Ultrathin Two-Dimensional Ordered Porous Carbon Host with Atomically Dispersed Electrocatalytic Sites toward High Volumetric Energy Lithium-Sulfur Battery

Despite multimodal approaches to increase the gravimetric capacity of lithium-sulfur (Li-S) batteries over the years, strategies on achieving high volumetric capacity (Q_v) at close to practical cell operating conditions with high areal sulfur loading and low electrolyte-to-sulfur (E/S) ratio are still lacking. Here, we report that a synergistic effect of a carbonaceous framework with precisely-controlled porous structure/dimension and highly-active, surface-mediated electrocatalysis by a ruthenium (Ru) single-atom electrocatalyst (SAC) composed of N₂RuCl₂ achieves high Q_v in Li-S batteries. Two-dimensional (2D) and hierarchically ordered porous structures of polymer interfacial self-assembly derived N-doped carbon nanosheets (NCNS) realize a highly-packed sulfur cathode with outstanding Li⁺ ion diffusivity and electrode stability, which have been considered as main impediments to achieving high Q_v in a dense sulfur cathode. Moreover, homogeneous incorporation of N₂RuCl₂ SAC which has novel Ru coordination environment with two N and Cl atoms on the surface of NCNS remarkably accelerated the reaction kinetics of Li-S electrochemistry and achieved high Q_v even at high sulfur loading (5.0 mg cm⁻²), extremely low E/S ratio (4.5 μL mg⁻¹), and low electrode porosity (50 %).