A 2D Covalent Triazine Framework as an Interconvertible Redox Mediator to Promote Sulfur‐Conversion Reactions

Abstract The sluggish sulfur conversion kinetics have significantly restricted the rate capability and cycling stability of lithium‐sulfur (Li‐S) batteries. To address this issue, a crystalline pyrene‐4, 5, 9, 10‐tetraone functionalized covalent triazine framework (CPTO‐CTF) is developed, incorporating well‐defined nanopores, a fully conjugated framework with abundant redox‐active moieties, which can act as an interconvertible and rejuvenated redox mediator to promote sulfur‐conversion reactions. The invertible chemical oxidation/reduction between PTO/lithiated PTO and sulfur species can facilitate the conversion reactions and lead to a high utilization of active materials. As a consequence, the CPTO‐CTF@S battery delivers high discharge capacity of 1233 mAh g ⁻¹ at 0.2 C, high‐rate capacity of 604 mAh g ⁻¹ at 5 C, and remarkable retention of 95.6% over 600 cycles. The integrated chemical‐ and electrochemical‐pathway further demonstrates its effectiveness in a prototype pouch cell, which delivers a substantial capacity of 810 mAh g ⁻¹ at 0.2 C.