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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.
The high-capacity silicon / carbon composite negative electrode material was successfully synthesized by high-temperature pyrolysis method and characterized by X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, galvanostatic charge-discharge test and cyclic voltammetry The results show that the silicon / carbon composites are composed of Si, C and a small amount of SiO2. The mass fraction of carbon in the silicon / carbon composites is about 39%. After the electrochemical tests, A, the initial charge capacity of the silicon / carbon composite material is 768 m Ah · g-1, the first coulombic efficiency is 75.6%, and the reversible specific capacity after 70 cycles is still 529 mAh · g-1. The average capacity decay rate is 0.44% These improvements in performance are attributed to the introduction of carbon in silicon / carbon composites, the presence of carbon coatings on the silicon surface provides a fast lithium transport path, reducing the impedance of the cell and stabilizing the electrode composition during charging and discharging.