Si–graphite composites as anode materials for lithium secondary batteries

Two types of Si–graphite (Si–C) composites are synthesized and evaluated for anode materials of lithium secondary batteries. The mechano-chemical milling and the rotational impact blending methods are applied to synthesize two types of Si–C composites. Graphite powders having Si on the surface (type A) is synthesized by mechano-chemical milling using the pitch as a binder. Si embedded inside the graphite particle (type B) is synthesized by rotational impact blending. The loading level of Si is about 20 wt% for both type Si–C composites. The location of Si is verified by observing cross sectional images of particle and conducting EDS mapping. The initial discharge capacity of type B has larger value than that of type A, while the type A shows better cycle performance than type B. The efficiency of first cycle is about 87% for both types A and B.