Lithium-sulfur batteries have large theoretical capacity and high energy density, and cathode materials have a wide range of sulfur sources and are environmentally friendly, and are expected to become the next generation of high-performance lithium-ion batteries. However, there are still many technical challenges in their commercial application, such as solid vulcanization. The poor conductivity of the material, the shuttle effect of the soluble polysulfide intermediates, and the large volume change during the charge and discharge process, these problems lead to low sulfur utilization and cycle life. How to significantly increase the discharge performance and stability, while limiting The shuttle effect of lithium sulfide has become one of the hot spots in current research.
Professor Wang Ruihu, researcher of Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, and Tian Dongxu, a professor at Dalian University of Technology, selected organic ligands containing boric acid and cyano groups, and built two functional groups containing triazine rings and boroxine rings by self-polymerization. Yuan's Binary Covalent Organic Framework (COF). This study not only solves the problem of the separation and purification of products that multiple ligands face through conventional orthogonal methods to construct binary COFs, but also uses this COF as the main sulfur entity. Its structural regularity, uniform pores and abundant active sites provide an ideal model for studying the chemical adsorption mechanism of host materials and polysulfides. Through electrochemical experiments and theoretical calculations, it was found that the triazine rings exhibit strong lithium-philic properties. The boro-oxygen hexafluoride exhibits high thiophilic performance. This amphiphilic effect enables TB-COF to exhibit excellent polysulfide adsorption capacity, effectively solves the polysulfide shuttle effect, and significantly improves the lithium-sulfur battery. The cycle stability can.
The research work was funded by the National Natural Science Foundation of China and the China National Academy of Sciences’ Strategic Leading Science and Technology project. The relevant research results were published on Energy Storage Materials. The first author of the paper was Assistant Researcher Xiao Zhibing.
