Structural and electrochemical properties of lithium vanadium fluorophosphate, LiVPO4F

The electroactive lithium vanadium fluorophosphate phase, LiVPO4F (PT, a=5.1687(2) A, b=5.3062(2)A, c=7.5031(3)A, a= 66.856(2)DG, B=67.004(2)DG, y=81.583(2)DG and cell volume = 174.2 1 (1) A3) has been synthesized by a two-step reaction scheme based on a carbothermal reduction (CTR) process. High-resolution electrochemical measurements reveal a structured voltage response for the lithium extraction process while the lithium insertion process proceeds via a two-phase reaction mechanism centered at around 4.2 V versus Li. Performance evaluation of a graphite/LiVPO4F lithium-ion cell indicates an average discharge voltage of 4.06 V coupled to an initial material utilization for the LiVPO4F of around 123 mAh g-1. Long-term cycling of this lithium-ion system demonstrates good capacity retention over the first 300 cycles. Based on the available data we believe the LiVPO4F offers considerable promise as a viable cathode replacement for LiCoO2.