Chem. J. Chinese Universities ›› 2021, Vol. 42 ›› Issue (8): 2500.doi: 10.7503/cjcu20210165

• Physical Chemistry • Previous Articles     Next Articles

A Highly Efficient One-step Preparation Method of Nano-silicon and Carbon Composite for High-performance Lithium Ion Batteries

WU Zhuoyan1(), LI Zhi2, ZHAO Xudong2, WANG Qian1, CHEN Shunpeng3, CHANG Xinghua4, LIU Zhiliang2()   

  1. 1.Comprehensive Energy Research Center,Institute of Science and Technology,China Three Gorges Corporation,Beijing 100038,China
    2.Key Laboratory of Superlight Materials and Surface Technology,Ministry of Education,College of Materials Science and Chemical Engineering,Harbin Engineering University,Harbin 150001,China
    3.Beijing National Laboratory for Molecular Science,College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China
    4.Key Laboratory for Mineral Materials & Application of Hunan Province,School of Mineral Processing and Bioengineering,Central South University,Changsha 410083,China
  • Received:2021-03-11 Online:2021-08-10 Published:2021-08-05
  • Contact: WU Zhuoyan E-mail:wu_zhuoyan@ctg.com.cn;zhiliangliu@hrbeu.edu.cn

Abstract:

Lithium-ion batteries(LIBs) have been widely applied in portable electronic devices and electric vehicles and energy storage industries. However, with the rapid development of our society, it is more and more difficult to meet the increasing demand of people for commercial LIBs because their energy densities are generally lower than 250 W·h/kg. Thus, it is urgent to further develop higher-capacity electrode materials to efficiently increase the energy densities of LIBs. Silicon is a very attractive anode material for LIBs with superhigh theoretical capacity(4200 mA·h/g), suitable working potential and abundant earth reserve. Although the pure Si material suffers from poor cycling performance due to very large volume change during repeated lithiation/delithiation, recent researches have shown that the homogeneous carbon composite for nano-silicon could improve the cycling performance effectively. But the preparation methods of nano-silicon and carbon composite are still very complicated, limiting the large-scale preparation and application. A highly efficient one-step method to synthesize the homogeneous composite between nano-silicon and carbon sheet(nano-Si/C) was developed through mechanically milling SiCl4, Mg2Si and commercial carbon sheets. During the milling process, nano-Si is produced from the bottom-up reduction of SiCl4. The in situ formed nano-Si can directly grow on the carbon sheet, further leading to homogeneous composite between nano-Si and carbon sheet. This method possesses a very high reaction efficiency as reactants convert into nano-Si and MgCl2 completely without the gene-ration of any impurities. The scanning electron microscopy(SEM) and transmission electron microscopy(TEM) display that the nano-Si supported on carbon sheet is around 30—80 nm in diameter. As the anode material for LIBs, the nano-Si/C sample shows a very high reversible capacity(2450 mA·h/g at 0.2 A/g), good rate performance(1040 mA·h/g at 4.8 A/g) and excellent long cycling stability(retaining 1400 mA·h/g even after 600 cycles at 2 A/g). The cyclic voltammograms of nano-Si/C at different sweep rates demonstrate the electrochemical kinetics is controlled by both lithium diffusion process and pseudocapacitance effect. The outstan-ding electrochemical performance is mainly attributed to the uniform composite nanostructures between small-sized nano-Si and carbon sheet, which can maintain the structural integrity and stable electrochemical properties after lithiation/delithiation cycles, as suggested by the electrochemical impedance spectroscopy and SEM images tested after cycles. Combining cheap reactants, simple preparation step and homogeneous composite structure, this method is very promising for low-cost and large-scale preparation of high-performance Si and carbon composite anode with good application prospect.

Key words: Lithium-ion battery, Anode material, Nano-Si/C composite, One-step synthesis method

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