Organic polymer paves the way for aqueous batteries

Aqueous batteries are safe and relatively low-cost, but their adoption in new energy storage systems — such as grid storage and electric vehicles — is limited due to material compatibility. Many electrode materials do not perform well in aqueous electrolytes. For organic redox polymers in particular, hydrophobicity has been a barrier. Like other polymer materials, they also present challenges when it comes to decomposition and recycling.

Now, researchers from Tohoku University have developed a new organic redox polymer that addresses these challenges. To overcome the hurdles, the researchers introduced p-dihydroxybenzene — an organic molecule with high charge storage capacity — into a polyamine, which is water-soluble due to its positive charge. This was achieved through a simple condensation reaction.

The resulting polymer retains high hydrophilicity, can be used as an electrode-active material at room temperature (25°C) and can be broken down into its raw components under mild conditions at temperatures below 100°C.

“This study provides a design strategy for making hydrophobic redox molecules compatible with aqueous systems. By combining high charge storage capacity with recyclability, we can open new directions for sustainable battery research,” said Kouki Oka, associate professor at the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University.

The research findings highlight two key benefits; the use of water-based electrolytes avoids the risk of fire associated with conventional flammable solvents. Second, because the new polymers are made from abundant elements and can be easily decomposed, they may help reduce resource consumption and plastic pollution.

“Our next step is to evaluate durability and other performance factors to understand the full potential of this material for real-world applications,” Oka said.

The research findings have been published in Polymer Journal.

Image credit: iStock.com/Seng kui Lim