Hydrogen Storage Alloy, Hydrogen Storage Alloy Electrode, Secondary Battery, And Method For Producing Hydrogen Storage Alloy

Abstract

Provided is a hydrogen storage alloy which is characterized in that two or more crystal phases having different crystal structures are layered in a c-axis direction of the crystal structures. The hydrogen storage alloy is further characterized in that a difference between a maximum value and a minimum value of a lattice constant a in the crystal structures of the laminated two or more crystal phases is 0.03 Å or less.

1 - 4 . (canceled) 
     
     
         5 . A hydrogen storage alloy containing two or more crystal phases having different crystal structures, wherein the two or more crystal phases are layered in the c-axis direction of the crystal structures and the hydrogen storage alloy has a composition defined by a general formula R1 d R2 e R4 f R5 g  (wherein R1 is one or more kind elements selected from the group consisting of rare earth metals including Y; R2 is one or more kind elements selected from the group consisting of Mg, Ca, Sr, and Ba; R4 is one or more kind elements selected from the group consisting of Ni, Co, Cr, Fe, Cu, Zn, Si, Sn, V, Nb, Ta, Ti, Zr, and Hf; R5 is one or two elements selected from Mn and Al; and d, e, f, and g satisfy 8≦d≦19; 2≦e≦9; 73≦f≦79; 1≦g≦4; and d+e+f+g=100) and satisfies 3.53≦(B/A)≦3.80 and 0.0593(B/A)+1.59≦rA≦0.0063(B/A)+1.81 in the case (B/A) is defined as (f+g)/(d+e) and rA (Å) is defined as the average atomic radius of R1 and R2. 
     
     
         6 . The hydrogen storage alloy according to  claim 5 , wherein the R1 is one or more kind elements R1′ selected from the group consisting of Ce, Pr, Nd, Sm, and Y and La at La/R1′ ratio of 5 or less; R2 is Mg; the R4 is one or two elements selected from Ni and Co; the R5 is Al; and the d, e, f, and g satisfy 16≦d≦19; 2≦e≦5; 73≦f≦78;and2≦g≦4. 
     
     
         7 . The hydrogen storage alloy according to  claim 5  having, as a main produced phase, a crystal phase having Pr 5 Co 19  type crystal structure or a crystal phase having Ce 5 Co 19  type crystal structure. 
     
     
         8 . A hydrogen storage alloy containing two or more crystal phases having different crystal structures, wherein the two or more crystal phases are layered in the c-axis direction of the crystal structures and the hydrogen storage alloy has, as a main produced phase, a crystal phase having Ce 5 Co 19  type crystal structure and a composition defined by a general formula La h R6 i R7 j Mg k R8 m  (wherein R6 is one or more kind elements selected from the group consisting of rare earth metals including Y and excluding La; R7 is one or more kind elements selected from the group consisting of Zr, Ti, Zn, Sn and V; R8 is one or more kind elements selected from the group consisting of Ni, Co, Mn, Al, Cu, Fe, Cr, and Si; and h, j, k and m satisfy 0≦j≦0.65; 2≦k≦5.5; 0.70≦h/(h+i)≦0.85;and h+i+j+k+m=100). 
     
     
         9 . A hydrogen storage alloy containing two or more crystal phases having different crystal structures, wherein the two or more crystal phases are layered in the c-axis direction of the crystal structures and the ratio of the crystal phase having CaCu 5  type crystal structure is 22% by weight or less. 
     
     
         10 . The hydrogen storage alloy according to  claim 9 , wherein the hydrogen equilibrium pressure is 0.07 MPa or less. 
     
     
         11 . The hydrogen storage alloy according to  claim 9  having a composition defined by a general formula R1 n R2 p R4 q R5 r  (wherein R1 is one or more kind elements selected from the group consisting of rare earth metals including Y; R2 is one or more kind elements selected from the group consisting of Mg, Ca, Sr, and Ba; R4 is one or more kind elements selected from the group consisting of Ni, Co, Cr, Fe, Cu, Zn, Si, Sn, V, Nb, Ta, Ti, Zr, and Hf; R5 is one or two kind elements selected from Mn and Al; and n, p, q, and r satisfy 16≦n≦23; 2≦p≦8; 68.5≦q≦76; 1≦r≦6.5; and n+p+q+=100). 
     
     
         12 . The hydrogen storage alloy according to  claim 9 , wherein the content of Mn is 5% by weight or less. 
     
     
         13 - 14 . (canceled) 
     
     
         15 . A method for producing a hydrogen storage alloy containing two or more crystal phases having different crystal structures, wherein the two or more crystal phases, are layered in the c-axis direction of the structures the method comprising a melting step of heat melting alloy raw materials at prescribed mixing ratio in inert gas atmosphere; a cooling step of rapid solidification the melted alloy; and an annealing step of further annealing the alloy subjected to the cooling step at a temperature that ranges from 860° C. to 1000° C. in inert gas atmosphere in pressurized state. 
     
     
         16 . The method for producing the hydrogen storage alloy according to  claim 15 , wherein in the annealing step a pressurizing condition is at a gauge pressure that ranges from 0.2 MPa to 1.0 MPa.