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

Inorganic Na₃Zr₂Si₂PO₁₂ 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. Na₃Zr₂Si₂PO₁₂ (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 cm² 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 Na₃V_1.5Cr_0.5(PO₄)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%.