New multiphase R-Mg-Ni based alloys with non-super and super stacking structures as a promising negative electrodes for Ni-MH batteries

• Published in: Journal of energy storage 2024-08, Vol.96, p.112740, Article 112740
• Main Authors: Verbovytskyy, Yuriy, Vlad, Khrystyna, Zavaliy, Ihor, Hreb, Vasyl, Kononiuk, Oleksandr
• Format: Article
• Language: English
• Subjects: Alloys; Electrochemical performance; Hydrogen storage; Ni-NH batteries; Rare-earth
• ISSN: 2352-152X
• DOI: 10.1016/j.est.2024.112740

This paper presents the effects of elemental substitution (R → Y or Ni → Co) in R-Mg-Ni (R = La, Nd, Pr) alloys on their electrochemical properties. The studied alloys were prepared by sintering and annealing pressed powdered precursors with magnesium. Samples were characterized by X-ray diffraction and energy dispersive analyses. The synthesized alloys exhibited a multiphase nature with both non-super and super stacking structures detected. Within La-based series, the electrode based on La3MgNi11Co3 and La4MgNi16Co3 alloys exhibits the highest discharge capacity of above 400 mAh/g and acceptable cyclic stability. The best cyclic stability of above 80 % after 50 cycles for both Ich/dis = 50 and 300 mA/g was observed for the La2YMgNi11Co3 electrode (Cmax = 384 mAh/g). La-based alloys showed higher high-rate dischargeability than Nd- and Pr-based alloys. HRD1000 for the La4YMgNi21Co3 electrode of 89 % was found as the highest one among all investigated electrode materials. In addition to above mentioned characteristics, the Tafel curves, cyclic voltammetric measurements as well as hydrogen diffusion coefficient calculation were performed and used for the analysis of the electrode characteristics. Maximum discharge capacity versus average volume per atom. [Display omitted] •New A2B7, A2B19 and AB4 (A = La, Pr, Nd, Y, Mg; B = Ni, Co) alloys have been studied.•Maximum discharge capacity of about 400 mAh/g was determined.•Acceptable cyclic stability of more than 80% is observed after 50 cycles.•The kinetic properties of the metal hydride electrodes have been established.