To reduce capacity drop even in rapid charging/discharging by using oxide powder of a specific component spinel structure with the internal distortion, the specific surface and the median system in specific ranges respectively.
This is oxide powder expressed by the composition formula, Li1+XMn2-XO4-r. In the formula, X and Y are 0≤X≤0.3333 and -0.1≤Y≤0.2, respectively. The internal distortion is ≤0.07%, the specific surface S, 0.2≤S≤9 (m2/g), and the median diameter (r), 0.5≤r≤10 (μm), respectively. These characteristics provide the following effects: The use of the active material expressed by the composition formula having excessive Li improves the cycle characteristics. The limiting of the internal distortion facilitates the delivery of the positive electrode active material and the electrolyte. Setting of the specific surface to a specific range increases the surface area contributing to the charging/discharging. The setting of the median diameter to the range further facilitates the delivery of the Li ions and improves an apparent density.
SASAKI ITSUKI
NORITAKE TATSUO
TAKATORI KAZUMASA
WATANABE NAOYOSHI
HATANAKA TATSUYA
