A Hot Rolling Press with Rubber Rollers (often referred to as a "Soft-Nip" calender or laminator) serves a very different purpose than the high-pressure steel-on-steel calendering used for densification.

Rubber or polymer-coated rollers provide a "conformable" nip. This is essential when you are laminating materials with slightly different thicknesses or surface textures. (1) Uniform Pressure Distribution: Unlike rigid steel, a rubber roller deforms slightly around the material. This ensures that a thin ion-exchange membrane is pressed evenly against an electrode, even if there are microscopic "valleys" in the slurry coating. (2) Surface Protection: If you are laminating a delicate separator or a solid-state electrolyte layer, rubber rollers prevent "pinholing" or mechanical crushing that can occur with high-pressure steel. (3) Bubble Removal: In R2R lamination, the "soft" contact helps "squeeze" out air pockets between layers, which is critical for maintaining low interfacial resistance.

References:

M. Yokota, et al., Effect of roll press on consolidation and electric/ionic-path formation of electrodes for all-solid-state battery, Journal of Power Sources Advances, 2021, 12, 100078

R. A. Altmaier, et al.,High-Linear-Energy Layered Fiber Batteries Using Roll-to-Roll Lamination and Laser Cutting, Adv. Mater. Technology, 2024, 9, 2400417.