Fluorinated solid electrolyte interphase enables interfacial stability for sulfide-based solid-state sodium metal batteries

Abstract

Sulfide solid electrolytes (SSEs) with high ionic conductivity and good mechanical flexibility are considered ideal for all-solid-state sodium metal batteries (ASSSMBs). Nevertheless, the detrimental interfacial issue between SSEs and Na metal presents a significant challenge for sulfide-based ASSSMBs. Herein, we demonstrate a facile and cost-effective method for constructing a controllable NaF-rich artificial interphase on the surface of sodium metal anodes by incorporating perfluoropolyether (PFPE). A stratified solid electrolyte interphase (SEI) composed a nanocrystalline NaF inner phase and organic outer shell, efficaciously seals the Na surface. The interfacial interactions between SSEs and Na metal is explored using Comsol and ab initio molecular dynamics simulations, revealing that the presence of a NaF-rich artificial interphase hinders the growth of sodium dendrites and mitigates the decomposition of the sulfide electrolytes. As a result, the symmetric cell exhibits stable Na plating/stripping cycling for 800 h at 0.1 mA cm−2. Overall, our PFPE-modified sodium metal anodes offer a promising avenue for the widespread application of high-performance ASSSMBs.