Here, we have adopted a new carbon coating with vitreous carbon derived from furfuryl alcohol. The vitreous carbon structure, formed after carbonization heat treatment at relatively lower temperatures, with inherently higher strength, hardness, resistance to chemical reaction, as well as lower porosity and permeability may result in better carbon coating layer. For the anode material, we combined chemically inert phase such as silicides with silicon into nanostructured composite particles which should have a much lower volumetric expansion after lithiation than pure silicon particles.

The specific surface area which would affect the irreversible capacity and charge retention ratio of the cell could be controlled by change of the heat treatment condition. The specific surface area was changed between 7m²/g and 70m²/g after coating of the alloy powder with the specific surface area of 3m²/g. By optimizing heat treatment conditions, we could obtained much improved initial capacity as well as significantly better charge retention ratio after 20 cycles.