POWDER FOR LITHIUM ION SECONDARY BATTERY NEGATIVE POLE MATERIAL, LITHIUM ION SECONDARY BATTERY NEGATIVE POLE AND CAPACITOR NEGATIVE POLE, AND LITHIUM ION SECONDARY BATTERY AND CAPACITOR

摘要

In a lithium ion secondary battery using a negative electrode material powder including a lower silicon oxide powder as a negative electrode material, a charge electric potential at 0.45-1.0 V relative to a Li reference upon initial charging results in a lithium ion secondary battery having a large discharge capacity with excellent cycle characteristics, which can be durable in practical use. On this occasion, the charge electric potential being 0.45-1.0 V relative to the Li reference upon initial charging means that an electric potential plateau caused by the generation of Li-silicate is observed, and the Li-silicate is uniformly generated in the negative electrode material. The negative electrode material powder according to the present invention having the charge electric potential of 0.45-1.0 V relative to the Li reference upon initial charging prevents the negative electrode material from being finely torn apart upon charging/discharging which results in cycle characteristic degradation, and excellent cycle characteristics are obtained. It is preferable for the negative electrode material powder according to the present invention to have an electrically conductive carbon film on the surface, and for the ratio of the electrically conductive carbon film to the surface of the powder to be 0.2-10 mass %.