First-Principles Study of Oxyhydride H^– Ion Conductors: Toward Facile Anion Conduction in Oxide-Based Materials

Abstract

H − ion conductor materials have the great potential to enable high-energy density electrochemical storage based on hydrogen. Fast H − conduction has been recently demonstrated in the La 2−x−y Sr x+y LiH 1−x+y O 3−y oxyhydride materials.However, little is known about the H − diffusion mechanism in this new material and its unique structure. The origin of such exceptional H − conduction in the oxide-based materials is of great interest. Using first-principles calculations, we studied the energetics and diffusion mechanisms of H − ions as a function of structures and compositions in this oxyhydride system. Our study identified that fast H − diffusion is mediated by H − vacancies and that the fast two-dimensional or three-dimensional H − diffusion is activated by different anion sublattices in different compositions. In addition, novel doping was predicted from ab initio computation to increase H − conductivity in these materials. The unique two-anion-site feature in this structural framework enables highly tunable lattice and minimizes the blocking of anion diffusion by oxygen sublattice, allowing high mobile-carrier concentration and good diffusion network. This conclusion offers general guidance for future design and discovery of novel oxide-based anion conductors.

A combined deep inelastic neutron scattering and ab initio lattice dynamics study of the hydride anion dynamics and bonding in La2LiHO3 oxyhydride

“…This complies well with reported results from QENS, where no dynamical behaviour was observed in the temperature range where Kobayashi et al observed hydride anion diffusion [1,2]. In addition, AIMD calculations suggest absence of hydride anion diffusion without vacancies present in the system [10]. Together, this suggests a possible discrepancy in the vacancy concentration for orthorhombic La 2 LiHO 3 synthesized by the high-pressure method as this compound is reported to display hydride anion conductivity [1].…”

“…Furthermore, a large vacancy population is a key to promote hydride anion diffusion in the perovskite layer of La 2 LiHO 3 . Our findings are supported by previous reports using QENS and AIMD [2,10]. By comparing, across the entire temperature range, the measured SD of the hydride anion momentum distribution in La 2 LiHO 3 with the prediction for free, non-interacting particles, we predict the onset of a diffusive regime close to the decomposition temperature, a phenomenon which was previously observed by QENS [2].…”

“…As the two anions types occupy the same anionic lattice, fast dynamics of both anions is a necessity to facilitate high conductivity of either specie. This observation is supported by ab initio molecular dynamics (AIMD) calculations stating that vacancies are needed to observe hydride anion mobility in La 2 LiHO 3 , LaSrLiH 2 O 2 and Sr 2 LiH 3 O [10]. However, the role of vacancies is not addressed experimentally and is still unresolved.…”

Single-atom-layer traps in a solid electrolyte for lithium batteries

“…The defect layer was modelled in a supercell consisting of two slabs of LLTO and two defect layers using the periodic boundary condition (CIF file attached as Supplementary Data 1). From the disordered structure of LLTO and the defect layer from experiments, the atomistic configuration of Li, La, and Ti in the supercell models was generated in a two-step process by comparing and ranking distinctive configurations using the scheme as in our previous work 64 according to electrostatic energies and DFT energies: (1) the atomistic configuration with the lowest GGA energy was selected from the DFT calculations on 100 distinctive configurations, which were obtained according to the minimum electrostatic energy out of 10000 symmetrically distinctive configurations using pymatgen 65 ; (2) the same process was repeated for ordering the atomistic configuration in the 2D defect layers to obtain a low-energy structure model of the defect for further calculations. The NEB calculations were performed with the supercell model of 11.83Å x 11.75Å x 31.84Å containing 378 atoms (detailed structure described in the CIF file attached as Supplementary Data 1).…”

Computation-Accelerated Design of Materials and Interfaces for All-Solid-State Lithium-Ion Batteries

“…In studies of SICs, AIMD simulations are performed to directly observe migration events, which are then provided as input for NEB calculations. [33][34][35][36][37] The results from AIMD simulations, together with the energy barriers for specific ion migration pathways from NEB calculations, provide detailed, atomistic-level information on ion diffusion.…”