Electrochemical and Kinetic Performance of Low-Cobalt and Cobalt-Free Rare-Earth AB5-Type Hydrogen Storage Alloys

To address the high cost of cobalt in rare-earth hydrogen storage alloys, this study developed cost-effective low-cobalt and cobalt-free AB₅-type alloys. The results demonstrate that all synthesized alloys displayed a single-phase LaNi₅ structure possessing a homogeneous elemental distribution. Low-cobalt (La, Ce) (Ni, Co, Mn, Al)₅ alloy 4SC and cobalt-free (La, Ce) (Ni, Mn, Al)₅ alloy 7D exhibited similarly excellent electrochemical performance, including high discharge capacity, long cycle life, and superior high-rate discharge (<i>HRD</i>) capability. In addition, the kinetic test results show that the exchange current densities of these two alloys were quite similar, measuring 302.97 mA g^-1 and 317.70 mA g^-1, respectively. However, the hydrogen diffusion coefficient of 7D was significantly higher than that of 4SC, reaching 9.45 × 10^-10 cm² s^-1, while that of 4SC was only 5.88 × 10^-10 cm²/s. This work establishes a theoretical foundation for industrial-scale and cost-effective AB₅-type hydrogen storage alloys, offering significant commercial potential.