We report a new Li-superionic chloride, Li2Sc2/3Cl4, that crystallizes in a disordered spinel structure, and exhibits an ionic conductivity of 1.5 mS cm−1 with a low activation energy barrier for Li+ ion diffusion of 0.34 eV. This material is the first spinel-type superionic halide. Structural elucidation via powder neutron diffraction reveals a significantly disordered Li+-ion distribution over available tetrahedral and octahedral sites within the lattice, forming an infinitely 3D connected Li+ ion diffusion pathway comprised of face-sharing octahedra and tetrahedra. Due to the high oxidative stability of Li2Sc2/3Cl4, all solid state lithium batteries employing Li2Sc2/3Cl4 and high voltage cathodes (LiCoO2, LiNi0.6Mn0.2Co0.2O2 or high-Ni LiNi0.85Mn0.1Co0.05O2) – without any coating – exhibit excellent electrochemical performance up to 4.6 V in terms of capacity retention and cycle life.
