Electrochemistry of Cu0.5 VOPO4 · 2H2O: A promising mixed metal phosphorous oxide for secondary lithium based batteries

Bimetallic mixed metal vanadium phosphorous oxide structures (MM'P_xO_y) have been the subject of much recent electrochemistry study. In analogy to silver vanadium phosphorous oxides, this study involves copper vanadium phosphorous oxide. Under galvanostatic discharge in lithium anode cells, the Cu_0.5 VOPO₄ · 2H₂O (CuVPO) material delivered ∼280 mAh/g to 1.5 V. Unlike silver vanadium phosphorous oxides, crystallographic evaluation indicated little structural change upon electrochemical reduction of CuVPO, with no significant change in interlayer spacing and no evidence of copper metal formation. Notably, secondary battery evaluation showed retention of ∼100 mAh/g at C/20 with little fade, a significant improvement under repeated cycling relative to a related silver based material.