Room-Temperature All-Solid-State Sodium Battery Based on Bulk Interfacial Superionic Conductor

All-solid-state sodium batteries (ASSSBs) are attractive alternatives to lithium-ion batteries for grid-scale energy storage due to their high safety and ubiquitous distribution of Na sources. A critical component for ASSSB is sodium-ion conducting solid-state electrolyte (SSE). Here, we report a high-performance sodium-ion SSE with the recently developed bulk interfacial superionic conductor (BISC) concept. The ionic conductivity and areal conductance of the Na⁺ BISC at 25 °C reaches 6.5 × 10^–4 S cm^–1 and 260 mS cm^–2, respectively. Using Na_xCo_0.7Mn_0.3O₂ (x ≈ 1.0, NaCMO) as the cathode active material, all-solid-state Na||NaCMO batteries exhibiting small overpotential and ∼180 cycle life are demonstrated under room temperature. This approach may also be used to prepare other metal ion, such as Mg²⁺, Al³⁺, and K⁺, based all-solid-state batteries.