Journal of Energy Chemistry ›› 2022, Vol. 69 ›› Issue (6): 428-433.DOI: 10.1016/j.jechem.2022.01.005

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Regulating the radical intermediates by conjugated units in covalent organic frameworks for optimized lithium ion storage

Shuai Gua,b, Xiaoxia Mab, Jingjing Chena, Rui Haoa, Zhiqiang Wanga, Ning Qina,b, Wei Zhenga, Qingmeng Gana, Wen Luoa, Muqing Lia, Zhiqiang Lia, Kemeng Liaoa, Hao Guoa, Guiyu Liua, Kaili Zhangb,*, Zhouguang Lua,*   

  1. aDepartment of Materials Science and Engineering, Shenzhen Key Laboratory of Interfacial Science and Engineering of Materials, Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China;
    bDepartment of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
  • Received:2021-11-14 Revised:2021-12-29 Accepted:2022-01-03 Online:2022-06-15 Published:2022-10-25
  • Contact: * E-mail addresses: kaizhang@cityu.edu.hk (K. Zhang), luzg@sustech.edu.cn (Z. Lu).

Abstract: Organic active units often transform into radical intermediates during the redox processes but exhibit poor cycling stability due to the uncontrollable redox of the radicals. Herein, we report a facile and effi-cient strategy to modulate the molecular orbital energies, charge transport capacities, and spin electron densities of the active units in covalent organic frameworks (COFs) via regulating the conjugated unit size to optimize the redox activity and stability of the organic radicals. COFs based on different imide conju-gated units exhibit tunable discharge voltages, rate performance and cycling stabilities. Detailed charac-terizations and theoretical calculation reveal that imide radicals are the important active intermediates during the redox processes of these COFs. Specifically, increasing the size of the imide conjugated units could effectively delocalize the radical electrons and improve the stability of the COFs electrodes. This study offers a very effective strategy to modulate the redox chemistry of organic materials for electro-chemical energy storage.

Key words: Organic electrodes, Radical intermediates, Covalent organic frameworks