Essential Science: Power paper can store electricity

Posted Dec 14, 2015 by Tim Sandle
Scientists have developed a new, very thin material with the ability to store energy. The material consists of nanocellulose and a conductive polymer. It has been dubbed "power paper."
Researchers at Sweden’s Linköping University’s Laboratory of Organic Electronics have developed...
Researchers at Sweden’s Linköping University’s Laboratory of Organic Electronics have developed an energy storage device consisting of nanocellulose and a conductive polymer.
Linköping University
An important concern of modern times is with finding new sources of renewable energy. While attention is paid to sunlight, wind, rain, tides, waves, and geothermal heat, within laboratories scientists are attempting to find ways to create more power; to retain power; and develop devices that can be charged and recharged multiple times. A new type of "paper" is a step forwards towards achieving new forms of renewable power.
The new "power paper" is remarkable in the way it can store energy. A single sheet of the paper is only 15 centimeters in diameter and just a few tenths of a millimetre thick. A sheet this size can store electricity equivalent to most supercapacitors. Moreover, the material can be recharged several hundred times without any loss of performance. The charge time is less than five seconds.
Screenshot of newly developed stretchable battery
Screenshot of newly developed stretchable battery
Yonggang Huang / Northwestern University
A supercapacitor is a device that falls between an electrolytic capacitor and a rechargeable battery. Most commercial devices can accept and deliver charge much faster than batteries. However, they tend to be much larger in size, making their use more appropriate for industrial systems.
The main use of supercapacitors is where a rapid charge/discharge cycle is required. An example is with regenerative braking, as with an elevator or a train. Regenerative braking slows an object by converting its kinetic energy into a form that used immediately.
The paper can store energy up to 1 Farad. A Farad is an internationally recognized unit of electrical capacitance. This is a large amount, given that most capacitors are measured in microfarads (units of one millionth of a Farad.)
The technology behind the paper uses film. Although advances with film to store electricity have been developed over the past few years, the ability to develop something that works across three dimensions is what makes the new paper unique.
These are some of the cellulose nitrate negatives found bundled together at Cape Evans in  Scott s H...
These are some of the cellulose nitrate negatives found bundled together at Cape Evans in "Scott's Hut."
courtesy of the Antarctic Heritage Trust
The structural basis to the film is nanocellulose. This is based on cellulosic fibers. These are created through the use of high pressure water, which breaks down plant based matter into incredibly thin sections. The sections are just 20 nanometers thick. A nanometer is equal to one billionth of a metre.
With the thin sections of cellulose formed, the fibers are placed in a water-based solution and an electrically charged polymer (PEDOT:PSS) is added. Polymers are compounds with a repeating series of units. Polymers can be natural or artificially produced; and example of a synthetic version is a plastic like polystyrene. Once added, PEDOT:PSS forms a thin coating around the nanocellulose fibers. To form 'paper' the process is from then on similar to other industrial processes. A pulp is produced which needs to be dehydrated and flattened.
Explaining this further, Jesper Edberg, one of the researchers, notes in a research note: "The covered fibres are in tangles, where the liquid in the spaces between them functions as an electrolyte."
The use of the film coating renders the paper a little like a sheet of plastic. However, it can be folded or turned into any manner of shapes, while still retaining its power retaining capability.
The ability of the paper to be recharged multiple times means it meets criteria as an environmentally friendly product. Furthermore, the paper is lightweight and waterproof.
The "power paper" has also smashed some power records, such as establishing a new world record for simultaneous conductivity for ions and electrons. In all, four world records have been broken. These are a little technical, and are defined by the research group as:
Highest charge and capacitance in organic electronics, 1 C and 2 F (Coulomb and Farad),
Highest measured current in an organic conductor, 1 A (Ampere),
Highest capacity to simultaneously conduct ions and electrons,
Highest transconductance in a transistor, 1 S (Siemens).
Without meaning to downplay the technicalities, these records reaffirm the ability of the "power paper" to hold large amounts of power and this carries with it great potential for electronics. The main obstacle to fully utilizing the 'power paper' is producing it on an industrial scale; and it is with this that the next wave of research will focus upon.
The new technology has been created at the Laboratory of Organic Electronics, located within the science department in Sweden's Linköping University. The application is discussed in the journal Advanced Science. The research paper is titled " An Organic Mixed Ion-Electron Conductor for Power Electronics."
This article is part of Digital Journal's Essential Science series. Other articles in the series are "Space-food for astronauts made from bacteria"; "Health effects of antibiotic use"; "Graphene makes improved night vision tech"; and "Personalized medicines, the health innovation."