The electrochemical characteristics of the ball-milled LaMg10NiMn alloys with Ni powders were investigated. It was found that the ball-milled LaMg10NiMn + 150 wt.% Ni composite exhibited higher first discharge capacity and better cycle performance. By means of the analysis of electrochemical impedance spectra (EIS), it was shown that the existence of manganese in LaMg10NiMn alloy increased the electrocatalytic activity due to its catalytic effect, and destabilized metal hydrides, and so reduced the hydrogen diffusion resistance. These contributed to the higher discharge capacity of the ball-milled LaMg10NiMn-Ni composite. According to the analytical results of X-ray diffraction (XRD), EIS and steady-state polarization (SSP) experiments, the inhibition of metal corrosion is not the main reason for the better cycle performance. The main reason is that the electrochemical reaction resistance of the ball-milled LaMg10NiMn-Ni composite is always lower than that of the ball-milled. LaMg10Ni2-Ni composite because the former one contains manganese, which is a catalyst for the electrode reaction. (C) 2008 Elsevier B.V. All rights reserved.