Junxian Zhang

Solid-state hydrogen storage in intermetallic hydrides represents a promising alternative to compressed and liquefied hydrogen, combining higher volumetric density with improved safety. Among ABn-type compounds (A = rare earth, B = transition metal, 2 ≤ n ≤ 5), AB3 and A2B7 phases are of particular interest owing to their complementary hydrogenation properties. Their performance is largely dictated by the structural compatibility between the [AB5] and [A2B4] subunits, especially the volumetric mismatch between them.This work investigates the pseudo-binary La-Y-Ni-Mn system, with the objective of understanding the influence of Mn substitution on the structural, microstructural, and hydrogenation properties of ABn-type compounds. Samples were synthesised by arc melting, followed by annealing to improve homogeneity, and characterised using laboratory X-ray diffraction, neutron powder diffraction, electron microscopy, and pressure-composition isotherm (PCI) measurements.All samples contain both AB3 and A2B7 phases, Mn substitution favourites formation of AB3 Phase. In the LaY2.3Ni11.5-xMnx system, La and Y occupy A-sites and Mn occupies exclusively B-type sites, resulting in anisotropic lattice expansion for AB3 phase. With increasing Mn content (x ≥ 1.8), microstructural analyses by EPMA and TEM revealed the formation of nanoscale AB- and AB5-type precipitates, which indicates a limit of solubility of Mn in the ABn. PCI measurements indicated good hydrogen storage capacity, low pressures plateau and reversibility.

All-solid-state batteries have garnered significant attention due to their potential to exceed the energy density of conventional lithium-ion batteries, particularly when alloying-based materials or lithium metal anodes are used. However, achieving compatibility with lithium metal remains a persistent bottleneck. In this study, we shed light on the potential of SnHPO₃ tin phosphite and Ni_3.4Sn₄ intermetallic as novel conversion/alloying anode materials for all-solid-state lithium batteries using Li₆PS₅Cl as the solid electrolyte. The two Sn-based active materials were nanostructured by ball-milling to demonstrate considerable promise for application in all-solid-state half-cells. Galvanostatic cycling at room temperature revealed electrochemical behavior based on conversion/alloying reactions akin to those observed in conventional lithium-ion batteries. Promisingly, both materials exhibited satisfying electrochemical stability, with coulombic efficiencies exceeding 97%. These findings indicate that Li₆PS₅Cl solid electrolyte is compatible with Sn-based alloying anodes.

The Y_xNi_2−yMn_y system was investigated in the region 0.825 ≤ x ≤ 0.95, 0.1 ≤ y ≤ 0.3. The alloys were synthesized by induction melting and corresponding annealing. The substitution of Mn for Ni (y = 0.1) favors the formation of a C15 structure with disordered Y vacancies against the superstructure of Y_0.95Ni₂. For y = 0.2 and 0.3, Mn can substitute in both Y and Ni sites. Single-phase compounds with a C15 structure can be formed by adjusting both the Y and Mn contents. Their hydrogen absorption–desorption properties were measured by pressure–composition isotherm (PCI) measurements at 150 °C, and the hydrides were characterized at room temperature by X-ray diffraction and TG–DSC experiments. The PCIs show two plateaus corresponding to the formation of crystalline and amorphous hydrides. The heating of the amorphous hydrides leads to an endothermic desorption at first and then a recrystallization into Y(Ni, Mn)₃ and YH_x phases. At higher temperatures, the Y hydride desorbs, and a recombination into a Y(Ni, Mn)₂ Laves phase compound is observed. For y = 0.1, vacancy formation in the Y site and partial Mn substitution in the Ni site enhance the structural stability and suppress the hydrogen-induced amorphization (HIA). However, for a larger Mn content (y ≥ 0.2), Mn substitutes also in the Y sites at the expense of Y vacancies. This yields worse structural stability upon hydrogenation than for y = 0.1, as the mean ratio r_{(Y, Mn)}/r_(Ni/Mn) becomes larger than for y = 0.1 r_{(Y, ☐)}/r_(Ni/Mn).

The effect of heat treatment on phase occurrence, crystal structures and hydrogen sorption properties of Y _0.5 La _0.2 Mg _{0.3− x} Ni ₂ compounds has been investigated. The targeted compounds were synthesized through induction melting and processed heat treatment at 700 and 900 °C, respectively. Phase occurrence and structural properties were studied by X‐ray powder diffraction (XRD). The global compositions and phase compositions have been determined by inductively coupled plasma‐optical emission spectrometer (ICP‐AES) and electron probe micro‐analysis (EPMA) respectively. The hydrogenation properties were characterized by pressure–composition isotherm measurements and cycle curves at 25 °C. The annealing temperature of 700 °C could boost the production of A ₂ B ₄ ‐type (Y, La, Mg) ₂ Ni ₄ (A = rare earth, B = transition metal) phase, the Mg evaporation leads to the formation of La‐doped AB ₃ phase. The La substitution limit inside the C 15 b Y _{0.7− z} La _z Mg _0.3 Ni ₄ phase is estimated around z = 0.16. An exchange phenomenon has been confirmed in Y _0.5 La _0.2 Mg _{0.3− x} Ni ₂ compounds meaning that partial Y atoms share 4c sites with Mg. The substitution of La raised the atomic‐size ratio r _A / r _B , resulting in a hydrogen‐induced disproportionation (HID) of C 15 b ‐type A ₂ B ₄ and C 15‐type AB ₂ phases upon hydrogen absorption and desorption. New A ₂ B ₄ phases with more Mg content (close to YMgNi ₄ ) prefer to form upon HID. The annealing process at 900 °C and Mg evaporation stimulate the generation of a non‐stoichiometric AB _2.6 Y _0.48 La _0.19 Mg _0.10 Ni ₂ compound, which shows a high reversible hydrogen absorption capacity of 1.63 wt%.