In situ assembly of MnO2 nanosheets on sulfur-embedded multichannel carbon nanofiber composites as cathodes for lithium-sulfur batteries

Abstract

Rechargeable lithium-sulfur batteries have been regarded as the promising next generation energy storage system due to their overwhelming advantages in energy density. However, their practical implementations are hindered by severe capacity fading and low sulfur utilization, which are caused by polysulfide shuttling and the insulating nature of sulfur. Herein, sulfur-embedded porous multichannel carbon nanofibers coated with MnO2 nanosheets (CNFs@S/MnO2) are rationally designed and fabricated as cathode for lithium-sulfur battery. The high conductivity of porous multichannel carbon nanofibers facilitates the kinetics of electron and ion transport in the electrodes, and the porous structure encapsulates and sequesters sulfur in its interior void space to physically retard the dissolution of high-order polysulfides. Moreover, the MnO2 shell exhibits a combination of physical and chemical adsorption for high-order polysulfides, which could sequester polysulfides leaked from the carbon matrix after long-time charge/discharge cycles, resulting in enhanced cyclic stability. As a result, the electrode delivers a specific capacity of 1286 mA h g−1 at 0.1 C and 728 mA h g−1 at 3 C. And the capacity could remain 774 mA h g−1 after 600 cycles at 1 C.