Cu对Sn-Co/C复合材料结构和电化学性能的影响

分别以单质Cu粉和CuCO3.Cu(OH)2为Cu源,采用固相烧结法制备锂离子电池Sn-Co-Cu/C复合材料,利用SEM、XRD和电池程控测试仪研究Cu对材料结构和电化学性能的影响。结果表明:Sn-Co/C复合材料由CoSn相和微量CoSn2组成,添加Cu粉或CuCO3.Cu(OH)2的Sn-Co-Cu/C均由大量CoSn、α-Co3Sn2和少量CoSn2组成;添加的Cu固溶于Sn-Co合金,使颗粒细化,同时比表面积也增大。添加Cu粉和CuCO3.Cu(OH)2的Sn-Co-Cu/C的首次充电、放电容量分别为467、319 mA.h/g和489、326 mA.h/g,经过40次循环后容量保持率分别为83.4%和86.8%;添加Cu导致多相的形成以及颗粒的细化,增加了Li+的扩散通道和增强了材料的结构稳定性,从而显著改善了材料的电化学性能。

Effects of Cu on structures and electrochemical properties of Sn-Co/C composite

The Sn-Co-Cu/C composites as novel anode material for lithium-ion battery were synthesized using Cu powder and CuCO3·Cu(OH)2 as Cu resource by solid-state sintering, respectively. The influences of Cu on the structures and electrochemical properties of the composites were analyzed by XRD, SEM and charge-discharge measurement. The results show that Sn-Co/C consists of CoSn2 and minor phase CoSn2, and Sn-Co-Cu/C is composed of CoSn, α-Co3Sn2 and a little CoSn2 phase. Cu atoms dissolving in Sn-Co alloy lead to the refinement of grains or particles and the increase of specific surface area. The initial charge and discharge capacity of Sn-Co-Cu/C synthesized from Cu element powders and CuCO3·Cu(OH)2 are 467, 319 mA·h/g and 489, 326 mA·h/g, respectively. After 40 cycles, the capacity retentions of them are 83.4% and 86.8%, respectively. The formation of multiphase and refinement of particles caused by adding Cu is beneficial for accelerating the diffusion velocity of Li ion and enhancing the stability of structure. So, the electrochemical properties are improved significantly.