Dying to make greener batteries
Plant molecule a replacement for cobalt
A common and ancient plant dye could replace cobalt and help deliver greener lithium-ion batteries, according to a study out of America.
Purpurin, an extract of the common Madder plant, turns out to have the right characteristics to use as a cathode, according to research led by The City College of New York (along with Rice University and the US Army Research Laboratory).
In a paper in Nature (abstract here), the researchers observe “reversible lithium ion storage properties of a naturally occurring and abundant organic compound purpurin, which is non-toxic and derived from the plant madder.”
More simply, purpurin’s molecule has aromatic rings with carbonyl and hydroxyl groups that can perform the cathode’s task of passing electrons around – meaning that it can serve in the place of cobalt in the lithium battery.
According to Phys.org, it’s easy to process as well: the purpurin is dissolved in alcohol, and lithium salts are added, allowing the lithium ions to bind with the purpurin - at room temperature.
The researchers say getting rid of cobalt would have a bunch of green benefits: it would remove a toxin from the batteries, and remove the high-temperature processing required to combine cobalt ions with lithium to make the batteries.
Li-ion batteries are also energy-hungry to recycle, according to Rice University’s Dr Leela Reddy, with the result that the fabrication and recycling of batteries costs 72 kilos of CO2 per kilowatt-hour of battery energy.
The study suggests purpurin could either be extracted from farmed madden, or the molecule synthesized. ®
Nice for phones, but even better for cars
Currently cobalt is only used in Li-ion batteries for small stuff like phones because while it has the best energy density it's not seen as safe enough to use in larger items more subject to damage like power tools and cars. If this has the same/better energy density it could replace the cobalt in phone batteries and reduce the odd cell phone catching fire, along with shaving a few grams off the weight.
But it would really be a big win for electric cars, as they'd get a longer range due to the higher energy density over the non-cobalt Li batteries they currently use, in addition to its lower weight reducing power required (though it's mostly aerodynamic drag at highway speeds) This also addresses one of the it's-really-not-so-green objections to electric cars.
This shows not only that there is what seems to be a good alternative but that researchers are looking at organic replacements which will help with long term resources.
Good luck folks!
Dying to make batteries?
I guess the plants die to enable the dyeing process...