Carbon dots-derived three-dimensional-ordered macroporous host with high penetrability and catalytic activity for LSBs under lean electrolyte

The practical energy density of lithium–sulfur batteries (LSBs) is seriously limited by the high electrolyte-to-sulfur ratios (E/S). The E/S can be reduced by employing hosts with easy-to-infiltrate structure that ensures the uniform distribution of a lean electrolyte and high catalytic activity that can suppress "shuttle effect" via accelerating the slow conversion of soluble polysulfides to insoluble sulfides. Among the easy-to-infiltrate structures, the three-dimensional-ordered macroporous (3DOM) structure is easier to scale preparation and more suitable for the existing industrial processes. However, it is difficult to obtain the 3DOM with (1) high penetrability due to the high viscosity of frequently-used organic polymer precursors and (2) high catalytic activity due to the low confinement effect, meaning that uniformly dispersed small-sized catalytic materials are difficult to load on 3DOM. Herein, using carbon dots (CDs) with both organic and inorganic properties as a precursor and aggregation limiting agent, a 3DOM host with high penetrability and homodispersed Ni particles of small sizes (Ni-CDs-3DOM) was synthesized. In this host: (1) CDs precursor with suitable viscosity can improve the penetrability. (2) CDs can effectively inhibit the agglomeration of Ni particles. (3) Uniformly dispersed small-size Ni particles offer high-efficiency catalytic activity toward sulfur reactions. Consequently, the Ni-CDs-3DOM/sulfur cathode exhibits high sulfur utilization and stable cycling performance even under high sulfur loading (5.5 mg·cm⁻²) and low E/S (6.5 μl·mg⁻¹). This work indicates the usefulness of CDs in constructing hosts for LSBs with high energy density.