Li-ion batteries consist of current collector foils which are coated with slurries containing the active materials. For the cathode side of the Li-ion battery, the foil is typically aluminum, and the active material is metal oxide whereas on the anode side copper coated with graphite is commonly used. In the battery manufacturing process, the slurry is spread on the current collector surface with the technique called slot-die coating. The quality of the coating is highly dependent on the wettability between the current collector surface and the slurry. As both the surface energy of the substrate as well as the surface tension of the coating formulation play an important role in wettability, the surface tension of the slurry should be optimized to ensure optimum performance of the battery cell.
Composition of the slurries used in Li-ion battery manufacturing
Slurries used in Li-ion battery manufacturing are a mixture of active material, conductive agents, some polymeric materials, and solvents. The solvent used is organic, most typically N-methyl-2-pyrrolidone (NMP). There is, however, an increased interest in replacing the NMP with some other solvent such as DMF or even water for environmental reasons. In addition, after the deposition of the slurry on the electrode substrate, typically aluminum, a drying process is required to remove the solvent from the electrode. This is one of the most costly parts of the battery manufacturing process as it requires a significant amount of energy. If the time and temperature required for drying could be reduced, this could lead to significant savings in the process. Thus, alternative solvents are extensively searched for.
To facilitate the spreading of the slurry on the electrode surface and prevent cracking during the drying process, the surface tension of the slurry should be optimized. Any changes made to the composition of the slurry will have a potential effect on the surface tension, so it is important to measure it.
To hear more about the surface tension measurement of battery slurries, please register for the webinar through the link below.
Susanna is an Application Scientist at Biolin Scientific. In her PhD thesis, she developed fabrication methods for a new type of inorganic-organic polymers. Microfabricated polymer chips were utilized as tool for biomolecule separation in analytical chemistry.