(Phys.org)—Tannins may be best known for their presence in red wine and tea, but in a new study researchers have demonstrated for the first time that tannins from tree bark can also serve as battery cathode materials. As tree bark is approximately 15% tannins by weight, tannins are naturally abundant, which is one factor that makes them a promising material for designing sustainable, low-cost, metal-free, high-performance batteries.
Besides their widespread availability, another reason why tannins appear to be such a promising battery material is their high levels of phenol—they have the highest phenol content among any polymer produced by living organisms. High levels of phenol are important because the primary charge storage mechanism of the tannin-based battery is a reversible chemical reaction in which phenol is converted into quinone.
The researchers, led by Hongli Zhu at Northeastern University in Boston, along with PhD student Alolika Mukhopadhyay as the lead author and coauthors from the National Renewable Energy Laboratory in Golden, Colorado, have published a paper on the tannin battery cathode in a recent issue of Nano Letters.