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Interview with me and the German Commission for Electrical, Electronic & Information Technologies (DKE)

Redox-flow batteries (RFBs) are emerging as a key technology for stabilizing renewable energy systems. They store energy in liquid electrolytes contained in external tanks, allowing flexible scaling of capacity and long operational lifetimes. This makes them ideal for medium-duration energy storage—bridging the gap between short-term lithium-ion batteries and long-term hydrogen solutions.

Germany is a global leader in RFB development, driven by research institutions such as the Fraunhofer Institute for Chemical Technology and several specialized companies. Dr. Jens Noack emphasizes the importance of international standardization, particularly within the IEC and EU frameworks, to ensure quality, comparability, and interoperability of systems and materials.

Through innovation and coordinated standardization efforts, Germany aims to strengthen its role as a “hidden champion” in redox-flow technology and support a more resilient, sustainable energy infrastructure.

The complete interview is available here: https://www.dke.de/de/arbeitsfelder/components-technologies/news/hidden-champion-redox-flow-batterien

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Marie-Curie Project SPACER started!

The SPACER project team at the kick-off meeting in September 2025. (Copyright: Fraunhofer ICT)

On September 1st, 2025, the Marie Curie project SPACER was launched. Following PREDICTOR in 2024, it is the second concurrent MSCA project in which the RFB group at Fraunhofer ICT participates and acts as coordinator.

The MSCA Doctoral Network SPACER (“Shaping Porous Electrode Architecture to Improve Current Density and Energy Efficiency in Redox Flow Batteries”) aims to develop novel, hierarchically structured electrodes for redox flow batteries (RFBs) capable of achieving high current densities (~1 A cm⁻²) and energy efficiencies above 85–90%, while reducing electrode costs by up to 50% compared to current technologies.

SPACER integrates multiscale modeling, innovative electrode fabrication (such as stereolithography, 3D printing, and textile-based approaches), and advanced characterization techniques (including EPR) in three iterative development cycles (micro, meso, and macro). Optimized electrode architectures will be validated in mini-stacks (TRL 6) in collaboration with industrial partners.

The project also provides a structured training program for 17 PhD researchers across 10 European countries, fostering interdisciplinary expertise at the interface of materials science, electrochemistry, modeling, and device integration.

By combining fundamental research with applied validation, SPACER aims to significantly advance the development of cost-effective, high-performance energy storage technologies, while training a new generation of experts in porous electrode design to support Europe’s energy transition.

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New paper pulished – Aqueous iron-based redox flow batteries for large-scale energy storage

The rapid advancement of flow batteries offers a promising pathway to addressing global energy and environmental challenges. Among them, iron-based aqueous redox flow batteries (ARFBs) are a compelling choice for future energy storage systems due to their excellent safety, cost-effectiveness and scalability. However, the advancement of various types of iron-based ARFBs is hindered by several critical challenges, including hydrogen evolution, inferior reversibility of metal deposition and stripping, and undesirable dendrite formation in hybrid flow systems with metal plating/stripping on the negative electrode. Additionally, all-soluble iron-based ARFBs face limitations in redox species solubility and electrolyte stability. To address these issues, various strategies have been developed, such as modifications to electrolytes, electrodes and separators, as well as flow stack optimization. This review provides a comprehensive overview of iron-based ARFBs, categorizing them into dissolution-deposition and all-soluble flow battery systems. It highlights recent advancements in the field and explores future prospects, focusing on four key areas: materials innovation and mechanistic understanding; flow battery system design and engineering; new electrochemistry explorations; and interdisciplinary strategies. By offering insights into these emerging directions, this review aims to support the continued research and development of iron-based flow batteries for large-scale energy storage applications.

Full paper is available here.

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New paper published – A multi-parameter analysis of iron/iron redox flow batteries: effects of operating conditions on electrochemical performance

Challuri_2025

Iron/iron redox flow batteries (IRFBs) are emerging as a cost-effective alternative to traditional energy storage systems. This study investigates the impact of key operational characteristics, specifically examining how various parameters influence efficiency, stability, and capacity retention. IRFB systems with a volume of 60 mL per tank (20.25 Ah L−1) demonstrated superior capacity utilization, achieving a coulombic efficiency (CE) of up to 95% and an energy efficiency (EE) of 61% over 25 charge/discharge cycles.

The full article can be accessed here: https://doi.org/10.1039/D5YA00139K