Pulp mill waste product derivate could be new energy storage material

Along with breakthroughs in energy generation technology, various alternative power generation technologies gain a lot of attention in media. The issue of sustainability in energy storage is commonly neglected, but the dwindling resources needed to manufacture energy storage devices as well as the environmental impact during their disposal are inspiring researchers to find better solutions.

Instead using metal oxides to conduct the charge, researchers from the Linköping University (LiU) in Sweeden are looking for a new and intelligent way to store energy with the help of biological waste products from pulp mills. Their goal is to offer ways to store electricity from renewable energy source at the sites where it is produced.

Olle Inganäs, Professor of Biomolecular and Organic Electronics at LiU, drew inspiration from nature where the process of photosynthesis employs quinines (electrochemically active molecules based on benzene rings comprised of six carbon atoms) to transport electrons charged by solar energy. The by-product the researchers chose is brown liquor – a raw material that contains a biological polymer largely composed of lignin. Lignin constitutes 20-30 percent of the biomass of a tree, so it represents a sustainable resource that can be produced in various regions.

In their effort to utilize the quinones as charge carriers in batteries, Inganäs and his Polish colleague Grzegorz Milczarek devised a thin film made of electrochemical oxidation of pyrrole (polypyrrole) in solutions of lignin derivatives from the brown liquor. The film, which has only 0.5 microns in thickness, is used as a polymer cathode in the battery.

The quinone group in lignin is used for electron and proton storage and exchange during redox cycling, thus combining charge storage in lignin and polypyrrole into energy storage.

For more information, read the article published in journal Science: “Renewable cathode material from the biopolymer/conjugated polymer interpenetrating networks”.