The “dual-layer sulfur cathode” strategy: An In2S3/Bi2S3@rGO heterostructure as an interlayer/modified separator for boosting the areal capacities of lithium-sulfur batteries

The specific energies and energy densities of lithium-sulfur (Li-S) batteries are influenced by various cell parameters, including the sulfur loading, the sulfur weight percentage in the cathode, and the electrolyte/sulfur ratio. An In2S3/Bi2S3@rGO heterostructure was obtained by growing indium sulfide nanoparticles on the surface of bismuth sulfide nanoflowers in a graphene oxide (GO) solution via a one-step solvothermal approach. This structure was introduced as a modified separator/dual-layer sulfur cathode for Li-S batteries. The Bi2S3/In2S3 heterointerfaces act as active sites to speed up interfacial electron transfer, along with the entrapment, diffusion, and transformation of lithium polysulfides. A Li-S cell containing a dual-layer sulfur cathode (thin layer of In2S3/Bi2S3@rGO sandwiched between two thick layers of sulfur) and coupled with an In2S3/Bi2S3@rGO-coated separator suppressed the polysulfide shuttle effect. The cell based on the dual-layer sulfur cathode technology and operated at a current rate of 0.3C achieved a high capacity (7.1 mAh cm-2) after the 200th cycle, giving an electrolyte/sulfur ratio (10 µL mg-1) under a high sulfur loading (11.53 mg cm-2). These results demonstrate the unique nature of the dual-layer sulfur cathode technique, which can yield high energy density Li-S batteries with high sulfur loadings and low electrolyte/sulfur ratios.