Boosting Performance of Na–S Batteries Using Sulfur-Doped Ti₃C₂T_<i>x</i> MXene Nanosheets with a Strong Affinity to Sodium Polysulfides

Abstract

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 <i>in situ</i> 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-Ti₃C₂T_<i>x</i>) nanosheets were applied as an electrode host material in room temperature sodium-sulfur batteries. The S-Ti₃C₂T_<i>x</i> 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).