酚醛树脂包覆氧化天然石墨作为锂离子电池负极材料

Phenolic Resin Coated Natural Graphite Oxide as an Anode Material for Lithium Ion Batteries

天然石墨经过浓硫酸氧化处理,酚醛树脂包覆并高温碳化后形成具有核壳结构的碳包覆氧化天然石墨复合材料.采用扫描电子显微镜(SEM),透射电子显微镜(TEM),X射线衍射(XRD),激光显微拉曼光谱(Raman)等检测技术对氧化处理以及酚醛树脂热解碳包覆前后天然石墨材料的结构与形貌进行分析与表征.结果表明,氧化处理与适量的酚醛树脂热解碳包覆有效修复了天然石墨表面的一些缺陷结构,使其表面更为光滑.电化学测试结果显示,经过氧化处理与酚醛树脂热解碳包覆后天然石墨材料电化学性能得到明显提高.酚醛树脂包覆量为9%时,复合材料表现出最好的电化学性能,其首次放电比容量为434.0mAh·g-1,40次循环后,放电比容量保持在361.6mAh·g-1,而未经处理的天然石墨放电比容量仅为332.3mAh·g-1.该改性方法有效提高了天然石墨材料的比容量,对其进一步应用具有重要意义.

A core-shell structure of the carbon-coated natural graphite oxide composite was successfully prepared. Natural graphite was initially oxidized using concentrated sulfuric acid and then carbon coated by the carbonization of phenolic resin at high temperature. Scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, and Raman techniques were used to characterize the morphology and structure of the natural graphite materials before and after oxidation and carbon coating by the pyrolysis of the phenolic resin. The results showed that the surface of the natural graphite particles became smoother and the surface defects were effectively modified after oxidation and carbon coating. The electrochemical test results showed that the electrochemical performance of the natural graphite improved significantly by oxidation with sulfuric acid and by carbon coating. When the covering amount of phenolic resin was 9% the modified natural graphite material gave the best electrochemical performance. Its initial discharge capacity was 434.0 mAh·g^-1 and it remained 361.6 mAh·g^-1 after 40 charge-discharge cycles. The discharge capacity of the untreated natural graphite was only 332.3 mAh·g^-1. The modification approach that improved the capacity of the natural graphite effectively is of great significance for the application of natural graphite in lithium ion batteries.