Supercapacitors are most interesting in the area of rechargeable battery based energy storage because they offer an unbeatable power density, quick charge/discharge rates and prolonged lifetimes in comparison to batteries. The book covers inorganic, organic and gel-polymer electrolytes, electrodes and separators used in different types of supercapacitors; with emphasis on material synthesis, characterization, fundamental electrochemical properties and most promising applications. Keywords: Supercapacitors, Rechargeable Batteries, Organic Electrolytes, Inorganic Electrolytes, Gel Polymer based Supercapacitors, Redox Electrolytes, Starch-Based Electrolytes, Flexible Supercapacitors, Pseudocapacitors, Carbon Nanoarchitectures for Supercapacitors, Photo-Supercapacitors, Bimetal Oxides/Sulfides for Electrochemical Supercapacitors.