Zinc-iodine battery retains nearly all capacity over 1,000 cycles in new study

A water-based zinc-iodine battery held on to nearly all its storage capacity after thousands of charge and discharge cycles in lab tests led by University College London (UCL). The researchers developed an electrolyte that keeps reactive forms of iodine stable in water, allowing the battery to draw more capacity from the same material. The study tackles a problem that has limited the use of water-based batteries in large energy storage projects. These batteries offer a potential alternative to lithium-ion systems, which can pose a fire risk, but their relatively low energy density makes it harder to store large amounts of electricity. Getting more capacity from iodine The team’s design allows iodine to transfer 4 electrons during charging and discharging, up from 2 in conventional iodine battery chemistry. That gives the battery access to more of iodine’s storage capacity. The difficulty is keeping the highly reactive forms of iodine that emerge along the way from reacting with water. Earlier experiments addressed this problem with highly concentrated electrolytes containing halogens. Those mixtures helped stabilize iodine but were corrosive and costly, making them difficult to manufacture at scale. The UCL-led team changed the chemistry of the liquid immediately surrounding the iodine. Some molecules in the new electrolyte keep water away, while others bind to reactive forms of iodine and help prevent unwanted reactions. Putting the chemistry through thousands of cycles The researchers demonstrated the electrolyte in both pouch and coin cells. Pouch cells are the flat packages commonly used in phones and laptops. Coin cells are small, disk-shaped batteries typically used in devices with lower power demands. The chemistry worked in both formats. In separate durability tests, the zinc-iodine cells kept nearly all their initial storage capacity after thousands of cycles. That matters for grid storage, where batteries must repeatedly absorb surplus electricity from wind and solar farms and release it when generation drops. The researchers said the electrolyte design could also be adapted for aluminum-iodine batteries, giving them another chemistry to explore for stationary storage. Taking the battery beyond the lab Large battery farms currently rely on lithium-ion technology. Water-based designs could give grid operators another option, but the team still needs to test its electrolyte in larger systems and see how the cells behave under operating conditions closer to those of a battery farm. Those tests would help determine how well the capacity and durability observed in the lab carry over to a larger installation. “I am excited that our new chemistry can help aqueous batteries move one step closer to commercialization and wide deployment. Next steps include testing this technology at a larger scale and improving its performance under realistic operating conditions,” said Guanjie He, a professor at UCL Chemistry and the study’s corresponding author. First author Ruwei Chen said the work also points to a broader challenge in designing rechargeable iodine batteries. “We also need to understand how they interact with the water-based electrolyte and how those interactions change as the battery charges and discharges,” he said. The study was published in the Nature journal. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Atharva is a full-time content writer with a post-graduate degree in media & amp; entertainment and a graduate degree in electronics & telecommunications. He has written in the sports and technology domains respectively. In his leisure time, Atharva loves learning about digital marketing and watching soccer matches. His main goal behind joining Interesting Engineering is to learn more about how the recent technological advancements are helping human beings on both societal and individual levels in their daily lives.