Electrochemical properties of Mg-based hydrogen storage alloys prepared by hydriding combustion synthesis and subsequent mechanical milling (HCS+MM)

In this paper, a novel method, namely hydriding combustion synthesis (HCS) and subsequent mechanical milling (MM) was used to prepare Mg-based hydrogen storage electrode alloy. The phase structures and electrochemical properties of the alloys before and after MM were characterized by X-ray diffraction (XRD) analysis and galvanotactic charge-discharge cycle test, respectively. The XRD results showed that the structure of the as-milled alloys was nanocrystallite or amorphous-like state. Electrochemical measurements showed that the discharge capacity was improved greatly for the products of HCS+MM. The HCS product with only 5 h MM showed markedly increased discharge capacity up to 481.5 mAh/g for the first cycle, which was 10 times higher than the HCS product (39.4 mAh/g). The discharge capacity was further increased to 628.3 mAh/g for the HCS product after milling with nickel powder. Besides, the addition of nickel also led to an improved cycling stability of the alloy electrode during cycling in KOH electrolyte. It was indicated that the HCS+MM was promising for preparing Mg-based hydrogen storage electrode alloys.