Sodium 4-styrenesulfonyl(trifluoromethanesulfonyl)imide-based Single-Ion Conducting Polymer Electrolyte Incorporating Molecular Transporters for Quasi-Solid-State Sodium Batteries

Abstract

Sodium batteries are an attractive alternative for future energy storage as they can be produced with abundant and low-cost materials. Nonetheless, sodium-ion batteries (SIBs) are often composed of flammable and volatile carbonate-based liquid electrolytes. Polymer electrolytes have attracted significant attention as safer alternatives. Among polymer electrolytes, single-ion conductive polymer electrolytes (SIPEs) are considered particularly interesting because they can suppress dendrite growth, enabling high-performance solid-state sodium-(metal) batteries. In this work, a self-standing, flexible, quasi-solid-state SIPE is investigated, which is composed of sodium 4-styrene sulfonyl (trifluoromethanesulfonyl) imide (NaSTFSI), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) and pentaerythritol tetraacrylate (PET4A) blended with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). The SIPE membrane, including 50 wt% of molecular transporter, exhibits ionic conductivity of 2.0·10^-5 S cm^-1 and 2.2·10^-4 S cm^-1 at 20 °C and 90 °C, respectively, thermal stability up to 280 °C, electrochemical stability window up to 4.5 V vs. Na/Na⁺, and Na plating/stripping reversibility in symmetric Na|Na cells. The manufactured SIPE implemented in Prussian White(PW) | Na cells enables the delivery of 147 mAh g^-1 of PW at 15 mA g^-1 with a Coulombic efficiency of over 99%, which is comparable with the PW | Na cells using liquid carbonate electrolyte, confirming the suitability of the designed SIPE for sodium-(metal) batteries.