低含量微米硅改性石墨负极及其倍率性能提升

Modification of graphite anode with low-content micro-Si for enhanced rate capability

  • 摘要: 石墨负极材料因具备高充放电效率、低嵌锂电位、良好的安全性能等特性,在新能源领域得以广泛应用。但其比容量提升空间有限、倍率性能较差,难以满足如今新能源领域市场需求。本文以商业石墨和微米硅为原料,经异丙醇分散后,在球磨机中以5∶1的球料质量比、240 r/min转速进行物理结合,探究了低含量微米硅对石墨负极材料性能的影响规律。当两者质量比为19∶1时,所得5%-mSi/Gr负极在0.3 C电流密度下,其首次放电比容量为428.86 mAh/g,首次库仑效率为80.77%;在0.5 C电流密度下,200次循环后放电比容量为302.94 mAh/g,容量保持率(75.91%)远高于传统石墨负极(29.32%)。结果表明:本研究通过在石墨中引入低含量微米硅制备的改性石墨负极,不仅在一定程度上提高了石墨负极整体的比容量,还有效提升了其倍率性能。该研究成果为低成本制备锂离子电池用石墨负极并提升其倍率性能提供了参考。

     

    Abstract: Graphite anode materials have advantages such as high charge and discharge efficiency, a low lithium intercalation potential, and good safety, and have been widely applied in the field of new energy. However, their relatively low specific capacity and limited rate performance make it difficult to meet current market demand in the new energy sector. In this paper, commercial graphite and micron-sized silicon were used as raw materials. After dispersed in isopropyl alcohol, they were physically combined in a ball mill at a ball-to-material ratio of 5:1 and a rotational speed of 240 r/min. The influence of the mass ratio of graphite to silicon on the performance of the composite materials was investigated. When the mass ratio of the two materials was 19:1, the obtained 5%-mSi/Gr anode delivered an initial discharge specific capacity of 428.86 mAh/g with an initial coulombic efficiency of 80.77%, at a current density of 0.3 C. At a current density of 0.5 C, the discharge specific capacity was 302.94 mAh/g after 200 cycles, with a capacity retention rate of 75.91%, which is significantly higher than that of the conventional graphite anode (29.32%). These results show that introducing a low content of micron-sized silicon into the graphite anode, not only increases the overall specific capacity of the material to a certain extent, but also effectively improves the rate performance of the graphite anode. This work provides an experimental reference for improving the rate performance of low-cost graphite anodes for lithium-ion batteries.

     

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