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硅/碳復合材料的高溫熱解法制備及其電化學性能

Synthesis and electrochemical properties of silicon/carbon composites prepared by high temperature pyrolysis

  • 摘要: 采用高溫熱解方法成功地合成了高容量硅/碳復合負極材料.通過X射線衍射分析、熱重分析、掃描電子顯微鏡觀察、透射電子顯微鏡觀察、恒電流充放電測試、循環伏安法等手段研究了復合材料的性能.結果表明:硅/碳復合材料由Si、C以及少量SiO2組成;硅/碳復合材料中碳的質量分數約在39%左右;經電化學性能測試,在電流0.2 m A下,該硅/碳復合材料首次充電容量768 m Ah·g-1,首次庫侖效率75.6%,70次循環后可逆比容量仍為529 m Ah·g-1,平均容量衰減率為0.44%.這些性能改善歸因于硅/碳復合材料中碳的引進,硅表面存在的碳涂層提供了一個快速鋰運輸通道,降低了電池的阻抗并且充放電過程中穩定了電極的組成.

     

    Abstract: Silicon/carbon composites as anode materials for lithium batteries with high power capacity were synthesized by a high temperature pyrolysis method. The performances of the silicon/carbon composites were investigated by X-ray diffraction,thermogravimetric analysis,scanning electron microscopy,transmission electron microscopy,galvanostatic cell cycling,and cyclic voltammetry. It is found that the silicon/carbon composites consist of silicon,carbon and few silicon dioxide phases,and the carbon content is about 39%. Electrochemical cycling tests of button cells show that the specific capacity is far more than that of carbon materials. The initial charge capacity of the silicon/carbon composites is 768 m Ah·g-1 at a current of 0.2 m A and the initial coulombic efficiency is 75.6%.After 70 cycles the reversible specific capacity is 529.0 m Ah·g-1 and the average capacity deterioration rate of each cycle is 0.44%.These improvements can be attributed to the introduction of carbon in the Si/C composites and carbon coatings on the Si surface,which provide a rapid lithium transport pathway,reduce the cell impedance and stabilize the electrode structure during charge/discharge cycles.

     

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