Flexible and Conductive Membrane with Ultrahigh Porosity and Polysulfide-Conversion Catalytic Activity for Large-Scale Preparation of Li–S Batteries

Abstract

Li–S batteries still have various problems, including volume expansion, low S conductivity, and shuttling effect of polysulfides (LiPSs), requiring resolution. Herein, polyvinylidene fluoride (PVDF) is combined with carbon nanotubes (CNTs) and Fe2O3 through a one-step phase-inversion process to form a highly flexible and conductive membrane as a functional Li–S battery interlayer. The CNT skeleton is tightly entangled and crosslinked by PVDF to form a hierarchically porous framework, which is suitable for fast Li+ and electron transport and volumetric expansion of S and facilitated electrolyte diffusion. Additionally, the strongly negative F atoms can accelerate Li+ transport, promoting the fast redox reaction between S species and Li+. Furthermore, the uniformly doped Fe2O3 nanoparticles provide abundant active sites and broad reaction interfaces for highly efficient LiPS anchoring and catalytic conversion. Li–S batteries with the membrane as the interlayer exhibit an excellent cycle performance and reversible capacity of 631.2 mAh g–1 after 400 cycles at 1 C. Furthermore, in situ Raman spectroscopy shows that long-chain Li2S8 decreases, indicating that the interlayer can alleviate the shuttle of soluble LiPSs. This proposed strategy advances the practical application of Li–S batteries due to the facile and scalable production of the flexible membrane.