With the purpose of improving the electrochemical hydrogen storage properties of the alloys containing rare earth elements, an amorphous CoZnB was introduced into a La0.7Mg0.3Ni3.5 alloy to form a novel composite by ball milling. Electrochemical measurements demonstrated that both the high-rate dischargeability (HRD) and the maximum discharge capacity (C-max) of the composite electrodes were significantly improved. C-max of the composite electrodes could reach 487.5 mAh/g, which is much higher than that of pristine La0.7Mg0.3Ni3.5 alloy electrode (343.9 mAh/g). Moreover, HRD at a current density of 800 was increased to 93.1%. The electrochemical reaction kinetics was also investigated by linear polarization, anodic polarization, electrochemical impedance spectroscopy and potential-step discharge. It was found that, compared to pristine La0.7Mg0.3Ni3.5 alloy electrode, doping with CoZnB could give rise to a decrease of exchange current density and an increase of hydrogen diffusion coefficient, limiting current density and charge-transfer resistance. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.