Surface chemistry of tube-in-tube nanostructured cuprous sulfide@void@carbon in catalytical polysulfides conversion

Polysulfides trapping to prevent shuttle effect by a variety of polar materials has been intensively studied in Li-S batteries. However, the underlying chemical interaction and reaction kinetics remain poorly understood. Here, focusing on the fundamental understanding of the interfacial chemistry between sulfur cathode materials and lithium polysulfides, we investigated a Cu2S@void@C host of sulfur, that is, a tube-in-tube nanostructure with polar Cu2S inner tube, conductive carbon outer tube and space in between. We found the Cu2S nanotubes not only have strong adsorptivity to polysulfides through chemical interaction between the CuO surface layer and polysulfieds, but also have catalytic effect to lower the energy barrier of charge transfer at the polysulfides-electrolyte/electrode interface. The Cu2S nanotubes are able to enhance reaction kinetics of polysulfides lithiation/delithiation and Li2S nucleation/oxidation. A binder free electrode (G-Cu2S@S@C) with the exquisite 3D conductive network was prepared by encapsulating sulfur into Cu2S@void@C and subsequently wrapping with graphene nanosheets. Remarkably, the G-Cu2S@S@C cathode of 3.5 mg/cm2 sulfur loading amount shows a significantly prolonged cycling stability and enhanced rate performance.