A multi-phase hydrogen storage alloy comprising a hexagonal Ce.sub.2Ni.sub.7 phase and a hexagonal Pr.sub.5Co.sub.19 phase, where the Ce.sub.2Ni.sub.7 phase abundance is 30 wt % and the Pr.sub.5Co.sub.19 phase abundance is 8 wt % and where the alloy comprises a mischmetal where Nd in the mischmetal is <50 at % or a multi-phase hydrogen storage alloy comprising one or more rare earth elements, a hexagonal Ce.sub.2Ni.sub.7 phase and a hexagonal Pr.sub.5Co.sub.19 phase, where the Ce.sub.2Ni.sub.7 phase abundance is from about 30 to about 72 wt % and the Pr.sub.5Co.sub.19 phase abundance is 8 wt % have improved electrochemical performance. The alloys are useful in an electrode in a metal hydride battery, a fuel cell or a metal hydride air battery.

Described are solid-state energy storage devices and methods of making solid-state energy storage devices in which components of the batteries are truly solid-state and do not comprise a gel. Useful electrodes include metals and metal oxides, and useful electrolytes include amorphous ceramic thin film electrolytes that permit conduction or migration of ions across the electrolyte. Disclosed methods of making solid-state energy storage devices include multi-stage deposition processes, in which an electrode is deposited in a first stage and an electrolyte is deposited in a second stage.

Carbon or cobalt, which is used as a conductive agent in an electrode of an alkaline secondary cell, is oxidized by oxygen generated from a positive electrode. The conductive agent degraded by oxidization loses its conductivity through repetitive charge and discharge, resulting in shortening of the cycle life of the cell. In an alkaline secondary cell filled with hydrogen, hydrogen generated from a positive electrode is bound to the hydrogen. This prevents a conductive agent in an electrode from being degraded by oxidization. A cell with excellent cycle life characteristic is thus provided.

A layer cell includes an outer casing, a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrically conductive current collector passing through the positive electrode, the negative electrode and the separator in an axial direction of the outer casing. The positive electrode, the negative electrode and the separator are stacked in the axial direction of the outer casing. A first electrode which is one of the positive electrode and the negative electrode is in contact with an inner surface of the outer casing, but is not in contact with the current collector. A second electrode which is the other electrode is not in contact with the outer casing, but is in contact with the current collector. An outer edge of the second electrode is covered with the separator. A peripheral edge of a hole, through which the current collector passes, in the first electrode is covered with the separator.

Metal hydride batteries comprising an electrolyte composition which comprises an aqueous solution comprising potassium hydroxide (KOH) and one or more halide and/or oxyacid salts exhibit reduced degradation of the anode material during operation. The salts are for instance alkali metal salts. Anode materials exhibit for instance <100 % of the degradation of the same anode material in the same battery when replacing the electrolyte composition with 30 weight percent (wt %) aqueous KOH and the conductivity of the electrolyte composition is for instance 85 % of 30 wt % aqueous KOH. Anode materials are for example ABx high capacity hydrogen storage alloys comprising Mg where x is from about 0.5 to about 5 and which has a discharge capacity of 400 mAh/g.

A nickel hydrogen secondary battery 2 has an outer can 10, and an electrode group 22 accommodated together with an alkali electrolyte solution in the outer can 10. The electrode group 22 includes a positive electrode 24 and a negative electrode 26 stacked through a separator 28. The positive electrode 24 includes a first positive electrode active substance and a second positive electrode active substance. These first and second positive electrode active substances each contain nickel hydroxide as a main component, and the first positive electrode active substance and the second positive electrode active substance differ in the amount of magnesium solid-dissolved.

Provided is a hydrogen storing alloy represented by the general formula: (RE.sub.1-a-bSm.sub.aMg.sub.b)(Ni.sub.1-c-dAl.sub.cM.sub.d).sub.x (where 0.3<a<0.6; 0<b<0.16; 0.1<cx<0.2; 0dx0.1; 3.2<x<3.5; RE is at least one element selected from the group consisting of a rare earth element other than Sm, and Y, and essentially contains La; and M is Mn and/or Co). Also provided is a hydrogen storing alloy represented by the general formula: (RE.sub.1-a-bSm.sub.aMg.sub.b)(Ni.sub.1-c-dAl.sub.cM.sub.d).sub.x (where 0.1<a<0.25; 0.1<b<0.2; 0.02<cx<0.2; 0dx0.1; 3.6<x<3.7; RE is at least one element selected from the group consisting of a rare earth element other than Sm, and Y, and essentially contains La; and M is Mn and/or Co). Further provided is a nickel-metal hydride rechargeable battery including a negative electrode containing the hydrogen storing alloy.

A bipolar electrode (100) for a metal hydride battery includes a current collector (10), a negative electrode active material layer (20) provided on a first surface (10A) of the current collector (10), and a positive electrode active material layer (30) provided on a second surface (10B) of the current collector (10). The negative electrode active material layer (20) contains a metal hydride. The current collector (10) includes a steel sheet (13) and a NiFe alloy layer (15) formed on at least one surface of the steel sheet (13).

A battery 2 includes an outer can 10 and an electrode group 22 that is housed in the outer can 10 together with an alkaline electrolytic solution, in which a positive electrode 24 included in the electrode group 22 includes a positive electrode substrate and a positive electrode mixture supported on the positive electrode substrate, the positive electrode mixture includes nickel hydroxide, yttrium oxide serving as a first additive, and niobium oxide or titanium oxide serving as a second additive, a total amount of the first additive and the second additive is 0.1 parts by mass or more and 2.5 parts by mass or less per 100 parts by mass of the nickel hydroxide, a mass ratio of the first additive and the second additive is in a relationship of 1:0.2 to 5, and the positive electrode mixture after an activation treatment has a resistivity of 1 ?.Math.m or more and 10 ?.Math.m or less.

A hydrogen storage alloy suitable for a negative electrode of an on-board alkaline storage battery, and an alkaline storage battery using the alloy, which has an AB.sub.3-type crystal structure as a main phase, represented by: (Sm.sub.xLa.sub.yR.sub.z).sub.1-a-bMg.sub.aT.sub.bNi.sub.cCo.sub.dMe. (R is selected from Pr, Nd; T is selected from Ti, Zr, Hf; M is selected from V, Nb, Ta, Cr, Mo, W, Mn, Fe, Cu, Al, Si, P, B; the following conditions are met: 0<x<1.0, 0<y<1.0, 0.8?x+y?1.0, x+y+z=1.0; 0.93?(x?y).Math.(1?a?b)+4.5(a+b)?1.62, 0<a?0.45, 0?b?0.05, 0?d?0.7, 0?e?0.15, 2.85?c+d+e?3.15 and 0.01?d+e).