Bifunctional Fluorinated Anthraquinone Additive for Improving Kinetics and Interfacial Chemistry in Rechargeable Li–S Batteries

The uncontrollable Li deposition and severe lithium polysulfide (LiPS) shuttling hinder the commercial application in lithium–sulfur (Li–S) batteries. Here, we propose a bifunctional electrolyte additive, 1,4-difluoroanthraquinone (DFAQ), to be used for lithium regulation and acceleration of sulfur redox kinetics. DFAQ is conducive to form a rigid and smooth LiF-rich organic–inorganic hybrid solid electrolyte interphase (SEI), realizing reversible Li plating/stripping, restraining dendrite growth, and shielding Li anode from the detrimental side reaction with LiPSs. More importantly, DFAQ can be used as a redox mediator to enable an oxygen radical-mediated catalytic cycle to dramatically promote the conversion of LiPSs. Accordingly, the Li–S battery with DFAQ demonstrates ultrahigh discharge capacities, enhanced high-rate performance, and outstanding long-cycle stability (1693.4 mAh g^–1 at 0.5C over 700 cycles). Even under harsh conditions including high sulfur loading (5.8 mg_S cm^–2), ultrathin Li anode (50 μm), and low E/S ratio (5.0 μL mgS^–1), the Li–S battery with DFAQ shows 80 cycles in comparison to just 30 cycles for control battery. This work demonstrates a facile additive strategy originated from bond chemistry to build applicable Li–S batteries.