Modified electrochemical hydrogen storage alloy having increased capacity, rate capability and catalytic activity

Abstract

A modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy which has at least one of the following characteristics: 1) an increased charge/discharge rate capability over that the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy; 2) a formation cycling requirement which is reduced to one tenth that of the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy; or 3) an oxide surface layer having a higher electrochemical hydrogen storage catalytic activity than the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.

We claim:  
     
         1 . A modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy, said alloy comprising a base alloy and at least one modifying element, said base alloy consisting essentially of 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr, said modified alloy characterized by an increased charge/discharge rate capability over that the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         2 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 1   , wherein said increased charge/discharge rate capability over that of the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy comprises at least a 300% greater charge/discharge rate capability at a discharge rate of 1000 mA/g.  
     
     
         3 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 1   , wherein said at least one modifying element comprises Al, Co, Sn and optionally Fe.  
     
     
         4 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 3   , further comprising 0.1 to 10.0% Al, 0.1 to 10.0% Co, 0 to 3.5% Fe and 0.1 to 3.0% Sn.  
     
     
         5 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 4   , comprising, in atomic percentage, Ti 9.0%, Zr 26.2%, V 5.0%, Ni 38.0%, Cr 3.5%, Co 1.5%, Mn 15.6%, Al 0.4%, and Sn 0.8%.  
     
     
         6 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 1   , wherein said alloy has a higher exchange current density than the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         7 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 6   , wherein said exchange current density is at least 40 mA/cm 2  higher than that of the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         8 . A modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy, said alloy comprising a base alloy and at least one modifying element, said base alloy consisting essentially of 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr, said modified alloy characterized by a formation cycling requirement which is reduced to at least one tenth that of the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         9 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 8   , wherein said at least one modifying element comprises Al, Co, Sn and optionally Fe.  
     
     
         10 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 9   , further comprising 0.1 to 10.0% Al, 0.1 to 10.0% Co, 0 to 3.5% Fe and 0.1 to 3.0% Sn.  
     
     
         11 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 10   , comprising, in atomic percentage, Ti 9.0%, Zr 26.2%, V 5.0%, Ni 38.0%, Cr 3.5%, Co 1.5%, Mn 15.6%, Al 0.4%, and Sn 0.8%.  
     
     
         12 . A modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy, said alloy comprising a base alloy and at least one modifying element, said base alloy consisting essentially of 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr, said modified alloy characterized by an oxide surface layer having a higher electrochemical hydrogen storage catalytic activity than the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         13 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 12   , wherein said at least one modifying element comprises Al, Co, Sn and optionally Fe.  
     
     
         14 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 13   , further comprising 0.1 to 10.0% Al, 0.1 to 10.0% Co, 0 to 3.5% Fe and 0.1 to 3.0% Sn.  
     
     
         15 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 14   , comprising, in atomic percentage, Ti 9.0%, Zr 26.2%, V 5.0%, Ni 38.0%, Cr 3.5%, Co 1.5%, Mn 15.6%, Al 0.4%, and Sn 0.8%.  
     
     
         16 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 12   , wherein said oxide comprises an oxide of Mn.  
     
     
         17 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 16   , wherein said oxide comprises an oxide of Mn and Ni.  
     
     
         18 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 17   , wherein said oxide comprises an oxide of Mn, Ni, Co, Ti and optionally Fe, if Fe is present in the alloy.  
     
     
         19 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 16   , wherein said oxide comprises an oxide of Mn, Co and Ti.  
     
     
         20 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 12   , wherein said oxide comprises mixed fine and coarse grained oxides.  
     
     
         21 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 12   , wherein said oxide layer contains metallic catalytic particles of from 10-50 Angstroms in size dispersed therein.  
     
     
         22 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 21   , wherein said metallic catalytic particles are from 10-40 Angstroms in size.  
     
     
         23 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 22   , wherein said metallic catalytic particles are from 10-30 Angstroms in size.  
     
     
         24 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 23   , wherein said metallic catalytic particles are from 10-20 Angstroms in size.  
     
     
         25 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 24   , wherein said metallic catalytic particles are Ni—Mn—Co—Ti alloy catalytic particles.  
     
     
         26 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 21   , wherein said metallic catalytic particles are finely dispersed in said oxide from 10-20 Angstroms apart.  
     
     
         27 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 21   , wherein said metallic catalytic particles have an FCC crystalline structure.  
     
     
         28 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 21   , wherein said metallic catalytic particles have a NiCoMnTi and TiZr oxide support structure forming a super lattice to promote ionic diffusion and reaction.  
     
     
         29 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 12   , wherein said alloy has a higher surface area than the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         30 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 29   , wherein said alloy has a surface area of at least 0.2 m 2 /g higher than the base Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy.  
     
     
         31 . An electrochemical hydrogen storage alloy having an oxide surface containing metallic catalytic particles, said particles being from 10-50 Angstroms in size.  
     
     
         32 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said metallic catalytic particles are from 10-40 Angstroms in size.  
     
     
         33 . The electrochemical hydrogen storage alloy of    claim 33   , wherein said metallic catalytic particles are from 10-30 Angstroms in size.  
     
     
         34 . The electrochemical hydrogen storage alloy of    claim 33   , wherein said metallic catalytic particles are from 10-20 Angstroms in size.  
     
     
         35 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said metallic catalytic particles are Ni—Mn—Co—Ti alloy catalytic particles.  
     
     
         36 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said metallic catalytic particles are finely dispersed in said oxide from 10-20 Angstroms apart.  
     
     
         37 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said metallic catalytic particles have an FCC crystalline structure.  
     
     
         38 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said oxide comprises an oxide of Mn.  
     
     
         39 . The electrochemical hydrogen storage alloy of    claim 38   , wherein said oxide comprises an oxide of Mn and Ni.  
     
     
         40 . The electrochemical hydrogen storage alloy of    claim 39   , wherein said oxide comprises an oxide of Mn, Ni, Co, Ti and optionally Fe, if Fe is present in the alloy.  
     
     
         41 . The electrochemical hydrogen storage alloy of    claim 38   , wherein said oxide comprises an oxide of Mn, Co and Ti.  
     
     
         42 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said oxide comprises mixed fine and coarse grained oxides.  
     
     
         43 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said alloy comprises a base alloy and at least one modifying element, said base alloy consisting essentially of 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr, and said at least one modifying element comprises Al, Co, Sn and optionally Fe.  
     
     
         44 . The electrochemical hydrogen storage alloy of    claim 43   , further comprising 0.1 to 10.0% Al, 0.1 to 10.0% Co, 0 to 3.5% Fe and 0.1 to 3.0% Sn.  
     
     
         45 . The electrochemical hydrogen storage alloy of    claim 44   , comprising, in atomic percentage, Ti 9.0%, Zr 26.2%, V 5.0%, Ni 38.0%, Cr 3.5%, Co 1.5%, Mn 15.6%, Al 0.4%, and Sn 0.8%.  
     
     
         46 . The electrochemical hydrogen storage alloy of    claim 31   , wherein said oxide surface comprises TiZr oxide, FCC nickel particles, and regions of NiCoMnTi, said TiZr oxide, FCC nickel particles, and regions of NiCoMnTi interacting to form a super lattice which promotes ionic diffusion and reaction.  
     
     
         47 . A modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy comprising, in atomic percentage: 
       (Base Alloy) a Co b Fe c Al d Sn e , 
       where 
 said Base Alloy comprises 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr;  
 b is 0.1 to 10.0%; c is 0 to 3.5%; d is 0.1 to 10.0%; e is 0.1 to 3.0%; and  
 a+b+c+d+e=100%.  
 
     
     
         48 . The modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 47    comprising, in atomic percentage, Ti 9.0%, Zr 26.2%, V 5.0%, Ni 38.0%, Cr 3.5% Co 1.5%, Mn 15.6% Al 0.4% and Sn 0.8%.  
     
     
         49 . In a method of casting an ingot of a modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy comprising, in atomic percentage (Base Alloy) a Co b Fe c Al d Sn e , where said Base Alloy comprises 0.1 to 60% Ti, 0.1 to 40% Zr, 0 to 60% V, 0.1 to 57% Ni, 5 to 22% Mn and 0 to 56% Cr; b is 0.1 to 10.0%; c is0 to 3.5%; d is 0.1 to 10.0%; e is 0.1 to 3.0%; and a+b+c+d+e=100% the improvement comprising: 
 limiting the ingot thickness to less than about 5 inches.  
 
     
     
         50 . The method of casting an ingot of a modified Ti—V—Zr—Ni—Mn—Cr electrochemical hydrogen storage alloy of    claim 49   , further comprising limiting the ingot thickness to less than about one inch.