(540b) Supercapacitors Based on Graphene Quantum Dots for Efficient Energy Storage

Electrical double layer capacitors (EDLCs) store energy through physical adsorption of ions as a response to an applied potential difference. As their energy storage mechanism relies on physical interactions, EDLCs have high power densities, unlike batteries, which are often limited by the slow charge and mass transfer kinetics. Additionally, EDLCs can sustain millions of charging/discharging cycles. Nevertheless, they suffer from low energy densities. For a high energy density EDLC, it is critical to maintain a compact architecture with large ion-accessible surface area while also ensuring low ion transport and electrical resistance. We incorporate carbon quantum dots into thermally exfoliated graphene oxide sheets in the presence of a room temperature ionic liquid to form conductive carbon networks, enhancing ion transport kinetics and storage. This yields an electrode in which both carbon quantum dots and ionic liquid serve as spacers to effectively separate the thermally exfoliated graphene oxide sheets, while ionic liquid also functions as electrolyte. These findings demonstrate both energy and power density can be improved simultaneously by tailoring electrolyte composition and carbon quantum dot/thermally exfoliated graphene oxide ratio.