Solid-state NMR and first-principle calculations reveal the structure and dynamics of Li-N-H materials
Year: 2026
Type: preprint
Abstract: Lithium-nitrogen-hydrogen (Li-N-H) materials are promising for hydrogen storage, solid-state batteries, and lithium-mediated ammonia synthesis, yet their local structures and proton dynamics remain poorly understood because of compositional disorder and limited sensitivity of conventional diffraction methods. Here, we combine multinuclear solid-state nuclear magnetic resonance spectroscopy (1H, 7Li, 14N, and 15N ssNMR) with first-principles calculations to resolve the atomic environments and dynamics of Li3N, LiNH2, and Li1+xNH2-x (. 7Li NMR and density functional theory calculations identify distinct lithium sites in coexisting α- and β-Li3N phases and in tetragonal LiNH2. 1H and 15N NMR, together with 1H-detected 14N spectroscopy, reveal two distinct domains in synthesized lithium-rich Li1+xNH2-x that are not resolved by laboratory X-ray diffraction. Comparison with calculated NMR parameters assigns these domains to LiNH2 and Li2NH, respectively. Variable-temperature 1H-1H exchange spectroscopy shows that correlations between the two domains arise predominantly from spin diffusion rather than interdomain proton exchange, indicating nanoscale structural heterogeneity within a solid solution. Local proton motion occurs within the Li2NH environment and is restricted in the LiNH2 domains. These results establish a molecular-level relationship between local structure and proton mobility in Li-N-H materials, providing insights relevant to hydrogen storage, solid-state batteries, and ammonia synthesis.
Source: ChemRxiv
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221073979