Mechanistic insights into KOH-driven improvements in supercapacitor charge storage and stability

Abstract

Supercapacitors (SCs) have emerged as promising energy storage devices owing to their high power density (P_d), fast charge–discharge characteristics, and long operational lifespan, making them attractive candidates for next-generation energy technologies. The electrochemical behavior of SCs is largely governed by the nature of both electrode materials and electrolytes. Among the various electrolytic systems investigated, potassium hydroxide (KOH) has gained widespread acceptance because of its superior ionic conductivity and strong compatibility with a broad range of electrode materials. This review provides a comprehensive assessment of the influence of KOH electrolytes on the electrochemical performance of diverse material systems, including metal oxides, metal-based composites, metal ferrites, graphitic carbon nitride (g-C₃N₄)–based metal hybrids, reduced graphene oxide (rGO) based composites, and sulfur-containing compounds. Emphasis is placed on elucidating the fundamental mechanisms through which KOH governs charge storage processes, modulates electrode electrolyte interfacial behavior, and enhances cycling durability, offering valuable perspectives for the rational design and performance optimization of advanced supercapacitor systems.