Improved cyclic stability of Mg2Si by direct carbon coating as anode materials for lithium-ion batteries

Highlights: • Mg2Si is synthesized via a home-built continuous preparing apparatus and the carbon layer has been directly coated by a simple CVD method. • The experimental conditions of the carbon coated process are optimized. • The carbon layer could improve electronic conductivity, buffer volume change and reduce pulverization during the interaction/deintercation. • The Mg2Si/C with low carbon content (1.19%) delivers a stable discharge capacity of 320 mAhg-1 even after 100 cycles. -- Abstract: High-crystalline Mg2Si/C composites with uniform carbon layer were successfully synthesized by the decomposition of C2H2 gas onto the surface of pre-synthesized Mg2Si. The Mg2Si/C composites with a carbon content of 1.19% delivered a discharge capacity of 320 mA h g−1 after 100 cycles and a stable Coulombic efficiency over 95% after the first cycle, which is better than the bare Mg2Si. The uniform carbon layer could enhance the electronic conductivity, buffer the volume change and reduce the pulverization during the charge/discharge process, which might be responsible for the enhanced cyclic performance. The results indicate that the chemical vapor deposition (CVD) of the carbon layer with low carbon content can distinctly enhance the cyclic stability of Mg2Si, which can be extended to other anode materials