In addition to large volume change and sluggish kinetics, the capacity decay of silicon anodes is also related to the formation of a crystalline Li15Si4 phase during cycling. Herein, we have demonstrated that refining cheap coarse-grained Si by ball milling with metal carbides (Mo2C, Cr2C3, etc.) can reduce the Si crystallite size significantly and can thus suppress the formation of the crystalline Li15Si4 during cycling, which increases the life of Si-based anode materials significantly. Si-Cr3C2@few-layer graphene (SC@G) composite anode materials were designed and prepared by plasma milling (P-milling) to achieve a considerable capacity of 881.8 mA h g-1 after 300 cycles at 1 A g-1. A study of the microstructure of the SC@G indicated that the refined amorphous-nanocrystal Si grains were distributed uniformly around multiscale Cr3C2 particles, which were covered by few-layer graphenes. The rigid Cr3C2 skeleton, which acts as a good conductive material, can increase the conductivity of the SC@G composite, avoid the agglomeration of refined Si, and regenerate Si nanosized grains during lithiation and delithiation. These results showed that the SC@G anode material exhibited an excellent overall performance based on its high capacity and long cycle stability, as well as excellent lithium-ion diffusion kinetics for lithium storage.
Keywords: Li15Si4 phase; Si; lithium-ion batteries; metal carbide; plasma milling.