CARBON POWDER SUITABLE TO NEGATIVE ELECTRODE MATERIAL FOR NON-AQUEOUS SECONDARY CELL

摘要

A carbon powder suitable for a negative electrode of a nonaqueous secondary battery is provided to inhibit the deterioration of current density and rate characteristics and to obtain a carbon powder which does not decompose propylene carbonate. A carbon powder is based on graphite and has a V2/V1 ratio of 1-2, wherein V1 is a pore volume having a diameter of 2-50 nm and V2 is a pore volume having a diameter of 50-200 nm in a pore distribution curve obtained by the analysis of a nitrogen adsorption isotherm using BJH (Barrett-Joyner-Halenda) method. The carbon powder comprises a natural graphite powder; and the carbon generated on the surface of the natural graphite powder by the heat treatment of a carbon precursor. Preferably the carbon generated by the heat treatment of a carbon precursor is prepared by solid phase mixing a pitch powder having an average diameter of 500 micrometers or less and a graphite powder, and heat treating the mixture at 900-1,500 deg.C under nonoxidative atmosphere.