VC@NCNTs: Bidirectional catalyst for fast charging Lithium-sulfur batteries

The development of catalytic materials has become a general trend of lithium-sulfur batteries (LSBs) research. Although catalysts have been extensively studied on the sulfur reduction reaction, little is known of their role in sulfur oxidation reaction. In this study, highly dispersed vanadium carbide anchored on N-doped carbon nanotubes (VC@NCNTs) was prepared as a bidirectional catalyst for LSBs. Density functional theory, visual adsorption experiments, symmetrical cell cyclic voltammetry, chronoamperometry and dimensionless analysis, and activation energy calculations were used to study the adsorption catalytic effect of polysulfide. Detailed experimental results indicate that VC@NCNTs can capture polysulfide and convert it efficiently, reducing the activation energy (Ea) to considerably improve both directions of redox kinetics. Density functional calculations (DFT) confirm the adsorption strength of VC@NCNTs and electroactivity. The bifunctional VC@NCNTs catalyst exhibited promising practical performance in a lithium-sulfur cell, including high reversible capacity (1053 mAh g⁻¹), excellent and steady coulombic efficiency (∼100%), and admirable battery fast charging performance (3 C). This research establishes bidirectional electrocatalysis as a promising pathway to tackle kinetic hysteresis in the redox process for LSBs.