When manufacturing electrodes for batteries, electrode material is applied as a thin paste in a rectangular pattern to a copper or aluminum foil. The pattern is interrupted by short sections of uncoated foil, which are essential to conduct away the electrical current. For these sections, the coating process must be interrupted and restarted again and again. A particular challenge is to enable sharp edges without smearing the material at very high production speeds. Precision is the key to electrode coating: even small production errors render battery cells unusable. "Due to the high reject rate and low throughput, lithium-ion batteries are now more expensive than they should be," says Professor Wilhelm Schabel of KIT.
Doctoral student Ralf Diehm in Schabel's research group has now achieved a decisive further development. He equipped the nozzle for the electrode material with a vibrating membrane that cyclically stops and restarts the application of the coating paste. "Since this membrane is much lighter than mechanical valves, very fast reaction times and thus high speeds are possible," explains Diehm. "Previously, the manufacturing process was limited to speeds of about 30 to 40 meters per minute. With the new technology we can achieve up to 150 meters per minute for electrode coating.