Nowadays, electric vehicles, grid and renewable energy, and consumer electronic devices, use lithium-ion batteries due to their high energy density, high power density, and long-life cycles. The 2019 Nobel Prize in Chemistry award to John Goodenough, Stanley Whittingham, and Akira Yoshino proves the importance of this technology to modern society. 

Figure 1 – Common applications of lithium-ion batteries.

Lithium-ion batteries are still today a hot topic as the demand for improved batteries performance continues to rise. This demand also pushes the field to alternative technologies like solid-state batteries, lithium-air batteries, and lithium-sulphur batteries.  This post will provide an overview of the fabrication process of lithium-ion batteries and how FOM is enabling researchers worldwide to improve its performance. 

The manufacturing process of lithium-ion batteries typically involves different sequential steps and different technologies. In figure two, we show some of the principal industrial steps involved in manufacturing these batteries.

Figure 2 – Different fabrication steps of Li-ion batteries.

Slurry preparation
In the first step, slurry preparation, the slurry components (binder, active material, conductive agent, solvents, and additives) are mixed to form a uniform solution with the desired properties for the coating process.

Coating and drying
The next step is coating and drying. At this stage, the prepared slurry is coated onto the respective current collector (substrate) by slot die coating with the target wet film thickness. Current collectors are copper foils, in the case of the positive electrode, and aluminum foil for the negative electrodes.  After coating, the slurry solvents need to be removed from the substrates. Finally, the drying occurs in an oven, and a dried film is obtained.

Calendering
Two cylindrical rolls compress the electrodes (metal foil+ coated film) in the calendering step. Then, significant pressure is applied to the rolls, and the electrode thickness is reduced. Also, during this stage, the porosity is reduced, leading to an increase in density and adhesion. 

Cutting electrodes
The electrodes are then cut to the desired shape and dimension of the cells. In this step, the cut must be clean to avoid any potential cell malfunction. Common defects such as burr or dross result in separator protrusion and local electric stress. There are two main methods used to cut the electrodes, die-cutting or rotary knife. More recently, laser cutting has been introduced to provide a non-contact method, faster processing time, and higher flexibility in cell design changes.

Cell assembly
The electrodes are then stacked together with the separator in subsequent layers to form the battery in this step. The battery casing and format are defined at this stage. These include cylindrical, prismatic, button, and pouch formats. At the end of this step, the cells are ready to be filled with the electrolyte and subsequently tested.

Electrolyte filling and formation
At this stage, the electrolytes are introduced into the cell. This is a critical process as it has a direct impact on the battery performance. The filling process aims to inject the necessary amount of electrolyte into the cell in the shortest time. Typically, the voids of the cell stack are not totally filled after the first filling cycle, which requires subsequent cycles. This step is very time-consuming and can take a few weeks until a battery is ready to be completed.

As previously referred, slot die coating is a crucial coating technology in producing the electrodes for lithium-ion batteries. Although it is widely available at industrial battery production, its use at laboratory scale is still at early stages. FOM have been working with customers and partners worldwide to develop a solution that brings the industrial battery production concepts to the lab. This allows researchers to test new material formulations and coating parameters in a very short period. Furthermore, the research findings can be easily transferred to industrial production lines.

Figure 3 – FOM arcRC for battery electrode coating
Learn more about the arcRC

Our arcRC mimics industrial roll-based coating in a smaller, lab-friendly form factor.  By integrating industry-grade components and a user-friendly interface, the arcRC provides a seamless, accelerated user workflow and excellent control for coating a wide variety of active materials.  The small footprint allows the arcRC to be placed inside a glovebox to work with air-sensitive materials. In addition, the adjustable slot-die angle provides a unique control of the flow and shear of the inks/slurries.

It is an ideal solution for users aiming to bridge the gap between fundamental research and pilot-scale production, emphasizing developing roll-supported coating processes.