Self-conversion templated fabrication of sulfur encapsulated inside the N-doped hollow carbon sphere and 3D graphene frameworks for high-performance lithium–sulfur batteries

A nanoarchitecture of sulfur encapsulated inside the N-doped hollow carbon sphere and 3D graphene framework (S@NHC-GFW) is designed via a self-conversion template and self-assembly strategy. Herein, ZnS nanospheres serve as scaffold and sulfur source for the formation of 3D graphene frameworks and their subsequent conversion into sulfur through a facile oxidation reaction. Our self-template conversion route for in situ encapsulation of sulfur inside a carbon shell can prevent the aggregation of sulfur and effectively control uniformity. Hollow carbon nanostructure offers an internal void space, which can accommodate the volumetric change in sulfur upon lithiation. N-doped carbon shell serves as a physical barrier and offers active sites for the chemical adsorption of polysulfides, thereby effectively alleviating the loss of polysulfides. In addition, graphene introduction in the construction of a 3D conductive network interconnected with different S@NHC spheres under plane-to-point mode is beneficial to the continuous transfer of electrons in different dimensions. Consequently, the conductivity of the whole electrode increases. Given these advantages, S@NHC-GFW can serve as a cathode with a good rate capability and an excellent long-term cycling stability.