Design and synthesis of an interfacial layer of the polysulfide immobilizer for lithium-sulfur batteries by the one-pot hydrothermal method

To overcome the low electrical conductivity and large volume expansion of a sulfur cathode during electrochemical reactions, a composite of SnO₂ nanoparticles with 5–10 nm size dispersed on reduced graphene oxide (rGO) sheets and sulfur (rGO/SnO₂/S) was prepared by a one-pot hydrothermal process. This cathode shows 1.2-fold higher interfacial Li ion diffusivity (1.8 × 10⁻¹² cm² s⁻¹) than that of an rGO/S cathode (1.5 × 10⁻¹² cm² s⁻¹). This improvement is attributed to the synergistic effect of the hybrid matrix comprising rGO sheets and SnO₂. The rGO sheets provide a fast electron pathway and accommodate a large amount of sulfur. Moreover, the dispersed SnO₂ nanoparticle acts as an immobilizer to prevent the dissolution of polysulfide during the electrochemical reaction. The synthesized rGO/SnO₂/S cathode also exhibits an electrical resistivity of 4.4 × 10⁻¹ Ω cm due to interfacial modification. Further, it exhibits improved electrochemical performance with an initial discharge capacity of 1591.57 mA h g⁻¹ at 0.1 C, which stabilizes to 606.98 mA h g⁻¹ at 0.2 C after 100 cycles. In addition, it shows a discharge capacity of 575.45 mA h g⁻¹ even at a high current density of 5 C.