Long-life Li–S batteries based on enabling the immobilization and catalytic conversion of polysulfides

Herein, novel hierarchical mesoporous nitrogen-rich carbon nanospheres comprising one-dimensional (1D) bamboo-like carbon nanotubes encapsulating Fe3O4 nanoparticles synthesized through a simple and convenient strategy are used as a high-efficiency host for lithium-sulfur batteries (Li-S batteries). With the large internal cavity, all the nanospheres can effectively ensure high sulfur loading and mitigate the shuttling of the polysulfide. The externally grown bamboo-like carbon nanotubes build up an admirable three-dimensional network for facilitating the rapid transport of ions to improve redox kinetics. Moreover, both experimental and theoretical studies have shown that there is a chemical coupling between the two valence iron ions in Fe3O4 and sulfur for the benefit of the fixation of sulfur, playing a role in catalyzing the conversion of the polysulfide. Combining the above virtues, 2.1 mg cm(-2) sulfur loading still retains a high discharge capacity of 538.5 mA h g(-1) after 1800 cycles at 1C and the capacity decay is only 0.023% per cycle. With a higher sulfur loading (5.5 mg cm(-2)), a stable reversible capacity of 739.4 mA h g(-1) is also acquired.