Phase structure and electrochemical properties of the Ml1−x Mg x Ni2.80Co0.50Mn0.10Al0.10 (x =0.08, 0.12, 0.20, 0.24, 0.28) (Ml=La-rich mixed lanthanide) alloys were studied. X-ray diffraction (XRD) analysis and Rietveld refinement show that the alloys consist mainly of LaNi5 and (La,Mg)Ni3 phase. Due to variation in phases of the alloys, the maximum discharge capacity, the high rate dischargeability (HRD), and the low temperature dischargeability increase first and then decrease. The maximum discharge capacity increases from 322mAhg−1 (x =0.08) to 375mAhg−1 (x =0.12), and then decreases to 351mAhg−1 (x =0.28) with increasing x. As the case of x =0.20, HRD at 1200mAg−1 and discharge capacity at 233K reaches 41.7% and 256mAhg−1, respectively. The cycling stability is improved by substituting La with Ml and B-site multi-alloying, and the capacity retention of Ml0.72Mg0.28Ni2.80Co0.50Mn0.10Al0.10 at the 200th cycle is 71%.