Polyimide-Linked Hexaazatriphenylene-Based Porous Organic Polymer with Multiple Redox-Active Sites as a High-Capacity Organic Cathode for Lithium-Ion Batteries

Abstract

The development of high-capacity, sustainable cathode materials remains a critical challenge in advancing lithium-ion battery technologies for next-generation energy storage. Organic electrode materials (OEMs) represent a promising alternative to conventional inorganic cathodes, owing to their composition from earth-abundant elements and chemically tunable structures that enable high theoretical capacities. Herein, a polyimide-linked porous organic polymer (HAT-PTO) is reported to be synthesized via a straightforward hydrothermal reaction from redox-active hexaazatriphenylene (HAT) and pyrene-4,5,9,10-tetraone (PTO) building blocks. The resulting HAT-PTO framework incorporates multiple redox-active C═O and C═N centers, delivering a high theoretical capacity of 484 mAh g−1. To overcome limitations in electronic conductivity, hybrid materials are synthesized by in situ growth of HAT-PTO on multiwalled pristine (CNT) and carboxyl-functionalized carbon nanotubes (cCNT). Notably, the HAT-PTO-cCNT hybrid delivers a high capacity of 397 mAh g−1 at C/10, outstanding rate capability of 225 mAh g−1 at 20 C, and long-term cycling stability, retaining 171 mAh g−1 after 6000 cycles at 2 C. Ex situ FT-IR, supported by density functional theory (DFT) calculations, confirms the involvement of both HAT and PTO units in the charge storage mechanism. This work presents a molecular design strategy and scalable synthesis approach toward high-performance organic cathodes, paving the way for durable, high-rate lithium-organic batteries.