Patent ID: 8535460

Claim:
A low Co hydrogen storage alloy having a CaCu 5 crystal structure that can be represented by the general formula MmNi a Mn b Al c Co d , wherein Mm is a Misch metal, 4.31≦a≦4.7, 0.3≦b≦0.65, 0.2≦c<0.37, ≦0<d≦0.2, wherein, in a composition of 5.25≦a+b+c+d<5.30, the a-axis length of the crystal lattice is not less than 500.5 pm and not more than 502.7 pm, and the c-axis length is not less than 405.6 pm and not more than 406.9 pm, wherein the pulverization residual rate obtained by the following equation is 50% or more: Pulverization residual rate (%)=(post-cycling particle size/pre-cycling particle size)×100, when a hydrogen storage alloy is ground and screened to select particles with a particle size in the range of 20 μm and 53 μm to provide hydrogen storage alloy powder, and after measuring with a particle size distribution measuring device the average particle size (pre-cycling particle size, D 50 ) of the hydrogen storage alloy powder; 2 g of the hydrogen storage alloy powder is weighed and placed into a PCT holder; the surfaces thereof are cleaned twice under hydrogen pressure of 1.75 MPa; then activation is carried out twice by introducing hydrogen of 3 MPa; next, a cycle test using a PCT device is then repeated 50 times, wherein hydrogen gas of 3 MPa is introduced into 2.0 g of the hydrogen storage alloy powder to absorb hydrogen, and the hydrogen is desorbed at 45° C.; and the average particle size of the hydrogen storage alloy powder after the test of the 50 cycles (post-cycling particle size, D 50 ) is measured with a particle size distribution measuring device.