Impact of Mesoporous Carbon Structure on Sulfur Utilization and Electrochemical Performance in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LiSBs) have emerged as a promising alternative for next-generation high-energy-density storage systems due to their exceptional theoretical specific capacity (1675 mAh/g) and high energy density (2600 Wh/kg). However, achieving practical performance remains challenging due to issues such as poor sulfur utilization, polysulfide shuttling, and limited cycle stability. The structural and compositional properties of mesoporous carbon materials in the cathode, particularly CMK-3, CMK-5, and CMK-8, play a crucial role in overcoming these limitations. These materials influence electrical conductivity, sulfur retention, and electrochemical stability, making their selection and optimization vital for improving LiSB efficiency. This study systematically investigates the interplay between sulfur loading, energy density, discharge capacity, and carbon structure at the cell level using experimental characterization. Results indicate that CMK-8 offers the most favorable performance, combining high sulfur loading capacity with strong polysulfide retention and enhanced cycling stability due to its large pore volume and interconnected structure. CMK-3 displays moderate electrochemical stability, particularly at lower sulfur loadings, but suffers from performance decline under high loading conditions. In contrast, CMK-5 exhibits the weakest electrochemical performance, with significant capacity fading and poor coulombic efficiency, indicating that its pore architecture is less suitable for effective sulfur confinement and long-term cycling. The findings reveal that moderate sulfur loading, rather than excessive sulfur incorporation, yields the best balance between high discharge capacities, capacity retention, and long-term cycling performance. By optimizing carbon pore structures, sulfur distribution, and cathode architecture, this research offers valuable insights into the design of high-performance LiSBs. The results contribute to the development of next-generation LiSBs with enhanced energy densities, paving the way for their practical deployment in energy storage applications, electric vehicles, and portable electronics.