石墨相氮化碳表面包覆改善锂离子电池正极材料LiCoO_2电化学性能的研究

Critical Influence of Graphitic Carbon Nitride Coatingon the Electrochemical Performance Improvement of LiCoO_2 Composite Cathode Material for Lithium Ion Battery

通过简单的固相法和液相法,分别制备出石墨相氮化碳(g-C_3N_4)表面改性的商品化LiCoO_2复合材料,采用扫描电子显微镜观察改性后的材料,发现g-C_3N_4都均匀地包裹在LiCoO_2表面。两种g-C_3N_4-LiCoO_2复合材料被用作锂离子电池的正极材料,电化学测试结果显示,固相法制得的g-C_3N_4-LiCoO_2复合材料在0.2C的倍率下充放电测试,首次比容量达167mA·h·g^(-1),循环80次后,比容量仍达132mA·h·g^(-1),高于未经g-C_3N_4包裹的纯LiCoO_2(98mA·h·g^(-1));液相法制得的Y-C_3N_4-LiCoO_2复合材料循环稳定性明显优于同类材料,循环80次后容量保持率均在95%以上。试验证实,g-C_3N_4表面改性的策略具有一定的实用价值,改性后,材料优异的电化学性能归因于g-C_3N_4的包裹处理,这不仅增强了固体电解质界面(SEI)的稳定性,也抑制了锂离子嵌入/脱出电极材料时引起LiCoO_2体积的变化。

Graphitic carbon nitride（g-C3N4）coated LiCoO2composite was prepared by simple solid phase method and liquid phase method.Scanning electron microscopy reveals that both composites were uniformly coated by g-C3N4.The g-C3N4-LiCoO2composite was used as high capacity cathode material for lithium ion battery.G-C3N4-LiCoO（2 ）cathode material synthesized by solid phase method displayed remarkable higher initial discharge capacity（167 mA·h·g^（-1））and reversible capacity（132 mA·h·g^（-1））compared to pure LiCoO2（98 mA·h·g^（-1））at 0.2 C rate after 80 cycles.Y-C3N4-LiCoO2cathode material synthesized by liquid phase method shows excellent cycling stability capacity retention of 95%at 0.2 C rate after80 cycles.And the feasibility of the g-C3N（4 ）surface coating strategy was verified by above tentative experiments.The significantly improved electrochemical properties of g-C3N4-LiCoO（2 ）composite can be attributed to g-C3N（4 ）coating treatment,which not only enhanced the stability of the solid-electrolyteinterface（SEI）film but also acted as a buffer layer for the large volume change of LiCoO2particles during lithium intercalation and deintercalation.