Chicago—Lithium-ion battery manufacturers have been making electrodes the same way for decades. They coat metal foils with a slurry of electrode materials in a toxic solvent. Massive ovens dry the sheets, and complex systems recover the solvent.
Coating electrodes with a dry powder mixture instead would eliminate solvents and shrink energy use and capital costs. For gigascale battery factories, that change could save hundreds of millions of dollars. But it’s difficult to create uniform, defect-free coatings with dry processes.
Researchers at Northwestern University have found that plastering the surface of metal oxide cathode particles with graphene should help (ChemRxiv 2026, DOI: 10.26434/chemrxiv-2026-lkcw). “At the lab scale, electrodes with the graphene-coated active material perform better than control electrodes in terms of higher capacity, longer cycle life, and lower resistance,” said Jeffrey Lopez, a chemical engineering professor at Northwestern. Lopez presented his group’s findings at the American Chemical Society Fall 2026 meeting during a talk Wednesday in the Division of Energy and Fuels.
Dry electrode processing involves mixing metal oxide particles with a binder, usually polytetrafluoroethylene (PTFE), and conductive carbon and pressing the mixture onto metal foils. “You sort of make this Play-Doh and then run it through big rollers, and it comes out as a sheet, like making pasta,” Lopez said.
A scanning electron micrograph shows polytetrafluoroethylene (PTFE) threads holding together metal oxide cathode particles that are coated with graphene. The coating procedure enables electrodes to be processed without solvent and requires very little PTFE binder. Credit:
Jeffrey Lopez/Northwestern University
Compared with wet processing, the dry method allows you to make thicker electrodes with more charge-storing material and therefore higher energy density. But the lack of solvent presents a challenge. The solvent in wet processing helps the chains of the binder polymer to stretch and bind the cathode materials to the metal foil. Without solvent, the polymer chains need other energy inputs to expand, Lopez said.
So the team covered the surface of the metal oxide particles, “which look like meatballs,” with graphene sheets—much like “papier-mâché-ing a balloon,” Lopez said. The monolayer graphene changes the surface energy and helps the particles interact strongly with the PTFE so that the binder and carbon are better dispersed to coat the metal foils evenly with as little as 0.1 wt % binder, leading to cathodes with a capacity of 10 mAh/cm2. That’s almost three times the capacity of typical commercial cells, Lopez said.
The improved binder dispersion also cuts the electrode’s resistance to the flow of ions by half, he said, which should allow for fast charging and high power output. And while the graphene coating easily allows lithium ions through, it protects the electrolyte from getting degraded by the catalyzing nickel oxide in the cathode particles.
Sang-Young Lee, a chemical engineer and battery expert at Yonsei University, said that “since graphene is one of the lowest-friction solid-state lubricants, it outperforms other surface modification strategies in the context of dry coating.” The low-friction graphene coatings should also minimize cost by reducing wear and prolonging the life of equipment, he said.
Tesla is starting to use PTFE-based dry electrode processing in some manufacturing lines, and other carmakers also plan to switch. Lopez said the new work should inform how industry optimizes dry electrodes in the future.
He and his team are also exploring fluorine-free binder alternatives to replace PTFE. “We’ve started playing with polyethylene derivatives,” specifically an ethylene-methacrylic acid ionomer, he said. “The push towards PTFE-free is really tough, but it’s a really exciting thing to work on.”
Prachi Patel is a senior editor and physical sciences reporter at C&EN based in Pittsburgh.
