Nucleophilic Ring-Opening of Thiolactones: A Facile Method for Sulfhydrylization of a Carbon Nanotube-Based Cathode toward High-Performance Li–S Batteries

Low conductivity and lack of chemical restriction are the two main factors that limit the rate performance and cycle stability of lithium–sulfur battery cathode materials. Herein, we developed a simple quasi-click reaction to release sulfhydryl groups simultaneously via thiolactone and amino nucleophilic ring-opening, which was used to coat carbon nanotubes as the cathode in Li–S batteries. Density functional theory (DFT) calculations and experiments both demonstrated that carbon nanotube supported sulfhydryl polymer (TLP@CNT) forms strong S–S covalent bonds with sulfur and polysulfides through sulfur impregnation, resulting in effectively inhibiting the shuttle effect. Also, it is remarkable that a stable cross-linked network serving as a physical barrier and chemical absorption deriving from abundant electron-rich donors (e.g., −NH 2, −CO(NH)−) in a TLP@CNT/S cathode can synergistically suppress the shuttle effect. Thus, the capacity retention of the TLP@CNT/S cell can reach up 80.88% with a small decay of 0.038% per cycle at the current of 1 C even after 500 cycles. All these features demonstrate that sulfhydryl polymer prepared via a rapid and effective nucleophilic ring-opening of thiolactones can emerge as a potential candidate as a sulfur cathode and may open a new route for the design of a superior sulfur cathode toward high-performance Li–S batteries.