锂离子蓄电池负极材料石墨的改性与性能研究

Study on modification and performance of graphite for anode of lithium ion batteries

采用机械球磨方法制备出锂离子蓄电池用石墨∕SnO改性负极材料。研究了不同SnO含量对材料结构及电化学性能的影响。利用X射线衍射(XRD)和扫描电子显微镜(SEM)对改性产物的结构特性进行表征,并测试它们的电化学性能。XRD测试分析表明:改性产物保持了石墨的主体结构。电性能测试结果表明:适量的SnO有利于提高石墨材料的比容量,当SnO的加入量为16%(质量分数)时,改性石墨显示出较优的电化学性能,比容量从纯石墨的332mAh·g-1提高到696mAh·g-1,20周期循环容量下降14%,循环性能优于纯SnO(20周期循环容量下降68%)。由此可见以高电导率的石墨为基质,通过添加一定量的SnO对石墨进行改性,使其在石墨基质中形成高度弥散的SnO,SnO首次分解反应产生的Li2O阻止了Sn形成聚集体,改善了石墨或SnO单独作为电极材料时的性能。

The negative electrode materials for lithium ion battery were prepared by mechanical milling of graphite∕SnO. The influence on the structure and electrochemical properties of the materials caused by different content of SnO has been investigated. The XRD patterns and SEM were used to study the structure properties of products. The products were also electrochemically characterized. The XRD analysis showed that the modified graphite kept as main layer. The electrochemical performance tests showed that compared to the pure graphite, modified graphite exhibited the higher specific capacity, and the best electrochemical performance was shown by a composite containing 16% of SnO, of which the specific capacity increased from 332 mAh·g-1 with the pure graphite to 696 mAh·g-1 . After 20 cycles, the capacity loss was14%, lower than that of pure SnO (68% loss in the same number of cycles). The improved electrochemical performance of modified products are probably related to the conductivity of the graphite matrix, a high dispersion of the SnO phase, and the presence of Li2O matrix formed in the first electrochemical decomposition reaction of SnO with lithium. Li2O conduced to hinder the Sn particles agglomeration and improved the performance of electrodes.