Improvement of high- and low-temperature characteristics of nickel-metal hydride secondary batteries using rare-earth compounds

Improvement of high- and low-temperature characteristics of nickel–metal hydride secondary batteries using rare-earth compounds is discussed. High-temperature charge characteristics are improved by coating a sintered positive electrode with yttrium hydroxide due to the increased oxygen evolution overpotential. Low-temperature discharge characteristics are also improved by adding rare-earth oxides into a negative electrode due to the increased ratio of metallic nickel at the surface of the hydrogen-absorbing alloy.