Building batteries from plant roots

    A new plant-based extract used as a clothing dye for over 3500 years could also provide a green alternative to the metal ores used to make lithium-ion batteries.
    The extract, called purpurin, comes from the root of the madder plant. Purpurin, along with other biologically-based color molecules, contain carbonyl and hydroxyl groups able to pass electrons back and forth in the same way as traditional electrodes. Purpurin can be made and stored at room temperature, with a color change signaling when the binding process is complete. And because it is organic, batteries made from the material would be non-toxic, and could be easily disposed of.