锡钴合金电沉积层的结构与锂离子嵌脱行为

Structure and Properties of Electrodeposited Sn-Co Alloy Electrodes as Anode Material for Lithium-Ion Secondary Batteries

应用电沉积方法制备Sn-Co合金镀层.X-射线衍射和扫描电子显微镜分析表明,该Sn-Co合金镀层为六方固溶体结构,含Co量为20%的Sn-Co合金,其沉积层呈现(110)择优取向.表面微孔随沉积层Co含量的增加而增多.以Sn-Co合金镀层作锂离子电极材料,电化学性能测试表明,其首次充电曲线表现出锡钴合金、锡及锡氧化物与锂合金化的多个反应综合特征,随后的充电曲线趋于稳定,呈现L i-Sn-Co合金化反应特征;具有择优取向和多孔结构的Sn-Co合金电极材料的充放电性能较好,首次库仑效率为63.9%,经过20次充放电循环后,其充电容量为461mAg/h,库仑效率为99%.

The Sn-Co alloy deposits were prepared by eleetroplating. The structure and electrochemical performanee of the eleetroplated Sn-Co alloys have been investigated in detail. Experimental results show that the porous Sn-Co alloy film exhibits hexagonal solid solution, with Sn as the solvent, Co as the solute. The texture of the Sn-Co alloy coating exhibits （110） preferred orientation. Eleetroehemical tests show that the porous Sn-Co alloy coating electrodes can deliver a discharge capacity of 643mAh/g in the first cycle. At the 20b cycle the charge was 461mAh/g. At initial charge curve the irreversible capacity is probably associated to a combination of processes, which may include the reduction of small amount of tin dioxide and cobalt oxide on electrode surface, solvent decomposition and the formation of a passivating film on the electrode surface. The porous Sn-Co alloy electrodes can partly accommodate the volume expansion and phase transition during cycling, and would improve the cycle life of the electrode. They are also beneficial to diffusion of Li into/out of maeroporous materials, and improve dischargeability/ehargeability at charge discharge cycle.