2LiX-GaF ₃ (X = Cl, Br, I) electrolytes offer favorable features for solid-state batteries: mechanical pliability and high conductivities. However, understanding the origin of fast ion transport in 2LiX-GaF ₃ has been challenging. The ionic conductivity order of 2LiCl-GaF ₃ (3.20 mS/cm) > 2LiBr-GaF ₃ (0.84 mS/cm) > 2LiI-GaF ₃ (0.03 mS/cm) contradicts binary LiCl (10 ⁻¹² S/cm) < LiBr (10 ⁻¹⁰ S/cm) < LiI (10 ⁻⁷ S/cm). Using multinuclear ⁷ Li, ⁷¹ Ga, ¹⁹ F solid-state nuclear magnetic resonance and density functional theory simulations, we found that Ga(F,X) _n polyanions boost Li ⁺ -ion transport by weakening Li ⁺ -X ⁻ interactions via charge clustering. In 2LiBr-GaF ₃ and 2LiI-GaF ₃ , Ga-X coordination is reduced with decreased F participation, compared to 2LiCl-GaF ₃ . These insights will inform electrolyte design based on charge clustering, applicable to various ion conductors. This strategy could prove effective for producing highly conductive multivalent cation conductors such as Ca ²⁺ and Mg ²⁺ , as charge clustering of carboxylates in proteins is found to decrease their binding to Ca ²⁺ and Mg ²⁺ .

Establishing structure–property correlations is of paramount importance to materials research. The ability to selectively detect observable magnetization from transitions between quantized spin states of nuclei makes nuclear magnetic resonance (NMR) spectroscopy a powerful probe to characterize solids at the atomic level. In this article, we review recent advances in NMR techniques in six areas: spectral resolution, sensitivity, atomic correlations, ion dynamics, materials imaging, and hardware innovation. In particular, we focus on the applications of these techniques to materials research. Specific examples are given following the general introduction of each topic and technique to illustrate how they are applied. In conclusion, we suggest future directions for advanced solid-state NMR spectroscopy and imaging in interdisciplinary research.