Vitamin C‐Derived Oxygen‐Functionalized Carbon Dots as a Novel Modulator for Regulating Zn ²⁺ Deposition and Stabilizing Aqueous Zinc‐Ion Batteries

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) are promising alternatives to lithium‐ion batteries due to the natural abundance of zinc and inherent safety, but dendrite growth on Zn anode and parasitic side reactions impair their lifespan and large‐scale applications. Herein, we introduce vitamin C‐derived, oxygen functionalized carbon dots (VC‐CDs) as a novel modulator to aqueous electrolyte. Negatively charged VC‐CDs preferentially adsorb on Zn anode, homogenizing electric fields and enabling uniform Zn ^{2 +} deposition, and their coordination with Zn ^{2 +} promotes ion migration, boosting full‐cell capacity by 15% at 1 A g ^{− 1} . Accordingly, the Zn||Zn symmetric cells deliver a long‐term stable cycling lifespan of 2000 h, whereas the Zn||Cu asymmetric cells attain an exceptional Coulombic efficiency of 99% across 2000 cycles. Furthermore, the Zn||VO ₂ full cells exhibit remarkable cycling stability, retaining 80% of their initial capacity after 2000 cycles at a current density of 4 A g ^{− 1} . Notably, the practical feasibility of VC‐CDs is further corroborated in both Zn||VO ₂ and Zn||I ₂ pouch cells, which highlights their great potential for advancing next‐generation aqueous zinc‐ion battery technologies.