Nitrogen-Doped Two-Dimensional Carbon Nanosheets for High-Sulfur-Loading Lithium-Sulfur Batteries via a Lignin-Based High-Internal-Phase Pickering Emulsion Strategy

Attributable to sulfur's significant theoretical energy density, its affordability, and its environmentally friendly nature, lithium-sulfur batteries (LSBs) are recognized as advanced energy storage technologies with considerable potential. Nonetheless, the solubility and migration of polysulfides within the electrolyte substantially hinder their practical implementation. To address this issue, we developed a nitrogen-doped two-dimensional (2D) wavy carbon nanosheet material (NCN) by using the Pickering emulsion templating method. Nitrogen doping enhances the surface polarity of the two-dimensional carbon material, promoting electrolyte penetration and providing strong chemical adsorption of polysulfides. The distinctive two-dimensional wavy structure enhances lithium-ion transport and regulates polysulfide dissolution and diffusion throughout the electrochemical cycle, resulting in an enhanced electrochemical performance. Therefore, the S@NCN cathode shows a discharge specific capacity, reaching 936 mAh g^-1 at 1 C. Despite a sulfur load reaching 7.2 mg cm^-2, the S@NCN cathode achieves a specific capacity of 823 mAh g^-1. These findings indicate that the NCN is a high-performance 2D carbon material for sulfur cathodes, effectively improving the electrochemical stability of LSBs and showing great potential for future applications as a cathode material in LSBs.