Fabrication of electrospun bilayer separators for lithium-sulfur batteries: A surface and structure dual modification strategy

摘要

The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur (Li-S) batteries, which can be improved by separator modification. This study develops a bilayer separator based on an effective surface and structure dual modification strategy. This bilayer separator (named as TCNFs/SPNFs) is constructed by the integration of a carbon-based nanofiber layer (surface modification layer) with a polymer-based nanofiber layer (structure modification layer) through a facile electrospinning process. The excellent electrolyte wettability of the nanofibers accelerates lithium-ion migration, while the good electronic conductivity of the carbon layer facilitates fast electron conduction. The TiO2 and SiO2 nanoparticles embedded in the separator provide abundant active sites for immobilizing the polysulfides. Owing to these synergistic effects, this multi-functional separator helps inhibit the shuttling problem and thus enhances the active sulfur utilization. The as-prepared battery with the TCNFs/SPNFs separator delivers significantly enhanced the electrochemical performances, producing a low capacity decay rate of 0.061% per cycle at 1 C over 1000 cycles and an admirable rate capacity of 886.7 mAh g(-1) at 2 C. Even with a high sulfur loading of 4.8 mg cm(-2), a remarkable areal capacity of 6.0 mAh cm(-2) is attained. This work is believed to provide a promising strategy to develop novel separators for high performance Li S batteries.

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