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-  2018 

Preparations and Electrochemical Performances of Carbon Coated Silicon/Graphite Composites

DOI: 10.13208/j.electrochem.170728

Keywords: 锂离子电池,负极材料,硅基复合材料,碳包覆,
lithium ion battery
,anode materials,silicon-based composite materials,carbon coating

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摘要 本文以工业硅粉(600目)为原料,通过高能球磨和热解包碳方法制备了碳包覆纳米硅,在此基础上采用简单的机械球磨方法制备了碳包覆/石墨复合材料,并系统研究了碳包覆量及硅/石墨比例对碳包覆硅/石墨复合材料电化学性能的影响. 与商业纳米硅粉/石墨复合材料相比,工业硅粉/石墨复合材料的循环性能及倍率性能均得到改善. 通过高能球磨和热处理法得到的碳包覆材料为无定形碳和晶态硅材料的复合,所获碳包覆硅材料一次颗粒的粒径在100 ~ 200 nm左右. 碳包覆量对材料的电化学性能有着重要影响,Si/C-2-1复合材料表现出高的可逆比容量、良好的倍率性能和循环稳定性,在0.1C倍率下,可逆比容量高达492.6 mAh·g-1,循环100周后容量保持率达 85.8%,1C 电流密度下放电比容量达369.7 mAh·g-1,为 0.1C 的73.9%. 提高碳包覆硅/石墨复合材料中硅含量的比例可以提升其比容量,当硅含量达到20%时,Si/C-2-3复合材料在0.1C倍率下可逆比容量达到600.4 mAh·g-1,但材料循环性能有所下降,说明石墨在稳定硅/碳复合材料循环性能方面发挥着非常重要的作用.
In this work, the carbon coated silicon (Si@C) composite materials were synthesized based on the industrial silicon powder (600 meshes) via a high energy ball milling combing with in-situ carbon coating (carbonization) method. The Si@C/graphite (Si/C) composite anode materials were prepared by a simple mechanical ball-milling approach. The effects of carbon coating and the ratio of Si to graphite on electrochemical performances of Si/graphite composite materials were investigated systematically. Compared with the nano-Si/graphite composites, the Si/C composites showed higher reversible capacity, better rate capability and cycle performance. The Si@C materials composited of amorphous carbon and crystal silicon with the primary particles size of 100 ~ 200 nm. The Si/C-2-1 composite also revealed high reversible specific capacity, good rate performance and cycling stability. The Si/C-2-1 exhibited the reversible capacity of 492 mAh·g-1 with a capacity retention of 85.8% after 100 cycles at 0.1C. Moreover, the reversible discharge capacity reached 369.7 mAh·g-1 when cycled at 1C, corresponding to 73.9% of that at 0.1C. The Si/C-2-3 which contained 20% silicon displayed a higher reversible capacity of 600.4 mAh·g-1 when cycled at 0.1C. However, the cycling stability of these composites decreased with increasing Si content, indicating that the graphite content played an important role to improve the cycle performance of the composite


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