Supercapacitors for energy storage applications: Materials, devices and future directions: A comprehensive review

Supercapacitors, also known as ultracapacitors or electrochemical capacitors, represent an emerging energy storage technology with the potential to complement or potentially supplant batteries in specific applications. While batteries typically exhibit higher energy density, supercapacitors offer distinct advantages, including significantly faster charge/discharge rates (often 10–100 times quicker), superior power density, and exceptional cycle life, enduring hundreds of thousands more charge/discharge cycles than conventional batteries. This review provides a comprehensive analysis of the current state of supercapacitor research and technology. Key materials are examined, including various nano-carbons, conductive polymers, MXenes, and hybrid composites, which offer high specific surface area, tailored porosity, and electrochemical stability. The charge storage mechanisms, primarily electric double layer formation and rapid surface redox reactions, are elucidated. Major applications of supercapacitors, ranging from consumer electronics to electric vehicles, are highlighted, and fundamental challenges and knowledge gaps in the field are critically analyzed. Furthermore, significant technological advances and novel applications of supercapacitors in the near future are forecast, including integration with energy harvesting systems, advanced microelectronics, and utility-scale stationary storage. Perspectives on optimized design, fabrication, and characterization methodologies that will drive the performance and longevity of supercapacitors to meet diverse energy storage requirements are provided. This review encompasses the breadth of active research while identifying promising directions that may enable supercapacitors to outperform batteries in specific domains and contribute significantly to energy solutions in the coming years. [Display omitted] •Carbon, metal oxides, polymers, MXenes, and MOFs explored as materials to enhance supercapacitor performance and storage•Aqueous and unconventional electrolytes' impact on improving charge storage capacities in supercapacitors discussed•Novel device designs, including hybrid and asymmetric configurations, enhance electrochemical performance and storage•Strategies for high-performance supercapacitors focus on electrode-electrolyte interfaces and material development•Interdisciplinary approach vital for overcoming limitations and advancing next-gen supercapacitor energy solutions