CARBON MATERIAL FOR LITHIUM ION SECONDARY BATTERIES

摘要

Disclosed is a negative electrode material whereby lithium ion secondary batteries can be obtained that have sufficiently low irreversible charge/discharge capacity and superior high-temperature storage characteristics, and in which gas production is reduced during the initial cycle and during high-temperature storage. A carbon material for lithium ion secondary batteries is characterized in that the O/C value in the content of surface functional groups represented by formula 1 is not less than 1% and not more than 4%, and the sum of the Cl/C value in the content of surface functional groups represented by formula 2 and the S165/C value in the content of surface functional groups represented by formula 3 (Cl/C + S165/C) is not less than 0.05% and not more than 0.5%. formula 1: O/C value (%) = concentration of O atoms derived based on the peak area of the O1s spectrum in X-ray photoelectron spectroscopy (XPS) analysis/concentration of C atoms derived based on the peak area of the C1s spectrum in XPS analysis × 100 formula 2: Cl/C value (%) = concentration of Cl atoms derived based on the peak area of the Cl2p spectrum in XPS analysis/concentration of C atoms derived based on the peak area of the C1s spectrum in XPS analysis × 100 formula 3: S165/C value (%) = concentration of S165 atoms derived based on the peak area of the peak near 165 eV in the spectrum corresponding to S2p in XPS analysis/concentration of C atoms derived based on the peak area of the C1s spectrum in XPS analysis × 100