Effect of elemental substitution on the structure and hydrogen storage properties of LaMgNi4 alloy

In operando neutron diffraction study of LaNdMgNi9H13 as a metal hydride battery anode

“…Ternary La-Mg-Ni intermetallics include three different stoichiometric ratios between Aelements (A = Mg and Rare Earths RE) and B-elements (B = Ni), AB 3 , A 2 B 7 and A 5 B 19 , which all show a good performance as battery anodes in the high energy/high power Ni-MH batteries [11,12]. These compounds belong to the hybrid AB x layered structures, where individual Laves type AB 2 layer, La 2-y Mg y Ni 4 , and Haucke type AB 5 layers, LaNi 5 , stack along the hexagonal/trigonal axis in different ratios (AB 3 = AB 5 + 2 AB 2 ; A 2 B 7 = AB 5 + AB 2 ; A 5 B 19 = 3 AB 5 + 2 AB 2 ).…”

“…A detailed review on the structural, thermodynamic and electrochemical properties of the metallic hydrides belonging to the pseudo-binary family RE-Mg-Ni has been published recently [13]. Improving the hydrogen storage properties of La-Mg-Ni-based alloys by such methods as elemental substitution in the alloy composition [12,[14][15][16], rapid quenching [17], composite alloying (by Mn, Al) and surface modification [18] have been employed by several groups. Among these methods elemental substitution was found to be the most efficient way to improve the cycling stability of La-Mg-Ni-based alloys.…”

The Crystal Structures in Hydrogen Absorption Reactions of REMgNi4-Based Alloys (RE: Rare-Earth Metals)

“…In fact, the design of intermetallic compounds that do not form ionic or complex hydrides is one approach to obtain efficient hydrogen storage materials. So far, REMgNi 4 -based alloys, such as RE (2−x) Mg x Ni 4 (RE: rare-earth metals; 0 < x < 2), have been reported to exhibit reversible hydrogen absorption and desorption reactions at ambient temperatures [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. In these reactions, hydrogen atoms are located at interstitial sites in the lattice of RE (2−x) Mg x Ni 4 and three hydride phases are formed [19][20][21][22][23][24][28][29][30][31][32][33] the α-, β-, and γ-hydride phases, respectively.…”

“…The experimentally reported hydride phases with their unit cell parameters, formation enthalpy of the hydrides, and hydrogen contents are listed in Table 1. In RE (2−x) Mg x Ni 4 , the atomic radii of the components, which are influenced by the addition of Mg with a smaller atomic radius than RE atoms [34], selection (radius) of the RE element, and compositional ratios, are crucial parameters for reversible hydrogen absorption and desorption reactions [14][15][16][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] and for avoiding hydrogen-induced amorphization (HIA) [35,36]. Absorbed hydrogen in RENi 2 without Mg is hardly released at ambient temperature because of the considerably lower hydrogen desorption pressure than the ambient pressure.…”

“…Shtender et al reported that the γ-hydride phase was formed by Co doping in Ni atomic sites as in YMgNi 2 Co 2 or YMgCo 4 [19]. Although most studies on RE (2−x) Mg x Ni 4 have mainly focused on Ni [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], Co doping at Ni atomic sites or replacement of Ni atoms with Co have also been attempted in RE = La [25], Ce [29], Pr [30], Nd [30,31], and Tb [32,33], in which, Co could lead to increased hydrogen storage capacities and decreased equilibrium hydrogen absorption reactions. A new hydride phase with a monoclinic structure has been reported [33].…”