Application of carbon quantum dots in supercapacitors: A mini review

Supercapacitors (SCs), which include electric double-layer capacitors (EDLCs), asymmetric capacitors (ACs), and hybrid ion capacitors (HICs), defined as an electrochemical energy storage device with high power density, have attracted a lot of attention due to their appealing properties, such as good security, excellent power density, low maintenance cost, quick charging, and long cycling life. Nonetheless, the low energy density of commercial supercapacitors limits their practical applicability; thus, significant efforts have been undertaken to improve their energy density. Carbon quantum dots (CDs or CQDs) have received increased attention in the energy storage field due to their unique electrical properties and crucial role in hosting numerous functional groups on the surface. CDs have recently been widely used in electrode materials to improve the energy density of supercapacitors by functioning as an electrode material additive or derivative material. The application of CDs in supercapacitors will be summarized in this review. In addition, the constraints and potential future development directions will be discussed at the same time.