Partially oxidized Ti3–yNbyC2Tx MXene nanosheets as efficient sulfur hosts and separator modification for LiS batteries

Abstract

MXenes hold significant potential in lithium-sulfur (LiS) 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 Ti_3–yNb_yC₂T_x (OTi_3–yNb_yC₂T_x) heterostructure has been prepared by in-situ oxidization of Ti_3–yNb_yC₂T_x MXene in anhydrous ethanol. The incorporation of niobium (Nb) species within the Ti₃C₂T_x matrix plays a pivotal role: augmenting the catalytic conversion of polysulfides and concurrently fortifying the cyclic stability of the electrode constituents. When employed in LiS batteries separator and cathode, it delivers impressive rate performance and durability. The OTi_2.7Nb_0.3C₂T_x/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 1C. 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.