Regulating the kinetic behaviours of polysulfides by designing an Au–COF interface in lithium–sulfur batteries

Abstract

The kinetic behaviors of polysulfides related to sluggish/incomplete conversion and repeated shuttles are the key factors behind the unsatisfactory performance of Li–S batteries. Herein, an Au-decorated covalent organic framework/graphene (Au–COF/rGO) is employed to construct a multifunctional interface to solve such issues. The narrow porous structure of COF can confine the diffused polysulfides via a physical barrier, and Au can further anchor and facilitate the catalytic conversion of intercepted polysulfides. Meanwhile, the well-conducting rGO nanosheets are also able to act as an upper current collector to activate polysulfides to quickly participate in the next electrochemical reaction. Thus, an orderly connection between the confinement–capture–conversion of polysulfides is formed. Additionally, the good lithium affinity of Au and imine linkages on COF can promote Li⁺ diffusion, achieving a fast charge of batteries. Attributed to the multi merits of the Au–COF/rGO interface, the assembled Li–S batteries not only deliver an ultra-high specific capacity (1525 mA h g⁻¹ at 0.1C) with a prominent rate performance (568 mA h g⁻¹ at 4C), but also exhibit outstanding cycling performance in both the cases of conventional and high sulfur loadings. The rational design of the Au–COF/rGO interface provides a new insight into developing advanced Li–S batteries.