This hydrophobic barrier allows batteries to store more energy from fluctuating power sources such as solar or wind.
In a release from Leibniz Institute for Interactive Materials (DWI) in Germany, researchers outlined how the use of a polymer with intrinsic microporosity (PIM) allowed for efficient fluctuating energy storage. The key is a hydrophobic membrane in the battery, which remains stable over a period of 100 charging and discharging cycles (one week) and has an energy efficiency of up to 99 percent.
“We were pleasantly surprised when we discovered tiny pores and channels in the hydrophobic material and they appear to be filled with water,” said Matthias Wessling, vice scientific director at the Leibniz Institute for Interactive Materials and chair of chemical process engineering at RWTH Aachen University. “These water channels allow protons to travel through the membrane with high speed. The vanadium ions, however, are too large to pass the membrane.”
This can be used instead of a Nafion membrane, which is often used in hydrogen fuel cell applications. The big difference is that this type of polymer tends to swell when exposed to water.
Instead of swelling, the PIM holds the water inside its pores, not inside the polymer itself. In fact, it condensed when exposed to water.
The researchers still find this behavior “puzzling,” the report said, but it nevertheless opens up opportunities. They still need to find out whether the membrane is stable for a long period of time, as well as to find out whether it can be an effective transport model in redox flow batteries, which uses the membrane to separate vanadium atoms.
