Cobalt-free Materials for Nickel-metal Hydride Battery: Self-discharge Suppression and Overdischarge-resistance Improvement

Abstract

For use of the large-sized Ni-MH battery in the social-infrastructure, it is important to improve its self-discharge suppression and overdischarge resistance as well as its high-power and long cycle-life performances. The use of the RE 0.9 Mg 0.1 Ni 3.9 Al 0.2 alloy as the negative electrode of a Ni-MH battery effectively suppressed the self-discharge compared to the use of the conventional AB 5 -type alloy. Meanwhile, a carbon-coated Ni(OH) 2 prepared using a fluid-bed coating method exhibited a better overdischarge resistance than that using the conventional CoOOHcoated one. The Co, which is an expensive rare metal, is completely removed from the Ni-MH battery using these Co-free electrodes. The Co-free Ni-MH battery combines several good battery characteristics, such as a low selfdischarge and overdischarge resistance.