碳源对Sn-Co/C复合材料显微组织和电化学性能的影响

摘要

The Sn-Co/C composites as anode material for lithium-ion battery were synthesized by solid reaction sintering method using glucose and acetylene black as carbon sources, respectively. The influence of carbon source type on the structures and electrochemical properties of materials was analyzed. The result shows that Sn-Co alloy with Sn and Co mole ratio of 1:1 consists of CoSn phase and minor CoSn2 phase. Most of pyrolytic carbon from glucose and acetylene black exists on the surface of Sn-Co alloy particle, and a few distributes in interior of Sn-Co alloy particle. Therefore, the pyrolytic carbon and acetylene black hinders the transformation reaction of Sn-Co alloy, leading to the residual of a small amount of CoSn2 or Co3Sn2 phase and hindering the growth of grain or particle of Sn-Co alloy at some degree, which refines the grains or particles of Sn-Co alloy. The addition of pyrolytic carbon and acetylene black is beneficial for improving the electronic conductivity and Li+ diffusion in Sn-Co/C composite, and the former is better. The initial discharge capacity of Sn-Co/C composite adding glucose is 325 mA∙h/g at a current density of 0.05 mA/cm2, after 100 cycles the capacity retention is above 70.8%, which is 26.8% higher than that of Sn-Co alloy, therefore, the Sn-Co/C composite has good structure stability.%分别以葡萄糖和乙炔黑为碳源，采用固相烧结法制备Sn-Co/C锂离子电池负极复合材料，探讨碳源种类对材料结构和电化学性能的影响规律。结果表明：摩尔比为1：1的Sn-Co合金由CoSn相和微量CoSn 2相组成；在Sn-Co/C复合材料中，大部分葡萄糖热解炭和乙炔黑存在于Sn-Co合金颗粒表面，少部分进入颗粒内部，会在一定程度上阻碍Sn-Co合金的相变反应，残留微量CoSn 2和Co 3 Sn 2相，同时阻碍Sn-Co合金晶粒或颗粒的长大，起到细化晶粒或颗粒的作用。添加葡萄糖热解炭和乙炔黑有利于提高Sn-Co/C复合材料的电子导电和Li+扩散，从而提高其电化学活性；并且添加葡萄糖的Sn-Co/C复合材料电化学性能更好，在电流密度为0.05 mA/cm2条件下的首次可逆放电容量为325 mA∙h/g，经过100次循环后的容量保持率达到70.8%，循环性能比Sn-Co合金的提高26.8%，显示出良好的结构稳定性。