Partially oxidized Ti3–Nb C2T MXene nanosheets as efficient sulfur hosts and separator modification for Li–S batteries

MXenes hold significant potential in lithium-sulfur (Li–S) battery applications due to its robust polysulfide adsorption and catalytic effect on polysulfide transformation achieved by adjustable transition metals and surface functional groups. Introduction of heteroatoms can prompt an electron distribution and refine MXenes surface structure, thereby substantially enhancing its electrochemical capabilities. Herein, partially oxidized Ti3–yNbyC2Tx (O-Ti3–yNbyC2Tx) heterostructure has been prepared by in-situ oxidization of Ti3–yNbyC2Tx MXene in anhydrous ethanol. The incorporation of niobium (Nb) species within the Ti3C2Tx matrix plays a pivotal role: augmenting the catalytic conversion of polysulfides and concurrently fortifying the cyclic stability of the electrode constituents. When employed in Li–S batteries separator and cathode, it delivers impressive rate performance and durability. The O-Ti2.7Nb0.3C2Tx/S cathode exhibits an initial discharge capacity of 1260 mA·h/g at a current density of 0.1 C, and a minuscule capacity decay rate of a mere 0.029% per cycle over 2000 cycles at 1 C. Even at a significantly elevated current density of 4 C, an appreciable capacity of 640 mA·h/g is sustained. This research opens new avenues to explore MXene heterostructures with both superior electrocatalytic and adsorption properties for alkali metal-S batteries.