Nb 2 CT x MXene boosting PEO polymer electrolyte for all‐solid‐state Li‐S batteries: two birds with one stone strategy to enhance Li + conductivity and polysulfide adsorptivity

Abstract All‐solid‐state lithium‐sulfur (Li‐S) battery is regarded as next‐generation high energy density and safety battery system. The key challenge is to develop a compatible high‐performance solid‐state electrolyte. Herein, a two birds with one stone strategy is proposed to simultaneously enhance Li + conductivity and polysulfide adsorptivity of poly(ethylene oxide) (PEO)‐based polymer electrolyte via the integration of Nb 2 CT x MXene. Moreover, the sheet size of Nb 2 CT x MXene is crucial for the enhancement of Li + conductivity and polysulfide adsorptivity, attributing to the difference in a specific surface area related to the percolation effect. By tuning the sheet size of Nb 2 CT x MXene from 500–300 nm to below 100 nm, the ionic conductivity of the PEO electrolyte is increased to 2.62 × 10 −4 S·cm −1 with improved Li + transference number of 0.37 at 60 °C. Furthermore, theoretical calculation and X‐ray photoelectron spectroscopy (XPS) conjointly prove that polysulfides could be effectively adsorbed by Nb 2 CT x nanosheets via forming Nb−S bonding to inhibit their shuttle in the PEO framework. As a result, the all‐solid‐state Li‐S cell exhibits an initial capacity of 1149 mAh·g −1 at 0.5C and good cycling stability with 491 mAh·g −1 after 200 cycles. The results demonstrate the necessity of polysulfide inhibition and the application of Nb 2 CT x MXene in PEO‐based electrolytes for all‐solid‐state Li‐S batteries.