In-situ constructed solvated carbon quantum dot clusters to achieve uniform Zn plating in aqueous zinc ion batteries

Zinc ion batteries (ZIBs) have become the most competitive candidates for the next-generation energy storage systems due to its low-price, good safety and high theoretical capacity. However, the uncontrollable dendrite growth and parasitic side reactions still hinder the practical application of the zinc ion batteries. Herein, a hybrid functionalized carbon quantum dots (FCQDs)/ZnSO4 electrolyte is in-situ synthesized via a simple one-pot hydrothermal method with glucose as precursor. The created FCQDs possess abundant anionic groups like hydroxyl, carboxyl and sulfonic acid groups, and those anionic groups can strongly absorb Zn2+ ions and then the FCQDs, Zn2+ and water molecules together generate a special solvation structure of solvated carbon quantum dot clusters [FCQDsZnx(H2O)y]2x+. The solvated FCQDs clusters can help to in-situ induce the uniform Zn deposition through a co-plating of Zn atoms and the functionalized FCQDs. Additionally, this unique solvation structure promotes easier dissociation of solvation water molecules, thus decreasing the de-solvation energy. The lower de-solvation energy barrier can help to restrain the water decomposition and the related by-products. Benefiting from the construction of this unique solvated FCQDs clusters, the hybrid electrolyte with FCQDs endows a better performance of both Zn||Zn symmetric cells and full ZIBs.