Study on natural graphite modified by H_2O_2 as anode material for lithium ion battery

摘要

In the present experiment, flake natural graphite was modified by liquid-phase oxidation method using H_2O_2 as an oxidant. It was proved that the oxygen content at the surface of the graphite decreased and the electrochemical performance was improved after oxidation. With the help of XPS and RTIR measurements, that the removal of carboxylic groups and the enhancement of ester groups caused the decrease of the total oxygen content. Thermogravimmetric analysis indicated that the stability of graphite structure was not distinctly improved by oxidation. The change of surface structure was benefiticial to decrease the consumption of lithium ion in the process of the formation of solid electrolyte interface (SEI) film and inhibit the decomposition of solvent and electrolyte which resulted in the decease of irreversible capacity. The coulombic efficiency of first cycle for the oxidized sample increased from 86.7% to 89.8% and the irreversible capacity decreased a little in the first twenty cycles. Therefore, it was concluded that the oxidized natural graphite had already met the requirement of the application of lithium ion battery.