Swedish researchers at the Laboratory of Organic Electronics of Linkoping University have prepared a special kind of paper that can store electrical charge. The paper constructed from Nano cellulose and a variety of conductive polymer can stock up as much charge as stored by super capacitors available currently.

Improving upon thin film capacitors

Xavier Crispin who is the professor of organic electronics explains that the paper capacitors are superior to the very thin film capacitors, which have been around for some time. Being few tenths of a millimeter in thickness, they can be considered to have a three dimensional structure compared to the film capacitors. The paper can be produced in varying thicknesses.

Details of the fabrication of the paper capacitor have been published in Advanced Science. Apart from Crispin, who is the principal author of the scientific paper, several other scientists from the Technical University of Denmark, University of Kentucky, KTH Royal Institute of Technology and Innventia have also contributed to the article, based on their research.

A 15cm wide sheet can store about 1Farad of electricity, which is roughly the same capacity as that of the super capacitors. The paper can be charged up to hundreds of time and each charging cycle takes up only a few seconds.
The researchers feel that these paper capacitors could provide diverse storage capacities for stocking up energy from renewable energy sources for different weather conditions including sunny, cloudy, calm, and windy.

Robust structural foundation

The basic material of the paper is Nano cellulose. This consists of fibers of cellulose broken down into strands as narrow as 20 nm by passing water at very high pressure through it. The Nano cellulose fibers are made into a suspension with water. This is treated with an electrically charged emulsion of a PEDOT:PSS polymer in water. The polymer coats the fibers to give it a plastic feel.

The space in between the tangled fibers is filled with the water-based electrolyte. The conductivity for electrons and ions in the electrolyte is a record high. This makes for the especially high energy storage capacity. The scientists expect that the capacity can be increased further by adjusting the fabrication process.

Advantages over conventional storage units

Since it is derived from easily accessible raw materials like renewable cellulose and polymer, the researchers expect that power paper will gain popularity as a storage device. It is light and wieldy. Furthermore, it is environmentally friendly, as the manufacture process does not require heavy metals and other harmful chemicals. A particularly convenient feature is that it is waterproof.

The technique for making the power paper is almost the same as used for making regular paper from wood pulp. The difference lies in the addition of polymer coating on the Nano cellulose strands. Professor Magnus Berggren of Linkoping University reveals that the real challenge is developing the paper on an industrial scale. He hopes that the grant of SEK 34 million awarded by the Swedish Foundation of Strategic Research will help them in their endeavor to develop a machine for their production. The Knut and Alice Wallenberg Foundation are supporting the research, as well.