SILICON OXIDE AND NEGATIVE-ELECTRODE MATERIAL FOR A LITHIUM-ION SECONDARY BATTERY

Provided is a silicon oxide to be used for a negative electrode active material of a lithium-ion secondary battery, characterized in that : a g-value measured by an ESR spectrometer is in the range of not less than 2.0020 to not more than 2.0050; and given that A, B, and C are the area intensities of peaks near 420 cm, 490 cmand 520 cmrespectively in a Raman spectrum measured by a Raman spectroscopy, A/B is not less than 0.5 and C/B is not more than 2. The silicon oxide is used as a negative electrode active material, whereby a lithium-ion secondary battery having excellent cycle characteristic and initial efficiency in addition to high capacity can be obtained. The silicon oxide preferably has a spin density in the range of not less than 1×10spins/g to not more than 5×10spins/g. A negative electrode material for lithium-ion secondary battery contains not less than 20% by mass of this silicon oxide as a negative electrode active material.