Better Membranes Make Better Flow Batteries

Flow batteries could one day provide the long term storage of electricity needed to make renewable energy commercially viable everywhere. They have the potential to cost less than lithium-ion batteries and avoid some of the pitfalls associated with lithium-ion, such as fires and explosions. They tend to take up more room but that is seldom an issue when it comes to grid scale storage. Conceptually, flow batteries are simple devices. Two chambers filled with liquid, one with a positive charge, the other with a negative charge. Separate the two liquids with a membrane that allows electrons to pass back and forth and voila! You have a battery.

The membrane is the secret to making the whole thing both economical and durable. Most flow batteries today use flourinated membranes which are expensive — up to 20% of the total cost of a battery. Cheaper membranes simply don’t stand up very long to the highly alkaline environment found inside a typical flow battery.

According to research paper published recently in the journal Joule, scientists at the Lawrence Berkeley National Lab say they have have developed a versatile yet affordable battery membrane from a class of polymers known as AquaPIMs. These polymers make inexpensive and long lasting grid batteries possible based solely on abundant materials such as zinc, iron, and water. AquaPIM membranes work with different battery chemistries, from metals and inorganics to organics and polymers, and they help create stable cells which last far longer before degrading.

The team also developed a simple computer modeling technique that shows how different battery membranes impact the life expectancy or a flow battery. That tool should accelerate early stage R&D for flow-battery technologies, particularly in the search for a suitable membrane for different battery chemistries.

“Our AquaPIM membrane technology is well-positioned to accelerate the path to market for flow batteries that use scalable, low-cost, water-based chemistries,” Brett Helms, a principal investigator in the Joint Center for Energy Storage Research and lead researcher, tells Environment News Network. “By using our technology and accompanying empirical models for battery performance and lifetime, other researchers will be able to quickly evaluate the readiness of each component that goes into the battery, from the membrane to the charge-storing materials. This should save time and resources for researchers and product developers alike.”

Anything that could drive the renewable energy revolution forward is a good thing.