Self-Supporting Carbon Nanofibers with Ni-Single-Atoms and Uniformly Dispersed Ni-Nanoparticles as Scalable Multifunctional Hosts for High Energy Density Lithium-Sulfur Batteries

The energy density of lithium-sulfur batteries (LSBs) is currently hampered by modest sulfur loadings and high electrolyte/sulfur ratios (E/S). These limitations can potentially be overcome using easy-to-infiltrate sulfur hosts with high catalytic materials. However, catalytic materials in such hosts are very susceptible to agglomeration due to the lack of efficient confinement in easy-to-infiltrate structures. Herein, using carbon dots as an aggregation limiting agent, the successful fabrication of self-supporting carbon nanofibers (CNF) containing Ni-single-atoms (Ni_SA ) and uniformly dispersed Ni-nanoparticles (Ni_NP ) of small sizes as multifunctional sulfur hosts is reported. The Ni_SA sites coordinated by such Ni_NP offer outstanding catalytic activity for sulfur reactions and CNF is an easy-to-infiltrate sulfur host with a large-scale preparation method. Accordingly, such hosts that can be prepared on a large scale enable sulfur cathodes to exhibit high sulfur utilization (66.5 mAh cm^-2 at ≈0.02 C) and cyclic stability (≈86.1% capacity retention after 100 cycles at ≈0.12 C) whilst operating at a high sulfur loading (50 mg cm^-2 ) and low E/S (5 µL mg^-1 ). This work provides a blueprint toward practical LSBs with high energy densities.