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キーワード:
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要旨:
Lithium zirconate (LZO) is a prototype material for studies of Li+ ion mobility with a wide range of possible applications such as a ceramic breeder for nuclear reactors, a reversible sorbent for carbon dioxide capture, a coating for cathodes and anodes or even directly as an anode material in lithium-ion batteries (LIBs). Solid state nuclear magnetic resonance (NMR) is a powerful experimental technique with the potential to provide microscopic insights into Li+ ion dynamics in solid materials, in particular if combined with theory to interpret the measured spectra. We use first-principles atomistic simulations based on density functional theory (DFT) to investigate the Li+ ion migration mechanisms in LZO. Computed barrier heights for several possible Li+ ion exchange pathways are in very good agreement with the experimentally reported values and confirm the relevance of lithium vacancies for the observed Li+ ion mobilities. Additionally, 7Li NMR isotropic spectral parameters such as quadrupolar coupling constants and chemical shifts, can be obtained by the gauge-including projector-augmented-wave (GIPAW) method in very good agreement with the experimental values, underpinning the validity of the computational models. The close analysis of these spectral parameters shows a clear correlation to simple descriptors for the local structural environment of the Li+ ions, opening up a pathway to further modelling based on computationally cheaper methods. We note, however, that there is also a consistently poor agreement with experimental data for 7Li anisotropic properties like the asymmetry parameter of the electric field gradient (EFG) tensor, which calls for further theoretical method development in this field.
