Correlating Polysulfide Solvation Structure with Electrode Kinetics towards Long-Cycling Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are promising due to ultrahigh theoretical energy density. However, their cycling lifespan is crucially affected by the electrode kinetics of lithium polysulfides. Herein, the polysulfide solvation structure is correlated with polysulfide electrode kinetics towards long-cycling Li-S batteries. The solvation structure derived from strong solvating power electrolyte induces fast anode kinetics and rapid anode failure, while that derived from weak solvating power electrolyte causes sluggish cathode kinetics and rapid capacity loss. By contrast, the solvation structure derived from medium solvating power electrolyte balances cathode and anode kinetics and improves the cycling performance of Li-S batteries. Li-S coin cells with ultra-thin Li anodes and high-S-loading cathodes deliver 146 cycles and a 338 Wh kg-1 pouch cell undergoes stable 30 cycles. This work clarifies the relationship between polysulfide solvation structure and electrode kinetics and inspires rational electrolyte design for long-cycling Li-S batteries. The polysulfide electrode kinetics regarding the sulfur cathode and the lithium anode are promoted as the solvating power of the polysulfide solvation structure increases. Both too fast and slow electrode kinetics induce rapid failure of Lithium-sulfur batteries. The polysulfide solvation structure with medium solvating power balances the cathode and anode kinetics and improves the cycling performance of high-energy-density Lithium-sulfur batteries.image

Automated summary

This study investigates the relationship between polysulfide solvation structure and electrode kinetics in lithium-sulfur batteries and proposes methods to improve their cycling performance. The solvation structure derived from strong solvating power electrolyte leads to rapid anode kinetics, while that derived from weak solvating power electrolyte causes slow cathode kinetics. A solvation structure with medium solvating power balances both cathode and anode kinetics, enhancing the cycling performance of lithium-sulfur batteries.