MIT team develops organic alternative to cobalt cathodes

Most Li-ion batteries feature a cathode that contains cobalt, a metal that offers high stability and energy density. However, cobalt’s extraction – particularly in the Democratic Republic of Congo – occurs in some of the worst mining conditions on Earth, linked with child labour and widespread environmental damage. As the majority of cobalt deposits are located in politically unstable countries, this also makes the price of the material volatile.  

“Cobalt batteries can store a lot of energy, and they have all of features that people care about in terms of performance, but they have the issue of not being widely available, and the cost fluctuates broadly with commodity prices,” said Mircea Dincă, the WM Keck Professor of Energy at MIT.

“And, as you transition to a much higher proportion of electrified vehicles in the consumer market, it’s certainly going to get more expensive.”

About six years ago, Dincă’s lab began working on a project funded by Lamborghini to develop an organic battery that could be used to power electric cars. The team developed a material consisting of many layers of TAQ (bis-tetraaminobenzoquinone), an organic small molecule that contains three fused hexagonal rings. These layers can extend outward in every direction, forming a structure similar to graphite.

Within the molecules are chemical groups called quinones, which are the electron reservoirs, and amines, which help the material to form strong hydrogen bonds. Those bonds make the material highly stable and also very insoluble, preventing it from dissolving into the battery electrolyte and extending its lifetime. The work is published in the journal ACS Central Science.

“One of the main methods of degradation for organic materials is that they simply dissolve into the battery electrolyte and cross over to the other side of the battery, essentially creating a short circuit,” said Dincă.

“If you make the material completely insoluble, that process doesn’t happen, so we can go to over 2,000 charge cycles with minimal degradation.  

The researchers estimate that the material cost of assembling these organic batteries could be about one-third to one-half the cost of cobalt batteries. Lamborghini has already licensed the patent on the technology, and Dincă’s lab is now exploring possible replacement of lithium with sodium or magnesium, which are cheaper and more abundant metals than lithium.