NOVELTY - A hydrogen storage alloy has a bulk region and an interface region, which comprises catalytic metallic particles supported by a support matrix and voids, the catalytic metallic particles having diameters of less than 100 Angstrom, the catalytic metallic particles and the voids being distributed throughout the interface region, where volume fraction of the voids in the interface region is greater than 5%.    USE - The hydrogen storage alloy is for an anode active material used in a negative electrode useful for electrochemical cell (claimed) (galvanic or electrolytic), batteries (e.g. nickel metal hydride battery) or fuel cells. It is useful for thermal hydrogen storage. It is useful for flat cells, wound cells, cylindrical cells, prismatic cells, sealed cells and vented cells. Batteries are used in hybrid electric vehicle or electric vehicle, and as starter batteries in vehicles such as automobiles, buses and tractors.    ADVANTAGE - The hydrogen storage alloy has excellent kinetics at low temperatures and excellent cycle life. The electrochemical cell may provide greater than or equal to20% of the peak power measured at 35degreesC at temperatures of less than or equal to -30degreesC.    DETAILED DESCRIPTION - A hydrogen storage alloy has a bulk region and an interface region, which comprises catalytic metallic particles supported by a support matrix and voids, the catalytic metallic particles having diameters of less than 100 Angstrom, the catalytic metallic particles and the voids being distributed throughout the interface region, where volume fraction of the voids in the interface region is greater than 5%, the hydrogen storage alloy having x-ray lattice constant (c) to x-ray lattice constant (a) c/a lattice constant ratio of greater than or equal to0.805.    Two further INDEPENDENT CLAIMS are included for an electrochamical cell using the hydrogen storage alloy as an anode active material and a hydrogen storage alloy which has a hysteresis of less than or equal to 0.12.    DESCRIPTION OF DRAWING(S) - The figure shows the empirical function used to calculate the percentage of nickel in the A-sites of the alloys as a result of copper addition from the ratio of copper in the B-element.