Improving critical current density and cycling stability of NaSICON solid electrolytes by powder aerosol deposited CuO interlayers

Solid-solid interfacial instabilities remain major obstacles for the industrialization of cost-effective, high energy density solid-state sodium batteries (SSSB). In this work, a conversion-type CuO interlayer was successfully deposited onto both sides of Na 3 Zr 2 Si 2 PO 12 (NZSP) solid electrolyte (SE) discs by powder aerosol deposition (PAD) to enhance the interfacial compatibility between sodium metal and SE. While unmodified symmetric cells suffer from progressive interfacial degradation, and limited critical current density, incorporating PAD-CuO interlayers on NZSP SE discs significantly reduces interfacial resistance and increases the critical current density up to 5.0 mA cm −2 . This value is further increased to 7.4 mA cm −2 by thermal post-treatment. Long-term galvanostatic cycling demonstrates stabilized overvoltages during plating/stripping experiments, indicating progressive interphase activation and improved Na + transport. Overall, these results demonstrate that PAD enables the fabrication of functional interlayers for stabilizing the Na|NZSP interface and may provide a foundation for fully PAD-processed scalable architectures in next-generation SSSBs.