Elaborately Designed Micro-Mesoporous Graphitic Carbon Spheres as Efficient Polysulfide Reservoir for Lithium-Sulfur Batteries

Hybrid micro-mesoporous graphitic carbon spheres (M-MGCSs) featuring ordered mesoporous graphene-like cores and uniform microporous carbon shells are designed by transformation of self-assembled Fe3O4 nanoparticle supraparticles and are used as an efficient, dual spatially confined sulfur reservoir for lithium-sulfur (Li-S) batteries. Such rationally designed M-MGCSs synergistically combine the merits of micro- and mesoporous carbons when used as the sulfur host in Li-S batteries: the core having interconnected spherical mesopores of 9.0 nm provides sufficient space for loading S-8 molecules, while the shell having micropores of 0.6 nm can entrap only small S2-4 molecules, which are converted into electrolyte-insoluble polysulfides during discharge, minimizing the outward diffusion of long-chain polysulfides from the core. These advantageous structural features, combined with the highly graphitic nature and mesoscale spherical morphology of M-MGCSs, enable Li-S cathodes with greatly improved performance even at high sulfur areal loadings.