Fe对Sn_xCo_y/C负极材料电性能的影响

Influence of Fe on electrochemical performance of Sn_xCo_y/C anode materials

采用固相烧结和球磨相结合的方法制备了锂离子电池负极复合材料SnxCoy/C和SnxCoyFe0.2/C(x:y分别取2:1、1:1、2:3),考察了Fe对SnxCoy/C复合材料结构和电化学性能的影响。XRD分析表明,对于未添加Fe的烧结样品,x:y=2:1体系由CoSn2、CoSn相和少量Sn单质组成;x:y=1:1体系由CoSn相组成;x:y=2:3体系由Co3Sn2相组成。添加Fe以后,在x:y=2:1和2:3体系的物相都未发生改变,而x:y=1:1体系有新相Co3Sn2生成。并且XRD计算还表明,Fe的添加有助于晶粒细化。另外,对所有烧结样品进行球磨会使晶粒进一步细化。电性能分析表明,对于未添加Fe的球磨样品,首次放电容量和首次充放电效率都随着Sn含量的增加而增加,而循环性能则随着Sn含量的增加而减小。添加Fe的球磨样品,与未添加Fe的样品相比,首次放电比容量、充放电效率和循环性能都增大,并且添加铁的球磨样品的首次放电容量和充放电效率随着Sn含量的增加而增加,Sn2CoFe0.2/C的首次放电比容量和充放电效率最大,分别为565mAh/g和86.7%;而循环性能随着Sn含量的增加而减小。其中Sn2Co3Fe0.2/C的循环性能最好,经过25次充放电后放电容量保持了首次放电容量的90.9%。

SnxCoy/C and SnxCoyFe0.2/C（x：y=1：2,1：1,2：3） composites as anode materials for lithium-ion batteries were prepared using solid-state sintering and ball milling,and the influences of Fe on the structures and the electrochemical properties of SnxCoy/C composites were investigated.For the sintered samples without addition of Fe,XRD illustrates that system of x：y=2：1 consists of CoSn2、CoSn phase and a small amount of elementary substance of Sn;the system of x：y=1：1 consists of CoSn phase;system of x：y=2：3 consists of Co3Sn2 phase.The samples of addition of Fe,all of phases did not change in the system of x：y=2：1 and 2：3,but new phase of Co3Sn2 was formed in the system of x：y=1：1.XRD illustrates that the addition of Fe contributed to the grain refinement.In addition,the grain of sintered samples using milling can be further refined.The electrochemical analysis show that for the sintered samples of no addition of Fe,the initial discharge capacity and initial charge-discharge efficiency are both improved with increasing content of Sn,but cycle performance is improved with decreasing content of Sn.Compared with the samples without addition of Fe,the initial discharge capacity and initial charge-discharge efficiency are both improved for samples of addition of Fe,and the initial discharge capacity and the initial charge-discharge efficiency are both improved with increasing content of Sn.The initial discharge capacity and initial charge-discharge efficiency of Sn2CoFe0.2/C is the largest,which is 565 mAh/g and 86.7%,respectively.But the cycle performance is decreasing with the Sn content increased.The cycle performance of Sn2Co3Fe0.2/C is the best of them.The reversible capacity remains above 90.9% of the initial discharge capacity after 25 charge-discharge cycles.