Addition of Cu for carbon coated Si-based composites as anode materials for lithium-ion batteries

A carbon coated Si-Cu3Si-Cu composite, prepared by simple precipitation and pyrolysis, was investigated as an anode material for lithium-ion batteries. Electrochemical tests demonstrated that the first charge and discharge capacities of the material were about 830 and 680 mAh/g, respectively, with 82% of the first cycle efficiency. Ex situ X-ray diffractometer indicates that copper silicide formed during pyrolysis is not an active material for electrochemical reaction with lithium, and is believed to improve the electrical contact during cycling. The cycle life performance of this material showed that the initial discharge capacity of 680 mAh/g could be maintained up to 87% after 30 cycles. The improved cycling performance was attributed to enhanced electrical contact by metal silicide and pyrolyzed carbon.