Polysulfide-mediating properties of nickel phosphide carbon composite nanofibers as free-standing interlayers for lithium–sulfur batteries†

Issues such as the polysulfide shuttle effect and sulfur loss challenge the development of high-energy-density lithium–sulfur batteries. To address these limitations, a tailored approach is introduced using nickel phosphide carbon composite nanofibers (Ni_xP/C) with controlled surface oxidation layers. These nanofibers feature a hierarchical structure that leverages the benefits of nickel phosphide nanoparticles and a carbonaceous matrix to enable efficient sulfur encapsulation and suppress polysulfide diffusion. Comprehensive characterization and electrochemical testing reveal that Ni_xP/C, when employed as interlayers in a cell with a bio-waste-derived carbon-based sulfur cathode, significantly enhance electrochemical performance by increasing charge–discharge capacities and reducing charge-transfer resistance. Post-mortem analyses further show effective polysulfide trapping and conversion on the cathode side, preventing their shuttle to the anode, which results in a remarkable cycle stability of up to 200 cycles at 2C with a high discharge capacity of about 800 mA h g⁻¹. These findings confirm the potential of Ni_xP/C to improve lithium–sulfur battery technologies and demonstrate their applicability in diverse lithium–sulfur cell configurations.