One sheet, 15 centimetres in diameter and a few tenths of a millimetre thick is capable of storing as much as 1 Farad, which is similar to the supercapacitors currently on the market. The material can be recharged hundreds of times and each charge only takes a few seconds.
"Thin films that function as capacitors have existed for some time. What we have done is to produce the material in three dimensions. We can produce thick sheets,” said Xavier Crispin, professor of organic electronics and co-author to the article published in Advanced Science.
Other co-authors are researchers from KTH Royal Institute of Technology, Innventia, Technical University of Denmark and the University of Kentucky.
The material, power paper, looks and feels like a slightly plastic paper.
The structural foundation of the material is nanocellulose, which is cellulose fibres which, using high-pressure water, are broken down into fibres as thin as 20 nm in diameter. With the cellulose fibres in a solution of water, an electrically charged polymer (PEDOT:PSS), also in a water solution, is added. The polymer then forms a thin coating around the fibres.
"The covered fibres are in tangles, where the liquid in the spaces between them functions as an electrolyte,” explained Jesper Edberg, doctoral student, who conducted the experiments together with Abdellah Malti, who recently completed his doctorate.
The new cellulose-polymer material has set a world record in simultaneous conductivity for ions and electrons, which explains its capacity for energy storage. The material also opens the door to continued development toward even higher capacity. Unlike the batteries and condensers currently on the market, power paper is produced from simple materials – renewable cellulose and an easily available polymer. The paper is light in weight, requires no dangerous chemicals or heavy metals and is waterproof.
The new power paper is just like regular pulp, which has to be dehydrated when making paper but there remains a challenge to develop an industrial-scale process for the material.
"Together with KTH, Acreo and Innventia we just received SEK 34 million from the Swedish Foundation for Strategic Research to continue our efforts to develop a rational production method, a paper machine for power paper,” said Professor Magnus Berggren, director of the Laboratory of Organic Electronics at Linköping University.