Effect of Mg₃MnNi₂ on the electrochemical characteristics of Mg₂Ni electrode alloy

Mg₂Ni-x mol% Mg₃MnNi₂ (x = 0, 15, 30, 60, 100), the novel composite alloys employed for hydrogen storage electrode, have been successfully synthesized by a method combining electric resistance melting with isothermal evaporation casting process (IECP). X-ray diffraction (XRD) analysis results show that the composite alloys are composed of Mg₂Ni phases and the new Mg₃MnNi₂ phases. It is found on the electrochemical studies that maximum discharge capacities of the composite alloys increase with the increasing content of the Mg₃MnNi₂ phase. The discharge capacity of the electrode alloy is effectively improved from 17 mAh g^-1 of the Mg₂Ni alloy to 166 mAh g^-1 of the Mg₃MnNi₂ alloy. Among these alloys, the Mg₃MnNi₂ phase possesses a positive effect on the retardation of cycling capacity degradation rate of the electrode materials. Cyclic voltammetry (CV) results confirm that the increasing content of the Mg₃MnNi₂ phase effectively improves the reaction activity of the electrode alloys. Surface analyses indicate that the Mg₃MnNi₂ phase can enhance the anti-corrosive performance of the particle surface of these composite alloys.