Lithium‐ion Mobility in Li ₆ B ₁₈ (Li ₃ N) and Li Vacancy Tuning in the Solid Solution Li ₆ B ₁₈ (Li ₃ N) _{1− <i>x</i>} (Li ₂ O) _<i>x</i>

Abstract All‐solid‐state batteries are promising candidates for safe energy‐storage systems due to non‐flammable solid electrolytes and the possibility use metallic lithium as an anode. Thus, there is a challenge design new understand principles of ion conduction on atomic scale. We report concept compounds with high mobility based rigid open‐framework boron structure. The host–guest structure Li 6 B 18 (Li 3 N) comprises large hexagonal pores filled 7 N] strands that represent perfect cutout from α‐Li N. Variable‐temperature NMR spectroscopy reveals very in template phase remarkably low activation energy below 19 kJ mol −1 thus much lower than pristine formation solution 2 O) over complete compositional range allows tuning defects not possible N O.