Hollow Carbon Nanofibers Filled with MnO₂ Nanosheets as Efficient Sulfur Hosts for Lithium-Sulfur Batteries

Lithium-sulfur batteries have been investigated as promising electrochemical-energy storage systems owing to their high theoretical energy density. Sulfur-based cathodes must not only be highly conductive to enhance the utilization of sulfur, but also effectively confine polysulfides to mitigate their dissolution. A new physical and chemical entrapment strategy is based on a highly efficient sulfur host, namely hollow carbon nanofibers (HCFs) filled with MnO₂ nanosheets. Benefiting from both the HCFs and birnessite-type MnO₂ nanosheets, the MnO₂@HCF hybrid host not only facilitates electron and ion transfer during the redox reactions, but also efficiently prevents polysulfide dissolution. With a high sulfur content of 71 wt % in the composite and an areal sulfur mass loading of 3.5 mg cm^-2 in the electrode, the MnO₂@HCF/S electrode delivered a specific capacity of 1161 mAh g^-1 (4.1 mAh cm^-2) at 0.05 C and maintained a stable cycling performance at 0.5 C over 300 cycles. Keep the sulfur: Hollow carbon nanofibers filled with MnO₂ nanosheets (MnO₂@HCF) were synthesized and shown to be a suitable sulfur host for lithium-sulfur batteries. As the polysulfides are physically entrapped by the carbon shells and chemically bound by the MnO₂ nanosheets, this nanocomposite sulfur cathode displayed excellent specific/areal capacities and a good cycling stability. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.