Motoo Tadokoro

Nickel electrode active material; a nickel electrode and a nickel alkali storage cell using such nickel electrode active material; and production methods of such material, electrode, and cell

Fine-grained nickel electrode active material, each of which contributing to electrode reaction; production method of the fine-grained nickel electrode active material; and a nickel alkali storage cell of high capacity which is excellent in over discharge characteristics. In order to produce the fine-grained nickel electrode active material, fine-grained nickel hydroxide is precipitated by adding a given amount of alkali to solution in which at least a nickel compound is dissolved while the solution is stirred. Each of the fine-grained nickel hydroxide has pores with 20 vol % or more of a combined volume of the pores being composed of pores of diameter 60 Å or greater. Next, a given amount of alkali is gradually added to suspension including the fine-grained nickel hydroxide and dissolved cobalt compound so that cobalt hydroxide is precipitated on the external surface of the fine-grained nickel hydroxide. The fine-grained nickel electrode active material is produced in the above mentioned way. Each of the fine-grained nickel electrode active material comprises a nickel hydroxide and cobalt oxide having distorted crystal structure and oxidation number higher than +2. The nickel hydroxide has pores whose diameters are 60 Å or greater. And the volume of such pores amounts to 20 vol % or more of the combined volume of all of the pores.

Development of hydrogen-absorbing alloys for nickel-metal hydride secondary batteries

Abstract The effect of the stoichiometry of Mm(Ni 0.64 Co 0.2 Mn 0.12 Al 0.04 ) x alloy on the hydrogen absorption capacity, and the reactivity of two-phase alloys in alkaline solution, were investigated. Furthermore, the electrochemical characteristics of non-stoichiometric hydrogen-absorbing alloys with a second phase were investigated. Nonstoichiometric hydrogen-absorbing alloys ( x =4.5–4.8) with boron added were found to have higher electrochemical capacities and superior electrochemical reactivities than those of stoichiometric alloys without boron added.