Sn_(0.35-0.5x)Co_(0.35-0.5x)Zn_xC_(0.30)复合材料的制备及电化学性能

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Sn_0.35-0.5xCo_0.35-0.5xZn_xC_0.30 (摩尔分数x分别为0, 0.05, 0.10, 0.15和0.20), 考察了Zn添加量对材料结构和电化学性能的影响. 烧结粉末样品的XRD分析表明, 随着Zn含量的增多, 在CoSn主相基础上, 先形成少量CoSn₂相, 随后形成少量Co₃Sn₂, Zn和Sn相. 大部分 Zn原子固溶于CoSn相. 电性能分析表明, 随着Zn含量的增加, 首次放电容量和充放电效率都呈现先增加而后趋于稳定的趋势, 当x=0.15时, 首次放电容量和充放电效率都接近最大值, 分别为343 mA-h/g和73.8%; 经过 25 cyc充放电后放电容量保持了首次放电容量的87.6%. 这表明Zn原子固溶引起的晶格畸变和多种相生成导致相界数量的增多, 加快了Li⁺动力学扩散速度, 从而显著改善了电化学性能. 选择烧结粉末样品Sn_0.275Co_0.275Zn_0.15C_0.30进行球磨, 晶粒和颗粒的细化使样品的放电容量显著提升, 但对首次放电效率和循环性能改善不明显.

SYNTHESIS AND ELECTROCHEMICAL PROPERTIES OF Sn_(0.35-0.5x)Co_(0.35-0.5x)Zn_xC_(0.30) COMPOSITE

A series of Sn_0.35-0.5xCo_0.35-0.5xZn_xC_0.30(x=0, 0.05, 0.10, 0.15, 0.20) composites as novel anode materials used in lithium-ion batteries were synthesized from Sn, Co, Zn element powders and carbon black using solid-state sintering and ball milling, and the influences of Zn content on the structures and the electrochemical properties of those materials were analyzed. XRD data of the sintered powders illustrated that minor amount phase CoSn₂ is formed firstly in the CoSn matrix phase with increasing content of Zn. Then, a little amounts of Co₃Sn₂, Zn and Sn are also precipitated. Most of Zn atoms dissolve into CoSn phase and lead to lattice distortion of the matrix. As a result, the lattice parameters a, c and unit cell volume V of CoSn phase are all reduced first and then enlarged with increasing content of Zn. Electrochemical analysis showed that the initial discharge capacity and initial charge-discharge efficiency are both improved first and then tended to stablility with increasing content of Zn, and as x=0.15, reach the maximums, 343 mA-h/g and 73.8%, respectively. The reversible capacity remains above 87.6% of the initial discharge capacity after 25 charge-discharge cycles. The lattice distortion caused by Zn solution and the formation of multiphase are beneficial for accelerating the diffusion of Li⁺ and enhancing the stability of structure, so the electrochemical properties are improved significantly. The sintered powder Sn_0.275Co_0.275Zn_0.15C_0.30 was milled for different times (t=10, 20 and 30 h), and it is shown that the refinements of grains and particles improved discharge capacity obviously, however, charge-discharge efficiency and cycle performance changed little.