Capturing Polysulfides with a Functional Anhydride Compound for Lithium-Sulfur Batteries

Lithium-sulfur batteries are the focus of the current development of high-energy storage devices. However, their practical application is hindered by the fast capacity decay caused by the "shuttle effect" of intermediate lithium polysulfides during cycling. In this study, we combine graphene (G) with the organic molecule 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) to form the G-PTCDA composite as the host material of sulfur cathodes. In particular, PTCDA with the conjugated benzene rings and the anhydride group is absorbed tightly on graphene through pi-pi stacking and thus enhances the polarity and conductivity of the G-PTCDA composite. Meanwhile, PTCDA can capture the otherwise dissolved intermediate polysulfides on the sulfur cathode by forming the Li-O bond with the oxygen atoms on the acid anhydride group in a collaborative manner. Thus, the "shuttle effect" can be effectively depressed, and the electrochemical performance is improved during discharge and charge cycling. We hope that the findings of this study can provide a deeper understanding of the design and preparation of the sulfur-based composite cathode material with functional organic molecules for lithium-sulfur batteries.