Synthesis And Properties Of Solid Electrolyte Li_1.4Al_0.4Ti_1.6（PO₄）₃

Solid electrolytes are a key technology in the next-generation high performancepower sources. They are promising replacements for current organic liquid electrolytes inhigh energy and power densities electrochemical devices. Lithium super ionic conductorsare good candidates for solid electrolytes because of their high ionic diffusion in themobile ion sub lattice at temperatures well below their melting points. There have beenconcerted efforts in search of lithium super ionic conductors of diverse structural forms，including crystalline，glassy，polymer，and composite. However, suffer from low Li+conductivity, small operating voltage windows or low chemical and electrochemicalstabilities in air, which prevent them from being used in practical applications.Li1+xAlxTi2-x(PO4)3(x=0.3-0.5) ceramics with the NASICON structure have beenwidely studied as one of the most promising candidates because of its advantages interms of device fabrication, stability, safety and excellent electrochemical properties. Thepreparation and properties of the glass-ceramics based on LiTi2(PO4)3with NASICON-analogy structure were studied systematically in this dissertation. The main conclusionsare as follows:(1) The LATP glass-ceramics were prepared by a Sol-gel method. Powder refinementprocess and tableting process were studied. We found that when the duration timeof grinding over140min and the pressure of the milling machine stay between200~300Mpa，there is a high possibility to obtain perfect pellets than othercircumstances. The as-prepared pellets express a Li-ion conductivity of.(2) Modified sol-gel method abridges the time cost of synthesizing titanium sol，increasing the efficiency of the preparation process. The grain size of theas-prepared powder with high phase purity were between100~300nm. We alsofind out that the change thermal treatment temperature greatly affects the phaseconstitute, relative density as well as grain size and thus harm the ion conductivity and activation energy of material. The highest Li-ion conductivity of wasobtained from the pellets heatreated at900℃for6h,with a relative density of97%.The activation energy of the pellets is0.27eV.(3) When adjusting the percentage of ethanol and citrate solution above2:5, result ina better distribution of tetrabutyl titanate in the citrate solution, forming atransparent uniform Titanium solution. Utilizing ethanol solution of Titanium tosynthesize LATP would obtain powder with regular grain size around300nm, andthe ratio of element is close to that of the stoichiometric ratio. According to ourstudy, the constitution of material is affected by PH of presume solution. A higherphase purity is shown when PH stay between5~7.5.The relative density ofmaterial is affected by the temperature of heat treatment. A sample with Li-ionconductivity of4.15×10-4S/cm is synthesized with the solution PH=7and6h ofheat treatment under the temperature of900℃.