- Iron current battery runs 6,000 cycles without measurable loss of capacity
- New electrolyte chemistry reduces degradation and membrane crossing problems
- Ferrous materials offer a low-cost alternative for large-scale renewable energy storage
Researchers in China say they have made new advances in iron-based flow batteries that could reduce the cost of storing renewable energy while extending useful life.
The team from the Institute of Metal Research under the Chinese Academy of Sciences developed a newly designed electrolyte that allowed an alkaline iron flow battery to run through more than 6,000 cycles without measurable capacity decay, according to results published in Advanced energy materials.
Iron current batteries have been studied for years, but have struggled with stability issues that limit long-term use. Active materials inside the battery tend to degrade or leak through membranes, reducing efficiency and shortening life.
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Iron is 80 times cheaper than lithium
The researchers addressed these limits by redesigning the molecular structure of the negative electrolyte used inside the system.
The team synthesized 11 iron complexes built from 12 organic ligands before identifying a compound known as [Fe(HPF)BHS]⁴⁻ as the most stable candidate.
Its bulky structure creates physical shielding around the iron center, while negatively charged groups help prevent unwanted reactions and reduce material crossing across the membrane.
Tests showed the battery operated at 80 mA·cm⁻² for more than 6,000 cycles without capacity decay and an average coulombic efficiency of 99.4%, based on performance data released by the research team.
Under higher current conditions, the system reached a maximum power density of 392.1mW·cm⁻² while energy efficiency was maintained at 78.5%, indicating stable performance under higher electrical demand.
Researchers linked the cycle count to long-term use and estimated the performance to be equivalent to more than 16 years of daily use without measurable degradation.
Iron is more than 80 times cheaper than lithium as a raw material, which could make large-scale energy storage much cheaper, provided the technology is successfully scaled.
Iron is also widely available, ranking among the most abundant metals on Earth, reducing concerns about supply shortages compared to lithium.
All-iron flow batteries use water-based electrolytes instead of flammable liquids found in lithium-ion systems. That chemistry removes the necessary conditions for thermal runaway, which is the chain reaction that can lead to battery fires or explosions.
Large-scale energy storage remains one of the major technical challenges linked to the expansion of renewable energy, as electricity production from solar and wind fluctuates depending on weather conditions.
The research improves the stability of iron-based electrolytes, but long-term testing outside of controlled environments will determine how well the chemistry performs in real grid installations.
Via SCMP
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