锂离子电池高比容量FeSn_2-C复合负极材料的合成与性能

Sn基合金负极材料具有高达990 mAh·g-1的理论比容量,但其也存在因脱嵌锂过程发生巨大的体积变化而导致循环性能较差的问题.本文以Sn、Fe、石墨为原料利用简易的高能球磨法成功制备了具有核壳结构的FeSn2-C复合物,系统研究了球磨时间、FeSn2相含量对材料物相结构及电化学性能的影响,并分析了电极的失效机理.研究表明,球磨时间的增加有利于FeSn2金属间化合物相的形成及材料颗粒的细化,进而有利于材料比容量的增加及循环性能的提升;FeSn2相含量的增加能够提高FeSn2-C材料的比容量,但会降低FeSn2-C电极的循环稳定性.经工艺优化及组分调节,球磨24 h合成的Sn20Fe10C70材料具有最优的电化学性能,材料的比容量在540mAh·g-1左右,并能稳定循环100次,是一种非常有发展前途的锂离子电池高比容量负极材料.

Synthesis and Properties of FeSn2-C Composites as Anode Materials for Lithium-Ion Batteries

Tin has a theoretical specific capacity as high as 990 mAh·g^-1, and is thus a potential anode material for high-energy-density lithium-ion batteries. However, it suffers from a huge volume change during lithiation/delithiation process, leading to poor cycle performance. In this paper, core/shell structured FeSn₂-C composites were successfully synthesized by a simple high-energy ball milling technique with Sn, Fe, and graphite powder as raw materials. The FeSn₂-C composite was evaluated as an anode material for lithium-ion batteries. The influence of milling time and final phase composition on the microstructure and electrochemical performance of FeSn₂-C composites was systematically investigated. The failure mechanism of the FeSn₂-C electrode was also analyzed. The results reveal that long milling time can promote the mechanical alloying process of the FeSn₂ phase and reduce the particle size of the FeSn₂-C composite, which are beneficial for the increase of the specific capacity and the improvement of the cycle performance of the FeSn₂-C electrode. A high FeSn₂ phase content leads to a high specific capacity of the FeSn₂-C composites but poor cycling stability of the electrode. The optimized Sn₂₀Fe₁₀C₇₀ composite prepared by ball milling for 24 h (500 r ·min^-1) shows the best electrochemical performance with a capacity about 540 mAh·g^-1 for 100 cycles. The synthesized Sn₂₀Fe₁₀C₇₀ composite is a promising anode material for highenergy-density lithium-ion batteries.