Designing Effective Solvent–Catalyst Interface for Catalytic Sulfur Conversion in Lithium–Sulfur Batteries

Sulfur-based redox materials are promising next-generation energy storage solutions. Identifying electrode and electrolyte properties that facilitate polysulfide reduction reactions is critical for rational material designs for sulfur-based batteries. In this study, we reveal that the effectiveness of the polysulfide reduction is governed by the resolved binding strength of polysulfide on the electrode surface, which is dictated by the competition between electrode's polysulfide chemisorption strength and solvent's polysulfide solvation strength. Using titanium-based model compounds (TiX) as examples, we show that the polysulfide reduction kinetics and sulfur utilization increase with increasing polysulfide chemisorption strength of TiX, which can be associated with the decreasing electronegativity of nonmetal element (X). Strong coordinating solvent reduces catalyst's efficacy by reducing the binding strength between polysulfide and the catalysts, highlighting that a weak solvent coordination is a critical selection criterion for effective catalysis in Li-S batteries. Our study reveals physical origins controlling the catalytic processes of polysulfide reduction reactions and unravels the interplay of solvent-polysulfide-catalyst competition for achieving higher-energy and reversible sulfur-based energy storage. Copyright © 2019 American Chemical Society.