Enabling fast diffusion/conversion kinetics by thiourea-induced wrinkled N, S co-doped functional MXene for lithium-sulfur battery

Abstract

The long lifespan of high-energy density lithium-sulfur batteries (LSBs) is still hindered by severe polysulfide (PS) shuttling and sluggish sulfur reduction/evolution kinetics process. Herein, we report a facile preparation of thiourea-induced wrinkled nitrogen and sulfur co-doped functionalized MXene (NSMX) to modify the separator to enhance the ion diffusion and conversion kinetics for high-energy LSBs. The combination of theoretical calculations and experimental conclusions demonstrates that the introduction of N, S heteroatoms induces the shift of the d-band center in transition metal Ti towards the Fermi level and results in the robust bonding effect between N/S atoms and Li atom in PS, hence exhibiting admirable adsorption capability to PS and fast catalytic PS reversible conversion rate, which quickly deplete soluble high-order PS and expedites the depletion of the Li2S6 in high potential. The 2D wrinkled polar surface with excellent conductivity assures fast electron transfer and ion migration. Profiting from the enhancement of S utilization and the reduction of unfavorable accumulated Li2S6, the LSBs equipped with NSMX modified separators exhibit a high specific capacity of 1249 mAh g−1 at 0.2 C. At a high rate of 5 C, the LSBs also delivered an impressive reversible capacity of 600 mAh g−1. Moreover, a high capacity and stable cycling can be achieved even under the condition of high S load and lean electrolyte consumption.