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:

Alun Salt. ORCID 0000-0002-1261-4283

When he's not the web developer for AoB Blog, Alun Salt researches something that could be mistaken for the archaeology of science. His current research is about whether there's such a thing as scientific heritage and if there is how would you recognise it?

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