Cobalt-free batteries could power the cars of the future

Many electric vehicles are powered by batteries containing cobalt, a metal that carries high financial, environmental and social costs.

MIT researchers have now designed a battery material that could offer a more sustainable way to power electric cars. The new lithium-ion battery includes a cathode made from organic materials, instead of cobalt or nickel (another metal often used in lithium-ion batteries).

In a new study, researchers showed that this material, which could be produced at a much lower cost than cobalt-containing batteries, can conduct electricity at similar speeds to cobalt batteries. The new battery also has comparable storage capacity and can be charged faster than cobalt batteries, the researchers report.

“I think this material could have a big impact because it works very well,” says Mircea Dincă, the WM Keck Professor of Energy at MIT. “It is already competitive with existing technologies, and it can save many of the costs, difficulties and environmental problems associated with extracting the metals that currently go into batteries.”

Dincă is the lead author of the study, published today (January 18) in the journal ACS Central Science. Tianyang Chen Ph.D. ’23 and Harish Banda, a former postdoctoral fellow at MIT, are lead authors of the paper. Other authors include Jiande Wang, a postdoctoral fellow at MIT; Julius Oppenheim, MIT graduate student; and Alessandro Franceschi, researcher at the University of Bologna.

Cobalt Alternatives

Most electric cars are powered by lithium-ion batteries, a type of battery that recharges when lithium ions pass from a positively charged electrode, called a cathode, to a negative electrode, called an anode. In most lithium-ion batteries, the cathode contains cobalt, a metal that provides high stability and energy density.

However, cobalt has significant drawbacks. A rare metal, its price can fluctuate considerably and much of the world’s cobalt deposits are found in politically unstable countries. Cobalt mining creates dangerous working conditions and generates toxic waste that contaminates the land, air and water surrounding the mines.

“Cobalt batteries can store a lot of energy and have all the features that people are interested in in terms of performance, but they have the problem of not being widely available and their cost fluctuates widely depending on raw material prices. to a much higher proportion of electrified vehicles in the mainstream market, it will definitely become more expensive,” says Dincă.

Due to the many disadvantages of cobalt, much research has been conducted attempting to develop alternative materials for batteries. One such material is lithium iron phosphate (LFP), which some automakers are starting to use in electric vehicles. Although still useful in practice, LFP has only about half the energy density of cobalt and nickel batteries.

Organic materials are another attractive option, but until now most of these materials have not been able to match the conductivity, storage capacity and lifespan of cobalt-containing batteries. Due to their low conductivity, these materials typically need to be mixed with binders such as polymers, which help them maintain a conductive network. These binders, which make up at least 50 percent of the overall material, reduce the battery’s storage capacity.

About six years ago, Dincă’s lab began working on a Lamborghini-funded project to develop an organic battery that could be used to power electric cars. Working with porous materials that were part organic and part inorganic, Dincă and his students realized that a fully organic material they had made looked like it could be a powerful conductor.

This material is made of several layers of TAQ (bis-tetraaminobenzoquinone), a small organic molecule containing three fused hexagonal rings. These layers can extend outward in all directions, forming a structure similar to graphite. Inside the molecules are chemical groups called quinones, which are the reservoirs for electrons, and amines, which help the material form strong hydrogen bonds.

These hydrogen bonds make the material very stable and also very insoluble. This insolubility is important because it prevents the material from dissolving into the battery electrolyte, as some organic battery materials do, thereby extending its life.

“One of the main methods of degradation of organic materials is that they simply dissolve in the battery electrolyte and pass to the other side of the battery, essentially creating a short circuit. If you render the material completely insoluble, this process does not happen, so we can achieve more than 2,000 charge cycles with minimal degradation,” explains Dincă.

Strong performance

Tests of this material showed that its conductivity and storage capacity were comparable to traditional cobalt-containing batteries. Additionally, batteries with a TAQ cathode can be charged and discharged faster than existing batteries, which could speed up the charging rate of electric vehicles.

To stabilize the organic material and increase its ability to adhere to the battery’s current collector, which is made of copper or aluminum, the researchers added filler materials such as cellulose and rubber. These charges represent less than a tenth of the overall cathode composite, so they do not significantly reduce the battery’s storage capacity.

These charges also extend the life of the battery cathode by preventing it from cracking when lithium ions enter the cathode while the battery is charging.

The raw materials needed to manufacture this type of cathode are a quinone precursor and an amine precursor, which are already commercially available and produced in large quantities as commodity chemicals. Researchers estimate that the material cost of assembling these organic batteries could be about a third to half the cost of cobalt batteries.

Lamborghini has licensed the patent on this technology. Dincă’s lab plans to continue developing alternative materials for batteries and is investigating the possibility of replacing lithium with sodium or magnesium, which are cheaper and more abundant than lithium.

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and education.