Abstract:The effects of Mn content on microstructure and electrochemical properties of LaNi_4.2−xCo_0.6Mn_xAl_0.2 alloys were investigated systematically. The results of XRD analyses indicate that the substitution of Mn does not change the crystal structure, but along with the increase of Mn substitution quantity, the volume of the crystal increases and the ratio of axial to radial lattice parameters (a/c) first increases, then decreases. With the increase of Mn substitution quantity in LaNi_4.2−xCo_0.6Mn_x Al_0.2, the discharge capacity, charge efficiency, the self-discharge and high rate discharge capacity increase first and then decrease. The discharge capacity reaches the highest value of 367 mA∙h/g (x=0.1) at 0.2C.

Key words: hydrogen storage alloys; crystal structure; electrochemical properties; Mn substitution