Synergistic Adsorption‐Catalytic Effect Based on Hierarchical Porous Structure and Lewis Acidic Cu + Sites in Cu 2 O@MXene for Boosting the Performance of RT Na–S Batteries

Abstract

ABSTRACT Room‐temperature sodium–sulfur (RT Na–S) batteries offer high energy density and low cost but suffer from poor conductivity, sluggish redox kinetics, and polysulfide shuttling. This study introduces a multifunctional Cu 2 O@MXene separator with a hierarchical porous structure and a 3D MXene network for fast electron transport. The hierarchical porous structure provides physical confinement, while the polar Cu─O bonds and Cu + Lewis acid centers in Cu 2 O provide chemical anchoring and catalytic sites for sodium polysulfides (NaPSs). Experimental evidence and theoretical calculations reveal that MXene serves as an electronic reservoir to protect Cu + catalytic active sites from reduction, enabling NaPSs anchoring through interfacial Cu─S and Ti─S bonds. Benefiting from this synergistic adsorption‐catalytic mechanism, the Cu 2 O@MXene interlayer enhances NaPSs confinement and accelerates sulfur redox kinetics. Consequently, Cu 2 O@MXene‐PP cells achieve 942.1 mAh g −1 after 100 cycles at 0.2 C and ultralong cycling stability of 574.9 mAh g −1 after 3500 cycles at 2 C. Under a sulfur loading of 4.65 mg cm −2 , the cell retains 3.1 mAh cm −2 after 105 cycles. Theoretical calculations further reveal that Cu 2 O@MXene enables stronger NaPSs adsorption and improves the thermodynamical favorability of the Na 2 S 2 to Na 2 S conversion. This work provides reasonable guidelines for designing Cu‐based catalytic separators in high‐performance RT Na‐S batteries.