Effects of metal additive on electrochemical performances of Mg-based hydrogen storage materials prepared by hydriding combustion synthesis and subsequent mechanical milling (HCS+MM)

Mg2Ni-based hydride was prepared by hydriding combustion synthesis (HCS), and subsequently modified with various metal elements (Ti, Co, Cr and Y) by mechanical milling. The effects of the modifications on electrochemical properties of the hydride were investigated. Both of the maximum discharge capacity and the high rate dischargeability (HRD) are increased by the modification of Co, while the cycling stability is improved for the hydride modified with Ti, Cr and Y. The Tafel polarization shows that the addition of the metals has a positive effect on improving the anti-corrosion ability. The electrochemical kinetics was also characterized by linear polarization, electrochemical impedance spectroscopy and potentiostatic discharge. The results show that the hydrogen diffusion coefficient and the electrochemical reaction resistance are increased by the modifications, but the exchange current density decreases.