Stabilizing Na₃Zr₂Si₂PO₁₂/Na Interfacial Performance by Introducing a Clean and Na-Deficient Surface

Most Li+/Na+-conducting solid electrolytes are unstable in moisture, and the formed hydroxides and carbonates on their surfaces result in the increase of the interfacial resistance between solid electrolytes and alkali metal anodes. In this study, heat treatment was used to remove the byproduct coating on the surface of Na3Zr2Si2PO12 (NZSP) that also leads to the generation of Na-ion deficient surface simultaneously. This surface chemistry approach was used to reduce the interfacial resistance and suppress Na-dendrite growth during Na plating. A combination of the metallic Na wetting test, density functional theory, and electrochemical measurement was employed to investigate the origins of ultralow interfacial resistance and mechanism between the Na-ion deficient surface and the metallic Na anode. The analysis demonstrates that the Na-ion-deficient surface effectively improves the contact between NZSP and the metallic Na anode. Moreover, an ultrathin passivating layer involving Na2O was formed between NZSP with metallic Na that protected the NZSP electrolyte from the reduction by metallic Na. This study not only motivates the need for further understanding of the surface chemistry of NZSP but also provides guidelines for the future design of the Na-ion solid–electrolyte interface.