微氧化处理对球形石墨结构及电化学行为的影响

研究了微氧化处理对球形石墨的晶体结构、表面形貌和电化学行为的影响. 采用XRD、Raman光谱和SEM等手段分析了样品的结构和形貌, 并采用恒电流充放电测试、粉末微电极技术和慢速扫描循环伏安法(SSCV)研究了微氧化前后石墨负极的电化学行为. 结果表明, 微氧化后石墨颗粒中的结构缺陷增多, 近表面区域的无序度增大, 面内平均晶粒尺寸L_a减小, 且菱形相含量降低, 石墨呈不规则的鳞片状, 部分层面的边缘有卷曲与刻蚀现象. 微氧化后石墨负极的第三次脱锂容量从345.5 mAh/g增加至381.4 mAh/g, 且其循环性能得到有效改善. 同时, 微氧化后锂离子较容易从石墨中脱出, 脱锂过程中一阶Li-GICs(lithium-graphite intercalation compounds, 简称Li-GICs)向二阶Li-GICs的阶转变可在较低的电位下发生.

Influences of Mild Oxidation Treatment on the Structure and Electrochemical Behavior of Spherical Graphite

The effects of mild oxidation treatment on the crystal structure,morphology and electrochemical behavior of spherical graphite were investigated.The structure and morphology of the samples were characterized by XRD,Raman spectra and SEM analysis,respectively.The electrochemical behavior of the samples was studied using galvanostatic charge/discharge test,powder cavity microelectrode technique and slow scan rate cyclic voltammograms.The results indicate that structural defects in graphite particles and disordered degree of near surface region of graphite increase after modification,while the average in-plane crystallite domain size La and content of rhombohedral phase decrease.The graphite particles present irregular flake shape and some graphene sheets show flexual and sculptural margin.Electrochemical measures show that reversible capacity of modified graphite increases from 345.5 mAh/g to 381.4 mAh/g,and cycling performance is improved.During deintercalation process of the modified graphite,stage transformation from stage 1 Li-GICs(lithium-graphite intercalation compounds) to stage 2 Li-GICs begins to happen at lower voltage,compared with that of the raw graphite.