Oxygen Defect‐Rich WO3−x–W3N4 Mott–Schottky Heterojunctions Enabling Bidirectional Catalysis for Sulfur Cathode

Abstract

AbstractThe serious shuttle effect and intrinsically sluggish oxidation–reduction reaction kinetics of polysulfides severely hinder the practical commercialization of lithium–sulfur (Li–S) batteries. Herein, oxygen‐defect‐rich WO3−x–W3N4 Mott–Schottky heterojunctions are designed as efficient catalysts. Based on theoretical calculations and comprehensive experimental characterization, WO3−x–W3N4 exhibits a lower free energy change (1.03 eV) and Li2S decomposition energy barrier (0.92 eV) than WO3 and W3N4, which significantly enhances the sulfur reduction reaction (SRR) activity. Furthermore, a relationship between the catalytic activity and the energy gaps in the d and p bands centers (Δd–p) is also established, with the low Δd–p of the heterojunction leading to a lower antibonding state energy, which promotes electron transfer and interfacial redox kinetics. Oxygen vacancies can improve the catalytic effect without affecting adsorption. Hence, the Li–S battery using WO3−x–W3N4@CC/S exhibited outstanding rate and duration performance (913.9 mAh g–1 at 2 C, stable 400 cycles at 1 C). Impressively, the battery achieves a high areal capacity of 5.0 mAh cm−2 under a high sulfur loading of 4.98 mg cm−2.