Carbon Coated Si-Metal Silicide Composite Anode Materials Prepared by High-Energy Milling and Carburization for Li-Ion Rechargeable Batteries

In this article, we report a novel Si-Metal silicides/Carbon composite anode material for lithium-ion rechargeable batteries. The composite powder comprised of Si, FeSi 2 and CrSi 2 were synthesized by high-energy mechanical milling and then a primary carbon was formed over the Si-silicide at 900°C. The prepared composite powder was agglomerated and subsequently a thin carbon layer was coated. The X-ray diffraction results revealed that the Si and silicide crystal size decrease with respect to milling time. The critical milling time to achieve the completely nano-scale powders was 5 h. The composite powder exhibits randomly distributed carbon-coated Si-silicide. The TEM microstructure revealed homogeneous distribution of nanocomposite powder consists a very fine nanoparticles of the order of ∼30 nm. The prepared Si-silicide/C composite powders exhibited good capacity retention with an average coulombic efficiency of 99.6%. The composite powders showed good cyclability, 1076 mAh g −1 at 50 th cycle and 959 mAh g −1 at 100 th cycle. The electrode internal microstructure revealed a shell-like carbon-coated Si-silicide phases, and a complete amorphization of nanocrystalline Si during the initial cycling, while the inactive silicide phase remains unchanged. Consequently, the size reduction of Si-silicide and carbon coating over it greatly enhanced the cycling performance of the electrode.