A low temperature MgH2-AlCl3-SiO2 system to synthesize nano-silicon for high-performance Li-ion batteries

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 406; p. 126805
• Main Authors: Yu, Jiage, Wang, Kun, Song, Wenlong, Huang, Hui, Liang, Chu, Xia, Yang, Zhang, Jun, Gan, Yongping, Wang, Feng, Zhang, Wenkui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2021
• Subjects: High Si yield; Li-ion batteries; Low temperature MgH2-AlCl3-SiO2 melt system; Nano-Si; Low temperature MgH2-AlCl3-SiO2 melt system; High Si yield; Nano-Si; Li-ion batteries
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.126805

[Display omitted] •A new MgH2-AlCl3-SiO2 system is developed to synthesize nano-Si at a low temperature.•The reaction is a controllable liquid-solid process with high Si yield of 97.6% at 200 °C.•The Si-200 product exhibits high reversible capacity and good cycling stability. Nano-silicon is a star anode material for the next generation Li-ion batteries with the merits of high theoretical capacity and low voltage plateau. To date, it remains a great challenge to efficiently convert low-cost silica (SiO2) into nano-Si at a low temperature due to the solid Si-O band (the bond energy is 460 kJ mol−1). Herein, a low temperature MgH2-AlCl3-SiO2 melt system is developed to synthesize nano-Si through the reduction of SiO2 by MgH2 in the molten AlCl3. It is confirmed to be a controllable liquid-solid process with no side reactions and high Si yield of 97.6%. The battery grade nano-Si product can be obtained by suitable post-treatment without undesirable HF etching. This reaction can be initiated at as low as 150 °C, which is much lower than mostly reported synthesis routes of nano-Si. The nano-Si product with an average particle size of 22.4 nm exhibits superior electrochemical storage capacity of 1185 mA h g−1 over 300 cycles at 0.2 A g−1 and a low increased thickness of 14.5% at 2 A g−1 over 500 cycles. We believe that this low temperature melt system not only paves the new path of synthesizing nano-Si, but also gives a new insight into the effects of nanoscale particle size on the electrochemical performance of Si anode.