Lithiated Sulfur-Incorporated, Polymeric Cathode for Durable Lithium-Sulfur Batteries with Promoted Redox Kinetics.

Even though lithium-sulfur (Li-S) batteries have made much progress in terms of the delivered specific capacity and cycling stability by the encapsulation of sulfur within conductive carbon matrixes or polar materials, challenges such as low active sulfur utilization and unacceptable Coulombic efficiency are still hindering their commercial use. Herein, a lithium-rich conjugated sulfur-incorporated, polymeric material based on poly(Li2S6-r-1,3-diisopropenylbenzene) (DIB) is developed as a cathode material for high rate and stable Li-S batteries. Motivated by extra Li+ ions affording fast Li+ redox kinetics across the conjugated aromatic backbones, the Li-rich sulfur-based copolymer exhibits high delivery capacities (934 mAh g-1 at 120 cycles), impressive rate capabilities (727 mAh g-1 even under a current of 2 A g-1), and long electrochemical cycling performance over 500 cycles. Moreover, by use of the elastic nature and thermoplastic properties of the sulfur-incorporated, polymeric material, a prototype of a flexible Li-S pouch cell is constructed by using a poly(Li2S6-r-DIB) copolymer cathode and paired with the flexible carbon cloth/Si/Li anode, which exhibits stable electrochemical performance (658 mAh g-1 after 100 cycles) and operational capability even under folding at various angle (30°, 60°, 90°, 120°, 150°, 180°). This work extends the molecular-design approach to obtaining a high-performance organosulfur cathode material by introducing extra Li+ ions to promote redox kinetics, which provides valuable guidance for the development of high-performance Li-S batteries for practical applications.