Bridging EDLC and pseudocapacitive mechanisms through materials design: recent advances in supercapacitor electrodes

The global demand for efficient and sustainable energy storage has driven research on high-performance supercapacitors as battery complements. This review analyzes recent advancements in the material design of supercapacitors, emphasizing the relationship between the structure, composition, and electrochemical performance. It categorizes developments in carbon-based materials, transition metal oxides and hydroxides, and metal–organic framework (MOF)-derived composites, highlighting how nanostructuring, heteroatom doping, and hybridization enhance the charge storage capacity, conductivity, and cycling stability of these materials. This review integrates insights from recent experimental and theoretical studies to clarify the electrochemical double-layer and pseudocapacitive mechanisms and provides a comparative evaluation of the energy and power density benchmarks. Key findings show that hierarchical porosity, conductive interfaces, and defect engineering improve ion transport and redox kinetics, while sustainable synthesis from biomass precursors and low-temperature processing address scalability and environmental concerns. These findings have implications for the design of next-generation flexible, hybrid, and high-voltage supercapacitors for renewable energy and wearable electronics. This review offers a roadmap for advancing material innovations to enhance the performance, cost-effectiveness, and sustainability of supercapacitor technologies.