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1. WO2007011572 - HYDROGEN STORAGE ALLOYS HAVING IMPROVED CYCLE LIFE AND LOW TEMPERATURE OPERATING CHARACTERISTICS

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Claims
1. A hydrogen storage alloy having a bulk region and an interface region, said interface region comprising catalytic metallic particles supported by a support matrix and voids, said catalytic metallic particles having diameters of less than about 100 A, said catalytic metallic particles and said voids being
distributed throughout said interface region, wherein the volume fraction of said voids in said interface region is greater than 5%, said hydrogen storage alloy also having a c/a lattice constant ratio greater than or equal to 0.805.
2. The hydrogen storage alloy according to claim 1, wherein said hydrogen storage alloy is non-stoichiometric.
3. The hydrogen storage alloy according to claim 1, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of 4.80 to 5.20.
4. The hydrogen storage alloy according to claim 3, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of 4.90 to 5.10.
5. The hydrogen storage alloy according to claim 4, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of

4.95 to 5.05.
6. The hydrogen storage alloy according to claim 1, wherein said c/a lattice constant ratio is greater than or equal to 0.809.

7. The hydrogen storage alloy according to claim 1, wherein the hysteresis of said hydrogen storage alloy is less than or equal to 0.12.
8. The hydrogen storage alloy according to claim 1, wherein said hydrogen storage alloy has the formula ABxCu7, wherein,
A is one or more elements selected from La, Ce, Pr, Nd, Mm, and other rare earth elements;
B is one or more elements selected from Ni, Mn, Co, Al, Cr, Ag, Pd, Rh, Sb, V, and Pt;
4.8 < x < 5.2; and
0.01 ≤ y < 0.35.
9. The hydrogen storage alloy according to claim 8, wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said hydrogen storage alloy is at least 35 percent.
10. The hydrogen storage alloy according to claim 9, wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said hydrogen storage alloy is at least 45 percent.
11. The hydrogen storage alloy according to claim 8, wherein the atomic ratio of copper to component B in said hydrogen alloy is in the range of 0.01 to 0.20.
12. The hydrogen storage alloy according to claim 11, wherein the atomic ratio of copper to component B in said hydrogen storage alloy is in the range of 0.01 to 0.06.
13. The hydrogen storage alloy according to claim 8, wherein A comprises 60 to 65 atomic percent La, 24 to 28 atomic percent Ce, 2 to 4 atomic percent Nd, and 6 to 10 atomic percent Pr; B comprises 78 to 84 atomic percent Ni, 4 to 8 atomic percent Co, 5 to 9 atomic percent Mn, and 4 to 8 atomic percent Al; and
0.18 ≤ y ≤ 0.30.
14. The hydrogen storage alloy according to claim 8, wherein 0.15 < y < 0.30.
15. The hydrogen storage alloy according to claim 8, wherein 4.95 ≤ x ≤ 5.05.
16. An electrochemical cell comprising:
a negative electrode including an anode active material including a hydrogen storage alloy having a bulk region and an interface region, said interface region comprising catalytic metallic particles supported by a support matrix and voids, said catalytic metallic particles having diameters of less than about 100 A, said catalytic metallic particles and said voids being
distributed throughout said interface region, wherein the volume fraction of said voids in said interface region is greater than 5%, said hydrogen storage alloy also having a c/a lattice constant ratio greater than or equal to 0.805 and/or a hysteresis less than or equal to 0.12.
17. The electrochemical cell according to claim 16, wherein said electrochemical cell provides at least 20% of the peak power measured at 35°C at temperatures less than or equal to -300C.
18. The hydrogen storage alloy according to claim 16, wherein said hydrogen storage alloy is non-stoichiometric .
19. The hydrogen storage alloy according to claim 16, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of 4.80 to 5.20.
20. The electrochemical cell according to claim 16, wherein said non-stoichiometric hydrogen storage alloy has a pseudo B/A ratio in the range of 4.90 to 5.10.
21. The electrochemical cell according to claim 20, wherein said non-stoichiometric hydrogen storage alloy has a pseudo B/A ratio in the range of 4.95 to 5.05.
22. The hydrogen storage alloy according to claim 16, wherein said C/A lattice constant ratio is greater than or equal to

0 . 809 .
23. The electrochemical cell according to claim 16, wherein said non-stoichiometric hydrogen storage alloy has the formula ABxCuy, wherein,
A is one or more elements selected from La, Ce, Pr, Nd, and Mm;
B is one or more elements selected from Ni, Mn, Co, Al, Cr, Ag, Pd, Rh, Sb, V, and Pt;
4.8 < x ≤ 5.2; and
0.01 < y ≤ 0.35.
24. The electrochemical cell according to claim 23 , wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said non-stoichiometric hydrogen storage alloy is at least 35 percent.
25. The electrochemical cell according to claim 24, wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said non-stoichiometric hydrogen storage alloy is at least 45 percent.
26. The electrochemical cell according to claim 23, wherein the atomic ratio of copper to component B in said non-stoichiometric hydrogen alloy is in the range of 0.01 to 0.20.
27. The electrochemical cell according to claim 26, wherein the atomic ratio of copper to component B in said non-stoichiometric hydrogen storage alloy is in the range of 0.01 to 0.06.
28. The electrochemical cell according to claim 23, wherein
A comprises 60 to 65 atomic percent La, 24 to 28 atomic percent Ce, 2 to 4 atomic percent Nd, and 6 to 10 atomic percent Pr; B comprises 78 to 84 atomic percent Ni, 4 to 8 atomic percent Co, 5 to 9 atomic percent Mn, and 4 to 8 atomic percent Al; and
0.18 ≤ y ≤ 0.30.
29. The electrochemical cell according to claim 23, wherein 0.15 ≤ y ≤ 0.30.
30. The electrochemical cell according to claim 23, wherein 4.95 ≤ x ≤ 5.05.
31. A hydrogen storage alloy having a bulk region and an interface region, said interface region comprising catalytic metallic particles supported by a support matrix and voids, said catalytic metallic particles having diameters of less than about 100 A, said catalytic metallic particles and said voids being
distributed throughout said interface region, wherein the volume fraction of said voids in said interface region is greater than 5%, said hydrogen storage alloy also having a hysteresis less than or equal to 0.12.

32. The hydrogen storage alloy according to claim 31, wherein said hydrogen storage alloy is non-stoichiometric.
33. The hydrogen storage alloy according to claim 31, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of 4.80 to 5.20.
34. The hydrogen storage alloy according to claim 33, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of 4.90 to 5.10.
35. The hydrogen storage alloy according to claim 34, wherein said hydrogen storage alloy has a pseudo B/A ratio in the range of

4.95 to 5.05.
36. The hydrogen storage alloy according to claim 31 having a c/a lattice constant ratio greater than or equal to 0.805
37. The hydrogen storage alloy according to claim 31, wherein said c/a lattice constant ratio is greater than or equal to 0.809.
38. The hydrogen storage alloy according to claim 31, wherein said hydrogen storage alloy has the formula ABxCuy, wherein,
A is one or more elements selected from La, Ce, Pr, Nd, Mm, and other rare earth elements;
B is one or more elements selected from Ni, Mn, Co, Al, Cr, Ag, Pd, Rh, Sb, V, and Pt;
4.8 ≤ x < 5.2; and
0.01 < y < 0.35.
39. The hydrogen storage alloy according to claim 38, wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said hydrogen storage alloy is at least 35 percent.
40. The hydrogen storage alloy according to claim 39, wherein the percentage of Ni transferred to A-sites from B-sites versus the total amount of Cu contained in said hydrogen storage alloy is at least 45 percent.
41. The hydrogen storage alloy according to claim 38, wherein the atomic ratio of copper to component B in said hydrogen alloy is in the range of 0.01 to 0.20.
42. The hydrogen storage alloy according to claim 41, wherein the atomic ratio of copper to component B in said hydrogen storage alloy is in the range of 0.01 to 0.06.
43. The hydrogen storage alloy according to claim 38, wherein A comprises 60 to 65 atomic percent La, 24 to 28 atomic percent Ce, 2 to 4 atomic percent Nd, and 6 to 10 atomic percent Pr,- B comprises 78 to 84 atomic percent Ni, 4 to 8 atomic percent Co, 5 to 9 atomic percent Mn, and 4 to 8 atomic percent Al; and

0.18 ≤ y < 0.30.
44. The hydrogen storage alloy according to claim 38, wherein 0.15 ≤ y ≤ 0.30.
45. The hydrogen storage alloy according to claim 38, wherein 4.95 < X ≤ 5.05.