Nitrogen‐Doped and Sulfonated Carbon Dots as a Multifunctional Additive to Realize Highly Reversible Aqueous Zinc‐Ion Batteries

Abstract Aqueous zinc‐ion batteries (ZIBs) using the Zn metal anode have been considered as one of the next‐generation commercial batteries with high security, robust capacity, and low price. However, parasitic reactions, notorious dendrites and limited lifespan still hamper their practical applications. Herein, an eco‐friendly nitrogen‐doped and sulfonated carbon dots (NSCDs) is designed as a multifunctional additive for the cheap aqueous ZnSO 4 electrolyte, which can overcome the above difficulties effectively. The abundant polar groups (‐COOH, ‐OH, ‐NH 2 , and ‐SO 3 H) on the CDs surfaces can regulate the solvation structure of Zn 2+ through decreasing the coordinated active H 2 O molecules, and thus redistribute Zn 2+ deposition to avoid side reactions. Some of the negatively charged NSCDs are adsorbed on Zn anode surface to isolate the H 2 O/SO 4 2‐ corrosion through the electrostatic shielding effect. The synergistic effect of the doped nitrogen species and the surface sulfonic groups can induce a uniform electrolyte flux and a homogeneous Zn plating with a (002) texture. As a result, the excellent cycle life (4000 h) and Coulombic efficiency (99.5%) of the optimized ZIBs are realized in typical ZnSO 4 electrolytes with only 0.1 mg mL ‐1 of NSCDs additive.