In-Line Metrology for Electrode Calendering Lines

In-line metrology is essential to battery manufacturing, particularly in the electrode calendering process. By measuring the thickness of the coatings on anode and cathode electrodes, manufacturers can ensure that their products meet the specific energy density and mechanical properties necessary for acceptance.

There are available measurement systems for battery manufacturers using various technologies, including shadow gauge and triangulation laser, to provide accurate, reliable coating thickness measurements. These measurements offer feedback for calender control systems and identify defects in the coating, such as when it is too thin, too thick, or has uniformity issues.

Overview

The calendering process is a critical step in lithium-ion battery production. The coated electrode is pressed between two large drums under high pressure during this process to reduce the mechanical thickness dimension. This step not only decreases the electrode porosity and increases the energy density but also improves mechanical characteristics such as adhesion and dimensional uniformity to fit packaging properly.

In-line metrology is also used to measure electrode coating weight. A sensor in the measurement and control system scans back and forth on the material, measuring the basis weight of the coating. This is useful in identifying defects such as coating edge defects, scratches and voids and helps to maintain coating uniformity and meet the required consistency.

In-line metrology

In-line metrology plays an essential role in battery manufacturing, particularly electrode calendering. It ensures that products meet the necessary energy density and mechanical properties while identifying defects and maintaining uniformity.

In lithium-ion battery manufacturing, a homogenous electrode thickness is critical for the overall performance and lifespan of the battery. One method used to measure electrode thickness is laser triangulation, which relies on angular reflection to determine the thickness. However, this method can be affected by diffused reflections, sensor angle changes, and color and reflectivity variations.

A newer technology, known as chromatic confocal laser technology, has been developed to overcome these issues. This method uses a white light source that is focused onto the target surface, and the reflected light is transmitted through a pinhole aperture and onto a spectrometer. This method is insensitive to diffused reflections and variations in surface conditions, roughness, and material differences, making it highly accurate with repeatability of fewer than 0.5 microns.

The measurement process is typically performed using a c-frame design, which maintains the alignment of the top and bottom measurement spots. The scanning platform allows the sensor to traverse the web as it is being made, and the measurement data can be presented in various ways, such as in heat maps and cross-sections.

In summary, the use of in-line metrology in calendering lines is essential for ensuring a homogenous thickness of the electrode during lithium-ion battery manufacturing, and chromatic confocal laser technology is highly accurate and insensitive to variations in surface conditions. The data collected can be used to automate the production process and improve the overall quality of the batteries.