A Polysulfide-Repulsive, In Situ Solidified Cathode–Electrolyte Interface for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur batteries are promising candidates for beyond-Li-ion electrochemical energy storage yet are hindered due to limited cycle lives. In case a liquid ether electrolyte is used, the S cathode suffers from an unstable electrode–electrolyte interface, at which soluble polysulfide intermediates form, dissolve, and shuttle between the two electrodes. When the cathode–electrolyte interface is solidified, the S cathode shows suppressed polysulfide dissolution. In this work, we show that a liquid polymer cathode additive, poly(hexamethylene diisocyanate), is able to react with soluble polysulfide species at the beginning of battery discharge to in situ form a solidified, polysulfide-anion-grafted organic cathode–electrolyte interface. In addition to serving as a physical barrier, the negatively charged interface helps to anchor polysulfides at the cathode surface via electrostatic repulsion. The solidified interface around the active S particles also forms an efficient, three-dimensional porous Li-ion conducting network to trigger improved electrode kinetics and avoid the formation of locally dead S. Benefiting from the improved interfacial electrochemistry, the Li–S battery shows admirable storage performance in terms of cycle life and rate capability to promise practical high-energy rechargeable batteries.