Ultrafine nano-Si material prepared from NaCl-assisted magnesiothermic reduction of scalable silicate: graphene-enhanced Li-storage properties as advanced anode for lithium-ion batteries

• Published in: Journal of alloys and compounds 2017-02, Vol.694, p.208-216
• Main Authors: Wang, Jie, Lü, Hong-Yan, Fan, Chao-Ying, Wan, Fang, Guo, Jin-Zhi, Wang, Ying-Ying, Wu, Xing-Long
• Format: Article
• Language: English
• Subjects: Anode material; Batteries; Carbon; Conductivity; Diffusion length; Electrical resistivity; Electrochemical analysis; Graphene; Lithium; Lithium ion battery; Lithium-ion batteries; Magnesiothermic reduction; Nanoparticles; Nanostructure; Particulate composites; Properties (attributes); Rechargeable batteries; Reduction; Silicon; Stability; Storage batteries
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.09.323

Herein, ultrafine nano-Si has been prepared via a NaCl-assisted magnesiothermic reduction with scalable silicate as Si source. In the high-temperature procedures of magnesiothermic reduction, as an effective heat scavenger, adjuvant NaCl promote the formation of interconnected Si nanoparticles with ultra-small size of 5–10 nm. When used as anode materials for lithium-ion batteries, reduced graphene oxide (rGO) plays a significant role in enhancing the electrochemical performance due to its high conductivity and flexibility by forming the nano-Si/rGO composite. The nano-Si/rGO composite exhibits much improved Li-storage properties in terms of superior high-rate capabilities and excellent cycle stability compared to the pure nano-Si as well as the micro-Si prepared from no addition of NaCl. It can deliver a high specific capacity of 1955 mA h g−1 at 100 mA g−1 with high initial columbic efficiency of >80%. In addition, nano-Si/rGO exhibits superior rate capability (891 mA h g−1 at 5 A g−1). The significantly enhanced Li-storage properties could be attributed to the synergistic effects of highly conductive rGO and nanosized Si particles in the nano-Si/rGO. While the former can improve the electrical conductivity, the latter will decrease the Li+ diffusion length, improve the capacity and optimize the cycling stability. [Display omitted] •Ultrafine nano-Si was prepared via a NaCl-assisted magnesiothermic reduction.•Heat scavenger NaCl promotes the formation of silicon nanograins of 5–10 nm.•Raw material is highly cheap and scalable silicate, promising its practicability.•Graphene nanosheets improve the Li-storage properties of nano-Si as anode for LIBs.•Final nano-Si/rGO exhibits high reversible capacity and superior rate capability.