Hydrogen-absorbing alloy, fabrication method thereof and alkaline storage battery
View Patent ↗An alkaline storage battery has a negative electrode using a hydrogen-absorbing alloy represented by a general formula Ln 1-x Mg x Ni y A z wherein Ln is at least one element selected from rare-earth elements including Y, Ca, Zr, and Ti, A is at least one element selected from Co, Fe, Mn, V, Cr, Nb, Al, Ga, Zn, Sn, Cu, Si, P and B, and 0.15≦x≦0.30, 0<z≦1.5, and 2.8≦y+z≦4.0 are satisfied. The hydrogen-absorbing alloy has a hexagonal system crystal structure or a rhombohedral system crystal structure as its main phase and has a subphase of line which average number of not less than 50 nm in thickness existing in the range of 10 μm×10 μm in the cross section of the main phase is 3 or less.
1. A hydrogen-absorbing alloy represented by a general formula
Ln 1-x Mg x Ni y A z
wherein:
Ln is at least one element selected from rare-earth elements including Y, Ca, Zr, and Ti;
A is at least one element selected from Co, Fe, Mn, V, Cr, Nb, Al, Ga, Zn, Sn, Cu, Si, P and B; and
0.15≦x≦0.30, 0<z≦1.5 and 2.8≦y+z≦4.0 are satisfied,
wherein
a main phase has a hexagonal system crystal structure or a rhombohedral system crystal structure, and
a subphase in the range of 10 μm×10 μm of a cross section of the main phase has an average number of a line of not less than 50 μm in thickness of 3 or less.
2. The hydrogen-absorbing alloy as claimed in claim 1 , wherein
the subphase has a different crystal structure from the hexagonal system crystal structure or the rhombohedral system crystal structure.
3. A fabrication method of a hydrogen-absorbing alloy represented by a general formula Ln 1-x Mg x Ni y A z wherein Ln is at least one element selected from rare-earth elements including Y, Ca, Zr, and Ti, A is at least one element selected from Co, Fe, Mn, V, Cr, Nb, Al, Ga, Zn, Sn, Cu, Si, P and B, and 0.15≦x≦0.30, 0<z≦1.5 and 2.8≦y+z≦4.0 are satisfied, comprising the steps of:
heat-treating the hydrogen-absorbing alloy at a temperature 10° C. to 110° C. lower than a melting point of hydrogen-absorbing alloy for one hour or more; and
rapid-cooling the hydrogen-absorbing alloy after the heat-treatment at a cooling speed of not less than 0.5° C./sec from a heat-treatment temperature.
4. The fabrication method of hydrogen-absorbing alloy as claimed in claim 3 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled from the heat-treatment temperature at a cooling speed of not less than 100° C./sec.
5. The fabrication method of hydrogen-absorbing alloy as claimed in claim 3 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled by soaking in a coolant.
6. The fabrication method of hydrogen-absorbing alloy as claimed in claim 4 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled by soaking in a coolant.
7. The fabrication method of hydrogen-absorbing alloy as claimed in claim 3 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled under an atmosphere of which major component is He.
8. The fabrication method of hydrogen-absorbing alloy as claimed in claim 4 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled under an atmosphere of which major component is He.
9. A fabrication method of hydrogen-absorbing alloy represented by a general formula Ln 1-x Mg x Ni y A z wherein Ln is at least one element selected from rare-earth elements including Y, Ca, Zr, and Ti, A is at least one element selected from Co, Fe, Mn, V, Cr, Nb, Al, Ga, Zn, Sn, Cu, Si, P and B, and 0.15≦x≦0.30, 0<z≦1.5, and 2.8≦y+z≦4.0 are satisfied, comprising steps of:
heat-treating the hydrogen-absorbing alloy at a temperature 10° C. to 60° C. lower than a melting point of hydrogen-absorbing alloy for one hour or more;
cooling the hydrogen-absorbing alloy after the heat-treatment;
heat-treating the hydrogen-absorbing alloy after the cooling at a temperature 10° C. to 110° C. lower than a melting point of hydrogen-absorbing alloy for one hour or more; and
rapid-cooling the hydrogen-absorbing alloy after the heat-treatment at a cooling speed of not less than 0.5° C./sec from a heat-treatment temperature.
10. The fabrication method of hydrogen-absorbing alloy as claimed in claim 9 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled from the heat-treatment temperature at a cooling speed of not less than 100° C./sec.
11. The fabrication method of hydrogen-absorbing alloy as claimed in claim 9 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled by soaking in a coolant.
12. The fabrication method of hydrogen-absorbing alloy as claimed in claim 10 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled by soaking in a coolant.
13. The fabrication method of hydrogen-absorbing alloy as claimed in claim 9 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled under an atmosphere of which major component is He.
14. The fabrication method of hydrogen-absorbing alloy as claimed in claim 10 , wherein the hydrogen-absorbing alloy after heat-treatment is rapid-cooled under an atmosphere of which major component is He.
15. An alkaline storage battery comprising a positive electrode, a negative electrode using a hydrogen-absorbing alloy, and an alkaline electrolyte, wherein the negative electrode uses the hydrogen-absorbing alloy according to claim 1 .
16. An alkaline storage battery comprising a positive electrode, a negative electrode using a hydrogen-absorbing alloy, and an alkaline electrolyte, wherein the negative electrode uses the hydrogen-absorbing alloy according to claim 2 .