Amorphous a-LATP (x = 03) fine powder with the composition of LI1+xAlxTi2-x(PO4)(3) in Li2O-Al2O3-TiO2-P2O5 system was prepared directly from a mixture of Li2O, gamma-Al2O3, TiO2, and P2O5 as starting materials, by using a mechanical milling (MM) technique at room temperature. A NASICON-type Li1+xAlxTi2-x(PO4)(3) (x = 0.3) (c-LATP (x = 0.3)) solid solution was obtained by the heat treatment of mechanochemically prepared amorphous a-LATP (x = 0.3) material. The sintered c-LATP (x = 0.3) pellet showed high lithium ion conductivity of the order of 10(-4) S cm(-1) at room temperature and activation energy of about 35 kJ mol(-1). The high-conducting lithium ion c-LATP (x = 0.3) solid electrolyte fine powders were investigated as surface modification materials of LiCoO2 cathode in lithium cells using nonaqueous electrolyte solutions. The c-LATP (x = 0.3)-modified LiCoO2 electrodes exhibited high capacity (ca. 180 mAh g(-1)) and good cycle performance with a high charge cut-off potential of 4.5 V (vs. Li/ Li+) in lithium cell. The increase in the electrode/electrolyte interfacial resistance for the LiCoO2 electrode modified with c-LATP (x = 0.3) fine powder was inhibited. (C) 2013 Elsevier B.V. All rights reserved.