Characterizations of the electrode/electrolyte interfacial properties of carbon coated Li3V2(PO4)3 cathode material in LiPF6 based electrolyte

Carbon coated monoclinic Li3V2(PO4)(3) cathode material was prepared by the carbothermal reduction method. Raman scattering showed the amorphous nature of the residual carbon in the material. HRTEM and XPS showed that a small amount of carbon penetrated into the Li3V2(PO4)(3) crystallites to form a surface carbon layer with thickness about 5-10 nm. The material showed a reversible discharge capacity of 120 mAh g(-1) (C/4 rate), 115 mAh g(-1) (1C rate) and 110 mAh g(-1) (2C rate) in the voltage window of 3.0-4.3 V. which kept excellent cycle stability in 300 cycles. The material suffered from capacity loss in the initial ten charge-discharge cycles. The irreversible capacity loss was mainly related to the progressive formation of a solid electrolyte interface (SEI) film which was clearly observed by HRTEM. FTIR analysis showed that the chemical species of the SEI film mainly contained some organic compounds such as ROCO2Li, RCO2Li, and aliphatic, as well as some inorganic compounds such as Li2CO3, LixPFy or LixPOyFz. The SEI film tended to be stabilized in the initial several cycles, which led to excellent electrochemical performance during long term cycling. (C) 2012 Elsevier Ltd. All rights reserved.