The work covers the full development chain, ranging from redox-active materials, electrolytes and electrochemical interfaces to cells, stacks, system integration, modelling and techno-economic assessment. The overarching objective is to advance electrochemical storage technologies from promising concepts towards robust, scalable and application-relevant solutions.
Redox-flow batteries are particularly attractive for stationary applications because power and energy can be scaled independently. Their successful implementation, however, requires more than a high-performing active material or an efficient cell. Electrolytes must remain stable over extended operating periods; electrodes, membranes and stacks must be designed for reliable operation; and the resulting system must create value within real energy systems. The research therefore combines experimental electrochemistry with engineering, data analysis and system-level assessment.
Flow-battery materials and electrolytes
A central research area is the development and evaluation of redox-active materials and electrolyte formulations. This includes established vanadium-based systems as well as iron-based, organic and hybrid approaches. Key performance criteria include energy density, power density, stability, safety, resource availability and technically realistic cost.
Electrochemical performance is considered together with the underlying chemistry. Solubility, redox potential, viscosity, conductivity, electrolyte balancing, side reactions and crossover strongly influence the practical suitability of an active material. This is particularly relevant for aqueous systems, where hydrogen evolution, oxidation by air, precipitation and chemical decomposition can limit long-term operation.
Iron-based flow batteries provide one example of this broader research direction. Iron offers clear advantages in terms of availability, cost and sustainability, while also presenting challenges related to hydrogen evolution, electrode kinetics and electrolyte stability. Research therefore combines electrolyte formulation, cell testing, diagnostics and operating strategies to identify realistic pathways towards robust and economically relevant systems.
Electrodes, cells, stacks and degradation
Materials only become useful storage technologies when they perform reliably in functioning cells and stacks. Research therefore addresses electrode materials, porous transport structures, flow-field design, membrane and separator selection, cell architecture and stack design.
A particular focus lies on the interaction between electrochemical reactions, mass transport, flow distribution and component ageing. Flow batteries are dynamic systems in which electrical, chemical, thermal and hydraulic processes are closely coupled. Changes in electrolyte composition, state of charge, temperature, current density or flow rate can affect efficiency, degradation and overall system reliability.
Understanding degradation is essential for commercial deployment. Research activities include the identification of capacity-loss mechanisms, electrolyte imbalances, crossover, electrode ageing, side reactions and operational effects. The objective is not only to describe degradation after it has occurred, but also to develop diagnostic approaches and operating strategies that identify critical changes early and support longer system lifetimes.
High-throughput electrochemistry and data-driven discovery
The number of possible redox-active molecules, electrolyte compositions, electrode structures and operating conditions is too large to be investigated efficiently through conventional sequential laboratory workflows alone. High-throughput electrochemistry, automation and data-driven methods therefore form an increasingly important research direction.
The PREDICTOR doctoral network addresses this challenge through the development of electrochemical high-throughput methods. Its objective is to combine automated experimentation, spectroscopy, electrochemical characterisation, data analysis and artificial-intelligence-supported decision-making in closed-loop discovery workflows. Such approaches can accelerate the identification of promising materials, electrolytes and electrodes while improving the reproducibility and comparability of experimental data.
Automation is only valuable when the generated data are reliable, interpretable and linked to relevant performance metrics. High-throughput methods therefore complement scientific judgement by enabling more systematic experimentation, broader parameter screening and faster learning from complex electrochemical systems.
Modelling, simulation and techno-economics
Experimental work is complemented by modelling and simulation across different scales. At cell level, models support the analysis of electrochemical kinetics, mass transport, flow behaviour and thermal effects. At stack and system level, they help to evaluate efficiency, operating windows, component interactions and control strategies.
Modelling is also essential for connecting laboratory results with real applications. A cell chemistry may appear promising under defined test conditions but perform differently when scaled, integrated into a stack or operated under fluctuating power profiles. System-level simulation can therefore support the design and assessment of storage systems for renewable-energy integration, microgrids, industrial energy supply and other stationary applications.
Techno-economic assessment forms an integral part of this work. It considers how active materials, components, manufacturing routes, operational requirements, lifetime and application scenarios influence the overall cost and value of a storage technology. This perspective helps to identify the most relevant development parameters and prevents laboratory-based optimisation from becoming disconnected from practical deployment.
System integration and energy applications
The value of stationary energy storage depends on its role within a wider technical and economic system. Research therefore considers how flow batteries can contribute to renewable-energy integration, grid support, load management, resilience and long-duration energy storage.
Experience from large demonstrator projects has shown that system integration requires close attention to monitoring, control, safety concepts, maintenance and operating strategies. It also requires a realistic understanding of the requirements of users, utilities, industry and public infrastructure. Research at Fraunhofer ICT therefore combines laboratory studies with technology development, pilot-scale testing and collaboration with industrial partners.
The aim is to develop storage systems that are not only electrochemically sound but also reliable, understandable and maintainable in practical operation.
Standardisation and technology transfer
Standardisation is an important element of research and innovation in flow batteries. Common terminology, reproducible test methods, meaningful performance indicators and safety-related requirements are necessary to compare technologies fairly and to support market development.
Research activities contribute to the development of frameworks for stationary flow-battery systems, including definitions, performance, safety, electrolytes, components and testing procedures. Engagement with international standards, including the IEC 62932 series, supports the transfer of scientific results into common and practical technical frameworks.
Technology transfer is equally important. Research creates the greatest impact when new knowledge can be used by other researchers, industry, policy makers and future technology developers. The work therefore combines scientific publication, intellectual property, international collaboration, doctoral training and industrial engagement.
Research environment
The research is embedded in the Department of Applied Electrochemistry at Fraunhofer ICT and in an international network of academic and industrial partners. Collaborative activities include CENELEST, the German-Australian Alliance for Electrochemical Technologies for Storage of Renewable Energy, as well as the European doctoral networks PREDICTOR and SPACER.
Together, these activities connect fundamental electrochemistry, materials development, automation, system engineering and practical implementation. The long-term objective is to advance electrochemical storage technologies that can make a meaningful contribution to resilient, flexible and sustainable energy systems.