Metabolites from fungi have some of the same properties as vanadium, which is used in batteries. New research shows that batteries can be made using naturally occurring bioquinones and thus make the battery industry less dependent on rare minerals that are not present in Europe.
Making batteries from fungi sounds fanciful. Nevertheless, this is the potential of a new discovery by researchers from Aalborg University, who show that bioquinones, specific metabolites derived from fungi, have properties that enable them to replace the relatively rare element vanadium in battery cells.
In addition to being rare and also not present in Europe, vanadium must be imported from China and other countries.
However, using vanadium in batteries may be yesterday’s news if the researchers can further develop their discovery into a perfectly good substitute.
“We have shown that bioquinones from fungi can store and release electricity in the same way as vanadium in conventional redox-flow batteries, a type of battery that is particularly used to store energy on a large stationary scale from, for example, solar cells and wind farms. If we can develop the technology to withstand being charged and discharged several thousand times, this sustainable and fungi-based battery chemistry could have a decisive role in the green transition,” explains a researcher behind the discovery, Jens Muff, Associate Professor, Department of Chemistry and Bioscience, Aalborg University.
The research has been published in Batteries & Supercaps.
TV show led to a good idea
The discovery originated when Jens Muff’s colleague Jens Laurids Sørensen saw a feature on the Danish TV show So Ein Ding focusing on potentially using electrochemically active organic substances in batteries. But the substances were chemically synthesised from refined crude oil.
Jens Laurids Sørensen specialises in fungi and their metabolites and thought that the structure of the substances was recognisable. He was convinced that he could find some fungal compounds with similar properties.
He therefore contacted Jens Muff to create a research collaboration specifically to identify fungal metabolites with electrochemical properties that can be used for battery technology. The initial choice was bioquinones, which potentially have the properties to reversibly accept and release electrons based on their functional quinone groups.
The first experiments confirmed this potential.
“We could store electricity, but the bioquinone we explored at this early stage was not suitable, so we decided to determine whether other known bioquinones would be more effective,” says Jens Muff.
990 bioquinones have battery potential
The researchers subsequently identified 990 known bio-based quinones, and Sebastian Kristensen took on the task of using computer simulations to investigate the electrochemical potential of each one.
Electrochemical potential reflects a substance’s ability to absorb and release electrons, and a battery works by having a substance with low potential release electrons to a substance with higher potential when discharged, thereby releasing energy. When the battery is charged, energy is applied in the form of voltage to force the electrons to flow back again. The difference in electrochemical potential between the two sides determines the cell voltage the battery can deliver, and the solubility of the substances determines the capacity of the battery.
The extensive simulation work identified phoenicin as a candidate substance to demonstrate the concept, and Jens Laurids Sørensen, together with colleagues from Aalborg University and the Technical University of Denmark, mapped the biochemical synthesis pathway so that the researchers could produce phoenicin in large quantities for their experiments.
“The problem is that the fungi do not produce these metabolites in very large quantities – and not at all sufficient to enable experimental testing. But after we identified the synthetic pathway, we could transfer it to a yeast that could produce phoenicin in the quantities needed to test whether reality matched the theory,” explains Jens Muff.
May replace vanadium in batteries
Charlotte Wilhelmsen was assigned to characterise phoenicin electrochemically and investigate its battery properties.
Phoenicin has negative electrochemical potential and was the negative electrolyte in the battery in the experiments. The studies were carried out in collaboration with a world-leading research group in aqueous organic redox-flow batteries from the University of Jena in Germany and demonstrated that phoenicin could replace vanadium in this type of battery.
The advantages of being able to replace vanadium with a biological molecule include that a few countries hold the global resources of vanadium and that the price of vanadium fluctuates with the demand for stainless steel, which also contains vanadium.
“Efficient and cheap energy storage is a bottleneck in the green transition, and geopolitically it makes good sense if we can biosynthesise compounds for use in batteries ourselves, so that we do not depend on raw materials from other countries. In addition, all the phoenicin needed can be produced in bioreactors, and Denmark is a world leader in biological production,” says Jens Muff.
Must be rechargeable 10,000 times
Jens Muff says that there are clear advantages to using a fungal quinone metabolite in batteries, but the researchers also need to solve challenges.
The advantage of phoenicin is that it is water-soluble in an alkaline solution, and that when the battery is depleted, you can pour the solution down the drain, after which the phoenicin is easily degraded.
However, this means that phoenicin is also more easily decomposable than, for example, vanadium, which does not decompose, and this affects the life of the battery.
“We can recharge a vanadium battery 10,000 times, but we are a long way off with bioquinones. We have shown that phoenicin can be used in batteries, and now we are working to make it stable enough that the capacity can meet the recharging requirements of various applications. We can do this by changing their structure through the biochemical synthesis pathway or by combining it with a final chemical modification. We are about to start collaborating with a group from the Technical University of Denmark to examine the latter possibility more closely,” concludes Jens Muff.
