Researchers in Australia have now addressed what they call a “critical bottleneck” in the manufacture of cathodes for aqueous zinc-iodine batteries, which are seen as a promising candidate for large-scale energy storage.
These batteries are cheaper, safer, and made of more abundant materials compared to existing lithium-ion batteries. But scientists still need to solve certain performance issues to make them powerful and long-lasting.
“We have developed a new electrode technique for zinc–iodine batteries that avoids traditional wet mixing of iodine,” says Professor Shi-Zhang Qiao of the University of Adelaide, who led the research.
“We mixed active materials as dry powders and rolled them into thick, self-supporting electrodes.
(A) Schematic of the dry manufacturing process for the cathode. Scanning electron microscope (SEM) images of (B) wet electrode and (C) dry electrode. (D–F) Digital photos of the dry electrode in different states. (G) Cross-section SEM image of the dry electrode. Credit: Wu et al 2025, Joule, https://doi.org/10.1016/j.joule.2025.102000
“At the same time, we added a small amount of a simple chemical, called 1,3,5-trioxane, to the [aqueous zinc] electrolyte, which turns into a flexible protective film on the zinc surface during charging.
“This film keeps zinc from forming sharp dendrites – needle-like structures that can form on the surface of the zinc anode during charging and discharging – that can short the battery.”
The new dry technique packs more active material into the cathode than wet-processed ones, which typically top out below 2mg of active material per cm2.
“The new technique for electrode preparation resulted in record-high loading of 100mg of active material per cm2,” says Han Wu from the University of Adelaide, first author of the study published in the journal Joule.
The dense, dry electrodes also reduced the amount of iodine escaping into the electrolyte, which degrades its performance.
(A) Schematic illustration of structural differences in wet and dry electrodes and impacts on performance. Credit: Wu et al 2025, Joule https://doi.org/10.1016/j.joule.2025.102000
“After charging the pouch cells we made that use the new electrodes, they retained 88.6% of their capacity after 750 cycles and coin cells kept nearly 99.8% capacity after 500 cycles,” says Wu.
According to Qiao, the new technology will “benefit energy storage providers, especially for renewable integration and grid balancing, who will gain lower-cost, safer, long-lasting batteries.”
“Industries needing large, stable energy banks, for example, utilities and microgrids, could adopt this technology sooner,” he says.
The team plans to further develop the technology to expand its capabilities.
“Production of the electrodes could be scaled up by using to reel-to-reel manufacturing,” says Qiao. This involves processing materials on continuous rolls, making it an efficient approach for high production volumes.
“By optimising lighter current collectors and reducing excess electrolyte, the overall system energy density could be doubled from around 45 watt-hours per kilogram (Wh/kg) to around 90 Wh/kg.” For comparison, existing lithium-ion batteries have an energy density of about 150–250 Wh/kg.
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