Polymer Electrolyte/Sulfur Double-Shelled Anisotropic Reduced Graphene Oxide Lamellar Scaffold Enables Stable and High-Loading Cathode for Quasi-Solid-State Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) can replace lithium-ion batteries by delivering a higher specific capacity. However, the areal capacity of current LSBs is low because the intrinsic limitations of sulfur make achieving a high sulfur loading difficult. Herein, the authors report vertically aligned reduced graphene oxide (rGO) with sulfur and poly(ethylene oxide)-based polymer electrolyte double-shell layers (VRG@S@PPE) as a high-loading sulfur cathode. The addition of vapor-grown carbon fiber (VGCF) into rGO is the key to success, as it allows for gas evacuation from internal nano/micropores without structural collapse, enabling perfect double-shell layer contact. Owing to the anisotropic rGO lamellar structure that enables straightforward ion/electron transport and provides numerous active sites, sulfur-infiltrated rGO reinforced via VGCF (VRG@S) exhibits a high capacity of 998 mAh g⁻¹ after 100 cycles at 0.1 C under high sulfur loading (6 mg cm⁻²). Interestingly, an additional polymer electrolyte layer further increases the cycle retention (1005 and 718 mAh g⁻¹ after 100 cycles at 0.1 and 1 C, respectively), because intimate contact between the solid polymer electrolyte and sulfur could suppress the loss of sulfur due to lithium polysulfide (LPS) shuttling or volume change during lithiation/delithiation. Therefore, it is possible to realize safe and stable quasi-solid-state LSBs with high sulfur loading.