US Patent 8734991 Negative electrode material for nonaqueous electrolyte secondary battery

This invention provides a negative electrode material for a rechargeable battery with a nonaqueous electrolyte, characterized in that the negative electrode material contains polycrystalline silicon particles as an active material, the particle diameter of crystallites of the polycrystalline silicon is not less than 20 nm and not more than 100 nm in terms of a crystallite size determined by the Scherrer method from the full width at half maximum of a diffraction line attributable to Si (111) around 2θ=28.4° in an x-ray diffraction pattern analysis, and the true specific gravity of the silicon particles is 2.300 to 2.320.