Dry manufacturing process enhances EV battery production

The electrodes used in lithium-ion batteries are usually made with a wet slurry of toxic solvents, using an expensive manufacturing approach that poses health and safety risks. Experiments at the US Department of Energy’s Oak Ridge National Laboratory have revealed significant benefits to a dry battery manufacturing process. This eliminates the solvent while showing promise for developing a battery that is durable, less weighed down by inactive elements and able to maintain high energy storage capacity after use.

Dry processing is an innovative alternative that saves factory floor space as well as energy, waste disposal and start-up expenses, yet until now, researchers have had limited understanding of how and why it works. The ORNL researchers analysed how the dry process affects the structure of battery materials and their electrochemical properties. Batteries generate energy as lithium ions travel between electrodes called the cathode and anode. The researchers focused on an electrode dry processing strategy, which involves mixing dry powders with a binder, then compacting the material to improve contact between the particles. This strategy could be applied to the anode and cathode by focusing on certain materials or mixing methods.

ORNL researchers, led by Jianlin Li and Runming Tao, measured the electrodes’ electrochemical performance in different conditions over various time frames. The ORNL team then reached a new understanding of how the dry-processed electrodes degrade. The batteries made using the dry process showed a “superb” ability to maintain their capacity after extended use, according to results reported in Chemical Engineering Journal. They are “highly chemically desirable” because their structure allows lithium ions to take a more direct path between the anode and cathode. The electrodes are also thicker, to allow higher energy loading while reducing inactive ingredients that increase size and weight.

“There are more active materials in the electrode and even after cycling, it will have few cracks,” Tao said. These advantages reflect a high energy density and long-term cyclability. The electrode can bend and flex well, demonstrating good mechanical strength and the winding capability needed for the mass production of batteries. The dry process could offer benefits to manufacturers and the US supply chain, as it is compatible with current electrode manufacturing equipment, while its reduced environmental impact makes battery plants suitable in more places.

Bryan Steinhoff, lead researcher on the project, said dry processing can eliminate the coating and solvent equipment currently necessary for large-scale battery production. “When you’re looking at the gigascale factories, you’re looking at billions of dollars in order to scale batteries up. If you can use a dry process instead, you can reduce your footprint by up to 40 or 50%, saving hundreds of millions of dollars and starting to enable the creation of an infrastructure to replace one that is largely dependent on Asia at the moment,” Steinhoff said.

The researchers aim to stabilise the material that attaches the anode components to a thin metal current collector. “A main goal for this project is to develop or identify a better binder for the dry process, because the current binder is not very stable for the anode environment,” Li said. The goal is to balance the benefits and drawbacks of the thicker electrode: it has the potential for higher energy loading and is easy to roll, but it may provide less power, since the ions have further to travel.

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