Nanoconfined Oxidation Synthesis of N-Doped Carbon Hollow Spheres and MnO2 Encapsulated Sulfur Cathode for Superior Li-S Batteries.

The sulfur cathode, as a new generation of lithium-ion battery cathode material, has a high theoretical energy density of about 2500 Wh kg-1 . However, the low conductivity of sulfur and the "shuttle effect", widely presenting in the lithiation/de-lithiation process, seriously hinder its practical application. Here, we report a new nanoconfined oxidation route (first complete oxidation of metal sulfide and subsequently partial oxidation of the generated S from sulfide) for S cathode encapsulated with MnO2 nanosheets and N-doped carbon hollow spheres. This nanoconfined oxidation route can successfully confine the sulfur particles in the interior of the carbon shell, and the rationally introduced nonpolar carbon and polar MnO2 can both reduce the dissolution of polysulfide during the charge-discharge process. The obtained well-defined S-MnO2 @C cathode exhibits high specific capacity with excellent cycling performance and superior rate capability.