Hydrothermal-assisted solid-state reaction synthesis of high ionic conductivity Li1+xAlxTi2-x(PO4)3 ceramic solid electrolytes: The effect of Al3+ doping content

The importance of developing solid electrolytes for solid-state batteries attracts great interest in Na super ionic conductor (NASICON)-type LiTi2(PO4)(3) for its high ionic conductivity, excellent stability at high potential and great stability in atmosphere. In this study, Al3+-doped LiTi2(PO4)(3) materials with the formula of Li1+xAlxTi2-x(PO4)(3) (x = 0, 0.1, 0.2, 0.3, and 0.4) are successfully prepared by hydrothermal-assisted solid-state reaction (HA-SSR). The influence of Al3+ doping content on the crystal structure, morphology, ionic conductivity, as well as activation energy of Li1+xAlxTi2-x(PO4)(3) is investigated. Al3+-doped LiTi2(PO4)(3) powders with well-organized morphology and homogeneous size distribution are successfully achieved. The solid electrolytes prepared with Al3+ doping exhibit larger particle size and higher crystalline property than that of the sample without Al3+ doping. High ionic conductivity (4.63 x 10(-4) S cm(-1)) and low activation energy (0.28 eV) are obtained for the sample with optimum substitution level (x = 0.3, Li1.3Al0.3Ti1.7(PO4)(3)); while the bare LiTi2(PO4)(3) solid electrolyte delivers conductivity of 1.40 x 10(-5) S cm(-1) and activation energy of 0.38 eV. The significantly increased ionic conductivity and reduced activation energy indicate that Al3+ doping is a good strategy to enhance the performance of LiTi2(PO4)(3) solid electrolyte for solid-state batteries.