Preparation And Doping Modification Of LiTaSiO₅ Solid Electrolyte

The organic electrolyte in commercial lithium-ion batteries has the defects of inflammable,explosive,and corrosive,which can easily lead to safety accidents.It is hopeful to use solid electrolytes to replace organic electrolytes.Therefore,the design and development of solid electrolyte materials with both performance and safety has become a research focus.In recent years,it has been found through high flux theoretical calculation that Li Ta Si O₅（LTSO）solid electrolyte has the advantages of high ionic conductivity,stable electrochemical performance,and wide electrochemical window,and has a potential application prospect.However,the conductivity of the solid electrolyte ions prepared in the present experiment is far lower than the theoretical value and it is easy to precipitate non-conductive phase,which greatly limits its development and application.Because of the above problems,this paper focuses on the main factors affecting the ionic conductivity of LTSO solid electrolytes through different synthesis methods,process optimization,and ion doping,hoping to improve the ionic conductivity of LTSO solid electrolytes.The main research work is as follows:（1）Li_1+xTa_1-xZr_xSi O₅ lithium-ion conductive glass was prepared by melt quenching method,and the glass-ceramic material with Li Ta Si O₅ as the main crystal phase was obtained by controlling the crystallization process of the glass.The effects of Zr⁴⁺content on glass forming,crystallization process,structure,and properties were studied by X-ray diffraction,Infrared spectroscopy,electronic scanning,and AC impedance spectroscopy.The results show that a certain amount of Zr⁴⁺can promote glass crystallization,inhibit Li_1+xTa_1-xZr_xSi O₅ phase decomposition,activate lattice,and improve the ionic conductivity of glass-ceramics.When x=0.1,the Li_1+xTa_1-xZr_xSi O₅lithium-ion conductive glass melted at 1620°C was crystallized at 980°C for 10 h,and the glass-ceramics with Li Ta Si O₅ as the main crystal phase were obtained.The ionic conductivity was 8.40×10^-6 S/cm.Compared with the pure glass phase structure;Conductivity went up by two orders of magnitude.（2）Li_1.1Ta_0.9Zr_0.1Si O₅（LTZSO）solid electrolyte was prepared by solid-phase synthesis method.The influence of the sintering process on the physicochemical properties of LTZSO electrolytes was investigated.The results show that properly increasing sintering temperature and holding time can promote the conversion of Li Ta O₃ to Li Ta Si O₅.When the holding time is 30 h,the conductivity of the LTZSO electrolyte reaches 4.32×10^-5 S/cm,the relative density is 87.63%,and the diffusion activation energy is 0.223 e V.（3）Li_1.1Ta_0.9Zr_0.1Si O₅-xwt%Li F（LTZSO-xwt%Li F）solid electrolyte was synthesized by doping LTZSO with Li F under the same technological conditions.The results show that the addition of Li F can promote the homogenization of LTZSO particles,increase the lattice parameters of LTZSO and improve the density of ceramic electrolytes.When x=0.4,the relative density of LTZSO-0.4wt%Li F electrolyte reaches90.81%,the total ionic conductivity is 8.31×10^-5 S/cm,and the diffusion activation energy is 0.203 e V.（4）The effect of Y³⁺doping on the microstructure and ionic conductivity of Li_1.1Ta_0.9Zr_0.1Si O₅ electrolyte was studied.The results show that the liquid phase produced by Y³⁺ion doping at the interface effectively reduces the sintering temperature of the electrolyte,promotes vacancy migration,significantly reduces the porosity of the electrolyte sample,improves the density of the sample,and improves the ionic conductivity of interface precipitated Li Ta O₃,reduces the grain size and interfacial impedance of sample.When x=0.01,the relative density of the electrolyte is92%,the total ionic conductivity is 1.11×10^-4 S/cm at room temperature,and the diffusion activation energy is 0.145 e V.