Recent advances on graphene quantum dots and their derivatives for energy storage devices

Graphene quantum dots (GQDs) consist of nano-sized fragments of graphene, typically in the range of 1–10 nm in size, and are often synthesized under extreme conditions (oxidative/reductive cleavage, electrochemical shearing, and pulsed laser burning). Extremely small size and edge effects give GQDs a high specific surface area, abundant surface active sites, chemical stability, low toxicity, physiological stability, and tunable fluorescence properties. Thus, GQDs have been widely used in the field of energy, catalysis, environment, biology, and optics etc. However, the synthesis and application of GQDs in energy storage systems (ESSs) are still at an early stage and lack timely and up-to-date research progress. In view of this, we summarize and discuss the most recent progress of the application of GQDs and their derivatives in energy storage devices, with an emphasis on their roles in enhancing lithium/sodium/zinc-ion battery performance (e.g., improving ion diffusion kinetics, suppressing dendrite formation, and stabilizing electrode-electrolyte interfaces), boosting solar cell efficiency through light absorption tuning and charge transport optimization, and elevating supercapacitor energy density via high surface area and pseudocapacitive contributions. Finally, reasonable suggestions for future challenges are presented.