Boosting High-Rate Li-S Batteries by an MOF-Derived Catalytic Electrode with a Layer-by-Layer Structure

Rechargeable high-energy lithium-sulfur batteries suffer from rapid capacity decay and poor rate capability due to intrinsically intermediate polysulfides' shuttle effect and sluggish redox kinetics. To tackle these problems simultaneously, a layer-by-layer electrode structure is designed, each layer of which consists of ultrafine CoS₂-nanoparticle-embedded porous carbon evenly grown on both sides of reduced graphene oxide (rGO). The CoS₂ nanoparticles derived from metal-organic frameworks (MOFs) have an average size of ≈10 nm and can facilitate the conversion between Li₂S₆ and Li₂S₂/Li₂S in the liquid electrolyte by a catalytic effect, leading to improved polysulfide redox kinetics. In addition, the interconnected conductive frameworks with hierarchical pore structure afford fast ion and electron transport and provide sufficient space to confine polysulfides. As a result, the layer-by-layer electrodes exhibit good rate capabilities with 1180.7 and 700 mAh g^-1 at 1.0 and 5.0 C, respectively, and maintain an impressive cycling stability with a low capacity decay of 0.033% per cycle within ultralong 1000 cycles at 5.0 C. Even with a high sulfur loading of 3.0 mg cm^-2, the electrodes still show high rate performance and stable cycling stability over 300 cycles.