Carbon-coated nitrogen, vanadium co-doped MXene interlayer for enhanced polysulfide shuttling inhibition in lithium-sulfur batteries

Abstract

Polysulfides (LiPSs) shuttling significantly impedes the real application of lithium-sulfur (Li–S) batteries. Herein, nitrogen (N), vanadium (V)-co-doped MXene with N-doped carbon coating layer (denoted as CNVM) is prepared and then used as the interlayer material between cathode and commercial separator to suppress the shuttle effect of LiPSs. The doped heteroatoms alter the structure of MXene, enhancing the adsorption ability by providing enormous chemisorption sites for LiPSs and also accelerating the electron transfer. Meanwhile, the N-doped carbon coating further improves the electrical conductivity and raises the chemical affinity to LiPSs. Finally, enhanced electrochemical reaction kinetics and accelerated polysulfide conversion are obtained. Thus, the as-assembled Li–S batteries using the CNVM interlayer display high discharge capacity of 1373 mAh g−1 at 0.1 C, outstanding rate performance of discharge capacity up to 723 mAh g−1 at 3 C, long cycling life, as well as low average capacity degradation of 0.075% per cycle. Also, the practical application of the multifunctional CNVM-based interlayer is further manifested by the stable electrochemical performance even under a high sulfur loading of 7.2 mg cm−2 and decent service states of the as-assembled pouch cells.