New P2-Type Honeycomb-Layered Sodium-Ion Conductor: Na₂Mg₂TeO₆

A novel solid sodium-ion conductor, Na₂Mg₂TeO₆ (NMTO) with a P2-type honeycomb-layered structure, has been synthesized for the first time by a simple solid-state synthetic route. The conductor of NMTO exhibits high conductivity of 2.3 × 10^-4 S cm^-1 at room temperature (RT) and a large electrochemical window of ∼4.2 V (versus Na⁺/Na). The conductor is remarkably stable, both in the ambient environment and within its metallic Na anode. This facile sodium-ion conductor displays potential for use in all-solid-state sodium-ion batteries (SS-SIBs).