Researchers from Fraunhofer Institute for Material and Beam Technology IWS have developed a new method of dry coating electrodes in a variety of batteries from lithium to sodium.
The DRYtraec solution was developed by an interdisciplinary research team at Fraunhofer IWS in Germany that focuses on the production of the battery electrodes.
The DRYtraec process uses similar raw materials as in the wet process— active material, conductive carbon and binders dispersed in a solvent to make a paste, initially applied to the metal foil— but works using a special binder instead of solvents.
The active materials form a dry mixture that is fed into a calender gap— a gap between two rollers rotating in opposite directions— but one of the rollers turns faster than the other to induce a shear force that ensures the binder forms thread-like networks known as fibrils.
The pressure and motion form a fine film on the faster-rotating roller that is transferred in a second calender gap onto a current collector foil.
This allows both sides to be coated simultaneously without significant additional work.
In the final step, the resulting coil is cut to the required size and the individual parts are stacked as appropriate in order to produce the finished battery.
The new process accelerates production and requires only one-third of the equipment space of a conventional solution, saving costs in number of ways.
Dr. Benjamin Schumm, group manager for Chemical Coating Technologies at Fraunhofer IWS, said: “The conventional coating process uses a wet chemical method that applies what is known as slurry.
“Extremely large machines with very long drying tracks are needed to ensure that the solvent will evaporate afterward. With DRYtraec, we can design this process more efficiently.”
The first prototype DRYtraec systems were commissioned as part of the “DryProTex” funding project to demonstrate it is possible to manufacture electrodes continuously, regardless of the type of battery.
Schumm said: “The range of possible uses for the technology is not limited to a particular cell chemistry.
“It could equally be used on lithium-ion cells as on lithium-sulfur or sodium-ion cells. We are even looking at solid-state batteries.
These will be increasingly important in the future, but the materials cannot tolerate wet chemical processing so DRYtraec® allows us to offer a very promising solution to this problem.”
Discussions are under-way with vehicle and cell manufacturers to plan the construction of a number of pilot systems.