利用机械球磨法得到Si和Mn原子比为3: 5的复合材料, 将此材料与20 wt%的石墨混合球磨得到Si3Mn5/C复合材料. 利用X射线衍射(XRD)和扫描电子显微镜(SEM)分析材料的物相和电极的微观结构. 结果表明: 所得材料中没有Si-Mn二元新相的生成, 材料的颗粒尺寸为0.5～2.0μm. 碳的加入抑制了活性中心Si在循环过程中的较大结构变化, 且Si-Mn复合物颗粒均匀地分散在碳的网格中, 增加了复合材料的电接触. 合成样品的电化学测试表明, 石墨的添加提高了Si-Mn复合材料的可逆容量和循环性能. Si-Mn/C复合物的首次可逆容量为347mAh·g-1, 充放电效率为70%. 进而经200℃热处理的Si-Mn/C电极的首次可逆容量为463mAh·g-1, 充放电效率为70%. 在30个循环后复合材料仍保持426mAh·g-1的可逆容量, 充放电效率稳定在97%以上.
Si-Mn/C composite was obtained by sequentially ball-milling the mixture of the silicon and manganese powders (atomic ratio of 3:5), followed by the addition of 20wt% graphite. The phase structure and morphology of the composite were analyzed by X-ray diffraction (XRD) and scanning electronmicroscope (SEM). The results of XRD showed that there was no new alloy phase in the composite obtained by ball milling. SEM micrographs confirmed that particle size was about 0.5～2.0μm and the addition of the carbon restrained the morphological change of active center (Si) during cycling. The Si-Mn particles were dispersed among the carbon matrix homogeneously, which ensured a good electric contact. Electrochemical tests showed that the material obtained by adding carbon achieved better reversible capacity and cycleability. The Si-Mn/C composite had a reversible capacity of 347mAh·g-1 and a coulombic efficiency of 70%, and the Si-Mn/C composite electrode annealed at 200℃ revealed a reversible capacity of 463mAh·g-1 and a charge-discharge efficiency of 70%. Moreover, the reversible capacity retained 426mAh·g-1 after 30 cycles with a charge-discharge efficiency of over 97
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