Li-Rich Organosulfur Cathode with Boosted Kinetics for High-Energy Lithium-Sulfur Batteries

Organosulfur materials containing sulfur-sulfur bonds are an emerging class of high-capacity cathodes for lithium storage. However, it remains a great challenge to achieve rapid conversion reaction kinetics at practical testing conditions of high cathode mass loading and low electrolyte utilization. In this study, a Li-rich pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/Se2S3) composite cathode is synthesized by deep lithiation to address the above challenges. The Li-rich molecular structure significantly boosts the lithium storage kinetics by accelerating lithium diffusivity and improving electronic conductivity. Even under practical test conditions requiring a lean electrolyte (Electrolyte/sulfur ratio of 4.1 mu L mg-1) and high loading (7 mg cm-2 of pPAN/Se2S3), DL-pPAN/Se2S3 exhibits a specific capacity of 558 mAh g-1, maintaining 484 mAh g-1 at the 100th cycle with an average Coulombic efficiency of near 100%. Moreover, it provides (electro)chemically stable Li resources to offset Li consumption over charge-discharge cycles. As a result the as-fabricated anode-free cell shows a superior cycling stability with 90% retention of the initial capacity over 45 cycles. This study provides a novel approach for fabricating high-energy and stable Li-SPAN cells. Deep lithiation of a pyrolyzed polyacrylonitrile/selenium disulfide (pPAN/Se2S3) composite cathode (DL-pPAN/Se2S3) has been performed to obtain a Li-rich organosulfur cathode. It accelerates the Li+ diffusivity, improves the electronic conductivity and more importantly provides (electro)chemically stable Li resources to offset Li loss over charge-discharge cycles. As-fabricated anode-free Li-S cell shows a high-energy density and excellent cycling stability.image