A new dry electrode for aqueous batteries delivers cathodes with more than double the performance of iodine and lithium-ion batteries

Researchers at the University of Adelaide have developed a new dry electrode technique for zinc–iodine batteries that avoids traditional wet mixing of iodine.

Researchers at the University of Adelaide have developed a new dry electrode for aqueous batteries which delivers cathodes with more than double the performance of iodine and lithium-ion batteries.

The team, led by Professor Shizhang Qiao, Chair of Nanotechnology, and Director, Centre for Materials in Energy and Catalysis, at the School of Chemical Engineering, has published their results in the journal Joule.

Aqueous zinc–iodine batteries offer unparalleled safety, sustainability, and cost advantages for grid-scale storage, but they suffer from performance issues compared to lithium-ion batteries.

The researchers devised a simple yet effective strategy to achieve high-energy, long-life zinc–iodine batteries. They mixed active materials as dry powders and rolled them into thick, self-supporting electrodes.

At the same time, they 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. This film keeps zinc from forming sharp dendrites that can short the battery.

The new technique for electrode preparation resulted in record-high loading of 100 mg of active material per cm2. After charging the pouch cells that use the new electrodes, they retained 88.6 per cent of their capacity after 750 cycles and coin cells kept nearly 99.8 per cent capacity after 500 cycles.

The researchers directly observed how the protective film forms on the zinc by using synchrotron infrared measurements.

This work paves the way for the development of next-generation metal–halogen batteries with superior performance and energy density.

“We have developed a new electrode technique for zinc–iodine batteries that avoids traditional wet mixing of iodine,” said Professor Qiao.

“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.

“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.”

There are several advantages of the team’s invention over existing battery technology:

* 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 has plans to develop the technology further to expand its capabilities.

“Production of the electrodes could be scaled up by using to reel-to-reel manufacturing,” said Professor Qiao.

“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.”

The researchers hope that their invention will lead to the development of even better and more efficient batteries in the future.