Porous Heteroatom-Doped Ti₃C₂T_<i>x</i> MXene Microspheres Enable Strong Adsorption of Sodium Polysulfides for Long-Life Room-Temperature Sodium–Sulfur Batteries

Abstract

The practical application of Na-S batteries is largely hindered by their low mass loading, inferior rate capability, and poor cycling performance. Herein, we report a design strategy for encapsulation of sodium polysulfides using Ti₃C₂T_<i>x</i> MXene. Porous nitrogen-doped Ti₃C₂T_<i>x</i> MXene microspheres have been synthesized by a facile synthesis method. Porous nitrogen-doped Ti₃C₂T_<i>x</i> MXene microspheres contain abundant pore structures and heteroatom functional groups for structural and chemical synergistic encapsulation of sodium polysulfides. Sodium-sulfur batteries, based on the as-proposed cathode, demonstrated outstanding electrochemical performances, including a high reversible capacity (980 mAh g^-1 at 0.5 C rate) and extended cycling stability (450.1 mAh g^-1 at 2 C after 1000 cycles at a high areal sulfur loading of 5.5 mg cm^-2). This MXene-based hybrid material is a promising cathode host material for polysulfide-retention, enabling high-performance Na-S batteries.