An organic-skinned secondary coating for carbon-coated LiFePO4 cathode of high electrochemical performances

Abstract

Carbon coating technologies for olivine-structured LiFePO4 have been successfully commercialized in lithium ion industries. However, up to today, there are still many challenges overcoming the low intrinsic ionic conductivity and surface instability limitations. Herein, we propose a lithium ion conductive organic-skinned secondary coating technique by applying sodium maleate onto the surface of a commercial carbon-coated LiFePO4 cathode. Very distinctive features of the organic skin secondary coating are highly uniform and continuous. More importantly, the abundant carbonyl groups on the LFP surface facilitates facial Li ion transport. The nanostructure tuned organic layer is able to effectively suppress the undesired side reactions at the electrode/electrolyte interface. With 6.0 wt% of the sodium maleate coating, rate capability and long-term cycling behavior of the LiFePO4 cathode at different temperatures are significantly improved. Notably, the well-known impedance rise of LFP cathode with increasing electrochemical cycles is effectively suppressed. An insight into the mechanisms of the secondary sodium maleate coating on the carbon-coated LiFePO4 cathode is discussed.