Hydrogen storage alloys, method for producing the same, and anodes for nickel-hydrogen rechargeable battery

Abstract

The present invention relates to hydrogen storage alloys, methods for producing the same, and anodes produced with such alloys for nickel-hydrogen rechargeable batteries. The alloys are useful as electrode materials for nickel-hydrogen rechargeable batteries, excellent, when used as anode materials, in corrosion resistance or activity such as initial activity and high rate discharge performance, of low cost compared to the conventional alloys with a higher Co content, and recyclable. The alloys are of a composition represented by the formula (1) and has a substantially single phase structure, and the crystals thereof have an average long axis diameter of 30 to 160 μm, or not smaller than 5 μm and smaller than 30 μm. The present anodes for rechargeable batteries contain at least one of these hydrogen storage alloys. RNi x Co y M z   ( 1 ) (R: rare earth elements etc., M: Mg, Al, etc., 3.7≦x≦5.3, 0.1≦y≦0.5, 0.1≦z≦1.0, 5.1≦x+y+z≦5.5)

1 - 6 . (canceled)  
     
     
         7 . A method for producing an alloy of  claim 10  comprising the steps of: 
 (A) melting materials for all alloy of a composition represented by the Formula (1) to prepare an alloy melt;    (B-1) cooling and solidifying said alloy melt into alloy flakes having an average thickness of 0.1 to 0.5 mm; and    (C-1) heat-treating said alloy flakes at 950 to 1100° C. for 30 minutes to 10 hours.    
     
     
         8 . A method for producing am alloy of  claim 10  comprising the steps of: 
 (A) melting materials for an alloy of a composition represented by the formula (1) to prepare an alloy melt;    (B-2) cooling and solidifying said alloy melt into alloy flakes having all average thickness of 0.05 to 0.2 mm; and    (C-1) heat-treating said alloy flakes at 900 to 1000° C. for 30 minutes to 10 hours.    
     
     
         9 . canceled  
     
     
         10 . An anode for a nickel-hydrogen rechargeable battery comprising, as anode materials: 
 a hydrogen storage alloy (a), a composition represented by the formula (1), wherein said alloy has a substantially single phase structure, and crystals of said alloy have an average long axis diameter of 30 to 160 μm;      RNi x Co y M z    (1)    wherein R stands for once or a mixture of rare earth elements including yttrium, M stands for Mg, Al, Mn, Fe, Cu, Zr, Ti, Mo, W, B, or mixtures thereof, x satisfies 3.7≦x≦5.3, y satisfies 0.1≦x≦0.5, satisfies 0.1≦x≦1.0, and 5.1≦x=Y=z≦5.5,    a hydrogen storage alloy (b), a composition represented by the formula (1), wherein said alloy has a substantially single phase structure, and crystals of said alloy have an average long axis diameter of not smaller than 5 μm and smaller than 30 μm, and    an electrically conductive material.    
     
     
         11 . The anode for a nickel-hydrogen rechargeable battery of  claim 10 , wherein a ratio of said hydrogen storage alloy (a) to said hydrogen storage alloy (b) existing in said anode materials is 99:1 to 90:10.  
     
     
         12 . The anode for a nickel-hydrogen rechargeable battery of  claim 10  wherein said R in the formula (1) for said alloys (a) and (b) is selected from the group consisting of La, Ce, Pr, Nd and mixtures thereof.  
     
     
         13 . The anode for a nickel-hydrogen rechargeable battery of  claim 12 , wherein a composition of said R in the formula (1) for said alloys (a) and (b) is 50 to 100 at % Ce, 0 to 50 at % Pr, and 0 to 50 at % Nd.  
     
     
         14 . The anode for a nickel-hydrogen rechargeable battery of  claim 10 , wherein said average long axis diameter of crystals of said alloy (a) is 30 to 120 μm.  
     
     
         15 . The anode for a nickel-hydrogen rechargeable battery of  claim 10 , wherein said average long axis diameter of crystals of said alloy (b) is 10 to 20 μm.