Inorganic Na3 Zr2 Si2 PO12 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. Na3 Zr2 Si2 PO12 (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 Na3 V1.5 Cr0.5 (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%.
Keywords: all-solid-state sodium batteries; interfacial stability; solid electrolytes; surface potential.
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