Aqueous zinc-ion batteries (ZIBs) are gaining attention as a safer and more affordable alternative to lithium-ion batteries (LIBs). While LIBs remain the most widely used energy storage technology, they come with safety risks due to their reliance on flammable organic electrolytes. In contrast, aqueous ZIBs use water-based electrolytes, making them non-flammable, environment friendly, and more affordable. Unfortunately, during charging and discharging, zinc-anodes in ZIBs undergo repeated plating and stripping that can trigger undesirable side reactions and sharp dendrite formation. This severely impacts their cycling performance and stability, reducing lifespan.
The main approach to address this issue is to ensure a uniform distribution of zinc ions on the anodes. To achieve this many studies have investigated the development of protective coatings; however, these coatings can limit zinc ion diffusion and increase electrical resistance, ultimately decreasing battery performance. Recently, selective-ion transport layers (SITL) have been proposed as a promising solution for achieving highly stable zinc anodes. However, their considerable thickness and complicated manufacturing processes have limited real-world use.
In a breakthrough, a research team led by Associate Professor Woo-Jin Song from the Department of Organic Materials Engineering at Chungnam National University, South Korea, designed a new ultra-thin SITL that is both effective and easy to produce. "In this study, we developed a nanoscale zinc-bonded polyacrylic acid (Zn–PAA) protective layer for zinc anodes via oxygen plasma treatment," explains Dr. Song. "Unlike conventional thick and complex coatings, our approach offers a simpler fabrication process and is scalable for large-area applications." Their study was made available online on May 08, 2025, and published in Volume 515 of the Chemical Engineering Journal on July 01, 2025.
This new SITL is based on polyacrylic acid (PAA). PAA can prevent direct contact between the zinc anode and water-based electrolyte, inhibiting corrosion. It also suppresses hydrogen-evolution reactions and the formation of a passivation layer caused by side reactions with anionic salts. This significantly reduces dendritic growth, stabilizing the anode interface. Thanks to its hydrophilicity, it also improves ion transfer between the electrolytes and the anode, promoting uniform distribution of zinc-ions and enhancing battery performance.
However, bare PAA tends to dissolve in water-based electrolytes, reducing cycling performance. To prevent this, the researchers applied oxygen plasma treatment to zinc-anode which enhanced adhesion between PAA the layer and the anode surface. The PAA was deposited on the treated zinc-anode using the cost-effective and scalable spin-coating technique, resulting in a nanoscale PAA coating. The PAA-coated anode was then heated on a hot plate, forming the zinc-bonded PAA (ZHP) layer.
