When a lemon and a couple of electrodes aren’t enough

From Rice University comes news taking the lemon, copper and zinc thing into the 21st century. A team led by Arava Leela Mohana Reddy has found a way to make more environmentally friendly power. The trick is to is use purpurin, an organic dye that can be turned into a highly effective, natural cathode for lithium-ion batteries.

“Green batteries are the need of the hour, yet this topic hasn’t really been addressed properly,” Reddy said. “This is an area that needs immediate attention and sustained thrust, but you cannot discover sustainable technology overnight. The current focus of the research community is still on conventional batteries, meeting challenges like improving capacity. While those issues are important, so are issues like sustainability and recyclability.”

The key to the process is the lithiation of purpurin. The dye takes up lithium ions as the charge flows. When the battery needs to be recharged the process can be reversed.

Lithiated purpurin
Purpurin, left, extracted from madder root, center, is chemically lithiated, right, for use as an organic cathode in batteries. The material was developed as a less expensive, easier-to-recycle alternative to cobalt oxide cathodes now used in lithium-ion batteries. (Credit: Ajayan Lab/Rice University)

It’s the reversibility of the process that makes it so useful for rechargeable batteries. What the team are looking for now are organic anodes and electrolytes. If they can find something that is as easy to obtain as purpurin, which might come from waste, then this could be a big step forward to making portable power biodegradable.

Reddy A.L.M., Nagarajan S., Chumyim P., Gowda S.R., Pradhan P., Jadhav S.R., Dubey M., John G. & Ajayan P.M. (2012). Lithium storage mechanisms in purpurin based organic lithium ion battery electrodes, Scientific Reports, 2 DOI:

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