Impact of H2O exposure on the structure and electrochemical performance of LiVPO4F cathode material

摘要

In this work, triclinic structured LiVPO4F is prepared by a simple two-step carbothermal reduction method and subsequently exposed to water under different storage conditions. The impact of exposure on the structure, morphology and electrochemical performance of LiVPO4F is investigated in detail. It is found that the effect of exposure at room temperature (20 degrees C) is slight. In contrast, exposure at 80 degrees C has great effect on the structure and electrochemical properties of LiVPO4F. Li, P and V dissolution into aqueous solution at 80 degrees C results in the formation of a yellowish solution. Electrochemical tests show that LiVPO4F samples aged in water at 80 degrees C for 3 and 5 days show poorer electrochemical properties than the pristine sample. LiVPO4F aged in water at 80 degrees C for 15 days exhibits higher initial reversible capacity compared with the pristine sample. However, it deteriorates rapidly in the following cycles due to the moisture-sensitive surface, which induces the formation of thick Li2CO3/Li3PO4 film on the surface and leads to a high charge transfer resistance and the degradation of electrochemical performance. (C) 2015 Elsevier B.V. All rights reserved.