Boosting Zinc-Ion Batteries with Carbon Dots

A research team led by Prof. Weishen Yang and Prof. Kaiyue Zhu from the Dalian Institute of Chemical Physics (DICP) at the Chinese Academy of Sciences utilized trace amounts of carbon dots to develop a dynamic hydrophobic monolayer at the zinc anode/electrolyte interface. Their findings were published in ACS Nano.

Aqueous zinc-ion batteries (ZIBs) are considered viable candidates for large-scale electrochemical energy storage due to their safety, low cost, and environmental compatibility. However, their practical application is limited by challenges such as dendrite formation and water-induced anode corrosion.

The proposed technique regulates the electric double-layer (EDL) structure of the zinc anode, altering the reaction kinetics of zinc deposition and dissolution while protecting the anode from water-induced corrosion, leading to a highly reversible zinc anode.

In the inner Helmholtz layer (IHL), water molecules and anions preferentially adsorb onto zinc, initiating side reactions. Meanwhile, hydrated zinc ions in the outer Helmholtz layer (OHL) encounter a significant desolvation energy barrier before entering the IHL and participating in electron transfer. To mitigate these issues, the researchers developed a strategy to modify the interfacial structure and minimize unwanted side effects.

The team led by Prof. Yang designed a dynamic hydrophobic monolayer at the Zn/electrolyte interface. By promoting the monolayer adsorption of hydrophobic carbon dots in the IHL, they effectively repelled sulfate ions and water molecules, reconstructing a hydrophobic IHL that facilitated the desolvation of hydrated zinc ions.

Furthermore, the dynamic interface of the hydrophobic carbon dot monolayer remained intact during zinc plating due to the strong adsorption of the carbon dots onto the anode and their weak coordination with Zn²⁺. This contrasted with the irreversible co-deposition observed when using hydrophilic carbon dots.

The dynamic interfacial protection provided by the hydrophobic carbon dots enabled the cycled zinc anode to maintain a compact, smooth surface free of byproducts. The Zn||MnO₂full and Zn||Zn symmetric cells exhibited stable cycling performance.

We develop a pioneering 'nanosized hydrophobic monolayer' strategy that effectively regulates the interfacial EDL structure for reversible and durable zinc anodes.

Weishen Yang, Professor, Dalian Institute of Chemical Physics

Journal Reference:

Yang, H., et. al. (2024) Enhancing Zinc Anode Reversibility through Dynamic Interface Engineering with Monolayer Hydrophobic Carbon Dots. ACS Nano. doi.org/10.1021/acsnano.4c14244