Aqueous zinc-ion batteries (ZIBs) hold great potential for large-scale electrochemical energy storage due to their safety, low cost, and environmental friendliness. However, their practical application is hindered by challenges such as dendrite formation and water-induced corrosion at the anode.
Dynamic and stable interface constructed by hydrophobic CDs during zinc deposition (Image by YANG Hanmiao)
Recently, a research group led by Prof. YANG Weishen and Prof. ZHU Kaiyue from the State Key Laboratory of Catalysis(SKLC) of the Dalian Institute of Chemical Physics(DICP), Chinese Academy of Sciences(CAS) utilized trace amounts of carbon dots to construct a dynamic hydrophobic monolayer at the zinc anode/electrolyte interface. This innovative approach regulates the electric double-layer (EDL) structure at the zinc anode, altering the reaction kinetics of zinc deposition and dissolution while effectively protecting the anode from water-induced corrosion, ultimately achieving a highly reversible zinc anode.
Since both Zn²⁺ deposition and side reactions occur within the microscale EDL structure formed at the Zn/electrolyte interface, water molecules, and anions preferentially adsorb in the inner Helmholtz layer (IHL), directly contacting zinc and triggering side reactions. Meanwhile, hydrated zinc ions in the outer Helmholtz layer (OHL) must overcome a high desolvation energy barrier to enter the IHL and undergo electron transfer. To address these challenges, the researchers aimed to develop a method to regulate the interfacial structure and prevent undesirable side reactions.
In a study published in ACS Nano, Prof. YANG's group demonstrated the construction of a dynamic hydrophobic monolayer at the Zn/electrolyte interface. They achieved the monolayer adsorption of hydrophobic carbon dots that repelled sulfate ions and water molecules in the IHL, thereby reconstructing a hydrophobic IHL that facilitated the desolvation process of hydrated zinc ions.
In addition, due to the robust adsorption of the hydrophobic carbon dots onto the anode and their weak coordination with Zn²⁺, the dynamic interface of the hydrophobic carbon dot monolayer remained well preserved during plating, demonstrating a striking departure from the irreversible co-deposition observed when with hydrophilic carbon dots.
Benefiting from the dynamic interfacial protection the hydrophobic carbon dots provided, the cycled zinc anode maintained a smooth and compact surface free of byproducts. The Zn||Zn symmetric cells and Zn||MnO2full cells exhibited exceptional cycling stability.
"We develop a pioneering 'nanosized hydrophobic monolayer' strategy that effectively regulates the interfacial EDL structure for reversible and durable zinc anodes," said Prof. YANG.
