For high-precision electrode calendering, transitioning from simple gap-control (setting the distance between rollers) to pressure-control is the key to achieving consistent energy density and ionic conductivity. In a pressure-controlled system, the machine uses hydraulic or servo-actuators to apply a specific, measurable force (typically in metric tons) regardless of slight variations in the initial coating thickness.

When using a pressure-control press, your goal is to optimize the Packing Density (PD) = m/(A*t). Where m is the mass of active material, A is the area, and t is the post-calendering thickness. (1) 10% Rule: For most lithium-ion cathodes (NMC/LFP), aim for a thickness reduction of approximately 10–20% per pass. Attempting more can cause "spring-back" or delamination. (2) Thermal Softening: Calendering at 60-100 °C reduces the yield strength of the PVDF binder, allowing for higher density at lower pressures and reducing the risk of foil cracking. (3) Linear Pressure: In production, pressure is often reported as N/mm (force divided by the width of the electrode). Lab machines that report total "Tons" should be converted to linear pressure for academic reporting.

References:

J. Zhang, et al., Investigation on mechanical and microstructural evolution of lithium-ion battery electrode during the calendering process, Powder Technology, 2022, 409, 117828

M. Abdollahifar, et al., Insights into Influencing Electrode Calendering on the Battery Performance, Adv Energy Mater., 2023, 13, 2300973.