UNIST Develops Technology to Improve Lifespan of Explosion-Free, High-Capacity ESS 'Flow Battery'

Schematic of Iron-Chromium Flow Battery [Provided by UNIST. Reproduction and database prohibited]

The Ulsan National Institute of Science and Technology (UNIST) announced on the 29th that it has developed a technology to extend the lifespan of the 'iron-chromium flow battery,' a large-capacity electricity storage system (ESS) that does not explode.

Unlike conventional batteries, flow batteries have electrode materials in the form of electrolytes dissolved in water.

They are suitable for storing renewable energy sources like wind and solar power, which have intermittent electricity production, because they use water instead of volatile electrolytes, posing no explosion risk, and their electricity storage capacity can be freely adjusted by simply modifying the amount of electrolyte.

In particular, iron-chromium flow batteries offer excellent price competitiveness. However, due to the low reactivity of chromium, charging is slow, output is weak, and capacity rapidly decreases during charge and discharge cycles, which has been identified as a limitation.

A research team led by Professor Hyun-Wook Lee of UNIST's Department of Energy and Chemical Engineering, in collaboration with Professor Dong-Hwa Seo of KAIST and Professor Guihua Yu of the University of Texas at Austin, has developed an iron-chromium flow battery that maintains its capacity even after charge and discharge cycles by adjusting the electrolyte composition.

The joint research team first confirmed that battery capacity rapidly decreases because hydroxide ions, which are generated in large quantities during the charging process, disrupt the electrolyte structure.

Subsequently, they derived an electrolyte mixing ratio that can stably maintain the chemical structure by adjusting the concentration ratio of hydroxide ions.

The research team confirmed that the iron-chromium flow battery using this ratio maintained its capacity and efficiency even after more than 250 charge and discharge cycles.

Professor Lee Hyun-wook explained, "This research demonstrates the possibility of creating high-output flow batteries that can be used for a long time, even with inexpensive iron-chromium electrolytes."

This research was supported by the Ministry of Science and ICT's National Research Foundation of Korea's Basic Research Laboratory International Cooperation Development Project, Individual Research Project, and the National Research Council of Science & Technology's Global TOP Strategic Research Group Support Project.

The research results were published online on the 2nd in 'Angewandte Chemie International Edition,' an academic journal in the field of chemistry. Yonhap News

'Iron-Chromium Flow Battery' UNIST Researchers, from left: Professor Lee Hyun-wook, Researcher Vidya Muralidharan (first author), and Dr. Jieun Jang (first author) [Provided by UNIST. Reproduction and database prohibited]