Facile synthesis of ZrO2 coated Li2CoPO4F cathode materials for lithium secondary batteries with improved electrochemical properties

A facile synthesis of a metal oxide (ZrO2) coating on the surface of high voltage type Li2CoPO4F cathode material using the conventional solution method is reported in this study. The Li2CoPO4F is prepared by a two step solid state method, followed by the application of wet coating containing various amounts of ZrO2. Among the samples, the 5 wt% ZrO2 coated Li2CoPO4F material shows the best performance with an initial discharge capacity of up to 144 mA h g(-1) within the voltage range of 2-5.2 V vs Li at 10 mA g(-1). Moreover, this ZrO2 coated cell demonstrates an enhanced capacity retention which is two times higher than that of the uncoated sample. The reversible extraction-insertion of one lithium unit from Li2CoPO4F is successfully carried out in a controlled environment, where the electrolyte decomposition is reduced using a highly durable ZrO2 coating. The nanosized coating over the Li2CoPO4F surface helps to attain a higher discharge capacity even at high current rates. As a consequence, the cell delivers a capacity of 104 mA h g(-1) at a high current rate of 100 mA g(-1). (C) 2012 Elsevier B.V. All rights reserved.