Hydrogen storage metal alloy, method for absorption and release of hydrogen using the said alloy and hydrogen fuel battery using the said method

A hydrogen storage metal alloy which has as its main phase a body-centered cubic structure-type phase exerting a two-stage or inclined plateau characteristic in a hydrogen storage amount vs hydrogen pressure relation, in which the composition ratio of constituent metals for the alloy is suitably adjusted to reduce the stability of the hydrogen occluded in the alloy during the low-pressure plateau region or the lower plateau region of the inclined plateau such that an alloy temperature (T2) during at least a period in a hydrogen release process can be brought to higher than an alloy temperature (T1) in a hydrogen-absorption process (T2>T1) whereby at least part of the occluded hydrogen will be made desorbable during the low-pressure plateau region in the above-mentioned two-stage plateau or the lower plateau region of the inclined plateau, wherein the alloy temperature (T1) during the hydrogen-absorbing process is brought to a range of from the extremely low temperature in the living areas on the earth to 373K, and wherein the hydrogen storage metal alloy is a V alloy not only having a suitably adjusted composition to reduce the stability of the occluded hydrogen but also containing 0 to 95 at % of at least one or more members selected from the group consisting of Nb, Ta, W, Mo, Ti, Cr, Mn, Fe, Al, B, Co, Cu, Ge, Ni and Si.