Spanish researchers validate 10,000 cycles for iron-lead flow battery

Spanish research center CIC energiGUNE has completed 10,000 charge-discharge cycles on an iron-lead redox flow battery, a design built from abundant materials and intended to store electricity for several hours in stationary applications.

The technology was tested at temperatures of 25 C to 30 C and uses iron and lead as active materials. Its single-electrolyte-loop design is intended to simplify the conventional flow battery architecture while reducing system costs and dependence on critical raw materials.

The battery also incorporates a fluorine-free membrane designed to reduce internal resistance and limit unwanted transport of chemical species between the two sides of the battery. CIC energiGUNE said the active materials have established industrial and recycling supply chains, potentially reducing dependence on critical materials.

The development is aimed at applications that require electricity to be stored for several hours, including storing excess renewable generation for later use by the electricity system.

Unlike conventional flow batteries with separate electrolyte circuits, the architecture developed by the Spanish research center uses a single electrolyte loop and fewer components.

Flow batteries store energy in electrolytes held in external tanks. Increasing the volume of electrolyte can therefore increase energy capacity, while power output depends primarily on the size and number of cells and stacks. This separation of power and energy allows systems to be configured for applications requiring several hours of storage without necessarily increasing both parameters proportionally.

CIC energiGUNE said the combination of this characteristic, high cycling capability and safety makes flow batteries suitable for solar and wind integration, grid-scale storage, microgrids and industrial energy management.

The iron-lead battery has progressed from initial laboratory cells to larger stacks. The next step is to develop kilowatt-scale modules through a combination of simulation, system design and experimental validation.

CIC energiGUNE is also researching other redox flow battery technologies, including new electrolytes and organic molecules, membranes adapted to different chemistries, electrodes, bipolar plates and stack components. It is also developing approaches to reduce the cost and vanadium consumption of vanadium-based flow batteries.

The center aims to move its developments from the materials and cell level toward complete systems through modeling, prototyping and cost and sustainability analysis. The 10,000-cycle validation represents a step toward scaling a technology designed for intensive cycling and long operating periods with reduced degradation.

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