锂离子电池硅炭负极材料的制备与电化学性能研究

Synthesis and electrochemical properties of nano-Si/C composite anodes for lithium-ion batteries

  • 摘要: 利用微胶囊技术将酚醛树脂包覆于纳米硅表面,然后在氩气保护下高温炭化,制得硅炭复合负极材料。首先采用4种不同质量比的酚醛树脂与纳米硅制备了硅碳复合材料,得到了不同炭质厚度的硅碳复合材料。通过对其循环性能和倍率性能的比较,发现酚醛树脂与纳米硅的质量比为1∶4,即碳层厚度为4.5 nm时,电化学性能最佳。随后对该种硅碳复合材料的综合电化学性能进行了测试,该材料作为负极制备的锂离子电池具有良好的电化学性能,在电流密度为100 mA g−1的条件下,其首次放电比容量为2382 mAh g−1,首次充电比容量为1667 mAh g−1,首次库伦效率为70%。经200次充放电循环后放电比容量为835.6 mAh g−1,库伦效率为99.2%。此外,其倍率性能非常优异,在100、200、500、1000、2000及100 mA g−1电流密度下,其平均放电比容量分别为1716.4、1231.6、911.7、676.1、339.8及1326.4 mAh g−1

     

    Abstract: Phenolic resin was coated on the surface of nano-Si by a microencapsulation technique, and then carbonized under Ar protection to prepare a nano-Si/C composite. The composites were first prepared using 4 different mass ratios (1∶2, 1∶4, 1∶6, 1∶8) of phenolic resin to nano-Si. The obtained average thicknesses of amorphous carbon coating were 7, 4.5, 3.7, 2.8 nm, respectively. By comparing the cycling and rate capability, the best electrochemical performance was obtained when this ratio was 1∶4, with a 4.5 nm amorphous carbon coating. The electrochemical properties of this material were then comprehensively evaluated, showing excellent electrochemical performance as an anode material for Li-ion batteries. At a current density of 100 mAg−1, the material had a first specific discharge capacity of 2 382 mAhg−1, a first charge specific capacity of 1 667 mAhg−1, and an initial coulombic efficiency of 70%. A discharge specific capacity of 835.6 mAhg−1 was retained after 200 cycles with a high coulombic efficiency of 99.2%. In addition, the nano-Si/C composite demonstrated superior rate performance. Under current densities of 100, 200, 500, 1 000 and 2 000 mAg−1, the average specific discharge capacities were 1 716.4, 1 231.6, 911.7, 676.1 and 339.8 mAh g−1, respectively. When the current density returned to 100 mA g−1, the specific capacity returned to 1 326.4 mAh g−1.

     

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