Fast Li‐Ion Conductivity in Superadamantanoid Lithium Thioborate Halides

Lithium thioborates are promising fast Li‐ion conducting materials, with similar properties to their lithium thiophosphate counterparts that have enabled the development of solid‐state Li‐ion batteries. By comparison, thioborates have scarcely been developed, however, offering new space for materials discovery. Here we report a new class of lithium thioborate halides that adopt a so‐called supertetrahedral adamantanoid structure that houses mobile lithium ions and halide anions within interconnected 3D structural channels. Investigation of the structure using single‐crystal XRD, neutron powder diffraction, and neutron PDF reveals significant lithium and halide anion disorder. The phases are non‐stoichiometric, adopting slightly varying halide contents within the materials. These new superadamantanoid materials exhibit high ionic conductivities up to 1.4 mS cm−1, which can be effectively tuned by the polarizability of the halide anion within the channels.