Researchers at Linkoping University’s Laboratory for Organic Electronics have demonstrated an organic battery for the first time. It is of the type known as “redox flow battery“, with a large capacity that can be used to store energy from wind turbines and solar panels, and as a power bank for automobiles.
The flow batteries Redox are stationary batteries where the energy is in the electrolyte outside the cell itself, as in a fuel cell. They are often marketed with the prefix “eco” as they open up the possibility of storing excess energy from, for example, the sun and the wind. Also, it seems to be possible to recharge them an unlimited number of times. However, redox flow batteries often contain vanadium, a rare and expensive metal. The electrolyte in which energy is stored in a redox flow battery can be water based, which makes the battery safe to use, but results in a lower energy density.
Mikhail Vagin, Principal Research Engineer, and his colleagues at the Laboratory for Organic Electronics, Norrköping Campus, have succeeded in producing not only a water-based electrolyte but also electrodes made of organic material, which greatly increases the energy density. In this way it is possible to manufacture completely organic redox flow batteries for storing, for example, energy from the sun and wind, and to compensate for the load variation in the electricity supply network.
They have used the conductive polymer PEDOT for the electrodes, which they have doped to transport positive ions (cations) or negative ions (anions). The water-based electrolyte they have developed consists of a solution of quinone molecules, which can be extracted from forest materials.
“Quinones can be derived from wood, but here we have used the same molecule, along with different variants of the conductive polymer PEDOT. It turns out that they are highly compatible with each other, which is like a gift from the natural world,” says Viktor Gueskine, engineer Principal Investigator of the Organic Electronics Laboratory, and one of the authors of the paper now published in the journal Advanced Functional Materials.
High compatibility means that PEDOT electrodes help quinone molecules switch between their oxidized and reduced states, thereby creating a flow of protons and electrons.
“Normally it is difficult to control the ion process, but we have succeeded here. We also use a fundamental phenomenon within electrocatalysis in which a special ion in solution, in this case quinone ions, is converted into electricity. The phenomenon is conceptualized by us as ion selective electrocatalysis, and probably exists in other types of membrane storage devices such as batteries, fuel cells and supercapacitors. This effect has never been discussed before. We showed it for the first time in redox flow batteries”, Mikhail Vagin says.
The organic redox flow batteries still have a lower energy density batteries containing vanadium, but are extremely cheap, fully recyclable, safe and perfect to store energy and compensate for load variations in the power supply network. Maybe in the future we will have an organic redox flow battery at home, like a power bank for the electric car.