Computational Investigation of Potassium–Sulfur Electrode Performance on Nitrogen-Rich Carbon Supports

Potassium–sulfur (K–S) batteries are emerging as promising candidates for next-generation energy storage due to their high theoretical specific capacity and the abundance of potassium. However, like other metal–sulfur systems, K–S batteries suffer from sluggish kinetics due to the shuttle effect, which leads to active material loss and reduced efficiency. In this study, we present a computational study of the discharging and charging behaviors of Li–S, Na–S, and K–S electrode systems supported on various carbon-based surfaces: pristine graphene, nitrogen-defected graphene (N3 and N4 configurations), graphitic carbon nitride, and melon-like graphitic carbon nitride. Density functional theory (DFT) calculations reveal that melon-like graphitic nitride provides the most favorable discharge profiles, as indicated by the corresponding Gibbs free energy curves. To evaluate charging behavior, we employed the nudged elastic band (NEB) method to study metal atom dissociation from polysulfides. Among the systems analyzed, the K–S electrode exhibited the lowest dissociation barrier, suggesting a more efficient charge/discharge mechanism. Our findings indicate that K–S batteries supported on melon-like graphitic carbon nitride as an anchoring material can outperform Li–S and Na–S systems in terms of efficiency and reversibility, offering promising directions for next-generation energy storage technologies.