| Preparation techniques for amorphous MgNi hydrogen storage alloy were explored by means of mechanical alloying. Amorphous MgNi+xwt.%B(x=0,2,5,10) and Mg1-xScxNi(x=0, 0.01) hydrogen storage alloys were successfully prepared by mechanical alloying, and the influence law of the addition of boron and the substitution of magnesium by micro scandium on structure and electrochemical properties of MgNi hydrogen storage alloy was studied by XRD, XPS, SEM, DSC and electrochemical properties testing. The results can be concluded as follows:For MgNi+x%B alloys, addition of boron promoted the alloy to form amorphous phase, increased the atom ratio of Ni/Mg at the alloy surface, but did not decrease the oxidation degree on the alloy surface. And the addition of boron enhanced the thermal stability of the amorphous alloy. As relative to MgNi alloy without boron addition, the crystallization temperature of the alloy with 5%B content increased 11.02oC. The discharge capacity of the alloy electrodes increased first, and then decreased with increasing the addition of boron. Compared with MgNi alloy electrode, the discharge capacity of MgNi+5%B alloy electrode was increased 21.8%. The electrochemical cycle stability of the alloy electrodes increased with increasing the addition of boron. Compared with MgNi alloy electrode, the cycle capacity retention rate S10 of MgNi+10%B alloy electrode was increased 67.8%. The kinetic properties of the alloy electrodes were improved by adding boron. Compared with MgNi alloy electrode, the high-rate dischargeability HRD400, the exchange current density I0 and the limited current density IL of MgNi+5%B alloy electrode were increased 35.0%, 351.5% and 20.2%, respectively. Addition of boron decreased the thermal stability of the electrode alloy hydrides.For Mg1-xScxNi alloys, the substitution of magnesium by micro scandium weakened the degree of oxidation on the alloy surface, and increased atom ratio of Ni/Mg at the alloy surface. The electrochemical test results showed that the substitution of magnesium by micro scandium improved the electrochemical properties of the alloy electrodes. The discharge capacity, the cycle capacity retention rate S10, the high-rate dischargeability HRD200, the exchange current density I0 and the limited current density IL of Mg0.99Sc0.01Ni alloy electrode were 8.0%, 14.7%, 30.4%, 202.7% and 77.8% higher than that of MgNi alloy electrode, respectively. The substitution of magnesium by micro scandium significantly decreased the thermal stability of the electrode alloy hydrides. |
