Copper phosphide, Cu3P, has been synthesized using a solvothermal route. The electrochemical reaction of this binary phosphide with lithium has been studied to describe the insertion/extraction mechanism. The discharge of the half-cell Cu3P/Li up to 0.1 V proceeds by lithium insertion into a Cu3P hexagonal structure and then by two successive biphasing processes involving the formation of LiCu2P and Li2CuP, respectively. Simultaneously, copper metal is extruded from the matrix. During the charge the reversible processes are observed. After 15 cycles a 400 mAh g(-1) specific capacity is retained. (C) 2004 The Electrochemical Society.