Metal hydride-air batteries and methods for their use are provided. An exemplary metal-hydride air battery includes an alkaline exchange membrane provided between the positive electrode and the negative electrode of the battery. The alkaline exchange membrane provides for transfer of hydroxide ions through the membrane. Optionally the alkaline exchange membrane limits transport of other species through the membrane.

A positive electrode for alkaline storage batteries that enables to improve the active material utilization rate, while suppressing the self-discharge. The positive electrode for alkaline storage batteries includes a support having conductivity, and a positive electrode active material adhering to the support. The positive electrode active material includes particles of a nickel oxide. The particles of the nickel oxide include a first particle group having a particle diameter of 20 m or more, and a second particle group having a particle diameter of less than 20 m. The first particle group includes a first component with cracks, and a second component without cracks. The proportion of the first particle group in the particles of the nickel oxide is 15 vol % or more, and the proportion by number of the first component in the first particle group is 15% or more.

Hydrogen storage alloys comprising a metal oxide containing 60 at % oxygen; and/or comprising a metal region adjacent to a boundary region, which boundary region comprises at least one channel; and/or comprising a metal region adjacent to a boundary region, where the boundary region has a length and an average width, where the average width is from about 12 nm to about 1100 nm; and/or comprising a metal oxide zone comprising a metal oxide, which oxide zone is aligned with at least one channel; and/or comprising a Ni/Cr metal oxide have improved electrochemical properties, for instance improved low temperature electrochemical performance.

A nickel-metal hydride battery of the present disclosure comprises: a positive electrode active material layer, a negative electrode active material layer, and an aqueous electrolyte, wherein a negative electrode active material contained in the negative electrode active material layer is a hydrogen storage alloy having an AB.sub.2 main phase, the A site includes Ti, Zr, or a combination thereof, and the B site includes Mn, Cr, Ni, Fe, or a combination thereof.

An alkaline secondary battery includes at least a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes at least one of manganese oxyhydroxide and manganese dioxide. The negative electrode includes a hydrogen storage alloy.

A nickel hydrogen secondary battery comprises an outer can and an electrode group accommodated in a hermetically sealed state together with an alkaline electrolyte solution in the outer can, wherein the electrode group comprises a positive electrode and a negative electrode stacked through a separator, wherein the negative electrode contains a hydrogen absorbing alloy powder that is an aggregate of particles of a hydrogen absorbing alloy, wherein the hydrogen absorbing alloy powder is such that when an average particle size of the particles is represented by M; a particle size of of the M is represented by P; and a particle size of of the M is represented by Q, a content of the particles having a particle size equal to or smaller than the P is lower than 20% by mass of the whole of the hydrogen absorbing alloy powder; and the content of the particles having a particle size equal to or smaller than the Q is lower than 10% by mass of the whole of the hydrogen absorbing alloy powder.

Disclosed is an alloy powder for electrodes for nickel-metal hydride storage batteries having a high battery capacity and being excellent in life characteristics and high-temperature storage characteristics. The alloy powder includes a hydrogen storage alloy containing elements L, M, Ni, Co, and E. L includes La as an essential component. L includes no Nd, or when including Nd, the percentage of Nd in L is less than 5 mass %. The percentage of La in the hydrogen storage alloy is 23 mass % or less. M is Mg, Ca, Sr and/or Ba. A molar ratio to a total of L and M is 0.0450.133. A molar ratio x of Ni to the total of L and M is 3.5x4.32, and a molar ratio y of Co is 0.13y0.5. The molar ratios x and y, and a molar ratio z of E to the total of L and M satisfy 4.78x+y+z<5.03.

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.

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.

An object of the present disclosure is to provide an anode material with a high capacity maintenance rate. To achieve the above object, the present disclosure provides an anode material to be used for a battery that contains an aqueous liquid electrolyte, the anode material comprising: a hydrogen storing alloy that reversibly stores and releases hydrogen; wherein the hydrogen storing alloy contains Ti, Cr, and V as main components, and is an alloy that contains a BCC phase as a main phase; a lattice constant of the BCC phase is 3.01 ? or more and 3.10 ? or less; and the Cr content in the hydrogen storing alloy is 20 at % or more.