Surface Potential Regulation Realizing Stable Sodium/Na Zr Si PO Interface for Room-Temperature Sodium Metal Batteries.

Inorganic Na Zr Si PO 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 Zr Si PO (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 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 . Superior interfacial performance is well retained even under 0.2 mA cm at room temperature. The robust interface is further signified by its excellence under higher current densities of up to 0.85 mA cm at 60 °C. A 4 V all-solid-state Na V Cr (PO ) /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 under 100 mA g for over 400 cycles with a Coulombic efficiency of over 99%.