Dendritic sp Carbon-Conjugated Benzothiadiazole-Based Polymers with Synergistic Multi-Active Groups for High-Performance Lithium Organic Batteries

Green organic materials composed of C, H, O, and N elements are receiving more and more attention worldwide. However, the high solubility, poor electrical conductivity, and long activation time limit the development of organic materials in practice. Herein, two stable covalent organic materials with alkynyl linkage between benzene rings and benzothiadiazole groups with different amounts of fluorine atoms modification (defined as BOP-0F and BOP-2F), are designed for lithium-ion batteries. Both BOP-0F and BOP-2F can achieve superior reversible capacities of approximate to 719.8 and 713.5 mAh g-1 over 100 cycles on account of the redox activity of alkynyl (two-electron involved) and benzothiadiazole units (five-electron involved) in these organic materials. While BOP-2F electrodes exhibit much more stable cycling performance than BOP-0F electrodes, especially without pronounced capacity ascending during initial cycling. It can be assigned to the synergy effect of alkynyl linkage and fluorine atom modification in BOP-2F. The lithium storage and activation mechanism of alkynyl, benzothiadiazole, and fluorine groups have also been deeply probed by a series of material characterizations and theoretical simulations. This work could be noteworthy in providing novel tactics for the molecular design and investigation of high-efficiency organic electrodes for energy storage. The C equivalent to C linked covalent benzothiadiazole-based organic polymer with fluorine side groups is obtained for lithium organic batteries and exhibits superior electrochemical properties through the optimized molecule structure among alkynyl, benzothiadiazole, and fluorine groups.image

Automated summary

In this study, two stable covalent organic materials, BOP-0F and BOP-2F, with alkynyl linkage and benzothiadiazole groups modified with different amounts of fluorine atoms, were designed and investigated. Both BOP-0F and BOP-2F exhibited superior reversible capacities in lithium-ion batteries due to the redox activity of alkynyl and benzothiadiazole units in these materials. BOP-2F electrodes showed more stable cycling performance compared to BOP-0F electrodes, attributed to the synergy effect of alkynyl linkage and fluorine atom modification. The lithium storage and activation mechanism of alkynyl, benzothiadiazole, and fluorine groups were also studied. This work provides novel tactics for the design and investigation of high-efficiency organic electrodes for energy storage.