News & Events
Elestor’s Hydrogen-Iron Flow Batteries: Powering Europe’s Resilient and Sovereign Energy Future
In its Innovation News Network article from 15 July 2025, Elestor illustrates how its hydrogen‑iron flow batteries can deliver long‑duration, modular energy storage to bolster Europe’s grid stability and strategic autonomy. The story highlights the team’s use of abundant, safe materials and regulatory-aligned design to ensure rapid deployment at scale.
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Permissible technology
Why we find it easy to gain approval for our hydrogen-iron flow battery from both regulators and the general public
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Trouw: "A full battery tank can bridge the dunkelflaute"
Vincent Dekker interviews Elestor about their breakthrough in hydrogen-iron flow batteries, designed to power entire neighborhoods through sunless, windless days at a fraction of the cost of traditional solutions.
Read moreLong-term performance of hydrogen-bromine flow batteries using single-layered and multi-layered wire-electrospun SPEEK/PFSA/PVDF membranes
Sanaz Abbasiab, Yohanes Antonius Hugob, Zandrie Bornemanac, Wiebrand Koutb and Kitty Nijmeijer*ac
aMembrane Materials and Processes, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands. E-mail: D.C.Nijmijer@tue.nl
bElestor BV P.O. Box 882, 6800 AW Arnhem, The Netherlands
cDutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 6336, 5600 HH Eindhoven, The Netherlands
Abstract
Sulfonated poly (ether ketone) (SPEEK), perfluorosulfonic acid (PFSA), and polyvinylidene fluoride (PVDF) were wire-electrospun. Subsequently, multiple electrospun layers in different arrangements were hot-pressed into sustainable membranes for use in hydrogen-bromine flow batteries (HBFBs). The relationship between the electrospun layer composition and arrangement, membrane properties, and battery performance was explored. Wire-electrospinning and hot-pressing improved SPEEK and PFSA/PVDF compatibility, yielding dense membranes. Higher SPEEK contents lead to rougher morphologies, while the insulating nature of PVDF decreases the ion exchange capacity (IEC) and HBr uptake compared to commercial PFSA. The multi-layer assembly negatively impacted the membrane transport properties compared to the single-layer arrangement. Although wire-electrospinning improves the polymer dispersion and fixed charge density, SPEEK-rich regions of the blend membranes lack the high selectivity of PFSA, thus reducing the ionic conductivity. This is especially clear in the multi-layer membranes with accumulated SPEEK in the intermediate layer in the through-plane direction. Following initial property comparisons, thinner wire-electrospun SPEEK membranes were prepared with area resistance in the PFSA-comparable range. Among the wire-electrospun SPEEK/PFSA/PVDF membranes, the single-layered membrane with 8 wt% SPEEK (SPF1-8; 62 μm) displayed stable HBFB performance at 200 mA cm−2 over 100 cycles (64 cm2 active area). Based on the ex-situ measurements and cell performance results, a total of ∼10.5 wt% SPEEK is suggested as the limit for both single and multi-layered wire-electrospun membranes, combined with a maximum membrane thickness of ∼50 μm. This ensures robust HBFB performance, positioning wire-electrospun SPEEK/PFSA/PVDF membranes as a PFSA alternative in energy storage.
Wire based electrospun composite short side chain perfluorosulfonic acid/ polyvinylidene fluoride membranes for hydrogen-bromine flow batteries
Yohanes Antonius Hugo a, b, Wiebrand Kout b, Antoni Forner-Cuenca a, Zandrie Borneman a, c, Kitty Nijmeijer a, c, *
a Membrane Materials and Processes, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600MB Eindhoven, the Netherlands
b Elestor B.V., 6827 AV Arnhem, the Netherlands
c Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 6336, 5600 HH Eindhoven, the Netherlands
⁎ Corresponding author. E-mail address: d.c.nijmeijer@tue.nl (K. Nijmeijer).
Abstract
A main component of a hydrogen-bromine flow battery (HBFB) is the ion exchange membrane. Available membranes have a trade-off between the major requirements: high proton conductivity, low bromine species crossover, and high mechanical and chemical stability. To overcome this, electrospinning of a highly proton conductive polymer (short side chain perfluorosulfonic acid (SSC PFSA)) and a hydrophobic inert polymer (polyvinylidene fluoride (PVDF)) was used to electrospin composite polymer fiber mats. Piles of multiple mats were hot pressed resulting in dense ion exchange membranes. Membranes with three different SSC PFSA/PVDF ratios were prepared, characterized, and subjected to short and long term (1500 h) HBFB testing. The electrospun membranes have performances very comparable to those of commercial membranes. For the SSC PFSA/PVDF electrospun membrane, a higher SSC PFSA loading gives a higher membrane proton conductivity compared to a lower loading, but at the expense of a higher bromine species crossover. The SSC PFSA/PVDF (50/50 wt%) membrane shows a coulombic efficiency of 98%, a voltaic efficiency of 80% and an initial available capacity of 105 Ah L− 1 at a current density of 150 mA cm− 2, which equals that of the current benchmark long side chain PFSA membrane. This performance is constant over 200 cycles during 2 months of continuous HBFB operation.
High selectivity-conductivity reinforced perfluorosulfonic acid membranes for hydrogen-bromine flow batteries.
Yohanes Hugo1, 2, Wiebrand Kout1, Friso Sikkema1, Zandrie Borneman2, Kitty Nijmeijer2
1Elestor B.V., 6812 AR Arnhem, the Netherlands
2Membrane Materials and Processes, Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, PO box 513, 5600 MB Eindhoven, The Netherlands
Abstract
Reinforced proton exchange membrane (PEM) were developed to increase the mechanical strength of thin membranes (≤30 µm) for PEM fuel cell applications. In hydrogen-bromine flow batteries (HBFBs), Br2 and Br– crossover through the membrane may affect the lifetime of HBFBs as a result of dissolution or passivation of the platinum catalyst. One study suggested that the reinforcement reduces the bulk Br2 and Br– transport and x-y (in-plane) swelling [1].
Data Centres Expo Europe, Amsterdam
This event focuses on innovations and infrastructure for modern data centers, including energy storage, energy efficiency, cooling, and digital connectivity.
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The Battery Day, Arnhem
The Battery Day in Arnhem is a one‑day conference held on 25 September 2025 at Cleantech Park (Industriepark Kleefse Waard), where Dutch battery pioneers, policymakers, startups, researchers, corporates and investors gather to connect, explore the latest innovations and funding opportunities, and strengthen the national battery ecosystem.
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Vakbeurs Energie, Den Bosch
The Vakbeurs Energie in Den Bosch is the Netherlands’ largest three‑day business platform for the built environment’s energy transition, held at the Brabanthallen in early October (October 7–9, 2025), bringing together around 450 exhibitors and over 20,000 professionals for networking, knowledge sessions, and showcasing innovations in sustainable energy, smart grids, storage, and building systems.
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Hydroverse Convention
The Hydroverse Convention in Essen is Europe’s premier hydrogen start‑up innovation event—organized by H2UB—and brings together over 600 international H₂‑experts, start‑ups, investors, industry leaders, and policymakers for pitch sessions, panel discussions and exhibitions to drive the hydrogen economy forward.
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International Flow Battery Forum
The International Flow Battery Forum is an annual conference that brings together industry leaders, researchers, and policymakers to discuss advancements, challenges, and commercialization of flow battery technologies for energy storage.
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Oasis Pressure Cooker Event
OASIS is a holistic programme to accelerate the development and uptake of system integration and storage SMEs in the offshore renewable energy (ORE) sector.
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