Synthesis and Study of the Application of Iron, Nitrogen-Doped High-Surface-Area Carbon for Li–S Batteries

Despite their promising theoretical performance, lithium–sulfur (Li–S) batteries are often limited by low efficiency, primarily due to the solubility of lithium polysulfides and the low conductivity of sulfur electrodes. Enhancing the incorporation of sulfur into porous carbon with improved polarity could significantly boost the Li–S battery performance. In this study, we doped carbon xerogels with nitrogen atoms and decorated them with iron-based nanostructures using a straightforward and scalable method. The decomposition of nitrogen-containing additives at varying temperatures─specifically 750 °C (FeNC-750) and 950 °C (FeNC-950)─resulted in alterations to the porosity of the xerogel compared to the pristine structure. After impregnating these structures with sulfur to develop the sulfur electrode, we assessed the electrochemical performance of FeNC-750@S and FeNC-950@S, varying the sulfur content and the electrolyte-to-sulfur (E/S) ratio. Our results indicated that the electrochemical performance of the sulfur electrode with high sulfur content was significantly influenced by both the E/S ratio and the porosity of the host materials. Notably, the sulfur electrode with over 80% sulfur content, designated FeNC-950@S₈₀, achieved a discharge capacity of 600 mA h g^–1 with an E/S ratio of 7.5 mL g^–1 and an electrode loading of 3.5 g cm^–2, demonstrating an excellent capacity retention of 96% over 100 cycles at a rate of 0.1 C.