Breakthrough in Iron-Chromium Redox Flow Batteries Enhances Renewable Energy Storage
A multinational research team has achieved a major breakthrough in iron-chromium redox flow batteries, resolving key degradation issues and paving the way for safer, scalable, and more affordable renewable energy storage solutions.
A significant advance in energy storage technology was announced on September 12, 2025, as an international team of scientists revealed a breakthrough in iron-chromium redox flow batteries, a promising alternative for large-scale renewable energy storage. The research, led by experts from South Korea's Ulsan National Institute of Science and Technology (UNIST), the Korea Advanced Institute of Science and Technology, and the University of Texas at Austin, directly addresses longstanding challenges of capacity decline and instability that have hindered the commercial viability of these batteries[1].
Iron-chromium redox flow batteries are notable for their use of water-based electrolytes, which make them inherently safer and less prone to fire or explosion compared to conventional lithium-ion systems. Unlike traditional batteries, flow batteries store energy in external tanks and use pumps to circulate electrolytes through a central cell, allowing for independent scaling of power and capacity. This architecture is particularly attractive for grid-scale applications, where flexibility and safety are paramount[1].
The breakthrough centers on the identification and mitigation of a specific degradation mechanism involving hexacyanochromate, a compound that, while improving charging speed, was found to destabilize the electrolyte through a side reaction. This reaction led to the replacement of cyanide ions with hydroxide ions, causing rapid capacity loss. By carefully balancing the ratio of these ions, the researchers were able to stabilize the electrolyte, resulting in batteries that maintained performance over 250 cycles in laboratory tests[1].
Technical Innovation and Global Collaboration
The research team’s findings, released in a joint statement and detailed in a peer-reviewed publication, highlight the potential for iron-chromium flow batteries to become a cost-effective and durable solution for storing energy from intermittent sources like solar and wind. Professor Hyun-Wook Lee of UNIST emphasized that the technology is especially promising for countries with abundant renewable resources and large land areas, such as China and several European nations, which require scalable storage to support their energy transitions[1].
Parallel efforts in China have produced similar results, with a local team reporting high efficiency after 850 cycles, while researchers in Canada are also developing water-based redox systems. These developments underscore the global momentum behind flow battery research and the growing consensus that such systems could play a pivotal role in decarbonizing electricity grids[1].
Implications for Renewable Energy and Grid Stability
Reliable, affordable energy storage is widely recognized as a critical enabler for the expansion of renewable energy. According to the research team, the improved iron-chromium batteries could help address the variability of solar and wind generation, which accounted for 15% of global electricity production last year. By storing excess energy for use during periods of low generation, these batteries can help stabilize grids and reduce reliance on fossil fuels, which are linked to climate change and increasingly severe weather events[1].
The researchers describe their work as a step toward “revolutionizing energy storage by integrating sustainability with cutting-edge innovation.” If successfully commercialized, the technology could accelerate the shift to cleaner energy systems worldwide, offering a safer and more sustainable alternative to existing battery chemistries[1].