A new halospinel superionic conductor for high-voltage all solid state lithium batteries

Abstract

We report a new Li-superionic chloride, Li₂Sc_2/3Cl₄, 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 Li₂Sc_2/3Cl₄, all solid state lithium batteries employing Li₂Sc_2/3Cl₄ and high voltage cathodes (LiCoO₂, LiNi_0.6Mn_0.2Co_0.2O₂ or high-Ni LiNi_0.85Mn_0.1Co_0.05O₂) – without any coating – exhibit excellent electrochemical performance up to 4.6 V in terms of capacity retention and cycle life.