New zinc battery uses ‘troublemaker’ protons to store more energy, lasts 500+ cycles

KAIST researchers have developed an electrode for water-based zinc-ion batteries that uses protons to add energy storage instead of treating them as a source of performance problems. The approach could help these batteries store more energy while maintaining performance during rapid charging and discharging. The electrode is built from a two-dimensional conductive metal-organic framework (MOF), a porous material made by connecting metal components with organic molecules. Researchers modified its microscopic pores with amine functional groups to control when different ions could enter the electrode. The key is the order in which the ions are stored. Zinc ions enter the electrode first at higher voltages, while much smaller protons are stored later as the voltage falls. This allows the electrode to use both charge carriers without letting proton reactions interfere with zinc-ion storage. That matters because aqueous zinc-ion batteries use water-based electrolytes, giving them advantages including lower fire risk and potentially lower costs. But zinc ions move relatively slowly through electrodes, making it difficult for the batteries to combine high energy storage with rapid charge and discharge. Zinc ions make room first Protons are much smaller and can move rapidly, but too many proton reactions can create byproducts on the electrode surface. Those byproducts can block zinc-ion movement and reduce battery performance. The KAIST team turned that weakness into part of the electrode’s operating strategy. Its Cu3(HHTATP)2 material contains amine groups that react with protons only when the battery reaches a specific voltage. The researchers liken the process to filling a bottle with large pebbles before adding fine sand. Zinc ions are stored first, and the smaller protons then occupy additional storage space. Testing showed that the electrode reached a storage capacity of 368.7 mAh g-1 at 0.5 A g-1. When the charging and discharging rate was increased 16-fold, it retained 46.9% of its initial capacity. The electrode also remained stable for more than 500 rapid charge-discharge cycles, suggesting that the sequential storage process can withstand repeated operation. X-ray analysis confirmed the sequence of zinc-ion and proton storage. The researchers also found that protons could be stored and released repeatedly, indicating that their contribution was reversible. Protons boost battery capacity The researchers say controlling the storage sequence addresses a major challenge in porous electrode materials: achieving both high capacity and rapid ion transport. Rather than preventing protons from participating in the battery reaction, the design determines when they can contribute. That molecular-level control could provide a way to increase the amount of energy stored in aqueous zinc-ion batteries without allowing unwanted proton reactions to dominate the electrode. Aqueous zinc-ion batteries are being explored for large-scale energy storage because they use water-based electrolytes and can offer a safer alternative to systems that rely on flammable electrolytes. Improving their capacity and ability to handle faster cycling could make them more useful for stationary energy storage applications. The researchers stressed that the work represents a material-design strategy rather than a finished commercial battery. The same principle could potentially be applied to other electrode materials to control multiple charge carriers. Professor Sarah S. Park from KAIST said, “This study demonstrates that protons, previously regarded as ‘troublemakers’ that could degrade battery performance, can instead be used to store more energy. We expect that applying this principle to various electrode materials will lead to the development of batteries capable of rapidly storing larger amounts of energy.” The study has been published in the international chemistry journal Chem. Get the latest in engineering, tech, space & science - delivered daily to your inbox.With over a decade-long career in journalism, Neetika Walter has worked with The Economic Times, ANI, and Hindustan Times, covering politics, business, technology, and the clean energy sector. Passionate about contemporary culture, books, poetry, and storytelling, she brings depth and insight to her writing. When she isn’t chasing stories, she’s likely lost in a book or enjoying the company of her dogs.