Porous Heteroatom-Doped Ti₃C₂T_x 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 x MXene. Porous nitrogen-doped Ti3C2T x MXene microspheres have been synthesized by a facile synthesis method. Porous nitrogen-doped Ti3C2T x 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.

Element‐Doped Mxenes: Mechanism, Synthesis, and Applications

“…Reproduced with permission. [ 48 ] Copyright 2021, American Chemical Society. e) Schematic illustration of the fabrication process and cycling performance of the flexible free‐standing N‐MXene@MnO 2 electrode.…”

“…prepared porous N‐doped Ti 3 C 2 T x MXene microspheres with rich pore structure and heteroatom functional groups, which can be used for structurally and chemically synergistic encapsulation of Na polysulfide (Figure 12c). [ 48 ] As a cathode material, this material exhibits high reversible capacity (980 mAh g –1 at 0.5 °C) and cycling stability (450.1 mAh g –1 capacity after 1000 cycles) (Figure 12d).…”

“…by elemental doping methods has been shown to be an effective strategy. [ 43,44 ] In general, element doping has the following advantages: 1) Transforming inert sites into electrochemically active species and improving the conductivity of the material; [ 45 ] 2) Effectively inducing Fermi energy; [ 46 ] 3) Adjust the electronic structure of the material by doping to create defects, and change its magnetic properties; [ 47 ] 4) Adjust the surface the nature of functional groups or chemical bonds that inhibit MXene rearrangement and facilitate polysulfide transitions; [ 48 ] 5) Enhance the photometric range, by adjusting the grating range, to improve the photoelectric effect of the material; [ 49 ] 6) Adjust the surface chemical properties and bandgap of materials to promote their catalytic performance. [ 50,51 ] Based on the characteristics of the atomic structure, element doping modulates the properties of the material itself by performing surface modification or lattice substitution on the original MXene, which significantly improves the stability and device performance.…”

“…d) Cycling performance of N-MXene@ MWCNT-MP and bare MXene/S cathodes at 2 C rate with a high S loading. Reproduced with permission [48]. Copyright 2021, American Chemical Society.…”

Atomic surface modification strategy ofMXenematerials forhigh‐performancemetal sulfur batteries

“…(B) Schematic preparation procedure of porous N‐MXene@MWCNT‐MP/S microspheres; Cycling performance of N‐MXene@MWCNT‐MP and bare MXene/S cathodes at 2 C rate with a high sulfur loading. Reproduced by permission 101 . Copyright 2021, American Chemical Society.…”