Electrochemical Principles and Energy Storage Mechanisms of Supercapacitors

Supercapacitors or Electrochemical capacitors have emerged as high performance devices that store energy and work between capacitors and batteries. They exhibit high power density, rapid charge-discharge capability, and long operational life. Unlike batteries that rely on slow bulk chemical reactions, supercapacitors energy store through rapid surface charge storing and fast reversible electrochemical reactions. This chapter presents a comprehensive review of the underlying electrochemical principles and highlights the two main energy collection mechanisms: electric double-layer capacitance (EDLC) and pseudocapacitance. The effects of electrode materials, electrolyte types, and device configuration on performance are examined. Additionally, common electrochemical characterization techniques and recent material innovations are discussed. Understanding these mechanisms is critical for improving energy and power density while ensuring long-term stability in practical applications.