A new blueprint for affordable, sustainable ‘flow batteries’ developed at Berkeley Lab for renewable energy could accelerate an electrical grid powered by the sun and wind.

One of the biggest problems with renewable energy sources is finding cost-effective solutions to storing that energy, especially when the sun is not shining or the winds are calm.

We have giant storage batteries designed for the electrical grid, called flow batteries. Basically, the batteries store an electrical charge in tanks of liquid electrolyte that is pumped through electrodes to extract the electrons; the spent electrolyte returns to the tank.

Flow batteries go beyond the technology of Lithium-ion batteries—the sort in laptops and Teslas. Lithium-ion batteries also backup power for hospitals, office parks, and even towns. But it has proven to be difficult to scale these batteries up to provide backup power for cities, like New York or Los Angeles.

Moreover, the flow batteries available today are not big enough to store power for large grid areas, and they would be expensive for utilities to use. Added to this is the cost of the electrolytes used in some batteries, such as vanadium, which has risen in price.

Battery membrane technology

There is a battery membrane technology developed by researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) that may point to a solution.

As reported in the journal Joule, the researchers developed a versatile yet affordable battery membrane — from a class of polymers known as AquaPIMs.

Based on the unique makeup of AquaPIMs, they are well poised to accelerate aqueous alkaline battery development, bringing back to the forefront low-cost and scalable battery chemistries that have been considered dead ends due to a lack of a selective and stable membrane under the extreme operating conditions of those cells.

The researchers used an architectural platform based on ladder polymers to address the rigidity of the polymer backbone. Such ladder polymers are often referred to as polymers of intrinsic microporosity (PIMs).

By adding ionizable and high-pH-stable amidoximes onto microporous ladder polymer backbones, the scientists arrived at a family of AquaPIMs that serve effectively as ion-selective membranes in aqueous electrochemical devices – making the AquaPIM platform. AquaPIM stands for “aqueous-compatible polymers of intrinsic microporosity.”

“Our AquaPIM membrane technology is well-positioned to accelerate the path to market for flow batteries that use scalable, low-cost, water-based chemistries,” said Brett Helms, a principal investigator in the Joint Center for Energy Storage Research (JCESR) and staff scientist at Berkeley Lab’s Molecular Foundry who led the study.

“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.”