Plant root used to create eco-friendly lithium-ion battery

Researchers have found an eco-friendly alternative to the metal ores currently favored in the electrodes of lithium-ion batteries. The new non-toxic and sustainable battery uses purpurin, a red/yellow dye extracted from the root of the madder plant that has been used for dying cloth for at least 3,500 years – meaning the substance can simply be grown rather than mined.

Currently, lithium cobalt oxide (LiCoO₂) is the material of choice for forming the cathode in Li-ion batteries. However, mining the cobalt and combining it with lithium at high temperatures to form the cathode is an expensive and energy-intensive process.

Making the purpurin electrode can be done at room temperature in a simple process which involves dissolving the purpurin in an alcohol solvent and adding lithium salt. After the solution turns from reddish yellow to pink, indicating the salt’s lithium ions have bonded with the purpurin, the solvent can be removed and the electrode is ready.

The researchers are confident their green Li-ion battery will be commercially produced in the next few years. This takes into account the time needed to improve purpurin’s efficiency or find and synthesize similar molecules.

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