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

Abstract

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.