以天然鳞片石墨为原料,利用电泳插层法制备出具有适当膨胀体积的微膨石墨,石墨的结构缺陷增多,具有较大的比表面积和增大的石墨层间距. 微膨石墨的可逆容量可以达到521 mAh/g;在0. 2 C倍率循环充放电30次容量最佳可保持在99%以上,在1. 0 C循环50次其容量可稳定在188 mAh/g,且表现出良好的倍率性能. 微膨石墨电化学性能的改善得益于其具有适当的比表面积及内部结构的改变. 交流阻抗测试显示微膨石墨的SEI膜阻抗和电荷传递阻抗小于鳞片石墨,具有良好的电化学活性.
Expanded flake graphites ( EFGs) with different expansion volumes were prepared by an electrophoresis intercalation method using natural flake graphite as the raw material, concentrated HNO3 and acetic anhydride as intercalates and KMnO4 as oxi-dant. Results indicate that the density of structural defects, and the surface area and d002 increase after the intercalation. EFG-0. 7 ob-tained with a KMnO4 mass percentage of 0. 7 wt% has a capacity of 521 mAh/g when used as the anode of a lithium ion battery, which is significantly higher than the theoretical capacity of natural graphite. EFG-0. 7 retains more than 99% of its capacity after 30 cycles at 0. 2 C and its capacity stabilizes at 188 mAh/g after 50 cycles at 1. 0 C. All the EFGs exhibit excellent performance in high-rate charge-discharge. The resistance of the solid-electrolyte interface film and the charge transfer resistance of the EFGs are smaller than natural flake graphite as revealed by electrochemical impedance spectroscopy. The improved electrochemical perform-ance of the EFGs can be ascribed to their increased surface area and d002 , and the larger number of structural defects.
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