Hydrogen storage alloy
View Patent ↗A hydrogen storage alloy suitable for prescribed pretreatment, that is, pretreatment wherein mechanical pulverization is performed after pulverizing a hydrogen storage alloy and absorbing/desorbing hydrogen is provided. The hydrogen storage alloy comprises a parent phase having a CaCu 5 -type, that is, an AB 5 -type crystal structure, wherein the A site is constituted from a rare earth element containing La; and the B site does not contain Co and contains at least Ni, Al, and Mn, with the ratio (Mn/Al) of the content of Mn (molar ratio) to the content of Al (molar ratio) being 0.60 or more and less than 1.56, and the ratio (La/(Mn+Al)) of the content of La (molar ratio) to the total content of the content of Al (molar ratio) and the content of Mn (molar ratio) being more than 0.92.
1. A hydrogen storage alloy comprising:
a parent phase having an AB 5 -type crystal structure,
wherein the A site is constituted from a rare earth element containing La,
wherein the B site does not contain Co and contains at least Ni, Al, and Mn, with the molar ratio (Mn/Al) of the content of Mn to the content of Al being 0.60 or more and less than 1.56, and the molar ratio (La/(Mn+Al)) of the content of La to the total content of the content of Al and the content of Mn being more than 0.92, and
wherein, in a pressure-composition isothermal chart (PCT curve) at 45° C. an equilibrium hydrogen pressure at a hydrogen storage capacity (H/M) of 0.5 is 0.014 MPa or more and 0.035 MPa or less.
2. The hydrogen storage alloy according to claim 1 , wherein the molar ratio (Mn/Al) of the content of Mn to the content of Al in the B site is 1.15 or more and less than 1.56.
3. The hydrogen storage alloy according to claim 1 ,
wherein the alloy is represented by a general formula: MmNi a Mn b Al c where Mm represents a rare earth element containing La, a is 4.2 or more and 4.6 or less, b is 0.1 or more and 0.6 or less, and c is 0.1 or more and 0.6 or less, and
wherein a ratio ABx of the total number of moles of elements constituting the B site to the total number of moles of elements constituting the A site satisfies 4.85≤ABx≤5.40.
4. The hydrogen storage alloy according to claim 1 ,
wherein the alloy is represented by a general formula: MmNi a Mn b Al c wherein Mm represents a rare earth element containing La, a is 4.2 or more and 4.6 or less, b is 0.1 or more and 0.6 or less, and c is 0.1 or more and 0.6 or less, and
wherein a ratio ABx of the total number of moles of elements constituting the B site to the total number of moles of elements constituting the A site satisfies 5.00≤ABx≤5.40.
5. The hydrogen storage alloy according to claim 1 , wherein an a-axis length obtained by powder X-ray diffraction measurement is 5.03 Å or more and 5.07 Å or less.
6. A negative electrode active material for a nickel-hydrogen battery comprising the hydrogen storage alloy according to claim 1 .
7. A nickel-hydrogen battery using the negative electrode active material according to claim 6 .
8. A nickel-hydrogen battery to be mounted on an electric vehicle or a hybrid electric vehicle, using the negative electrode active material according to claim 6 .
9. The hydrogen storage alloy according to claim 2 ,
wherein the alloy can be represented by a general formula: MmNi a Mn b Al c wherein Mm represents a rare earth element containing La, and a is 4.2 or more and 4.6 or less, b is 0.1 or more and 0.6 or less, and c is 0.1 or more and 0.6 or less, and
wherein a ratio ABx of the total number of moles of elements constituting the B site to the total number of moles of elements constituting the A site satisfies 4.85≤ABx≤5.40.
10. The hydrogen storage alloy according to claim 2 ,
wherein the alloy is represented by a general formula: MmNi a Mn b Al c wherein Mm represents a rare earth element containing La, and a is 4.2 or more and 4.6 less, b is 0.1 or more and 0.6 or less, and c is 0.1 or more and 0.6 or less, and
wherein a ratio ABx of the total number of moles of elements constituting the B site to the total number of moles of elements constituting the A site satisfies 5.00≤ABx≤5.40.