双氧水氧化天然石墨作锂离子蓄电池负极

Study on natural graphite modified by H_2 O_2 as anode material for lithium ion battery

用双氧水作氧化剂,对天然鳞片石墨进行了液相氧化改性。双氧水的氧化改性降低了天然石墨表面的含氧量,改善了其电化学性能。采用XPS和FTIR方法分析得知,氧化改性主要是去除了天然石墨表面的部分羧基(COOH)而增加了酯(COOR)的含量,正是这种表面官能团的转换导致了天然石墨表面的氧含量降低。热失重分析结果表明氧化改性对天然石墨的结构稳定性的提高作用不是很明显。天然石墨表面状态的变化有利于减少形成SEI膜时锂离子的消耗,抑制溶剂和电解质的分解,从而使首次循环的不可逆容量降低,氧化后的样品HONG的首次充放电效率从86.7%提高到89.8%,前40次的循环可逆放电容量基本没有衰减,都保持在320 mAh/g以上,这已经达到了实用化锂离子蓄电池负极材料的要求。

In the present experiment,flake natural graphite was modified by liquid-phase oxidation method using H 2 O 2 as oxidant.It was proved that the oxygen content on the surface of the graphite decreased and the electrochemical performance was improved after oxidation.With the help of XPS and FTIR measurements,that the removal of carboxylic groups and the enhancement of ester groups caused the decrease of total oxygen content.Thermogravimetric analysis indicated that the stability of graphite structure was not distinctly improved by oxidation.The change of surface structure was beneficial to decrease the consumption of lithium ion in the formation process of solid electrolyte interface (SEI) film and inhibit the decomposition of solvent and electrolyte which resulted in the decease of irreversible capacity.The coulomb efficiency of the first cycle for the oxidized sample increased from 86.7% to 89.8% and the irreversible capacity decreased a little during the first forty cycles. Therefore, it was concluded that the oxidized natural graphite had already met the applicable requirement of lithium ion battery.