Basque Country brings Spain to the forefront of battery research: 10,000 charge cycles with less critical chemistries
04/10/2026 10:30
Updated to
04/10/2026 10:30
Researchers at Spain’s CIC energiGUNE center have validated an iron-lead flow battery capable of enduring over 10,000 charge and discharge cycles. This technology is not intended for use in electric vehicles but rather for storing large amounts of electricity for hours, sourced from things like solar and wind farms. Its advantage lies in utilizing well-known materials with established supply chains and recycling processes, along with a simplified architecture featuring a single electrolyte circuit and a fluorine-free membrane, aimed at cutting costs and reducing reliance on critical raw materials.
That destination completely changes the rules of the game. In a car battery, weight, volume, and how much energy can be stored per kilogram are extremely important. In a fixed installation next to a photovoltaic plant, those factors become less significant compared to aspects such as cost, safety, lifespan, and the availability of materials. It is precisely in this context that CIC energiGUNE is testing its iron-lead flow battery.
Over 10,000 charge and discharge cycles
The system has completed 10,000 charge and discharge cycles in tests conducted at temperatures between 25 and 30 °C. This figure is particularly significant for stationary storage: a system that charges when there is an excess of solar production and delivers electricity later can perform cycles almost every day. The longer its lifespan, the more time it can remain operational before requiring major replacements.
The Spanish technology uses iron and lead as active materials, two elements with well-established industrial and recycling chains. This does not automatically make the system inexpensive nor guarantee that it will be commercialized on a large scale. It is still under development, and its next goal is to advance toward power modules in the kilowatt range.
A battery very different from that in an electric car
Flow batteries operate differently from traditional lithium-ion batteries. Energy is stored in electrolytes contained within external tanks. Increasing the size of these tanks allows more electricity to be stored, while power primarily depends on the size and number of cells and stacks.
This separation between power and energy capacity is particularly useful when storing electricity for several hours. The design developed by CIC energiGUNE also features a unique aspect: it uses a single electrolyte circuit, unlike conventional architectures that employ separate circuits. The goal is to reduce components and simplify the system.
It also uses a fluorine-free membrane, designed to lower internal resistance and prevent unwanted transfer of chemical species between the two sides of the battery.
Spain will need more and more stationary batteries
The interest in these technologies is growing as solar and wind power production increases. When there is ample renewable energy generation but low demand, a stationary battery can store that electricity to retrieve it hours later. In such applications, using a slightly heavier chemistry may matter little if it provides thousands of cycles, safety, and readily available materials.
Therefore, the future of batteries does not necessarily lie in finding a single optimal chemistry. Lithium may continue to dominate electric vehicles while technologies like flow batteries find their role in storing energy in grids, industries, microgrids, and renewable energy parks.
The Spanish research on iron-lead has just overcome a significant hurdle: proving it can function for over 10,000 cycles. The next most difficult step is to scale this up and determine whether such durability can also become a competitive advantage outside the laboratory.
