Patent ID: 7635512

Claim:
A nickel electrode material for use in a nickel electrode, comprising: a positive-electrode material comprising: positive active material particles which comprise as the main component at least one member selected from a group consisting of a nickel hydroxide, and a solid solution in a nickel hydroxide of one or more other elements and in which part of the nickel hydroxide has been oxidized; and a coating layer formed on a surface of the positive active material particles and comprising as a main component a high-order cobalt compound in which cobalt has an oxidation number greater than 2, wherein an average oxidation number of nickel in the positive active material particles and the cobalt in the coating layer is from 2.04 to 2.40, wherein the positive-electrode material has a tap density of 2.0 g/cm 3 or greater, and wherein the high-order cobalt compound is capable of being electrochemically oxidized and reduced, has an electric double-layer capacity, and has a peak for a (003) plane with a half width of 0.7 degrees or greater in an X-ray diffraction pattern.