Sustainable Batteries Take A Swig Of Brown Liquor

Everyone knows it: to take full advantage of solar and wind resources, we need to develop better ways to store the power they produce. That search is taking us from using molten salts at solar plants to using wind turbines to create hydrogen. Is there a place for batteries in this picture? Researchers at Linköping University (LiU) in Sweden think so – they’re looking into making sustainable batteries by using “brown liquor,” a cheap and renewable byproduct from paper pulp mills.

According to the LiU researchers, even though organic solar cells based on conductive plastic have lowered costs, as long as conventional batteries utilize expensive and limited resources like Cobalt, the technology will never be scalable. To find a renewable and cheap solution, Olle Inganäs, professor of biomolecular and organic electronics at LiU, and his Polish colleague Grzegorz Milczarek looked to nature’s process of photosynthesis.

image via Keith Weller / USDA

During photosynthesis, electrons charged by solar energy are transported around by quinones, which are electrochemically active molecules based on benzene rings of six carbon atoms. The brown liquor used in Inganäs’ battery is largely made of lignin, a biological polymer in the plant cell walls. To get the quinones to act as charge carriers in the batteries, the LiU team created a thin film of pyrrole and lignin derivatives which act as the cathode.

The LiU team hopes that these renewable batteries could solve the problem of high cost and nonrenewable materials plaguing conventional batteries. “Lignin constitutes 20-30 percent of the biomass of a tree, so it’s a source that never ends,” said Inganäs. When exactly the renewable batteries could be available and their cost remains unseen.

The Inganäs and Milczarek research was published in the journal Science.