Most renewable energy researchers are focusing on a type of battery called a flow battery for storing energy, in which electricity is stored in a tank of liquid electrolyte. However, making this technology cost-effective on the scale required for the power grid has proven challenging.

Researchers at Berkeley are helping with this problem through the development of an affordable battery membrane, which is the part of the battery that separates the cathode and the anode. Traditional fuel cells use a fluorinated membrane, but these membranes are expensive and aren't designed for a flow battery. The researchers have created a new type of membrane specifically for flow batteries made from polymers called AquaPIMs, or aqueous-compatible polymers of intrinsic microporosity.

AquaPIM membranes work with different battery chemistries, from metals and inorganics to organics and polymers, and they help create stable cells which last for longer without degrading. They are also considerably cheaper than the fluorinated polymer membranes which can make up to 15 to 20 percent of the cost of a battery.

The new membranes pave the way for cheaper and more reliable flow batteries for the electric grid, which could eventually power homes across the country with renewable energy from wind and solar.