Keeping Track of the Latest Innovations in EV Lithium-Ion Battery Manufacturing Our expertise

The performance of electrodes is determined by the mixing uniformity. The modification based on the current hydrodynamic shear mixing (HSM) system is at present the most economical improvement of mixing efficiency and uniformity.

The use of ball milling and ultrasonic mixing can significantly increase the mixing uniformity for dry powder mixing and high-concentration slurry. The cost and reliability of large-scale mixing need to be evaluated before they can be industrialized. Besides the mixing method, the mixing sequence is also an important aspect of particle distribution.

Two key processes in electrode fabrication are coating and drying. Using an organic solvent in the slurry may help increase the drying time and recovery cost significantly. However, modifying the current drying method would not directly resolve the challenges faced.

Solvent-free manufacturing emerges as an effective method to skip the drying process and avoid the organic solvent. This technology helps to form a continuous self-supporting electrode film, which is then laminated onto the current collector and becomes the final electrode.

Another benefit of solvent-free manufacturing is the potential of making thick electrodes, which are challenging for the traditional slurry cast method due to the structure distortion after the solvent evaporation.

The vacuum drying process generates intense energy and is time consuming. The present drying method usually places the electrodes under a low-pressure environment of 60 degrees Celsius to 150 degrees Celsius and is heated for more than 12 hours. Using an inert gas supply is also an option to add to the process. However, the lower moisture level may not always lead to better electrochemistry and mechanical properties.

Recently, a fast argon-purging post-drying method at room temperature is being more widely utilized. Results show that the electrode treated with quick argon-purging showed the highest capacity for rate and cycling tests. This shows that the argon-purging method has a strong potential to replace vacuum-drying, especially with its high throughput and low energy consumption benefits.

The optimization of electrode manufacturing processes is a complex subject. It involves robust characterization of the slurry components, either in isolation or in combination with various complementary analytical techniques.

The particle size and size distribution must be balanced, as it brings together various aspects like precursor yield, electrochemical performance, solids loading, and slurry stability. All these factors will influence the overall performance of the battery.

It is also important that the synthesized material has the right chemical (elemental) composition to maintain consistent product quality, stability, and product safety. There are several widely used analytical tools used for battery characterization during the manufacturing process:

• Laser diffraction for measuring particle sizes
• Automated imaging for quantifying particle shape
• Gel permeation chromatography for characterizing binders
• X-ray diffraction to define crystal structure of electrode materials
• X-ray fluorescence for analyzing the chemical composition and detecting elemental impurities
• Micro-electrophoresis for quantifying stability and surface interactions

These analytical tools will provide users with the relevant materials information and lay the foundation for optimizing the properties of the slurry ingredients. These tools also help to meet the objective of achieving the desired electrochemical performance and high electrode manufacturing efficiency.