Calendering

In the calednaring process the dried anode and cathode are run separately between rollers to compress the active layer. This brings the thickness and porosity to a given dimension.

Fundamentally this impacts:

  • porosity
  • adhesion
  • thickness
  • wettability
  • charge transport
  • homogeneity of the coatings

Get the calendering correct and it will improve: volumetric energy density, cyclic stability, rate capability of the cells and also enhance the structural stability of the active material.

In the calendering process we have to note the impact on the electrodes:

  • Aluminium electrodes typically elongate by around 1% after calendaring.
  • Copper electrodes don’t elongate during the calendaring.
cell manufacture schematic

Cell Manufacturing Process is broken down into 3 sections:

  1. Electrode Manufacturing
  2. Cell Assembly
  3. Cell Finishing

In total there are 14 steps in the cell assembly process.

Modelling

Meyer et al [2] looked at the calendering process and the compaction of a graphite anode and NMC cathode. They found that on the basis of the measured porosity reduction the compaction behavior of the line load was describable by an exponential model equation.

calendering process and modelling the compaction
Meyer et al [2]

Quality Control

Get the parameters right and the calendering process improves the cell, get the parameters wrong and the cell quality will be questionable. Thus it is really important to make the right measurements and control the process.

References

  1. Mozaffar Abdollahifar, Heather Cavers, Sören Scheffler, Alexander Diener, Mark Lippke,and Arno Kwade, Insights into Influencing Electrode Calendering on theBattery Performance, Advanced Energy Materials, Volume 13, Issue 40, October 27, 2023
  2. Chris Meyer, Henrike Bockholt, Wolfgang Haselrieder, Arno Kwade, Characterization of the calendering process for compaction of electrodes for lithium-ion batteries, Journal of Materials Processing Technology, Volume 249, 2017, Pages 172-178