Cobalt-Free Batteries Could Power the Next Generation of Electric Vehicles

A new battery cathode material, developed by chemists at the Massachusetts Institute of Technology (MIT), could provide a more sustainable option for powering the next generation of electric cars.

Instead of relying on scarce metals, such as cobalt or nickel, the new cathode is based on organic materials that can conduct electricity at similar rates to cobalt-containing batteries. Lithium-ion batteries with this new organic cathode material also charged up faster than their cobalt-containing counterparts, while still having a comparable storage capacity.

Novel battery materials that avoid the use of rare earth elements can have a positive impact on the environment by reducing mining operations, the researchers say, and so this new battery material could be a more sustainable alternative. The study is published in ACS Central Science.

Transitioning away from cobalt

Lithium-ion batteries are the most popular form of commercial rechargeable battery. These batteries comprise two electrodes – a positively charged “cathode” and a negatively charged “anode” – held apart by a separator. An electrolyte fills the remaining space in the battery, which allows the ions to flow freely between both electrodes during charging and discharging.

To improve the stability and energy density of lithium-ion batteries, most cathodes in lithium-ion batteries also contain small amounts of cobalt. While the addition of this element does help the performance of lithium-ion batteries, many are wishing to turn away from the use of this element considering the environmental damage and exploitative practices that have been associated with cobalt mines in the Democratic Republic of the Congo (DRC). Currently, the DRC provides over two-thirds of global cobalt supplies.

“Cobalt batteries can store a lot of energy, and they have all of [the] 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. And, as you transition to a much higher proportion of electrified vehicles in the consumer market, it’s certainly going to get more expensive,” said Mircea Dincă, the W.M. Keck Professor of Energy at MIT and the senior author of the new research.

To guide the move away from cobalt, researchers are interested in creating alternative battery materials that use less or no rare earth metals (including cobalt and nickel) that need extensive mining to acquire. Ideally, only highly abundant elements would be used to produce the next generation of batteries.

Currently, lithium-iron-phosphate (LFP) has emerged as a promising alternative material, with some car manufacturers already utilizing it in their electric vehicles. However, LFP only has approximately half the energy density of comparable cobalt- and nickel-containing batteries.

Organic materials are another exciting alternative, though current research efforts have generally been hampered by these materials having relatively low conductivities and storage capacities. This is because, to make the organic materials conductive, they are usually mixed with polymer binders that help maintain a strong conductive network. Unfortunately, such binders can make up to 50% of the overall material, which severely hampers the total storage capacity of organic batteries. 

Alternative battery materials

Six years ago, Dincă and his colleagues began working on a Lamborghini-funded project to develop an organic battery that could overcome these conductivity issues.

The result is a material made of many layers of TAQ (bis-tetraaminobenzoquinone), a small molecule with three hexagonal rings that form a structure similar to graphite when assembled into a layer. The TAQ molecules also contain certain functional groups that allow the molecules to form strong hydrogen bonds with each other, which improves the stability of the material and makes it very insoluble.

“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,” Dincă explained. “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.”

To further stabilize the organic material, the researchers also added a small amount of cellulose and rubber to the cathode. These fillers make up less than one-tenth of the cathode’s composition, meaning they do not interfere significantly with the battery’s overall storage capacity. These fillers help the cathode to better adhere to the battery’s current collector, as well as increase the overall lifetime of the battery cathode by preventing the formation of cracks.

Organic batteries match current batteries in performance

The researchers studied the structure of their new cathode material using a wide array of techniques, including in-operando X-ray diffraction, wide-angle X-ray scattering, mass spectrometry, scanning electron microscopy and ultraviolet/visible/near-infrared spectroscopy.

The researchers also carried out a series of benchmark electrochemical tests on their new cathode material, to measure its performance against traditional cobalt-containing batteries.

They found that batteries with an organic TAQ cathode had comparable conductivity and storage capacity metrics with cobalt-containing batteries. The TAQ cathode batteries also charged up faster than other batteries. Lamborghini has already licensed the patent on this new technology.

“I think this material could have a big impact because it works really well,” Dincă said. “It is already competitive with incumbent technologies, and it can save a lot of the cost and pain and environmental issues related to mining the metals that currently go into batteries.”

Compared to rare earth metals, the primary materials that make up the TAQ cathode are far easier to source; the quinone precursor and amine precursor used in its synthesis are already produced in large volumes commercially. The researchers estimate that the total materials cost for assembling a battery with this new cathode type could be as low as one-third the cost of current cobalt batteries.

Reference: Chen T, Banda H, Wang J, Oppenheim JJ, Franceschi A, Dincǎ M. A layered organic cathode for high-energy, fast-charging, and long-lasting li-ion batteries. ACS Cent Sci. doi: 10.1021/acscentsci.3c01478

This article is a rework of a press release issued by the Massachusetts Institute of Technology. Material has been edited for length and content.