close contact.After it is installed as a symmetric battery,a low interface impedance of only 85Ωcm² at the interface is realized.After modification,the assembled symmetric battery achieves a low interface impedance of 0.1mA/cm².The stable cycle is more than 100 times,and a low over-potential of only 17 mV is achieved at a current density of 0.02 mA/cm²,indicating the good cycle performance brought by the good interface contact,and the assembled all-solid-state battery achieves The stable cycle at 0.2 C rate is above 80,and the capacity retention rate during the cycle is 92.2%.After the cycle,the coulombic efficiency can also be stabilized at 93%,showing good cycle performance.