In order to enhance the electrochemical capacity of the Co-free AB5-type electrode alloy, Mm in the alloys was substituted with La and Co-free La x Mm1−x (NiMnSiAlFe)4.9 (x = 0, 0.45, 0.75, 1.0) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the substituting Mm with La on the electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that substituting Mm with La can enhance markedly the capacities of the as-cast and quenched alloys. When the amount of substituting Mm with La, x increased from 0 to 1.0, the maximum capacity of the as-cast alloys at 0.2C rate increased from 273.45 to 304.47mAhg−1, and the capacity retaining rate (R h) increased from 59.16 to 59.86%. The capacity of the as-quenched alloys with a quenching rate of 10ms−1 increased from 236.83 to 300.31mAhg−1, and the capacity retaining rate (R h) decreased from 78.69 to 62.29%. The substituting Mm with La had an insignificant effect on the activation capabilities of the as-cast and quenched alloys.