石墨烯改善锂离子电池正极材料LiCoO_2电化学性能的研究

Influence of graphene on the electrochemical performance of LiCoO_2 cathode materials for lithium-ion batteries

采用改性Hummers法制备了氧化石墨烯和通过化学还原法还原氧化石墨制得石墨烯,及以石墨烯作为正极材料LiCoO2的导电剂,并研究它们对锂离子电池电化学性能的影响。扫描电镜(SEM)和透射电镜(TEM)结果表明,石墨烯的表面褶皱使其能有效地包裹LiCoO2颗粒,形成面接触的导电界面,从而显著提高了导电性。充放电实验表明,石墨烯的加入有利于提高LiCoO2的电化学反应活性、放电容量和高倍率循环性能。相对于传统的炭黑,LiCoO2的放电容量在0.2 C下提高了10 m Ah/g。石墨烯/LiCoO2电池在1C倍率下,循环300次后,放电容量由145.0 m Ah/g衰减到137.8 m Ah/g,放电容量能保持初始容量的95.1%。石墨烯/LiCoO2电池在20 C倍率下的放电容量达到132.1 m Ah/g,是1 C放电容量的91.1%。

Graphite oxide（Go） was prepared by modified Hummers method, graphene was prepared by chemical reduction method, and graphene were used a conducting additives of LiCoO2 cathode materials in order to inves- tigate the effect of graphene on the electrochemical performance of lithium ion batteries. Images of scanning electron microscopy （SEM） and transmission electron microscopy （TEM） showed that the surface wrinkles of graphene wrapped LiCoO2 particles to form plane contacted interface, thus enhanced the conductivity of the cathode, improved greatly the high rate cycling stability. Charge-discharge tests indicated that the addition of graphene increased the electrochemical reaction activation of LiCoO2. Compared with carbon black, the dis- charge capacity of LiCoO2 at 0.2 C rate was improved 11 mAh/g. After 300 cycles, the capacity of graphene/Li- CoO2 battery decreased from 145.0 to 137.8 mAh/g, which was 95.1%0 of the initial discharging capacity.When the discharging rate increased to 20 C, the discharging capacity of graphene/LiCoO2 battery was 132.1 mAh/g, which was 91.1 G of the discharging capacity at a discharging rate of 1 C.