We present several approaches to produce electrodes and separators by extrusion. State-of-the-art processes for electrode production of lithium-ion batteries start with the preparation of low viscous slurries in a batch process. The slurry will then be coated via a slot die onto thin metal foils. The coating is subsequently dried to remove the solvent and calendered to adjust the porosity. These processes involve large amounts of hazardous solvents and have a high demand for energy (drying, solvent recovery).
COLLIN has built its first electrode coating line in 1999. Since then, we have improved our machines in many ways to deliver a complete solution to produce electrodes with less or even no solvent. The mixing of the electrode material can be performed by continuous compounding of the base ingredients in a twin-screw extruder. Due to high shearing and individual screw design a good dispersion of the active material within the binder is possible.This electrode material can then be applied via extrusion coating onto the metal foil. Since extrusion can work with much higher viscosities than slot die coating the amount of solvent can be reduced dramatically. To produce a homogeneous thickness profile the die design plays an important role to create a well-defined mass-flow at the die gap. Years of experience in combination with modern simulation tools ensure good results. To further optimize the electrode’s inner structure and thickness tolerance one or more calendering steps can be performed. A drying and therefore a solvent recovery is not necessary in this electrode coating process.
To produce electrode patches a continuous extrusion is combined with a shaping tool. This tool has a cavity the size of the desired patch and gives a very precise control over the dimensions of the electrode patch.
COLLIN also builds machines to produce separator films based on mono-axially stretched polyolefin films as well as gel-like separators which already contain the electrolyte in the polymer gel.