Electrochemical features of Ce2Ni7-type La0.65Nd0.15Mg0.25Ni3.20M0.10 (M = Ni, Mn and Al) hydrogen storage alloys for rechargeable nickel metal hydride battery

Rare earth-Mg-Ni-based alloys with Ce2Ni7-type superlattice structures as the negative electrode materials of nickel metal hydride batteries are laser-focused owing to their good overall electrochemical performance. However, the confusing conclusion about complex impact of element and phase composition on the electrochemical properties hinders the further promotion of the alloys. Here, we understand the effect of the substituted Ni-side elements on their electrochemical properties of the Ce2Ni7-type La-Nd-Mg-Ni-M-based (M = Ni, Mn and Al) alloys. It shows that the Ce2Ni7-type La0.60Nd0.15Mg0.25Ni3.20Al0.10 alloy electrode exhibits superior durability with the capacity retention rate of 91.1% after 100 cycles, 2.1% higher than the La0.60Nd0.15Mg0.25Ni3.30 alloy with a same structure. However, the alloy with Mn delivers the highest discharge capacity of 396.3 mAh g(-1) at 0.2 C and has advantage of rate performance, which even gives 206.9 mAh g(-1) at the large discharge current density of 5 C. The work is aimed to help design hydrogen storage alloys with improved electrochemical performance by making clear the effect of substituted Mn and Al. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Rare earth-Mg-Ni-based alloys with Ce2Ni7-type superlattice structures have gained attention as negative electrode materials for nickel metal hydride batteries due to their good overall electrochemical performance. However, the complex impact of element and phase composition on the electrochemical properties hinders their further promotion. Investigating the effect of substituted Ni-side elements on the electrochemical properties of Ce2Ni7-type La-Nd-Mg-Ni-M-based (M = Ni, Mn, and Al) alloys, it was found that the La0.60Nd0.15Mg0.25Ni3.20Al0.10 alloy electrode exhibited superior durability with a capacity retention rate of 91.1% after 100 cycles, 2.1% higher than the La0.60Nd0.15Mg0.25Ni3.30 alloy with the same structure. The alloy with Mn delivered the highest discharge capacity and had advantage of rate performance, even achieving 206.9 mAh g(-1) at a large discharge current density of 5 C. The study aims to assist in designing hydrogen storage alloys with improved electrochemical performance by clarifying the effect of substituted Mn and Al elements.