MOF-derived fluorine and nitrogen co-doped porous carbon for an integrated membrane in lithium–sulfur batteries

Abstract

The shuttle effect of polysulfides severely blocks the cycling performance and commercial application of lithium–sulfur (Li–S) batteries. Recently, metal–organic frameworks (MOFs) with abundant porosity, nanometer cavity size, and high specific surface areas have been considered to be an effective material in inhibiting polysulfide diffusion. However, the insulation properties of MOFs and the reuse of dissolved polysulfides are still challenging. Hence, in this study, a fluorine doped ZIF-8 derived porous carbon is designed and applied as a membrane modifier to mitigate the shuttle effect and maximize reuse of the dissolved polysulfides. A comparative study of a bare membrane, ZIF-8 carbonized material (N–C-1000) coated membrane and fluorine doped ZIF-8 derived porous carbon (F–N–C-1000) coated membrane was performed. The experimental results prove that a layer of ZIF-8 derived porous carbon coated membrane does improve the capacity and cycling stability. The results also show that the optimal candidate with enhanced capacity and cycling stability should be mainly ascribed to physical adsorption (abundant porosity), chemical adsorption (fluorine and nitrogen doping) and even reuse of dissolved polysulfides by the modified membrane.