Tetrathiafulvalene as a multifunctional electrolyte additive for simultaneous interface amelioration, electron conduction, and polysulfide redox regulation in lithium-sulfur batteries

Numerous efforts can improve reversible capacity and long cycling stability for lithium-sulfur (Li–S) batteries, however, challenges remain in achieving high sulfur utilization and suppressing the shuttle effect , especially for cells with a low electrolyte/sulfur (E/S) ratio. In this research, we utilize tetrathiafulvalene (TTF) as multifunctional catalyst for high-performance Li–S batteries through optimizing electrolyte chemistry for the first time. With TTF additive in electrolyte, it acts as π-electron donor molecule to improve the electron transport of Li 2 S x due to the van der Waals interaction , and promote LiNO 3 to Li 3 N to form highly conductive passivation layer on lithium anode (Li-anode). Furthermore, TTF functions as a catalyst to improve the redox kinetics of Li 2 S x thus slowing down the “shuttle effect”, improve the utilization of sulfur, and protect the Li-anode. As a result, the cell with TTF exhibits excellent performances with high discharge capacity (1359 mAh g −1 at 0.1C), long-term cycling stability (509 mAh g −1 after 500 cycles at 0.5C), and excellent cycling performance even at low E/S ratio (5.5 μL mg −1 ) (initial discharge capacity of 1129 mAh g −1 with a capacity decay rate of 0.20% per cycle at 0.1C for 200 cycles).