A new electrode design lets zinc-ion batteries use protons strategically, increasing energy storage while supporting rapid charging and more than 500 cycles in repeated operation.
KAIST researchers have developed a new electrode for water-based zinc-ion batteries that stores zinc ions and protons in sequence, potentially improving energy storage while maintaining performance during rapid charging and discharging.
The electrode uses a two-dimensional conductive metal-organic framework (MOF), a porous material created by connecting metal components with organic molecules. Researchers modified its structure with functional groups to control when different ions enter the electrode.
The key is the order in which the ions are stored. Zinc ions enter the electrode first at higher voltages, while smaller protons are stored later as the voltage falls. This arrangement allows the electrode to use both charge carriers without allowing proton reactions to interfere with zinc-ion storage.
That could address a limitation of aqueous zinc-ion batteries, which use water-based electrolytes and offer advantages including lower fire risk and potentially lower costs. Zinc ions, however, move relatively slowly through electrodes, making rapid charging and discharging difficult.
Protons are much smaller and can move more quickly, but excessive proton reactions can create by-products on the electrode surface. These deposits can obstruct zinc-ion movement and reduce battery performance. The researchers therefore designed the electrode to determine when protons can participate in the battery reaction.
Testing showed the electrode reached a storage capacity of about 570 mAh/g, while its capacity remained around 80% of the initial level after 500 cycles, according to the material shown in the article.
The researchers also found the electrode remained stable during repeated rapid charge-discharge operation. Their analysis indicated that the sequence of zinc-ion and proton storage could be controlled, suggesting the approach may help overcome the trade-off between high capacity and rapid ion transport.
The work points to a possible route towards safer, lower-cost aqueous zinc-ion batteries with improved energy storage and charging performance.
