Effect of silicon/carbon composite on properties of Graphite anode materials in Li-ion batteries

A carbon coated silicon and carbon coated graphite composites ((Si/C)@C) was prepared from silicon nanospheres, citric acid and graphite. Afterwards, (Si/C)@C was added as an additive to graphite to prepare anode material. The structure, morphology and electrochemical properties of the materials were characterized by XRD, SEM, TEM, and constant current charge/discharge tests. The results showed that the anode material consisted of silicon nanoparticles, graphite and carbon, and the silicon particles coated by an amorphous carbon layer. For graphite with different tap density and morphologies, the addition of (Si/C)@C additives can all improve the electrochemical properties of graphite. Among them, the anode material prepared by adding (Si/C)@C to graphite with high tap density and spherical structure has the best electrochemical performance with an initial discharge capacity of 460 mAh/g, a first coulombic efficiency of 89.8%, and a capacity retention of 87% after the 500th cycle.