Stabilizing the Na/Na₃Zr₂Si₂PO₁₂ interface through intrinsic feature regulation of Na₃Zr₂Si₂PO₁₂

NASICON-structured Na₃Zr₂Si₂PO₁₂ ceramics are deemed as promising electrolytes for all-solid-state sodium metal batteries (ASSSB). However, their practical applications are extremely hindered by poor interfacial performance, especially at room temperature. Here, we report that the intrinsic features of the Na₃Zr₂Si₂PO₁₂-based electrolyte, i.e., microstructure and composition, prominently impact its interfacial electrochemical behavior. Sc³⁺-substituted Na₃Zr₂Si₂PO₁₂ ceramic with a refined microstructure shows significantly enhanced ionic conductivity and reduced activation energy. Consequently, a robust contact and stable interface with low interfacial resistance (63 Ω cm² at 25°C) are realized between Na electrode and the electrolyte ceramic. Both sodium symmetric and all-solid-state cells based on this ceramic electrolyte present notable cycling stability and rate performance at room temperature, further confirming the importance of the active microstructure control of electrolyte in improving the Na⁺ transport capability and accelerating the formation of kinetically stable interphase at the Na/ceramic electrolyte interface.