Si/VGCF复合材料的储锂性能

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。

Lithium storage properties of Si/VGCF composite electrodes

Nano-silicon particles and vapor-grown carbon fiber composites (Si/VGCF) were prepared by liquid phase mixing method in order to improve the conductivity and cycling stability of the silicon anode of lithium ion batteries. The preparation conditions of the Si/VGCF, the optimum content of VGCF were investigated. The morphology and crystal structure of the Si/VGCF materials were characterized using Scanning Electron Microscopy and Transmission Electron Microscopy. The electrical conductivity, BET specific surface area and pore size of the Si/VGCF composites were tested and calculated. The electrochemical properties of Si/VGCF electrodes were tested by using cyclic voltammetry, galvanostatic charge-discharge and alternating current impedance methods. The results indicate that the hierarchical network structure formed by Si and VGCF has abundant ions and electrons conductive channels. Also, the structure with the rich pores can alleviates the volume effect of Si particles during the processes of the intercalation/deintercalation of Li , which significantly improves the utilization and electrochemical stability of the electrode active materials. When m(Si):m(VGCF) is 1:0.5, the Si/VGCF electrode delivers a reversible capacity of 1470 mAh?g-1 at a current density of 500 mA?g-1 after 100 cycles.