Li-ion batteries have been used in portable devices for decades. With the increasing demand for electric vehicles, the demand for Li-ion batteries has increased both from a performance and manufacturing point of view. The major cost driver in the Li-ion battery is the materials used but the manufacturing process still represents around 25 % of the total costs. In addition, the manufacturing process comprises around 70 % of the total embedded energy in a battery cell. Optimizing the manufacturing process can thus provide significant savings both in terms of cost and energy consumption.
In the Li-ion battery manufacturing process, there are several different points where interaction between solids and liquids needs to be considered. In all of these points, the wettability plays a pivotal role.
Slurry preparation
The electrode slurry is a complex mixture of active material, conductive additive, polymer binder, and solvent. The active material in the slurry is either carbon-based (anode) or Li-metal-based (cathode). The active material needs to be properly wetted to ensure good dispersion. The surface tension of the slurry is also important as that will affect the coating of the slurry on a current collector.
Coating and drying
In the coating process, the slurry is coated on the current collector which on the anode side is copper and cathode side is aluminium. The slurry needs to wet the current collector to ensure proper adhesion between the materials. The surface tension of the slurry plays a role but also the surface free energy of the current collector is important to consider.
Calendering
Calendering is done to improve the particle contact in the electrode which will lead to higher energy density. It will, however, also decrease the wettability of the electrode. Poor wettability can cause performance issues but also affects the electrolyte filling step done later in the process.
Cutting and cell assembly
The electrodes are then diced and packed together with the separator material. A separator is a porous polymeric membrane that separates the anode from the cathode. The wettability of the separator is important as poor wettability will increase the safety risks.
Electrolyte filling
Electrolyte filling is the most time-consuming process step in Li-ion battery manufacturing. To ensure proper and fast filling of the electrolyte the wettability between the different parts of the battery needs to be considered.
To learn more about wettability measurements in Li-ion batteries, please download the white paper 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.
