Application of Covalent Organic Frameworks in Sulfur-Based Battery Separators

Owing to the high storage capacity and multiple-electron-transfer chemistry of sulfur (S), sulfur-based (S-based) batteries with merits of high theoretical capacity/energy density, eco-friendliness, and abundant supply hold much potential for energy-storage/conversion devices. The capacity of S-based batteries is much higher than that of traditional-metal-oxide cathode-based lithium-ion batteries, which is regarded as the highest capacity of solid-state cathode materials at the current stage. As a vital component of S-based batteries, separators play a profound role in resolving urgent issues (e.g., shuttling effect, volume expansion, poor conductivity, and metal dendrites, etc.). So far, some pioneering works have been reported in the exploration of separators for S-based battery. On this basis, covalent organic frameworks (COFs), as a kind of functional materials, offer much possibility for S-based battery separators due to their advantages such as high porosity, crystalline and well-defined structures, designable struts, and tunable functions, etc. Herein, the reported works about COFs in S-based battery separators including their structural characteristics, preparation methods, application forms, and battery properties are summarized. Moreover, also, a brief perspective is proposed on the challenges of COFs applied in S-based battery separators, and new insights are provided for scientists in this field.