Designing dual-defending system based on catalytic and kinetic iron Pyrite@C hybrid fibers for long-life room-temperature sodium-sulfur batteries

Abstract

The poor conductivity and severe polysulfide dissolution greatly restrict the development of room-temperature sodium-sulfur (RT-Na/S) batteries. To address these issues, a dual-polysulfide-defending system based on catalytic and kinetic hybrid fibers is designed to realize high-performance and long-life for RT-Na/S batteries. The hollow carbon fibers filled with yolk-shell FeS2/C hollow nanocubes (FeS2[email protected]) are constructed as the flexible sulfur host. The highly conductive and porous network ensures fast electron/ion transports and facilitates high mass loading. More impressively, the polar FeS2 boxes ensure the strong chemical binding and high catalytic redox reaction on polysulfides, which produce the first defense on polysulfide shuttle. Meanwhile, the FeS2@C/carbon nanotubes (CNT) hybrid film works as the modifying layer on the separator, which builds the second defense to ion shuttle. Taken the advantages of both dual-polysulfide-defending system and the hierarchical polar electrode, the RT-Na/S battery achieves superior high-rate capability, long-term cycling stability and high energy storages. It obtains an ultralow capacity decay rate (0.024%) during 1000 cycles at the rate of 2C with a high mass loading of 7.6 mg cm−2. Therefore, this work not only designs a freestanding kinetic and catalytic host for sulfur electrodes, but also provides a new design on RT-Na/S batteries to realize long life, superior rate capability and high energy storage synchronously.