Molecular-level interfacial engineering unlocking Na3Zr2Si2PO12/poly(vinylidene fluoride-co-hexafluoropropylene) composite electrolytes toward quasi-solid-state sodium metal batteries

Polydopamine (PDA) coating promotes uniform dispersion of Na 3 Zr 2 Si 2 PO 12 in polymer matrix. • Polar groups of PDA enhance NaClO 4 dissociation via Lewis acid-base interactions. • PDA - modified Na 3 Zr 2 Si 2 PO 12 creates continuous Na + transport pathways. • PDA preferentially reduces to form a NaN-rich SEI suppressing dendrites. • The optimized solid-state electrolyte promises stable quasi-solid-state Na metal batteries. Composite solid-state electrolytes (CSSEs) are a promising candidate for quasi-solid-state sodium metal batteries (QSSSMBs) by combining the advantages of ceramic electrolytes and solid polymer electrolytes. However, poor interfacial compatibility between ceramic and polymer components greatly limits their full potential. Herein, we design and fabricate a CSSE by solution-casting a suspension containing polydopamine (PDA)-modified Na 3 Zr 2 Si 2 PO 12 (NZSP), denoted as PDA@NZSP, poly(vinylidene fluoride- co -hexafluoropropylene) and NaClO 4 . The PDA coating acts as an amphiphilic interfacial bridge improving the interfacial compatibility between inorganic filler and polymer matrix, which promotes a more homogeneous distribution of PDA@NZSP and facilitates interfacial Na + transport. The polar groups of PDA reconstruct the local Na + ClO 4 − coordination environment, suppress salt crystallization, and favor the formation of more weakly associated Na + species, contributing to a room-temperature ionic conductivity of 0.233 mS cm −1 and a Na + transference number of 0.73. Depth-resolved X-ray photoelectron spectroscopy of cycled Na anodes further reveals that PDA@NZSP modification is associated with a distinct distribution of N O-containing and fluorinated interphase species compared with pristine NZSP. Together with the favorable interfacial-resistance evolution and long-term Na plating/stripping behavior, these results demonstrate improved Na/electrolyte interfacial stability in the optimized CSSE-based quasi-solid-state configuration. Polydopamine-modified ceramic filler interfacial engineering enables efficient Na + transport and stable Na metal anodes for high-performance quasi-solid-state sodium metal batteries. Download: Download high-res image (164KB) Download: Download full-size image