Synthesis of Iron silicide-based composite particulates and their performance for lithium-ion battery negative electrode

We have fabricated the composite particulate aggregates, of which Iron silicides, Ca-Si compound and Si are tightly compounded, and evaluated their performance for the lithium-ion battery negative electrode. The particulates are prepared by the solid-state reaction between the layered CaSi₂ and FeCl₂ using our proposed `Solid-State Exfoliation Reaction (SSER)´ route. The Ca-Si compound is the material that was expected to have similar crystal structure to the layered CaSi₂. The co-existing Iron silicides are the materials with well-known phases (FeSi and Fe₃Si), however, they are fine particles. The fabricated composite particulates show a capacity per volume, at first cycle, ~ 6 times larger than that of the artificial graphite, MCF. The particulates with larger amount of Ca-Si compound and Si phases show higher capacity. It is suggested that fine particles of the Ca-Si compound and Si would work as the Li ion storage sites leading to such an excellent capacity values.