Highly improved electrochemical hydrogen storage performances of the Nd–Cu–added Mg2Ni-type alloys by melt spinning

• Elements Nd and Cu were jointly added in Mg2Ni-type alloy.
• Amorphous and nanocrystalline structures were obtained by melt spinning.
• Electrochemical performances of the alloys were investigated in details.
• Effects of Nd content and spinning rate on the properties were investigated.
• Mechanism of capacity degradation was discussed.

In order to improve the electrochemical hydrogen storage performances of the Mg2Ni-type alloy, Nd and Cu were added jointly. The (Mg24Ni10Cu2)100−xNdx (x = 0, 5, 10, 15, 20) alloys with nanocrystalline and amorphous structure were fabricated by melt-spinning technique. The effects of spinning rate and Nd content on the structures and electrochemical hydrogen storage performances of the alloys were investigated. The structure characterizations of XRD, TEM and SEM linked with EDS reveal that the as-cast (x = 15) alloy holds a multiphase structure, containing Mg2Ni major phase as well as some secondary phases Mg6Ni, Nd5Mg41 and NdNi. The as-spun Nd-free alloy displays an entire nanocrystalline structure, whereas the as-spun Nd-added alloys hold a nanocrystalline and amorphous structure, meanwhile, the degree of amorphization visibly increases with both spinning rate and Nd content rising, suggesting that the addition of Nd facilitates the glass forming of the Mg2Ni-type alloys. Furthermore, the addition of Nd and melt spinning dramatically improve the electrochemical hydrogen storage performances of the alloys. The discharge capacity and cycle stability of the alloys conspicuously augment with spinning rate growing. When the spinning rate rises from 0 (The as-cast was defined as the spinning rate of 0 m/s) to 40 m/s, the discharge capacity of the (x = 10) alloy is enhanced from 86.4 to 452.8 mA h/g, and capacity maintain rate (S20) (the capacity maintain rate at 20th cycle) from 53.2% to 89.7%, respectively.