Dual-defect engineering of catalytic cathode materials for advanced lithium-sulfur batteries

Abstract

Sluggish conversion reaction kinetics and spontaneous shuttle effect of lithium polysulfides (LiPSs) are deemed as the two big mountains that hinder the practical application of lithium-sulfur batteries (LSBs). Herein, dual-defect engineering strategy is implemented by introducing boron-doping and phosphorus-vacancy sites with MoP@NC composite as the precursor. Based on the experimental characterizations and theoretical calculations, B-MoP_1-x@NC-based electrode presents low oxidation potential, high lithium diffusivity, small Tafel slope and strong adsorption capability for polysulfides, which is beneficial to enhance the adsorption capability for LiPSs, reduce the lithium diffusion energy barriers and Gibbs free energy for the conversion reactions of LiPSs. As demonstrated, the corresponding Li-S/B-MoP_1-x@NC batteries can remain high reversible capacity of 753 mAh/g at 0.5 C after 300 cycles, and keep a stable capacity of 520 mAh/g at 0.5 C after 100 cycles even at the high-loading content of 5.1 mg/cm². According to the results of in-situ UV–vis spectra, the satisfactory battery performance majorly originates from the existence of dual-defect characteristics in B-MoP_1-x@NC catalyst, which effectively promotes the conversion reaction kinetics of LiPSs, and restrains the shuttle behavior of LiPSs. The key ideas of this work will enlighten the development of catalytic cathode materials for sulfur-based secondary batteries.