LiCo 0.5 Mn 0.5 PO 4 is readily prepared via a modified hydrothermal route to investigate the effect of Mn substitution on LiCoPO 4 . The results show that the Mn substitution plays a profound role in reducing the particle size and stabilizing the surface of the olivine materials, thus leading to highly improved electrochemical properties versus the pure LiCoPO 4 . The LiCo 0.5 Mn 0.5 PO 4 can deliver a reversible capacity of 126 mAh g −1 and maintain 88% of that over 30 cycles, thereby manifesting its potential for energy storage application.