New Dry Electrode Doubles Aqueous Battery Performance

According to a study published in Joule, researchers at the University of Adelaide have developed a new dry electrode for aqueous batteries. The resulting cathodes are more than twice as efficient as those used in iodine and lithium-ion batteries.

We have developed a new electrode technique for zinc–iodine batteries that avoids traditional wet mixing of iodine. We mixed active materials as dry powders and rolled them into thick, self-supporting electrodes. At the same time, we added a small amount of a simple chemical, called 1,3,5-trioxane, to the electrolyte, which turns into a flexible protective film on the zinc surface during charging.

Shizhang Qiao, Study Team Lead and Professor, University of Adelaide

Qiao is a Director and Chair of Nanotechnology at the Centre for Materials in Energy and Catalysis, within the School of Chemical Engineering.

Qiao added, “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.”

Aqueous zinc-iodine batteries offer strong safety, sustainability, and cost advantages for large-scale energy storage. However, their performance still lags behind that of lithium-ion batteries.

The new technique for electrode preparation resulted in record-high loading of 100 mg of active material per cm². 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. We directly observed how the protective film forms on the zinc by using synchrotron infrared measurements.

Han Wu, Research Associate, School of Chemical Engineering, University of Adelaide

Thanks to high iodine loading and a stable zinc interface, each battery can store more energy while remaining lightweight and cost-effective. This could make zinc-iodine batteries more suitable for grid-scale or large-scale energy storage.

The team's approach offers several advantages over existing battery technologies:

• Greater capacity: Dry electrodes hold more active material. While wet-processed electrodes typically reach less than 2 mA h cm⁻², the dry version exceeds this limit.
• Reduced shuttle loss and self-discharge: The dense, dry electrode structure helps prevent iodine from leaking into the electrolyte, which can otherwise reduce performance.
• Improved zinc stability: An in situ protective coating reduces dendrite formation, leading to longer battery life.

Qiao added, “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.”

The team plans to continue developing the technology to further increase its potential for practical use.

Professor Qiao stated, “Production of the electrodes could be scaled up by using to reel-to-reel manufacturing. 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⁻¹) to around 90 Wh kg⁻¹. We will also test the performance of other halogen chemistries such as bromine systems, using the same dry-process approach.”

Journal Reference:

Wu, H., et al. (2025) Aqueous zinc-iodine batteries with ultra-high loading and advanced performance. Joule. doi.org/10.1016/j.joule.2025.102000.