Effect of Mg content in the La3-xMgxNi9 battery anode alloys on the structural, hydrogen storage and electrochemical properties

• Published in: Journal of alloys and compounds 2021-03, Vol.856, p.157443, Article 157443
• Main Authors: Wan, ChuBin, Hu, Weikang, Denys, R.V., Nwakwuo, C.C., Solberg, J.K., Yartys, V.A.
• Format: Article
• Language: English
• Subjects: Alloys; Annealing; Anode effect; Anode electrodes; Crystal structure; Current density; Discharge; Electrochemical analysis; Electrodes; Homogeneity; Hydrogen storage; Hydrogen storage materials; Intermetallic compounds; La–Mg–Ni alloys; Magnesium; Metal hydride batteries; Metal hydrides; Nickel; Properties (attributes); Stability
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.157443

The present work is focused on the studies of structure, hydrogen storage and electrochemical properties of the La3-xMgxNi9 (x = 1.0, 1.1 and 1.2) alloys as active materials of negative electrodes in the Nickel-Metal Hydride (Ni/MH) batteries. A change of Mg content affects properties of the studied alloys such as the phase homogeneity, hydrogen storage and electrochemical capacities, cycle stability, and high-rate discharge performance. X-ray diffraction study shows that Mg substitution for La and annealing of the La3-xMgxNi9 alloys promotes the formation of more homogeneous materials, with a predominant formation of the target AB3 PuNi3 structure type intermetallics. The electrodes prepared from the annealed alloys show the maximum discharge capacities of ∼400 mAh g−1 at discharge current density of ∼60 mA/g. The high rate discharge-abilities (HRD) at the discharge current density of 350 mA g−1 keep high values of the remaining reversible discharge capacities, ∼86, 85 and 80%, for the La2MgNi9, La1·9Mg1·1Ni9 and La1·8Mg1·2Ni9 alloy electrodes, respectively. After 200 cycles with 100% depth of discharge (DOD), the La1·9Mg1·1Ni9 alloy electrode exhibits a very good cycling stability with its discharge capacity remaining at a level of ∼64% of its initial capacity. •La3-xMgxNi9 (x = 1.0; 1.1; 1.2) alloys crystallize with PuNi3 type trigonal structures.•Increase of Mg content results in a gradual contraction of the unit cells.•The as cast alloys showed presence of 6 different types of intermetallics.•Annealing leads to the predominant formation of the 1:3 and 2:7 intermetallics.•Maximum discharge capacity of the anodes reaches 400 mAh/g.