Tuning Sulfur Reduction via Unique Radical-Mediated Solid-Liquid-Solid Pathway for High-Rate Aqueous Zn-S Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Sluggish solid-solid sulfur conversion in aqueous Zn-S batteries causes high polarization and poor cycling stability.
• This limits the practical application of this promising electrochemical energy storage system.

Purpose of the Study:

• To introduce trimethylsulfoxonium iodide (TMSO+I-) as an electrolyte additive.
• To manipulate the solid-liquid-solid conversion pathway in Zn-S batteries by restructuring electron transport.

Main Methods:

• Investigated the role of trimethylsulfoxonium radical (TMSO*) in electron transfer.
• Analyzed the stabilization of polysulfide intermediates via orbital coupling.
• Evaluated the electrochemical performance of modified Zn-S cells.

Main Results:

• The TMSO* radical facilitated relayed electron transfer through reversible redox cycling.
• Stabilized TMSO*-polysulfide intermediates by lowering LUMO energy, streamlining electron transfer.
• Achieved high capacity (1728 mAh g-1), low overpotential (0.42 V at 0.1 A g-1), and stable cycling (>800 cycles, 80.21% retention at 15 A g-1).

Conclusions:

• The novel radical-mediated conversion mechanism significantly enhances Zn-S battery performance.
• Demonstrated potential for practical applications with a pouch cell achieving 95 Wh kg-1 energy density.