A high-performance zinc anode enabled by carbon quantum dots with H2O-structure-regulating capabilities

Aqueous Zn metal batteries offer high specific capacity and adequate safety, but suffer from limited stability and longevity primarily due to interfacial H2O-induced parasitic reactions on Zn anode. It thus is imperative to understand and control the interfacial H2O behavior for enhancing electrochemical performance of Zn anode. Herein, we formulate a functional aqueous Zn2+ electrolyte, containing well-dispersed Zn-doped carbon quantum dots (ZCDs) that can dynamically self-enrich on the Zn anode surface and thus endowed with unique interfacial “H2O-structure-regulating” capabilities. The Zn anode in contact with this exotic electrolyte demonstrates an essentially dendrite-free plating/stripping process, a 64.1% HER inhibition efficiency, a substantially prolonged cycle life (over 1500 h at 5 mA cm−2), an exceptional cumulative capacity of ∼3.75 Ah cm−2, and a capacity retention of a Zn||V2O5 battery up to ∼83% over 4000 cycles. A mechanistic study, using a combination of in situ spectroscopies and density functional theory calculations, provides direct spectroscopic evidence that the enriched ZCDs on the Zn surface reduce the proportion of reactive solvated H2O and thereof suppresses the H2O-induced parasitic reactions. The results reported here underscore the crucial significance of regulating the interfacial H2O structures on Zn2+ deposition process, and also provide inspirational design criteria for better Zn-based energy conversion and storage devices.