Solid electrolyte Li10GeP2S12 (LGPS) was successfully synthesized by optimizing the mechanical ball milling process and subsequent heat treatment process using Li, Ge, P and S as raw materials. The synthesis method has the advantages of low cost, simple process, short cycle and high efficiency. The synthesized LGPS possesses regular morphology and uniform particle distribution without agglomeration. Simultaneously, it presents a wide electrochemical voltage window of over 6.0 V (vs. Li+/Li), a low activation energy Ea of 25.5 kJ mol(-1) and the room temperature conductivity sigma(Li) of 3.27 x 10(-3) S cm(-1). The synthesized LGPS solid electrolyte exhibits good electrochemical stability and compatibility with lithium metal electrodes, making it possible to apply in all solid state batteries. (C) 2019 Published by Elsevier B.V.