硅/碳复合材料的高温热解法制备及其电化学性能

Synthesis and electrochemical properties of silicon/carbon composites prepared by high temperature pyrolysis

采用高温热解方法成功地合成了高容量硅/碳复合负极材料.通过X射线衍射分析、热重分析、扫描电子显微镜观察、透射电子显微镜观察、恒电流充放电测试、循环伏安法等手段研究了复合材料的性能.结果表明:硅/碳复合材料由Si、C以及少量SiO2组成;硅/碳复合材料中碳的质量分数约在39%左右;经电化学性能测试,在电流0.2 m A下,该硅/碳复合材料首次充电容量768 m Ah·g-1,首次库仑效率75.6%,70次循环后可逆比容量仍为529 m Ah·g-1,平均容量衰减率为0.44%.这些性能改善归因于硅/碳复合材料中碳的引进,硅表面存在的碳涂层提供了一个快速锂运输通道,降低了电池的阻抗并且充放电过程中稳定了电极的组成.

Silicon / carbon composites as anode materials for lithium batteries with high power capacity were synthesized by a high temperature pyrolysis method. The performances of the silicon / carbon composites were investigated by X-ray diffraction,thermogravimetric analysis,scanning electron microscopy,transmission electron microscopy,galvanostatic cell cycling,and cyclic voltammetry. It is found that the silicon / carbon composites consist of silicon,carbon and few silicon dioxide phases,and the carbon content is about39%. Electrochemical cycling tests of button cells show that the specific capacity is far more than that of carbon materials. The initial charge capacity of the silicon / carbon composites is 768 m Ah·g^-1at a current of 0. 2 m A and the initial coulombic efficiency is 75. 6%.After 70 cycles the reversible specific capacity is 529. 0 m Ah·g^-1and the average capacity deterioration rate of each cycle is 0. 44%.These improvements can be attributed to the introduction of carbon in the Si / C composites and carbon coatings on the Si surface,which provide a rapid lithium transport pathway,reduce the cell impedance and stabilize the electrode structure during charge / discharge cycles.