Hollow nitrogen-doped carbon/sulfur@MnO2 nanocomposite with structural and chemical dual-encapsulation for lithium-sulfur battery

Abstract

Although lithium-sulfur (Li-S) batteries are one of the most promising energy storage systems, the low electrical conductivity of sulfur, the serious shuttle of the dissolved lithium polysulfides (LiPSs) and the large volume change during cycling greatly hinder the practical application of Li-S batteries. To overcome these issues, we report the in situ growing MnO2 nanosheets on the hollow nitrogen-doped micropore-rich carbon (NMRC) to form NMRC/S@MnO2 nanocomposite with high sulfur content for advanced Li-S battery. The hollow nonpolar micropore-rich carbon nanospheres not only provide effectively structural confinement for active species but also accommodate the volume change during the charge–discharge process. The polar MnO2 nanosheets and doped nitrogen present strong chemisorption for LiPSs. Consequently, the synergistic dual-encapsulation from structural confinement and chemisorption makes the NMRC/S@MnO2 nanocomposite has a theoretical sulfur loading of 72% and exhibit a high initial specific capacity of 1144 mAh·g−1 and a reversible capacity of 1023 mAh·g−1 after 200 cycles at 0.2 C. Even after 1000 cycles at 2.0 C, a capacity of 590 mAh·g−1 is maintained, among the best results for Li-S batteries. Our work reveals that the carefully design of sulfur-based composites with structural and chemical dual-encapsulation is promising to push forward the practical implementation of Li-S batteries.