A Keggin-type polyoxometalate/COF thin separator for improving the performance of lithium–sulfur batteries

Abstract

Separators have an important influence on the safety and performance of lithium–sulfur batteries (LSBs). However, traditional commercial polyolefin separators have problems of poor thermal stability and catalytic activity. In this paper, a separator based on covalent organic skeletons (COFs) with rich N/O functional groups and Keggin-type polyoxometalate (PW₁₂/PMo₁₂) nanoparticles was studied by easy coating technology on the substrate of a polyolefin separator. It is worth noting that the hybrid coating layer structure makes the separator have the ability to reduce the shuttle effect, promote the catalytic conversion of polysulfide and improve the electrochemical performance. Among them, the obtained LSB equipped with a PW₁₂/DTQ-COF@PP separator provides a discharge capacity of 1084 mA h g⁻¹ at 0.1C and 550.6 mA h g⁻¹ at a high magnification of 2C. It is believed that the wettability, catalytic sites and nanoporous separator could provide promising insights for advanced polysulfide separators, improving the cycle life of LSBs.