Surface Potential Regulation Realizing Stable Sodium/Na3Zr2Si2PO12 Interface for Room‐Temperature Sodium Metal Batteries

Abstract Inorganic Na 3 Zr 2 Si 2 PO 12 is prospective with a high ionic conductivity but suffers large interfacial resistance and stability issues against sodium metal, hindering its practical application in all‐solid‐state sodium batteries. A surface potential regulation strategy is adopted to address these issues. Na 3 Zr 2 Si 2 PO 12 (NZSP) ceramic with homogeneously‐sintered surface is synthesized by a simple two‐step sintering method to promote its uniform surface potential, which is favorable for mitigating the potential fluctuations at the interface against Na metal and enhancing interfacial compatibility. The Na/NZSP interface can be stabilized for over 4 months with a low interfacial resistance of 129 Ω cm 2 at 25 °C. The symmetrical Na/NZSP/Na cell exhibits ultra‐stable sodium platting/stripping cycling for over 1000 cycles under 0.1 mA cm −2 . Superior interfacial performance is well retained even under 0.2 mA cm −2 at room temperature. The robust interface is further signified by its excellence under higher current densities of up to 0.85 mA cm −2 at 60 °C. A 4 V all‐solid‐state Na 3 V 1.5 Cr 0.5 (PO 4 ) 3 /NZSP/Na metal battery is demonstrated at ambient conditions, which exhibits superior rate capability and delivers a high reversible capacity of 103 mA h g −1 under 100 mA g −1 for over 400 cycles with a Coulombic efficiency of over 99%.