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.