An amphiphilic interface for constructing a uniform composite solid-state electrolyte towards long-life all-solid-state sodium metal batteries

Sodium composite solid-state electrolytes, composed of polymer matrices and oxide electrolyte fillers, have garnered considerable attention, due to a balance of ionic conductivity, flexibility, mechanical stability and electrochemical stability. However, the huge disparity in surface energy between inorganic and organic components induces a severe aggregation of the oxide filler within the polymer matrix. In this research, an amphiphilic polydopamine (PDA) compatibility layer was strategically applied to Na3Zr2Si2PO12 (NZSP) to mitigate the wettability differential between NZSP and poly(ethylene oxide) (PEO), which effectively mitigates the aggregation of NZSP within PEO, meliorates the dispersion of inorganic fillers, and constructs a uniform composite solid-state electrolyte membrane PCSE. Consequently, a composite electrolyte based on PDA@NZSP manifested enhanced electrochemical performance and cycling stability. The all-solid-state battery, assembled with PCSE, exhibited 1350 stable cycles at 60 °C with a low polarization overpotential and a high capacity retention (80.5%). Finite element simulation indicated a homogeneous Na+ flux density distribution at the electrode–electrolyte interface under an applied electric field, elucidating the pivotal role of the PDA amphiphilic interface in the construction of uniform composite solid-state electrolytes. This work provides a feasible solution for the construction of long-life all-solid-state sodium metal batteries.