History and Perspectives on Ultrafast Supercapacitors for AC Line Filtering

Supercapacitors (SCs) are considered to be a promising energy storage device owing to their high‐power characteristics and long‐term cycling stabilities. Recently, ultrafast SCs have been extensively studied in the context of replacing the aluminum electrolytic capacitors (AECs) that are currently used for alternating current (AC) line filtering applications. Since the ultrafast SCs are generally more compact owing to their higher energy density, as compared to the AECs, replacement of the AECs with the SCs can lead to miniaturization of electronic devices. Here the progress in the development of electrodes, electrolytes, and cell configurations of ultrafast SCs is reviewed and the challenging issues that need to be considered to extend their applications are discussed. In addition, this review provides integrated perspectives on further development of electrodes and electrolytes.