【作者】 李强；

【导师】 杨绍斌；

【作者基本信息】 辽宁工程技术大学 ， 材料学， 2009， 硕士

【摘要】 本文重点研究了过度金属元素Fe对锂离子电池锡钴合碳负极材料的结构和电性能的影响。采用固相烧结的方法首先制备SnxCoy/C复合材料,然后制备了SnxCoyFe0.2/C复合材料,在最优体系的基础上制备SnCoFex/C复合材料。XRD分析发现,在SnxCoy/C复合材料中,Sn2Co/C由CoSn2、CoSn相和少量Sn单质组成;SnCo/C含有CoSn相;Sn2Co3/C含有Co3Sn2相。在SnxCoyFe0.2/C样品中,Sn2CoFe0.2/C由CoSn2、CoSn相和少量Sn单质组成;SnCoFe0.2/C含有CoSn相,少量的Co3Sn2相形成;Sn2Co3Fe0.2/C只含有Co3Sn2相。添加的Fe元素以置换固溶的形式存在,添加Fe元素有助于细化晶粒。在SnCoFey/C样品中随着Fe含量的增大,SnCoFe0.1/C和SnCoFe0.2/C在CoSn主相基础上,新形成Co3Sn2相,随着Fe含量的继续增大先又形成少量FeSn2相以及Co和Sn相。并且随着Fe含量的增加晶粒尺寸也在减小。另外对所有烧结样品进行球磨,晶粒都得到了一步的细化。电性能测试表明,在SnxCoy/C复合材料中,首次放电容量和首次充放电效率都随着Sn含量的增加,Sn2Co/C样品的首次放电容量和首次充放电效率最大,分别为551mAh/g和77.5%;而循环性能则随着Sn含量的增加而减小,其中Sn2Co3/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88.4%;在SnxCoyFe0.2/C样品中,电性能与SnxCoy/C样品的电性能规律类似,Sn2CoFe0.2/C首次放电容量和首次充放电效率最大,分别为565mAh/g和86.7%;而循环性能则随着Sn含量的增加而减小,其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%。与SnxCoy/C相比,添加Fe后,放电容量、充放电效率和循环性能均有提升。在SnCoFey/C样品中,随着Fe含量的增加,SnCoFex/C的首次放电容量和充放电效率呈现先增加后减小,SnCoFe0.3/C的首次放电容量和充放电效率接近最大值,分别为359mAh/g和74%,经过25次充放电后放电容量保持了首次放电容量的91.4%。更多还原

【Abstract】 A novel investigate the influence of Fe on structures and electrochemical performance of Sn、Co and C anode composite material. Using solid-phase sintering and then ball milling, SnxCoy/C composite material,are prepared and then SnxCoyFe0.2/C composite material are prepared. In the optimal system, SnCoFex/C composite material are prepared.The results of X-ray diffraction indicated that in SnxCoy/C composite material, Sn2Co/C consists of CoSn2、CoSn phase and a small amount of elementary substance of Sn; SnCo/C contains SnCo phase; Sn2Co3/C contains Sn2Co3 phase. In SnxCoyFe0.2/C samples, Sn2CoFe0.2/C consists of CoSn2、CoSn phase and a small amount of elementary substance of Sn; SnCoFe0.2/C contains SnCo phase and a small amount of Sn2Co3 phase. Sn2Co3Fe0.2/C contains Sn2Co3 phase. Fe exist with the form of solid solution, and contributes to grain refinement. In SnCoFey/C samples, with increasing content of Fe, Co3Sn2 is formed firstly on the matrix of CoSn phase Then a little amounts of FeSn2、Co and Sn are formed. And with increasing content of Fe, grain sizes reduce. Besides, grain of sintered samples using milling could be further refined.Electrical performance test showed that in SnxCoy/C composite material, initial discharge capacity and initial charge-discharge efficiency are both improved with increasing content of Sn, ,while the cycle performance is decreasing. In SnxCoyFe0.2/C samples, initial discharge capacity and initial charge-discharge efficiency are also improved with increasing content of Sn,, while the cycle performance is decreasing; Compared with SnxCoy/C, initial discharge capacity、initial charge-discharge efficiency and the cycle performance are improved. In SnCoFey/C samples, with increasing content of Fe, the initial discharge capacity and initial charge-discharge efficiency are both improved first and then are decreasing, and the cycle performance is improved first and then tended to be stable;The initial discharge capacity and initial charge-discharge efficiency of SnCoFe0.3/C are the largest, and they are respectively 359mAh/g and 74%,and the reversible capacity remains above 91.4% of the initial discharge capacity after 25 charge-discharge cycles.更多还原