Sanyo Electric Co., Ltd.

Masutaka Ouchi

Mamoru Kimoto

Teruhiko Imoto

Nobuyuki Higashiyama

Kikuko Kato

Koji Nishio

Shin Fujitani

Yohei Hirota

Yasuhiko Itoh

Yoshihiro Masuda

A method of producing a hydrogen storage alloy, for use in alkaline storage batteries, includes two steps. A first step involves preparing alloy particles having a CaCu-type crystal structure and the compositional formula MmNiCoMnM, wherein M represents at least one element selected from the group consisting of aluminum (Al) and copper (Cu), 3.0&#x2266;x&#x2266;5.2, 0&#x2266;y&#x2266;1.2, 0.1&#x2266;z&#x2266;0.9, and 4.4&#x2266;x+y+z&#x2266;5.4. A second step involves immersing the alloy particles in an acid treating solution containing a cobalt compound and a copper compound, each in the amount of 0.1 to 5.0% by weight based on the weight of the alloy particles, and an organic additive to remove oxide films from and to reductively deposit cobalt and copper on a surface of each alloy particle to form a surface region surrounding a bulk region and having a graded composition. When the sum in percentage of numbers of cobalt (Co) atoms and copper (Cu) atoms present in the surface region is given by a and that in the bulk region by b, the relationship a/b&#x2267;1.3 is satisfied.

Method for production of hydrogen storage alloy for use in alkaline storage batteries

A hydrogen storage alloy, for use in alkaline storage batteries, having a CaCu -type crystal structure and represented by the compositional formula MmNi Co Mn M (wherein M represents at least one element selected from the group consisting of aluminum (Al) and copper (Cu); x is a nickel (Ni) stoichiometry and satisfies 3.0&lE;x&lE;5.2; y is a cobalt (Co) stoichiometry and satisfies 0&lE;y&lE;1.2; z is a manganese (Mn) stoichiometry and satisfies 0.1&lE;z&lE;0.9; and the sum of x, y and z satisfies 4.4&lE;x&plus;y&plus;z&lE;5.4). The hydrogen storage alloy includes a bulk region having a CaCu -type crystal structure and a substantially uniform composition and a surface region surrounding said bulk region and having a graded composition. When the sum in percentage of numbers of cobalt (Co) atoms and copper (Cu) atoms present in the surface region is given by a and that in the bulk region by b, the relationship a/b&gE;1.3 is satisfied.

Hydrogen storage alloy for use in alkaline storage batteries and method for production thereof

A hydrogen storage alloy electrode containing, as a principal active material, a powder of hydrogen storage alloy having a CaCu crystal structure and represented by the formula MmNi Co Mn M where M is at least one element selected from aluminum (Al) and copper (Cu), x is between 3.0 and 5.2, y is between 0 and 1.2, z is between 0.1 and 0.9, w is between 0.1 and 0.9, and the sum of x, y, z and w is between 4.4 and 5.4. The hydrogen storage alloy powder particles have a surface region and a bulk region enclosed within the surface region and have a higher nickel content in the surface region than in the bulk region. The hydrogen storage alloy electrode further contains an oxide and/or hydroxide of at least one rare-earth element selected from ytterbium (Yb), samarium (Sm), erbium (Er) and gadolinium (Gd).

Hydrogen storage alloy electrode and method for manufacture thereof

In a pasted hydrogen-absorbing alloy electrode of this invention, an active material layer made from a mixture of a hydrogen-absorbing alloy powder, a composite particle powder including carbon particles and a rare earth compound for partially coating surfaces of the carbon particles, and a binder is formed on a current collector. When this pasted hydrogen-absorbing alloy electrode is used in an alkaline storage battery, the alkaline storage battery can attain small increase of the internal pressure during charge, large discharge capacity in high rate discharge and good charge-discharge cycle performance.

Pasted hydrogen-absorbing alloy electrode for alkaline storage battery

A hydrogen storage alloy electrode for a battery is made of a hydrogen storage alloy powder which includes agglomerates of hydrogen storage alloy particles joined together through a metallic layer. A method of making the electrode includes forming agglomerates of hydrogen storage alloy particles joined together by a metallic layer which covers surface portions of the particles, and then forming the electrode using a resulting powder including the agglomerates.

Hydrogen storage alloy electrode and method for fabrication thereof

A hydrogen-absorbing alloy electrode for an alkaline secondary battery. The electrode is prepared by adding a transition metal salt to a paste comprising a hydrogen-absorbing alloy powder and binder. The electrode improves charge-discharge cycle performance and high rate discharge capacity at low temperature of an alkaline secondary battery.

Hydrogen-absorbing alloy electrode for alkaline secondary battery and method of manufacture thereof

A hydrogen-absorbing alloy electrode for an alkaline secondary battery. The electrode is made from a hydrogen-absorbing alloy containing nickel which has been treated with an acidic solution containing a chelating agent for nickel. The hydrogen-absorbing alloy electrode has good activity and a nickel-hydrogen battery having the hydrogen-absorbing alloy electrode as a negative electrode has a large high rate discharge capacity soon after being assembled, and inhibits an increase of internal pressure during discharge.

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Tokushima, Japan

Masutaka Ouchi