Structure and electrochemical characteristics of Mg–Ti–Ni-based electrode alloys synthesized by mechanical milling

The vacuum induction melting was adopted to fabricating Mg_50−xTi_xNi₄₅Al₃Co₂ (x = 0, 1, 2, 3, 4 at.%) composites protected by the high-purity helium atmosphere. Subsequently, the surface modification treatment of the as-cast alloys was carried out by mechanically coating nickel. The amorphous and nanocrystalline Mg_50−xTi_xNi₄₅Al₃Co₂ (x = 0–4) + 50 wt.% Ni hydrogen storing alloys as the negative materials in batteries were prepared through ball milling, and the influences of milling time and Ti dosage on the structure and electrochemical hydrogen storing behaviors of the corresponding samples were studied in detail. The electrochemical testing reveals that the as-milled alloys have excellent performances and can finish the electrochemical hydrogenation and dehydrogenation at indoor temperature. In the first cycle without activation, the ball milling alloy obtains the maximum value of discharge capacity. Discharge capacity and cyclic steadiness of the composites conspicuously grow as Ti content and milling duration increase. Concretely, the capacity retaining rate at 100th cycle and the discharge capacity of 30 h milling samples augment from 53% to 78% and from 435.2 to 567.2 mAh/g with changing Ti content from 0 to 4. The same performances of the alloy (x = 4) are enhanced from 61% to 78% and from 379.9 to 567.2 mAh/g, respectively, with extending milling duration. Moreover, high rate discharge ability, potential-step measurements, potentiodynamic polarization curves and electrochemical impedance spectrum manifest that the electrochemical kinetics properties can achieve significant amelioration as Ti content varies and milling duration is extended.