Potassium polysulfide cathodes in potassium-sulfur batteries: A comparison between liquid and gel polymer electrolytes

With the growing demand for sustainable energy storage technologies, potassium-sulfur (K-S) batteries have attracted attention as a viable alternative to lithium-ion systems. The abundance of resources, low cost, and high energy density of potassium and sulfur make them ideal candidates for large-scale use in these types of batteries. However, challenges such as the shuttle effect, the low electrical conductivity of sulfur, and significant volume changes during electrochemical reactions pose obstacles to their practical application. Recent research efforts have focused on developing strategies to address these limitations. This study investigates the design and performance of K-S batteries employing potassium polysulfide cathodes (K 2 S n , where 2 ≤ n ≤ 4) in combination with a polymer gel electrolyte derived from cellulose modified with poly(ethylene glycol) methyl ether methacrylate (PEGMA). The primary aim is to replace conventional liquid electrolytes with this gel-based system to enhance battery efficiency, stability, and safety. This approach effectively suppresses the shuttle effect and promotes efficient K + ion transport. Among the evaluated cathode materials, K 2 S 3 demonstrated the highest reversible capacity (574 mAh g -1 at 0.1 A g -1 ) and superior ion diffusion characteristics. By offering a novel solution, this research highlights new directions in development of practical K-S battery technologies.