Lithium Ion Conductivities of NASICON-type Li1+xAlxTi2-x(PO4)3 Solid Electrolytes Prepared from Amorphous Powder Using a Mechanochemical Method

Amorphous (a-LATP) powders with various nominal compositions of L1+xAlx-Ti2-x(PO4)(3) (x = 0, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6) in the Li2O-Al2O3-TiO2-P2O5 (LATP) system, were prepared directly from a mixture of Li2O, gamma-Al2O3, anatase-type TiO2, and P2O5 as the starting powder, using mechanical milling (MM) at room temperature. Crystalline LATP (c-LATP) powder with a NASICON-type structure was formed by the heat treatment of mechano-chemically prepared a-LATP powder. In addition, heat-treated c-LATP (x = 0.5, 0.6) powders included an impurity phase of crystalline Li5AlO4. The sintered c-LATP (x = 0) pellet without Al3+ doping exhibited a low electrical conductivity on the order of 10(-7) S cm(-1) at room temperature. On the other hand, the sintered Al3+-doped c-LATP (x = 0.3, 0.4, 0.45, and 0.5) pellets showed high electrical conductivities on the order of 10(-4)S cm(-1) at room temperature. The sintered c-LATP (x = 0.45) pellet exhibited the highest lithium ion conductivity (2.9 x 10(-4)S m(-1)) at 25 degrees C and the lowest activation energy (30 KJ mol(-1)). (C) The Electrochemical Society of Japan, All rights reserved.