Fully sp<sup>2</sup> Carbon‐Conjugated Covalent Organic Frameworks with Multiple Active Sites for Advanced Lithium‐Ion Battery Cathodes
Ning Fu, Ying Liu, Kun Kang, Xue Tang, Shiqi Zhang, Zhenglong Yang, Yan Wang, Pujun Jin, Yongsheng Niu, Ben Yang
Abstract
Abstract Covalent organic frameworks (COFs) hold great promise for rechargeable batteries. However, the synthesis of COFs with abundant active sites, excellent stability, and increased conductivity remains a challenge. Here, chemically stable fully sp 2 carbon‐conjugated COFs (sp 2 c‐COFs) with multiple active sites are designed by the polymerization of benzo[1,2‐b:3,4‐b′:5,6‐b′′]trithiophene‐2,5,8‐tricarbaldehyde) (BTT) and s‐indacene‐1,3,5,7(2H,6H)‐tetrone (ICTO) (denoted as BTT‐ICTO). The morphology and structure of the COF are precisely regulated from “butterfly‐shaped” to “cable‐like” through an in situ controllable growth strategy, significantly promoting the exposure and utilization of active sites. When the unique “cable‐like” BTT‐ICTO@CNT is employed as lithium‐ion batteries (LIBs) cathode, it exhibits exceptional capacity (396 mAh g −1 at 0.1 A g −1 with 97.9 % active sites utilization rate), superb rate capacity (227 mAh g −1 at 5.0 A g −1 ), and excellent cycling performance (184 mAh g −1 over 8000 cycles at 2.0 A g −1 with 0.00365 % decay rate per cycle). The lithium storage mechanism of BTT‐ICTO is exhaustively revealed by in situ Fourier transform infrared, in situ Raman, and density functional theory calculations. This work provides in‐depth insights into fully sp 2 c‐COFs with multiple active sites for high‐performance LIBs.