Covalent Organic Framework Hollow Rectangular Prism Enables Interfacial Binding of Li2S Cathode for High-Performance Lithium-Ion Sulfur Battery.

Abstract

Since its initial discovery by Dahn et al. in 2002, Li2S has emerged as a highly promising cathode material, circumventing the employment of Li metal in battery construction. However, its practical application has been significantly constrained by several challenges, including weak interfacial interactions between electrode components, the high activation potential of Li2S, and the absence of suitable binders capable of effectively managing internal stress during repeated charge-discharge cycles. In this study, an anthraquinone-based covalent organic framework (OH-AAn-COF) with a hollow rectangular prism morphology is introduced as a novel nano-mediator for Li2S cathodes. The porous structure of the COF, enriched with functional groups, facilitates enhanced interfacial binding between electrode components, establishing robust interfacial bridges between Li2S/Li2S and Li2S/electrolyte. This results in more cohesive interfacial interactions, thereby reducing the activation potential of Li2S, promoting the adsorption and redox conversion of polysulfides, and enabling faster electrochemical reactivity and improved cycling stability compared to conventional PVDF binders. Notably, the Li2S@C-OH-AAn-COF//graphite full cell, which operates without lithium metal, demonstrates exceptional cycling performance, achieving over 1000 cycles at 0.5C, surpassing the performances of most reported Li-S battery systems.