Hydrogen storage alloy for battery negative electrode that enables high discharge capacity with a small number of charge / discharge cycles and improvement of low-temperature, high-rate discharge capacity with high-rate initial activation treatment

摘要

Disclosed is a hydrogen occluding alloy used for a cathode of battery which enables to provide for a high discharge capacity at small number of charge/discharge cycles by a high-rate initial activation treatment and to increase a high-rate discharge capacity at low temperature. The hydrogen occluding alloy comprises; 32 to 38% of rare earth elements mainly comprising La and/or Ce, 0.1 to 17% of Co, 0.1 to 3.5 % of Al, 0.5 to 10 % of Mn and 0.005% to 0.2% of hydrogen, with the balance being Ni and inevitable impurities, and has a microstructure obtained by X-ray diffraction and microstructure observation with scanning electron microscope, the microstructure comprising a continuous phase and dispersed phase wherein the continuous phase is composed of Cacu3-type crystal structure and the dispersed phase is composed of three phases comprising Ce2Ni7-type crystal structure, rare earth element hydride which is a reaction product produced by the hydrogen heat treatment of the Ce2Ni7-type crystal structure and CaCu5-type crystal structure, and the dispersed phase of the CaCu5-type crystal structure is interposed in between the Ce2Ni7-type crystal structure and rare earth element hydride both of which are dispersed phases.