Si/FeSi_x@C-CNTs负极的合成及其储锂电化学性能研究

Synthesis and Electrochemical Properties of Si/FeSi_x@C-CNTs as Anode in Lithium Ion Battery

摘要: 硅具有理论比容量高，工作电压低和资源丰富等特点，被认为是最具潜力的下一代锂离子电池负极材料。但硅材料同时也存在着体积膨胀大(300%)，颗粒易粉化和导电性差等缺点，进而导致硅负极的电化学稳定性和动力学性能难以满足实用要求。本文以廉价的硅铁合金为原料，通过简单的机械球磨和化学气相沉积技术制备了硅碳复合材料Si/FeSi_x@C-CNTs (SFC-CNTs)，其独特结构由Si、导电FeSi_x、无定型碳层、交联碳纳米管网络共同组成，在电化学过程中对硅负极的导电性、锂离子扩散和体积膨胀起到了协同作用。相较于硅铁合金，SFC-CNTs复合材料的性能显著提升，在0.4 A∙g⁻¹的电流密度下放电容量为1466 mAh∙g⁻¹，首次库伦效率为78.2%，经100次循环后的容量仍保持有768 mAh∙g⁻¹。

Abstract: Silicon is considered to be the most potential anode material for the next-generation lithium-ion batteries due to its high theoretical capacity, low operating voltage and abundant sources. However, silicon materials also show some disadvantages, such as large volume expansion (300%), easy pulverization and poor conductivity, thus resulting in the poor electrochemical stability and kinetic properties, which is difficult to meet the practical requirements. In this work, the cheap ferrosilicon is used as raw material to synthesize the Si/FeSi_x@C particles encapsulated in carbon nanotube networks (SFC-CNTs) via the combination of mechanical milling and chemical vapor deposition methods. The unique structure of SFC-CNTs composite consists of Si, conductive Cu3Si, amorphous carbon layer, and the cross-linked CNTs, which can play the synergistic effects on the electronic conductivity, Li+ diffusion and volume expansion of Si anode during electrochemical process. Compared with ferrosilicon, the electrochemical properties of SFC-CNTs composite were significantly improved, which can deliver a discharge capacity of 1466 mAh∙g⁻¹ at 0.4 A∙g⁻¹ with ICE of 78.2%, and retain 768 mAh∙g⁻¹ after 150 cycles.