Tandemly promoting the sulfur redox kinetics through low concentration mixed organodiselenide and organoditelluride in Ah-level high-energy-density Li-S batteries

Abstract

Homogeneous redox mediation is efficient in alleviating the shuttling effect and slow redox kinetics of lithium polysulfides in lithium-sulfur batteries. However, their perfect performance is not fulfilled owning to the fact that the multi-step transformation of lithium polysulfides requests the multifunctional active positions for the tandem catalysis. Based on the redox comediation principles, a promoter of mixing organodiselenide and organoditelluride (mixed-Se/Te) was raised to induce tandem catalysis and boost the effective electrochemical conversion of lithium polysulfides. More specifically, diphenyl diselenide facilitated the liquid-liquid and solid-liquid transformation between lithium polysulfides and sulfur, while diphenyl ditelluride improved the solid-liquid transformation concerning lithium sulfide deposition. Consequently, even under high sulfur loading of 6.5 mg cm⁻² and low electrolyte/sulfur ratio of 5.88 µL mg⁻¹, the 10 mM low concentration mixed-Se/Te promoter offered a high discharge capacity of 6.6 mAh cm⁻² and high rate performance of 4.1 mAh cm⁻² at 0.5 C. Moreover, the assembled 1.5 Ah-level lithium-sulfur pouch cells provide an energy density of 332 Wh kg⁻¹ at 0.05 C and good cycling stability. Our research demonstrates the applicability of propelling continuous sulfur conversion reactions with detached active positions and is anticipated to stimulate deep molecular design of kinetic promoter to targeted energy-associated redox reactions.