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

In this paper we report the electrochemical characteristics of a novel cathode material Li2CoPO4F prepared by solid-state reactions The solid-state reaction mechanism involved in synthesizing the Li2CoPO4F also is analyzed in this paper When cycled between 2 0 V and 5 0 V during cyclic voltammetry measurements the Li2CoPO4F samples present one fully reversible anodic reaction at 481 V When cycled between 2 0 V and 5 5V peaks occurring at 481 V and 51 V in the first anodic scan evolved to one broad oxidative mound-like pattern in subsequent cycles Correspondingly the X-ray diffraction (XRD) pattern of the Li2CoPO4F electrode discharged from 5 5V to 2 0 v is slightly different from the patterns exhibited by a fresh sample and the sample discharged from 5 0V to 2 0V This difference may correspond to a structural relaxation that appears above 5V In the constant current cycling measurements the Li2CoPO4F samples exhibited a capacity as high as 109 mAh g(-1) and maintained a good cyclability between 2 0 V and 5 5V vs Li/Li+ XRD measurements confirmed that the discharged state is Li2CoPO4F Combining these XRD results and electrochemical data proved that up to 1 mol l i(+) is extractable when charged to 5 5 V Published by Elsevier B V