Si/VGCF复合材料的储锂性能

Lithium Storage Properties of Si/VGCF Composite Materials

以纳米硅颗粒为原料,采用液相法制备了硅纳米粒子与气相生长碳纤维(VGCF)复合的材料(Si/VGCF)。考察了Si/VGCF制备工艺和VGCF的最佳含量,分别采用SEM和TEM表征了Si/VGCF材料形貌和晶体结构,测试和计算了材料电导、BET比表面积和孔尺寸数据。采用循环伏安、恒流充放电和交流阻抗等测试了Si/VGCF复合电极的电化学性能,并与其他碳材料进行了对比分析。结果表明,Si与VGCF形成了多级框架结构,丰富了离子和电子传输网络;同时发达的孔结构也缓解了Si粒子在嵌/脱锂过程中的体积效应,使电极活性材料的利用率和电化学稳定性显著提高。当m(Si)∶m(VGCF)为1:0.5时,Si/VGCF复合电极在500 mA/g的电流密度下,充放电循环100次后,可逆容量高达1470 mA·h/g。

Si/vapor-grown carbon fiber(VGCF) composite materials were prepared by liquid phase mixing method using nano-silicon particles as raw materials. The preparation conditions of the Si/VGCF composite materials, the optimum content of VGCF were investigated. The morphology and crystal structure of the Si/VGCF samples were characterized using SEM and TEM. The electrical conductivity, BET specific surface area and pore size of the Si/VGCF composite materials were tested and calculated. The electrochemical properties of the Si/VGCF electrodes were investigated by cyclic voltammetry,galvanostatic charge-discharge measurements and electrochemical impedance spectroscopy. The properties of the Si/VGCF composite materials were compared with other carbon composite materials. The results indicated that Si and VGCF formed ahierarchical network structure, which enhanced the ions and electrons conductive channels. Also, the structure with the rich pores alleviated the volume effect of Si particles during the processes of the intercalation/deintercalation of Li^+, which significantly improved the utilization and electrochemical stability of the electrode active materials. For example, when m(Si)∶m(VGCF) was1∶0.5, the Si/VGCF electrode delivered a reversible capacity of 1470 mA·h/g at a current density of500 mA/g after 100 cycles.