JPH0514382B

PURPOSE:To increase the utilization of active material, and obtain high performance and steady capacity by adding 3-20wt% of cobalt hydroxide powder having green color and hexagonal crystal structure to active material powder mainly comprising nickel hydroxide. CONSTITUTION:Metal cobalt is dissolved in sulfuric acid solution or nitric acid solution and a compound is deposited from a neutral or weak alkaline region. This compound is cobalt hydroxide having green color and hexagonal crystal structure. 10% cobalt hydroxide and 90% nickel hydroxide power are mixed, and water and carboxymethylcellulose are added thereto to obtain a paste-like mixture. The paste is filled in a nickel fiber sinter having a porosity of 95% and a thickness of 1.5mm, and dried, then pressed to obtain a 0.7mm thick positive plate. As shown in the figure, the positive electrode I containing cobalt hydroxide has higher utilization of active material and shorter discharge time compared with a positive plate II containing beta-type cobalt hydroxide.