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.