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

Abstract

AbstractAqueous 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 ZnSO4 electrolyte, which can overcome the above difficulties effectively. The abundant polar groups (‐COOH, ‐OH, ‐NH2, and ‐SO3H) on the CDs surfaces can regulate the solvation structure of Zn2+ through decreasing the coordinated active H2O molecules, and thus redistribute Zn2+ deposition to avoid side reactions. Some of the negatively charged NSCDs are adsorbed on Zn anode surface to isolate the H2O/SO42‐ 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 ZnSO4 electrolytes with only 0.1 mg mL‐1 of NSCDs additive.