A look at hot versus cold roll calendering, why we might use hot vs cold and impact on electrodes.
This post has been built based on the support of and sponsorship from: Resonate Testing Ltd, Quarto Technical Services, Eatron Technologies and About:Energy
- Hot roll calendering provides higher energy density and adhesion by increasing compaction and removing moisture
- Cold roll calendering is better for thermally sensitive materials, eg Lithium Sulfur
The quality and repeatability of the resultant cells will also be dependent on the uniformity of the roll temperature.
The optimal calendering conditions, including roll temperature, depend fundamentally on the specific active material morphology, hence:
- structure
- density
- particle size distribution
- binder type
- mass loading
Since the calendering condition for every electrode must be optimized no universal conclusion or optimal temperature can be provided for a general material.
Calender Roll Temperature versus Chemistry
So what is the optimum calender roll temperature versus chemistry? We looked at a number of papers to offer an initial roll temperature and reasoning behind it. This is not extensive and as we have seen there are a number of other aspects that need to be considered such as energy use, LCA and capital investment.
NMC, LFP, Sodium Ion and Lithium Sulfur are all considered.
Manufacturing Cost
As the roll temperature is increased the manufacturing thermal energy requirement will increase, but the compaction resistance of the material decreases and hence the mechanical line forces decrease. Overall the quality of the active coated electrodes will improve and hence the waste should reduce. Hence the overall impact on the manufacturing cost is complex.
The capital cost of the calendering rolls will increase as they are more complex to design and require more component parts and supporting systems.
References
- Lippke, M.; Meister, J.; Schilde, C.; Kwade, A. Preheating of Lithium-Ion Battery Electrodes as Basis for Heated Calendering—A Numerical Approach. Processes 2022, 10, 1667