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

Abstract

La 2 MgNi 9 -related alloys are superior metal hydride battery anodes as compared to the commercial AB 5 alloys. Nd-substituted La 2-y Nd y MgNi 9 intermetallics are of particular interest because of increased diffusion rate of hydrogen and thus improved performance at high discharge currents. The present work presents in operando characterization of the LaNdMgNi 9 intermetallic as anode for the nickel metal hydride (Ni-MH) battery. We have studied the structural evolution of LaNdMgNi 9 during its charge and discharge using in situ neutron powder diffraction. The work included experiments using deuterium gas and electrochemical chargedischarge measurements. The alloy exhibited a high electrochemical discharge capacity (373 mAh/g) which is 20 % higher than the AB 5 type alloys. A saturated β-deuteride synthesized by solid-gas reaction at P D2 = 1.6 MPa contained 12.9 deuterium atoms per formula unit (D/f.u.) which resulted in a volume expansion of 26.1%. During the electrochemical charging, the volume expansion (23.4%) and D-contents were found to be slightly reduced. The reversible electrochemical cycling is performed through the formation of a two-phase mixture of the solid solution and -hydride phases. Nd substitution contributes to the high-rate dischargeability, while maintaining a good cyclic stability. Electrochemical Impedance Spectroscopy (EIS) experiments showed a decreased hydrogen transport rate during long-term cycling.

Study of hydrogen storage and electrochemical properties of AB2-type Ti0.15Zr0.85La0.03Ni1.2Mn0.7V0.12Fe0.12 alloy

“…This results in an increased hydrogen diffusion coefficient and improved high rate dischargeability of the annealed alloy. An improvement in the electrochemical characteristics after the annealing was observed by us earlier when studying AB3 and A2B7 type alloys, and the values of specific capacitance, HRD, and cyclic stability obtained in this study are quite comparable with the data for the La-Mg-Ni alloys [39][40][41][42][43][44]. Further studies of the effect of the rare earth metals on the improved electrochemical performance of the Zr-based Laves type alloys are required to better understand the mechanism governing catalytic interaction between the main phase and the rare earth containing secondary phases, to systematically extend observations available for the multiphase Zrbased alloys doped by La, Ce, Pr or Nd [45] or Zr-based C15 type Laves phase alloys doped by 3 wt.% La [46].…”

Revisiting the Crystal Structure of BaCe0.4Zr0.4Y0.2O3−δ Proton Conducting Perovskite and Its Correlation with Transport Properties

“…In this sense, in situ/in operando characterization techniques cover a major field of capabilities under development at worldwide large facilities − and, to an extensive scale, on laboratory level . Many examples of these techniques were applied to the study of materials related to batteries, − SOFCs, − and catalysis. − However, the kind of simultaneous measurements conducted in this work has not yet been reported for protonic conductor materials, despite the fact that the simultaneous characterization of crystallographic and electrochemical properties is fundamental for understanding H-transport processes as well as PC-SOFC limitations and advantages.…”

Effect of yttrium content in the La2−xYxMgNi9 battery anode alloys on the structural, hydrogen storage and electrochemical properties

“…10 However, D7 site (RNi 3 tetrahedra inside the AB 2 -type layers) is not occupied in the La 1.5 Y 0.5 MgNi 9 D 12.4 , while in contrast it is filled by 12% in La 2 MgNi 9 D 13 . Similarly, a depopulation of the D7 site has been also observed in LaNdMgNi 9 D 12.9 22 and was related to the smaller unit cell volume as compared to that of the La 2 MgNi 9 D 13 . 15…”

“…In contrast, Y occupies both the 3a and 6c sites in the mentioned layers, similar to the findings of our earlier publication for the LaNdMgNi 9 alloy (were Nd acted as an analogue of Y). 22 A different conclusion has been earlier reached in the reference publication. 23 It has been reported that in the isostructural PuNi 3 -type LaY 2 Ni 9 compound Y atoms preferentially occupy the 6c site (AB 2 layer) while La atoms are mostly located in the 3a site (AB 5 layer) leading to a partial ordering in the ternary compound formed in the La 1−x Ce x Y 2 Ni 9 (x Ce = 0, 0.5 and 1) alloys.…”

“…In contrast, Y occupies both the 3 a and 6 c sites in the mentioned layers, similar to the findings of our earlier publication for the LaNdMgNi 9 alloy (were Nd acted as an analogue of Y). 22…”