Silicon oxycarbide-derived hierarchical porous carbon nanoparticles with tunable pore structure for lithium-sulfur batteries

Most lithium-sulfur (Li-S) batteries have limited practical commercialization owing to extremely low S loading, insufficient cycle stability, and poor rate capability despite their high theoretical capacity. Herein, Li-S batteries with outstanding electrochemical performance under high S loading mass are achieved from hierarchical porous carbon nanoparticles (hPCNs) prepared via a scalable spray pyrolysis process. HPCNs are synthesized from organosilanol precursors, which contains phenyl and hydroxyl groups attached to silicon facilitating SiO_xC_y, SiO₄, and carbon nanonetwork formations. SiO_xC_y and SiO₄ phases can produce abundant micro- and mesopores, respectively, using template method. Consequently, hPCNs show high surface area (2789 m² g⁻¹) and pore volume (2.31 cm³ g⁻¹) allowing large amount of sulfur to be accommodated efficiently. When hPCN is applied as a multifunctional sulfur host, micropores can suppress lithium polysulfide dissolution, whereas mesopores can accommodate a large amount of sulfur, improving the energy density of the Li-S battery. In addition, the carbon nanonetworks improve redox kinetics with their excellent electrical conductivity. Therefore, sulfur-infiltrated hPCNs show a high initial capacity of 1229 mA h g⁻¹ and a capacity retention of 74% after 400 cycles at 1C rate.