Korea/Germany: New Energy Storage Are Membranes the Key Component for Energy Storage?

Editor: Dominik Stephan

Storing fluctuating and delivering stable electric power supply are central issues when using energy from solar plants or wind power stations. Here, efficient and flexible energy storage systems need to accommodate for fluctuations in energy gain. Scientists from Germany’s Leibniz Institute for Interactive Materials (DWI), RWTH Aachen University and Hanyang University in Seoul, Korea., now significantly improved a key component for the development of new energy storage systems.

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PhD student Tao Luo and postdoc Il Seok Chae are part of the research team that developed the new hydrophobic membrane with nanopores.
PhD student Tao Luo and postdoc Il Seok Chae are part of the research team that developed the new hydrophobic membrane with nanopores.
(Picture: DWI)

Aachen/Germany, Seoul/South Korea – Redox flow batteries are considered a viable next generation technology for highly efficient energy storage. These batteries use electrolytes, chemical components in solution, to store energy. A vanadium redox flow battery, for example, uses vanadium ions dissolved in sulfuric acid. Being separated by a membrane, two energy-storing electrolytes circulate in the system.

The storage capacity depends on the amount of electrolytes and can easily be increased or decreased depending on the application. To charge or discharge the battery, the vanadium ions are chemically oxidized or reduced while protons pass the separating membrane.

Membranes are the Heart of the Energy Storage System

The membrane plays a central role in this system: On the one hand, it has to separate the electrolytes to prevent energy loss by short-circuiting. On the other hand, protons need to pass the membrane when the battery is charged or discharged.

To allow efficient, commercial use of a redox flow batteries, the membrane needs to combine both these functions, which still remains a significant challenge for membrane developers so far.

Venturing Into the Unexplored: A New Way for Membranes

The current benchmark is a Nafion membrane. This membrane is chemically stable and permeable for protons and is well known for H2 fuel cell applications. However, Nafion and similar polymers swell when exposed to water and loose their barrier function for vanadium ions. Polymer chemists try to prevent vanadium leakage by changing the molecular structure of such membranes.

The researchers from Aachen and Seoul came up with a completely different approach: “We use a hydrophobic membrane instead. This membrane keeps its barrier functions since it does not swell in water,” explains Prof. Dr.-Ing. Matthias Wessling. He is the vice scientific director at the Leibniz Institute for Interactive Materials and heads the chair of Chemical Process Engineering at RWTH Aachen University.

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