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.