People may often purport the varying shades of green of rechargeable battery technology, especially when it comes to storing energy in hybrid and electric vehicles, or storing energy from intermittent sources, such as wind and solar power.
These are indeed noble goals every battery can be a part of, but when considering the other side of the coin, though, the battery itself, things may not appear so green.
For example, in 2010, some ten billion lithium-ion [Li-ion] rechargeable batteries were recycled, generating 159 pounds of carbon dioxide [CO2] per kilowatt-hours [kWh] of capacity. The 85kWh Li-ion battery pack in the Tesla Model S, for example, might generate 21 tons of CO2 over its ten-year lifespan, which is much better than, say, the 59 tons that a Ford Focus might generate.
When the Model S battery needs to be recycled, though, that process alone might add an additional 6 ¾ tons of CO2 back to the atmosphere, and even more to manufacture the new battery.
Chemists at the City College of New York [CCNY], working together with researchers at Rice University and the US Army Research Laboratory, have developed a greener alternative to the rare-earth metals that currently go into Li-ion batteries. As it turns out, the color molecule, purpurin, found in ancient red dye, is both electrically compatible, and completely biodegradable.
Extracted from the madder plant, purpurin molecules are ringed with carbonyl and hydroxyl groups, easily carrying an electrical charge. “These aromatic systems are electron-rich molecules that easily coordinate with lithium,” explained CCNY professor of chemistry, George John, “that a natural material or dye can be used for a battery, that is exciting, even for me.”
Green Li-ion batteries might not see market for a few years, but would certainly change the face of current battery technology. Even if they can’t improve on the range or longevity of the rechargeable batteries, they can make it easier to recycle and non-toxic for disposal. Growing crops of madder plant would also pull CO2 from the atmosphere, further reducing the carbon footprint of the new battery formulation.