Redox\nof Dual-Radical Intermediates in a Methylene-Linked Covalent Triazine\nFramework for High-Performance Lithium-Ion Batteries

Covalent\ntriazine frameworks (CTFs) are promising electrodes for rechargeable\nbatteries due to their adjustable structures, rich redox sites, and\ntunable porosity. However, the CTFs usually exhibit inferior electrochemical\nstability because of the inactivation of the unstable radical intermediates.\nHere, a methylene-linked CTF has been synthesized and evaluated as\na cathode for rechargeable lithium-ion batteries. Electron paramagnetic\nresonance (EPR) and in situ Raman characterizations demonstrated that\nthe redox activity and reversibility of α-C and triazine radical\nintermediates are essentially important for the charging/discharging\nprocess, which have been efficiently stabilized by the synergetic\nπ conjugation and hindrance effect caused by the adjacent rigid\ntriazine rings and benzene rings in the unique CTF-p framework. Additionally,\nthe methylene groups provided extra redox-active sites. As a result,\nhigh capacity and cycling stability were achieved. This work inspires\nthe rational modulation of the radical intermediates to enhance the\nelectrochemical performance of organic electrode materials for the\nnext-generation energy storage devices.