Chungnam National University researchers develop next-gen zinc batteries: artificial polymer nanolayers improve zinc battery stability

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.

In tests, the ZHP layer proved remarkably durable, resisting dissolution in aqueous solutions even under harsh ultrasonication. As a SITL, it was able to effectively suppress dendritic growth during plating/stripping processes in electrochemical tests and promoted the growth of uniform zinc crystals along the (002) crystallographic plane, producing a uniform zinc surface with high electrochemical activity. Consequently, the ZHP coated zinc-anode (Zn@ZHP) demonstrated stable operation for over 2200 hours in symmetric cell tests, far outperforming bare zinc anodes. In full cells, it retained 95% of its capacity after 500 cycles at a current density of 1 A g^-1. In pouch cells, the anode demonstrated stable cycling for over 300 cycles, even at high current densities of 10 mA cm^-2_.

“The enhanced stability of water-based electrolytes makes ZHP based ZIBs ideal for safety-critical industries such as grid-scale energy-storage systems and detection sensors.” remarks Dr. Song. “And due to their low cost and toxicity, these batteries are also well-suited for portable electronics and wearables.”

Overall, the innovative protective ZHP layer developed in this study represents a major step towards making ZIBs a practical, next-generation energy storage solution.

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Reference
DOI: 10.1016/j.cej.2025.162948  

About the Institute
Chungnam National University (CNU), located in Daejeon, South Korea, is a leading national university renowned for its excellence in research and education. Established in 1952, CNU offers diverse programs in engineering, medicine, sciences, and the arts, fostering innovation and global collaboration. Situated near Daedeok Innopolis, a major R&D hub, it excels in biotechnology, materials science, and information technology. With a vibrant international community and cutting-edge facilities, CNU continues to drive academic and technological advancements, making it a top choice for students worldwide.

Website: https://plus.cnu.ac.kr/html/en/

About Associate Professor Woo-Jin Song
Dr. Woo-Jin Song is an Associate Professor at the Department of Organic Materials Engineering at Chungnam National University. His group focuses on approaches for developing next generation of batteries through polymer synthesis and analysis. The Song group is also focused on polymer design for metal interface reactions. Before joining Chungnam National University, he completed postdoctoral training at Zhenan BaO’s lab at Stanford University. In 2018, he received his PhD in Energy and Chemical Engineering from Ulsan National Institute of Science & Technology (UNIST).