Supercapacitors (SCs) are energy storage devices that offer superior power density, faster charge–discharge speeds, and longer cycle life compared to batteries [11]. They store energy through the accumulation of electric charge at the interface between an electrode and an. . This review provides an overview of the fundamental principles of electrochemical energy storage in supercapacitors, highlighting various energy-storage materials and strategies for enhancing their performance, with a focus on manganese- and nickel-based materials. Key factors, such as electrode. . Energy storage systems (ESSs) are critical for addressing efficiency, power quality, and reliability, and they are vital for contemporary power systems, particularly within the context of direct current (DC) and alternating current (AC) systems. The latest achievements in the production, modeling, and characterization. .