Boosting Performance of Na–S Batteries Using Sulfur-Doped Ti₃C₂T_x MXene Nanosheets with a Strong Affinity to Sodium Polysulfides

Sodium–sulfur batteries using abundant elements offer an attractive alternative to currently used batteries, but they need better sulfur host materials to compete with lithium-ion batteries in capacity and cyclability. We report an in situ sulfur-doping strategy to functionalize MXene nanosheets by introducing heteroatomic sulfur into the MXene structure form the MAX phase precursor. By employing the vacuum freeze-drying method, a three-dimensional (3D) wrinkled MXene nanoarchitecture with the high specific surface area was prepared. The tailor-made wrinkled sulfur-doped MXene (S–Ti3C2Tx) nanosheets were applied as an electrode host material in room temperature sodium–sulfur batteries. The S–Ti3C2Tx matrix shows high polarity with sodium polysulfides, restricting the diffusion of sodium polysulfides. The MXene/sulfur electrode can achieve high areal sulfur loading up to 4.5 mg cm–2 as well as good electrochemical performance (reversible capacity of 577 mAh g–1 at 2 C after 500 cycles).