Recent advances in carbon dots: from multifunctionality to energy storage

Carbon dots (CDs), as a novel class of carbon-based nanomaterials, exhibit exceptional physical and chemical properties owing to their unique core-shell architecture. The carbon core, comprising hybridized sp²/sp³ carbon networks, delivers outstanding electrical conductivity, while the peripheral functional groups confer aqueous solubility and biocompatibility and contribute to their luminescence behavior, etc. The versatile properties of CDs have enabled broad applications in luminescence, photocatalysis, electrocatalysis, energy storage, etc. In the field of energy storage, aqueous zinc-ion batteries (AZIBs) and lithium-metal batteries (LMBs) represent two prominent technologies. Despite differences in materials and performance, both systems face critical challenges in commercialization, including dendrite growth, electrolyte instability, manufacturing complexities, and limited cycle life. This review traces the discovery of CDs, details their classification, and summarizes synthetic methodologies. It further highlights recent advances in luminescence, photocatalysis, and electrocatalysis, with a focused discussion on energy storage applications. Key emphasis is placed on CD-enabled modifications of electrodes and electrolytes for AZIBs and LMBs, addressing interfacial engineering and reaction kinetics. Finally, unresolved challenges are outlined and future research directions for CDs in next-generation energy storage systems are proposed.