The growing need for energy-storage solutions for a gamut of applications from electronic devices to large-scale energy systems has spurred an increase in research for innovative technologies. Considerable attention is being given to new chemistries beyond the widely used lithium-ion battery. Aqueous zinc-iodine batteries show promise as a potentially lower-cost, safer alternative made from more readily available resources. Challenges, however, include a short lifespan. Now, researchers at the University of Adelaide (Adelaide, South Australia; www.adelaide.edu.au) have developed a process that improves this shortcoming.
Professor Shizhang Qiao, chair of nanotechnology, and director, Centre for Materials in Energy and Catalysis, at the university’s School of Chemical Engineering, led the research team that developed a new dry electrode that avoids traditional wet mixing of iodine. Qiao explains, “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.”
Han Wu, team member and research associate at the School of Chemical Engineering, adds, “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.”
The new innovative technology (diagram) is said to have several advantages over existing technologies, including: a higher capacity than wet-processed electrodes; less self-discharge because the dense, dry electrodes reduce iodine escaping into the electrolyte, which degrades performance; and longer cycle life because the protective film prevents dendrite growth, giving improved stability of the zinc.
The team’s work was published in Joule. They plan to further develop the technology to expand its capabilities.