混酸提纯工艺对微晶石墨结构及电性能的影响

Effect of Mixed Acid Purification Process on Structure and Electrical Properties of Microcrystalline Graphite

为进一步提高微晶石墨纯度,将乳化煤油浮选后的微晶石墨经过多次HF-HCl混酸法提纯,分别制备锂离子电池负极材料。利用X射线衍射(XRD)、拉曼光谱(Raman)和扫描电镜(SEM)等方法分析了酸洗前后微晶石墨的结构特点和微观形貌,并通过恒电流充放电、交流阻抗等手段测试了样品的电化学性能。结果表明:乳化煤油浮选和HF-HCl酸洗两步法提纯的微晶石墨,纯度可提高到99.7%,比酸洗前微晶石墨杂质含量降低6.2%,样品层间距略有增加,结晶度略有提高;混酸提纯后微晶石墨首次充电容量、循环性能、倍率性能均优于酸洗前微晶石墨,且阻抗显著降低。

In order to improve purity of microcrystalline graphite, lithium ion batteries negative materials were prepared using microcrystalline graphite flotated by emulsified kerosene and purified several times by HF-HCl mixed pickling method. X-ray power diffraction , XRD, Raman spectrum(Raman) and scanning electron microscope (SEM)were used to analyze structure and microstructure of microcrystalline graphite before and after pickling. Then electrochemical properties of the samples were tested by means of constant current charge-discharge and ac impedance. The results showed that purification of emulsifying kerosene flotation and HF-HCl acid picking two steps increased to 99.7%, and the impurity content decreased by 6.2% compared with that before pickling. Layer spacing and crystallinity of samples increased a little. First charge capacity, cycle performance and rate capability of microcrystalline graphite by mixed acid were batter than that before acid pickling, resistance decreased significantly.