Australian researchers are reporting a breakthrough on aqueous zinc-iodine batteries, an up-and-coming alternative to lithium-ion batteries that promises to be safer, more sustainable and cheaper for grid-scale storage – if performance issues can be ironed out.
The team from the University of Adelaide team has developed a new “dry electrode” for zinc-iodine batteries that has been found to boost energy density, reduce battery degradation and ensure greater overall stability.
Professor Shizhang Qiao, director at the Centre for Materials in Energy and Catalysis at the university’s School of Chemical Engineering says the new electrode technique avoids traditional wet mixing of iodine, which can reduce storage capacity, degrade performance and shorten cycle life.
“We mixed active materials as dry powders and rolled them into thick, self-supporting electrodes,” said Qiao, who leads the research team.
“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.”
Han Wu, a research associate who also worked on the study, says the new technique for electrode preparation resulted in record-high energy storage results.
“After charging the pouch cells we made 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.
“We directly observed how the protective film forms on the zinc by using synchrotron infrared measurements,” Wu said.
The team says high iodine loading and a robust zinc interface mean much more energy can be stored in each battery at a lower weight and cost – a breakthrough that could bring zinc-iodine batteries closer to real-world use for large-scale or grid storage.
“The new technology will benefit energy storage providers – especially for renewable integration and grid balancing – who will gain lower-cost, safer, long-lasting batteries,” said Professor Qiao.
“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 and to investigate scaling up production of the electrodes 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,” Qiao said.
“We will also test the performance of other halogen chemistries such as bromine systems, using the same dry-process approach.”
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