A freestanding nitrogen-doped MXene/graphene cathode for high-performance Li–S batteries

Abstract

Lithium-sulfur batteries (LSBs) take a leading stand in developing next-generation secondary batteries with an exceptionally high theoretical energy density. However, the insulating nature and undesirable shuttle effect still need to be solved to improve the electrochemical performance. Herein, a freestanding graphene supported N-doped Ti₃C₂T _<i>x</i> MXene@S cathode is successfully synthesized <i>via</i> a straightforward no-slurry method. Due to its unique hierarchical microstructure, the MXene-C/S ternary hybrids with high capacity can effectively adsorb polysulfides and accelerate their conversion. Cooperatively, conductive rGO can ameliorate N-MXene nanosheet' restacking, making the lamellar N-Mxene coated sulfur particles disperse uniformly. The assembled Li-S battery with a freestanding Ti₃C₂T _<i>x</i> @S/graphene electrode provides an initial capacity of 1342.6 mA h g^-1 at 0.1C and only experiences a low capacity decay rate of 0.067% per cycle after. Even at a relatively high loading amount of 5 mg cm^-2, the battery can still yield a high specific capacity of 684.9 mA h g^-1 at 0.2C, and a capacity retention of 89.3% after 200 cycles.