Dual Core–Shell-Structured S@C@MnO₂ Nanocomposite for Highly Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have currently excited worldwide academic and industrial interest as a next-generation high-power energy storage system (EES) because of their high energy density and low cost of sulfur. However, the commercialization application is being hindered by capacity decay, mainly attributed to the polysulfide shuttle and poor conductivity of sulfur. Here, we have designed a novel dual core–shell nanostructure of S@C@MnO₂ nanosphere hybrid as the sulfur host. The S@C@MnO₂ nanosphere is successfully prepared using mesoporous carbon hollow spheres (MCHS) as the template and then in situ MnO₂ growth on the surface of MCHS. In comparison with polar bare sulfur hosts materials, the as-prepared robust S@C@MnO₂ composite cathode delivers significantly improved electrochemical performances in terms of high specific capacity (1345 mAh g^–1 at 0.1 C), remarkable rate capability (465 mA h g^–1 at 5.0 C) and excellent cycling stability (capacity decay rate of 0.052% per cycle after 1000 cycles at 3.0 C). Such a structure as cathode in Li–S batteries can not only store sulfur via inner mesoporous carbon layer and outer MnO₂ shell, which physically/chemically confine the polysulfides shuttle effect, but also ensure overall good electrical conductivity. Therefore, these synergistic effects are achieved by unique structural characteristics of S@C@MnO₂ nanospheres.