Engineering Hexaazatriphenylene Covalent Organic Frameworks/Carbon Nanotube Nanohybrids through In Situ Growth for Superior Anodic Lithium-Ion Storage

Abstract

Redox-active covalent organic frameworks (COFs) represent a promising class of sustainable organic electrode materials for lithium-ion batteries (LIBs). However, the tight layer stacking and poor inherent conductivity of COFs pose a major barrier to utilizing their internal redox-active sites. To circumvent the challenge, three phenazine-linked COFs hybrids (HHATP-COF@CNT, HDAB-COF@CNT, and HTAB-COF@CNT) are synthesized through the in situ polycondensation of hexaketocyclohexane with distinct aromatic multi-amine monomers on conductive carbon nanotube (CNT) surfaces, forming core–shell nanocomposites rich in redox-active hexaazatriphenylene (HAT) and aromatic ring moieties. Benefiting from the extended π-electron delocalization and high-density redox-active sites in COFs, synergized with the superior conductivity and flexible network of CNTs, these hybrids deliver high capacity, rate capability, and cycling stability. Consequently, the HHATP-COF@CNT core–shell anode delivers a high initial specific capacity of 926 mAh g–1 at 0.1 A g–1 and exhibits stable cycling performance over 1500 cycles at a high current density of 5.0 A g–1. Complementary XPS and FT-IR measurements under different states of charge/discharge unequivocally attribute the superior electrochemical performance to the rich redox-active HAT units and aromatic rings embedded in the conjugated COF architectures. This research highlights the significant potential of COF-based materials in enabling high-performance Li+ storage.