Layer cell includes an outer casing, positive electrode, negative electrode, separator disposed between the positive electrode and the negative electrode, and 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. 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. 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. Peripheral edge of a hole, in the first electrode is covered with the separator.

Alloy powder for electrodes that includes particles of a hydrogen-absorbing alloy having an AB.sub.2 type crystal structure. The hydrogen-absorbing alloy includes first elements that are located in an A site in the crystal structure and include Zr, and second elements that are located in a B site and include Ni and. Mn. The hydrogen-absorbing alloy includes a plurality of alloy phases having different Zr concentrations. In each of the alloy phases, the percentage of Zr in the first elements exceeds 70 atom %.

Provided is a hydrogen storage alloy which is characterized in that two or more crystal phases having different crystal structures are layered in a c-axis direction of the crystal structures. The hydrogen storage alloy is further characterized in that a difference between a maximum value and a minimum value of a lattice constant a in the crystal structures of the laminated two or more crystal phases is 0.03 or less.

A method for regenerating a nickel metal hydride battery is provided. The nickel metal hydride battery includes a hydrogen absorbing alloy that serves as a negative electrode material and a safety valve that opens when an internal pressure of a battery case is greater than or equal to a predetermined pressure. The method includes connecting a plurality of nickel metal hydride batteries in parallel. Each nickel metal hydride battery is formed by integrating one or more battery cells. The method further includes overcharging the nickel metal hydride batteries by supplying current from a charge unit that is connected in parallel to the nickel metal hydride batteries. The method further includes, when each nickel metal hydride battery is overcharged, restoring a discharge reserve of a negative electrode by releasing at least some of an oxygen gas generated at a positive electrode out of the battery case through the safety valve.

An ambient heat engine that is thermally coupled to its environment is provided. The ambient heat engine includes two complementary electrochemical cells. One cell has a positive voltage temperature coefficient and the other cell has a negative voltage temperature coefficient. The ambient heat engine further includes a controller and an electrical energy storage device. When the ambient temperature increases or decreases, the temperature variation creates a voltage differential between the two cells, and the controller discharges the higher voltage cell and uses a portion of the discharged energy to charge the lower voltage cell. The difference in energy is extracted by the controller and supplied to the electrical energy storage device. The controller includes circuitry for coupling energy from the energy storage device to the cells in order to compensate for self-discharge of the cells which may occur due to electronic leakage and diffusion phenomenon over extended periods of time.

Provided are bipolar batteries that include a stacked plurality of cells. Two or more of the cells include a cathode, an anode, a proton or hydroxide ion conducting polymer separator between the cathode and said anode, wherein in some aspects the separator includes or alone acts as a proton or hydroxide conducting electrolyte, and a bipolar metallic plate associated with the anode or the cathode. The cells optionally include and electrolyte that includes a polymer capable of conducting a proton or a hydroxide ion. The separator may in the form of a film and is optionally not bonded to either the anode or the cathode, or may be in the form of a coating on the anode, the cathode, or any combination thereof.

Hydrogen storage alloy powder, an anode, and a nickel-hydrogen rechargeable battery are provided, which are excellent in low-temperature characteristics and both in initial activity and cycle life at the same time, which properties are trading-off in conventional nickel-hydrogen rechargeable batteries. The alloy powder has a composition represented by formula (1) R.sub.1-aMg.sub.aNi.sub.bAl.sub.cM.sub.d (R: rare earth elements including Sc and Y, or the like; 0.005a0.40, 3.00b4.50, 0c0.50, 0d1.00, 3.00b+c+d4.50), and has an arithmetical mean roughness (Ra) of the powder particle outer surface of not less than 2 m, or a crushing strength of not higher than 35,000 gf/mm.sup.2.

Hydrogen storage alloys comprising a) at least one main phase, b) a storage secondary phase and c) a catalytic secondary phase, where the weight ratio of the catalytic secondary phase abundance to the storage secondary phase abundance is 3; or comprising a) at least one main phase, b) from 0 to about 13.3 wt % of a storage secondary phase and c) a catalytic secondary phase, where the alloy comprises from 0.05 at % to 0.98 at % of one or more rare earth elements; or comprising a) at least one main phase, b) from 0 to about 13.3 wt % of a storage secondary phase and c) a catalytic secondary phase, where the alloy comprises for example i) one or more elements selected from the group consisting of Ti, Zr, Nb and Hf and ii) one or more elements selected from the group consisting of V, Cr, Mn, Ni, Sn, Al, Co, Cu, Mo, W, Fe, Si, Sn and rare earth elements, where the atomic ratio of ii) to i) is from about 1.80 to about 1.98, exhibit improved electrochemical properties, for instance improved low temperature electrochemical performance.

Laves phase-related BCC metal hydride alloys historically have limited electrochemical capabilities. Laves phase-related BCC metal hydride alloys are provided herein with greater than 200 mAh/g capacities and commonly at or greater than 400 mAh/g capacities. By decreasing the temperature or increasing the hydrogen pressure the phase structure of the material a synergistic effect between multiple phases in the resulting alloy is achieved thereby greatly improving the electrochemical capacities.

Disclosed is a negative electrode for an alkaline secondary battery, which can suppress elution of iron to improve the long-period storage property of the battery capacity even under conditions in which elution of iron in a substrate into an electrolyte solution tends to occur, and which can also suppress lowering of initial capacity and increase in internal resistance. Even under conditions in which the elution of iron in the substrate into an electrolyte solution tends to occur, including a case where there is a thin conductive protecting layer at the surface or where the conductive protecting layer has defects, by adding magnesium or a magnesium compound to the negative electrode for an alkaline secondary battery (excluding the case where magnesium is contained as a constituent element of a hydrogen storage alloy), the elution of iron can be suppressed, and thereby, the long-period storage property of the battery capacity can be improved and the lowering of the initial capacity and the increase in internal resistance can be suppressed.