Preparation and electrochemical investigation of Li2CoPO4F cathode material for lithium-ion batteries

We report the electrochemical characteristics of a novel cathode material Li2CoPO4F/C, which was prepared via a ceramic process. In cyclic voltammetry (CV) measurements, two reactions taking place at 4.81V and 5.12 V in the first anodic scan evolve to one broad oxidative peak in the subsequent cycles. This shape change of CV curves demonstrates that the charge/discharge mechanism is varied after the first charge. Correspondingly the XRD pattern of Li2CoPO4F shows a minor difference after discharge from 5.5 V. Further experimental results prove that this change is associated with the second reaction peaked at 5.12 V. In the constant current cycling measurement, the prepared Li2CoPO4F exhibits a reversible capacity of 109 mAh/g between 2.0 and 5.5 V. The discharge capacity keeps stable in the first 12 cycles accompanied by the serious electrolyte decomposition between the interface of electrolyte and Li2CoPO4F.