Preparation of nanographite sheets supported Si nanoparticles by in situ reduction of fumed SiO2 with magnesium for lithium ion battery

• Explore low cost methods for the preparation of Si/nanographite sheets (Si/NanoGs) composite materials for Li ion battery.
• Prepared nanographite supported Si nanoparticles by direct Mg thermal reduction of mixtures of fumed SiO2 and nanographite.
• Si nanoparticles with average diameter of 20 nm and sheet like morphology are formed on the surface of nanographite sheets.
• Si/NanoGs materials show excellent electrochemical performance.

This work explores low cost methods for the preparation of Si/nano-graphite sheets (NanoGs) composite materials for Li ion battery. The Si/NanoGs composites are prepared by magnesium thermal reduction of mechanical mixture of fumed SiO2 and NanoGs under Ar atmosphere. The structure of the samples is characterized by XRD, Raman spectroscope, SEM, and HRTEM. The results show that highly crystallized Si nanoparticles with a sheet-like morphology are uniformly distributed on the surface of NanoGs (both edge and a-b plane). The average diameter of Si nanoparticles is ∼20 nm. Electrochemical characterization shows that an electrode has an initial lithium storage capacity of 1702.9 mAh g−1 at a current of 100 mA g−1. The storage capacity decreases to 975.7 mAh g−1 after 100 cycles. Since cheap commercial fumed SiO2 and graphite are used and the process is simple and easy to scale up, with further improvement, the method has potential for use in large scale production of high energy density Si/NanoGs anode materials at low cost.

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