Effect of Ce replacing La on the electrochemical performance of amorphous grain boundaries Mg-Ni-based materials

Abstract

Aiming at enhancing the electrochemical characteristic of RE-Mg-based composite, the partial substituting La with Ce experiment in the composites was conducted, and the surface modification treatment of the alloys was performed by mechanical coating Ni. By means of mechanical trituration, The La10-xCexMg80Ni5 (x = 0–2) + y wt% Ni (y = 50–200) compound materials which have the structures of nanocrystalline and amorphous were synthesized. In order to make sense of the principle action of Ce and Ni elements in structural and electrochemical properties of the material, some deep research were carried out. According to the final results, the as-milled composites have the electrochemical hydrogen absorption and hydrogen desorption abilities at room temperature. Having no use for activation, the as-milled composites can reach the maximum discharge capacities when the first cycling was carried out. With the Ni value x changed from 50 to 200, the discharge capacity was varied from 70.5 mAh/g to 902.1 mAh/g; moreover, the capacity retention rate at 20th cycle (S20) and high rate dischargeability (HRD) of the (x = 0) composite were heightened from 67.2 % to 82.3 %, from 50.6 % to 55.7 % respectively. The composites' (y = 100) discharge capacity has a maximum value 118.5 mAh/g when the Ce value x is 1. The capacity retention rate (S20) is enhanced from 53.3 % to 68.5 % by lifting Ce content from x = 0 to x = 2. what's more, the high-rate discharge ability (HRD), the electrochemical impedance spectrum (EIS), potentiodynamic polarization curves, and potential-step measurements all intimate that substituting La with Ce clearly promotes the composites' electrochemical kinetic properties, but maximum values emerge only when the x value is 1.