A battery designed to last
One of the main advantages of redox flow batteries is that they store energy in electrolytes contained in external tanks. This makes it possible to increase the amount of energy stored by increasing the volume of electrolyte without having to increase the system’s power output by the same proportion.
This characteristic, combined with their high level of safety and ability to withstand a large number of cycles, makes them particularly attractive for applications such as the integration of solar and wind farms, grid-scale energy storage, microgrids and energy management for large industrial consumers.
However, the most established commercial technology currently uses vanadium, whose cost and concentrated supply chain represent two of the main obstacles to wider deployment.
For this reason, one of the major challenges facing the sector is to find alternatives that retain the advantages of flow batteries while reducing both costs and dependence on critical raw materials.
The iron-lead solution developed by CIC energiGUNE is a step in this direction. Its single-flow configuration simplifies the system and reduces the number of components associated with conventional dual-circuit designs, while the active materials used benefit from well-established industrial and recycling supply chains.
The architecture also incorporates a fluorine-free membrane developed to reduce internal resistance and limit the unwanted crossover of species between the two sides of the battery. This solution helps simplify the system and strengthens the technology’s potential to compete in stationary energy storage applications, particularly where the aim is to reduce dependence on critical materials while maintaining competitive costs throughout the installation’s service life.
“A low-cost battery is of little use if it quickly loses performance, while a highly durable battery will struggle to reach the market if its materials or components are too expensive. Our work is precisely about finding that balance between cost, stability, efficiency and manufacturability,” says Ferret.
The iron-lead battery is one of the developments that exemplifies CIC energiGUNE’s strategy in this field, but the centre’s activity in redox flow batteries encompasses a range of different chemistries and components.
The research teams are working on new electrolytes and organic molecules, membranes adapted to different chemistries, electrodes, bipolar plates and stack components, as well as strategies aimed at reducing the cost and consumption of vanadium in current systems.
What distinguishes this approach is that development does not stop at the material level. CIC energiGUNE has the capabilities to study material behaviour from the molecular scale through to its integration into cells and stacks, subsequently incorporating modelling, system design, prototyping, and cost and sustainability analysis.
“Many technologies deliver very promising results when tested in a small cell. The real challenge begins when that performance has to be maintained over thousands of cycles and then transferred to higher-power stacks and modules,” explains the researcher.
The growing share of renewable energy sources is making this challenge increasingly relevant. Redox flow batteries are not intended to replace every energy storage technology, but they can play a particularly important role in applications where energy needs to be stored for many hours, cycled intensively and kept in operation for long periods with limited degradation.
