- Iron flow battery runs 6000 cycles without measurable capacity loss
- New electrolyte chemistry reduces degradation and membrane crossing problems
- Iron 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 their lifespan.
The team at the Metals Research Institute of the Chinese Academy of Sciences developed a redesigned electrolyte that allowed an alkaline iron-flow battery to operate for more than 6,000 cycles without a measurable drop in capacity, according to results published in Advanced energy materials.
Iron flow batteries have been studied for years, but have had stability issues that limit their long-term use. The active materials within the battery tend to degrade or leak through the membranes, reducing efficiency and shortening life.
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Iron is 80 times cheaper than lithium
The researchers addressed those limits by redesigning the molecular structure of the negative electrolyte used within 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 protection around the iron center, while the negatively charged groups help prevent unwanted reactions and reduce material crossing through the membrane.
Tests showed the battery operated at 80 mA·cm⁻² for more than 6,000 cycles with no decay and an average Coulombic efficiency of 99.4%, according to performance data released by the research team.
Under higher current conditions, the system achieved a maximum power density of 392.1 mW·cm⁻² while maintaining a power efficiency of 78.5%, indicating stable performance under higher electrical demand.
The researchers linked cycle counts to long-term use and estimated that performance is 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 less expensive, provided the technology grows successfully.
Iron is also widely available and 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 eliminates the conditions necessary for thermal runaway, which is the chain reaction that can cause battery fires or explosions.
Large-scale energy storage remains one of the main technical challenges linked to the expansion of renewable energy, as electricity generation from solar and wind energy fluctuates depending on weather conditions.
The research improves stability in iron-based electrolytes, but long-term testing outside of controlled environments will determine how well the chemistry performs in real grid installations.
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