Hydrogen absorbing alloy and secondary battery

A secondary battery, comprising:

• a positive electrode, a negative electrode containing a hydrogen absorbing alloy, and an alkaline electrolyte, wherein said hydrogen absorbing alloy has a composition represented by general formula (3) given below and contains not higher than 10% by volume including 0% by volume of a phase having an AB2 type crystal structure, and an intensity ratio calculated by formula (2) given below is lower than 0.15 including 0:
• I1/I2 (2)
• where I2 is an intensity of a highest peak in an X-ray diffraction pattern using a CuKα ray, and I1 is an intensity of a highest peak appearing at a value of 2θ that falls within a range of from 8° to 13° in the X-ray diffraction pattern, θ being a Bragg angle;
• R1-a-bMgaTbNiZ-XM3X (3)
• where R is at least one element selected from rare earth elements, said rare earth elements including Y, T is at least one element selected from the group consisting of Ca, Ti, Zr and Hf, M3 is at least one element selected from the group consisting of Co, Mn, Fe, Al, Ga, Zn, Sn, Cu, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P and S, the atomic ratios of a, b, X and z are respectively satisfy conditions of:
• 0.15≦a≦0.37, 0≦b≦0.1, 0.53≦(1−a−b)≦0.85, 0≦X≦2 and 3≦Z≦4.2.

A hydrogen absorbing alloy comprising a composition represented by general formula (3) given below,

• wherein a parallel growth region precipitates in at least one crystal grain of a principal phase, the parallel growth region having a crystal structure differing from a crystal structure of the principal phase, and an intensity ratio calculated by formula (2) given below is lower than 0.15 including 0:
• I1/I2 (2)
• where I2 is an intensity of a highest peak in an X-ray diffraction pattern using a CuKα ray, and I1 is an intensity of a highest peak appearing at a value of 2θ that falls within a range of from 8° to 13° in the X-ray diffraction pattern, e being a Bragg angle;
• R1-a-bMgaTbNiZ-XM3X (3)
• where R is at least one element selected from rare earth elements, said rare earth elements including Y, T is at least one element selected from the group consisting of Ca, Ti, Zr and Hf, M3 is at least one element selected from the group consisting of Co, Mn, Fe, Al, Ga, Zn, Sn, Cu, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P and S, the atomic ratios of a, b, X and z are respectively satisfy conditions of:
• 0.15≦a≦0.37, 0≦b≦0.1, 0.53≦(1−a−b)≦0.85, 0≦X≦2 and 3≦Z≦4.2.

A secondary battery, comprising a positive electrode, a negative electrode containing a hydrogen absorbing alloy, and an alkaline electrolyte,

• wherein said hydrogen absorbing alloy has a composition represented by general formula (3) given below, a parallel growth region precipitates in at least one crystal grain of a principal phase, the parallel growth region having a crystal structure differing from a crystal structure of the principal phase, and an intensity ratio calculated by formula (2) given is being lower than 0.15 including 0:
• I1/I2 (2)
• where I2 is an intensity of a highest peak in an X-ray diffraction pattern using a CuKα ray, and I1 is an intensity of a highest peak appearing at a value of 2θ that falls within a range of from 8° to 13° in the X-ray diffraction pattern, θ being a Bragg angle;
• R1-a-bMgaTbNiZ-XM3X (3)
• where R is at least one element selected from rare earth elements, said rare earth elements including Y, T is at least one element selected from the group consisting of Ca, Ti, Zr and Hf, M3 is at least one element selected from the group consisting of Co, Mn, Fe, Al, Ga, Zn, Sn, Cu, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P and S, the atomic ratios of a, b, X and z are respectively satisfy conditions of:
• 0.15≦a≦0.37, 0≦b≦0.1, 0.53≦(1−a−b)≦0.85, 0≦X≦2 and 3≦Z≦4.2.