Research Of Graphite Coated By Graphene As Anode Material For Lithium Ion Battery

Graphite is one of the most important anode materials for lithium ion battery. But, during charging and discharging, graphite can react with the electrolyte to induce solvation, volume expansion, the graphite layer falling off, resulting in affecting its electrochemical performance, although the theoretical specific capacity of graphite has372mAh/g, its specific capacity has330mAh/g, as well as poor cycle performance and capacity fades fastly during charging and discharging at large current density. So, it can not meet the needs of rapid development electronic products. Graphene has a large specific surface area, large capacity and good chemical and thermal stability. In this paper, we study that the graphite coated with graphene in order to prevent graphite from falling off and maintain its integrity. The result shows that the electrochemical performance of graphite materials can be improved. The work is as follows.Graphite(G1620) is produceded by Huzhou and the power battery material limited company. Graphite(G123) is produceded by Changzhou Zhongke Energy Technology limited company. G1620and G123were used as anode materials for lithium ion battery(LIB). A series of rGO/G1620and rGO/G123materials containing different contents of graphene were prepared using machinery ductile, high temperature thermal reduction, and graphene coating methods. The influence of the amount of graphene on the composites’ microcrystalline structure and electrical performances were studied. The morphology and structure of the samples were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical performance of all samples was evaluated by galvanostatic charge/discharge test and cyclic voltammograms (CV).By XRD test, G1620and G123materials coated graphene that have little effect on their structure compared with raw materials. By SEM, the graphene coated on the surface of G1620and G123materials. By CV, the graphite coated graphene can improve their electrochemical performance.The results show that graphene coated G1620with3%rGO has higher capacity and better cycle stability at10mA/g of current density in the range of0.005-2V voltage. The first discharge and charge capacities are482mAh/g and388mAh/g respectively, which are higher than those of G1620(388mAh/g and340mAh/g) with the first columbic efficiency of80%. The charge capacity still remains385mAh/g after30cycles, while G1620was only79mAh/g, and the capacity retention rate was99.5%.For G123coated by graphene with4%RGO has higher capacity and better cycle stability under the same measured conditions. The first discharge and charge capacities are510mAh/g and393mAh/g respectively, which are higher than400mAh/g and357mAh/g of G123, and the first columbic efficiency is77%. The charge capacity still remains387mAh/g after30cycles, which is higher252mAh/g of G123, and the capacity retention rate is98.5%.Graphene coating can improve the capacity and performance cycle of graphite materials. In this paper, G1620and G123anode materials coating by graphene have some advantages, such as large capacity and good cycling performance.