1. Matsushita Battery Industrial Company, Limited, EV Battery Development Center, 1, Matsushita‐Cho, Moriguchi, Osaka, 570, Japan
2. Matsushita Battery Industrial Company, Limited, Technology Development Center, 1, Matsushita‐Cho, Moriguchi, Osaka, 570, Japan
3. Department of Applied Chemistry, College of Engineering, University of Osaka Prefecture, 1‐1, Gakuen‐Cho, Sakai, Osaka 593, Japan