Supercapacitors: History, Theory, Emerging Technologies, and Applications

Supercapacitors (SCs) are highly crucial for addressing energy storage and harvesting issues, due to their unique features such as ultrahigh capacitance (0.1 ~ 3300 F), long cycle life (> 100,000 cycles), and high-power density (10 ~ 100 kW kg 1). Firstly, this chapter reviews and interprets the history and fundamental working principles of electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid SCs. Then, a brief overview of the electrolytes, including aqueous electrolytes, organic electrolytes, ionic liquids, and (quasi-)solid-state electrolytes is provided. The extensively studied electrode materials are then presented, such as transition metal compounds, carbon materials, conductive polymers, and metal-organic frameworks (MOFs). Finally, a summary covering future directions, prospects, and challenges in the commercialization of SCs is presented.