A Fish-Scale-like P-Doped Carbon Nanosheet/NiSe₂-CoSe₂ Heterojunction Interlayer Enabling Synergistic Catalysis and...

Li-S batteries (LSBs) are seen as a promising new-generation energy storage technology owing to their high theoretical energy density and economy. However, their practical use is still limited by the shuttle effect of lithium polysulfides (LiPSs) and slow reaction kinetics. Here, a unique fish-scale-like, phosphorus-doped carbon nanosheet-supported NiSe₂-CoSe₂ heterojunction (NiSe₂-CoSe₂/PC) was designed and synthesized as a functional interlayer for LSBs. The hierarchical porous architecture, together with the fish-scale-like surface, offers a high surface area (324.1 m² g^-1) and plenty of active sites, which substantially enhance the physical confinement and chemical anchoring toward LiPSs. Combined with the synergistic catalytic effect of the heterojunction, the NiSe₂-CoSe₂/PC coating on the polypropylene (PP) separator facilitates the electrochemical conversion of LiPSs and curbs undesired shuttling. Electrochemical tests show that the LSB with this modified separator retains a capacity of 517.6 mA h g^-1 after 500 cycles at 2.0 C, with a capacity loss of only 0.079% per cycle, and also delivers a discharge capacity of 779.8 mA h g^-1 at 3.0 C. Even under a high sulfur loading of 3.1 mg cm^-2, the LSB maintains a consistent capacity of 526.1 mA h g^-1 over 200 cycles at 0.2 C.