The production of battery films is subject to manufacturing tolerances of just a few microns. Micro-Epsilon offers 3D laser scanners to inspect the film edge and identify surface defects while capacitive sensors monitor the strip thickness with maximum accuracy.
The challenge in manufacturing modern batteries is to maximize their energy density, reduce their manufacturing costs and extend their useful life. To achieve these goals, sensors from Micro-Epsilon can be used throughout the entire manufacturing process. They perform various measurement tasks for machine monitoring, thickness control and quality assurance.
The revolution of previous drives has long been heralded, and the production processes are running at full speed. To increase the performance of energy storage devices while saving valuable resources, manufacturing processes are becoming increasingly complex. This requires innovative, high precision sensors that monitor the automated manufacturing processes inline.
A lithium-ion cell passes through many stations before final assembly. Production can be divided into three main process stages: electrode fabrication, cell assembly, as well as formation and aging. Sensors from Micro-Epsilon are used in all important process stages to solve various measurement tasks. Micro-Epsilon offers a wide product range with the largest variety of physical measurement methods for precise displacement and distance measurements. What makes it special is that all of Micro-Epsilon’s sensor technologies are developed, manufactured and distributed in-house. Therefore, customer-specific adjustments to the sensors can also be implemented if required.
Coating – Wet film thickness measurement of the anode and cathode materials
In the coating process, the film is coated either continuously or intermittently and over a width of up to 1000 mm. Important factors are the film and coating thickness, surface quality, cleanliness and avoidance of gas inclusions. To monitor the wet film thickness of the anode and cathode materials, an accuracy of <±1 μm is required at 150 to 500 µm object thickness. For this measurement task, it is recommended to use the thicknessGAUGE, which is an inline measuring system consisting of a linear unit with electromechanical drive, two confocal chromatic distance sensors, an automatic calibration unit and a multi-touch panel IPC. The confocal sensors measure the material surface from two sides using the differential method. Based on automatic calibration with a reference target, the distance between the two sensors is determined at regular intervals. In measuring mode, the two sensors each detect the distance to the material surface. The material thickness is calculated from the known distance between the two sensors and the distance values. Thanks to the high resolution of the confocal sensors, they reliably detect even the slightest deviations. The high precision of ±0.25 µm and the measuring rate of up to 5 kHz enable fully automated thickness measurement. Using the linear axis to move the thicknessGAUGE over the strip allows the complete transverse profile to be determined.
Following the coating process, the coated aluminum or copper film passes through the drying process. The drying speed is up to 100 m/min at 80 to 160 °C. After drying the anode and cathode materials, a thickness test is necessary for quality assurance. The required accuracy is 1 µm for a target thickness of 75 to 400 µm. Both confocal chromatic and capacitive sensors from Micro-Epsilon are particularly suitable for this measurement task. The sensors are optimized for industrial requirements, extremely compact and deliver the highest accuracy in the submicrometer range regardless of whether the surface is glossy or matt.
Confocal chromatic sensors offer modern technology allied with high speed and maximum precision. Micro-Epsilon’s versatile product range of confocal chromatic sensors is unique. They solve fast distance and displacement measurements reliably, without making contact or wear. Thanks to powerful controllers and precise sensors, the smallest details and structures on almost all surfaces can be measured with high accuracy. High-precision measurements are possible on reflective surfaces such as highly polished metals or liquids, on matt surfaces such as graphite and cathode materials (lithium/manganese/cobalt/nickel mixture), and on transparent materials such as glass or plastic plates. Due to the very fast exposure time control, the confocalDT system measures reliably even when the material changes from matt to glossy and vice versa.
Calendering – Roller gap measurement with calenders
Calenders are used to compact battery cell materials, such as electrode films for lithium-ion batteries. Two adjustable rolls ensure that the material mixture is rolled to the specified thickness. For consistent quality, the roller gap must be monitored continuously and with micrometer precision. Capacitive sensors from Micro-Epsilon ensure compliance with the extremely low tolerances. The sensor measures at a 90° angle to the roller.
Thanks to their innovative technology, capacitive sensors from Micro-Epsilon provide measurement values down to the submicrometer range even at extreme temperatures. They are suitable for operating conditions ranging from ultra-low temperatures, to clean rooms or ultra-high vacuums and industrial environments. Capacitive sensors from Micro-Epsilon also provide long-term stability as there are no integrated components that could reduce the service life. Another strength is the combination variety. Each capacitive sensor can be operated with any Micro-Epsilon controller without requiring any complex calibration.
Cutting – Edge curvature after cutting
In this manufacturing stage, a coated parent coil is cut into several daughter rolls. This is done either by laser cutting or with a rotating knife. After slitting, curvatures and deformations often appear on the film. However, clean cut edges are crucial for high quality. Therefore, the edge curvature must be checked, which is why the edge profile is measured to micrometer accuracy. For this purpose, scanCONTROL laser profile scanners are used. These are placed over the edge of the film and continuously record the profile. Due to their extremely high resolution and insensitivity to reflecting surfaces, these sensors provide stable measurement results and highly accurate 2D profiles, from which 3D point clouds can also be generated. These compact sensors can also be integrated into confined installation spaces.
Formation – Monitoring the temperature distribution
Charging and discharging the battery the first few times happens in the so-called formation stage. Especially during initial charging, temperature development is a decisive parameter and is therefore monitored using thermal imaging cameras. These provide an insight into the temperature distribution and possible short circuits. The thermoIMAGER thermal imaging camera is designed for demanding industrial serial applications. The lenses are focused via the integrated motorized focus, which means that even small measuring ranges can be resolved. Thanks to the powerful software, hot and cold spots can be monitored automatically. The camera is able to focus on and monitor up to three measuring fields simultaneously on a continuous basis. The integrated motorized focus enables convenient remote focusing. Measurement values can be transmitted to a controller, which in the event that limit values are exceeded, can trigger subsequent actions such as alarms, cooling or switching off. The compact and robust thermoIMAGER TIM thermal imaging camera is designed for industrial use. Commissioning is easy via the TIM Connect software included in the scope of supply. You can output measured values via Ethernet or a process interface (4-20 mA). No additional PC is required for operation in autonomous mode.
Micro-Epsilon offers precise sensors and measuring systems that perform in a wide range of measurement tasks for the many different manufacturing processes for electrodes, battery cells and battery modules. Benefit from a unique combination of application know how and a wide product range of high precision measuring devices provided by one single source!
Author:
MICRO-EPSILON MESSTECHNIK GmbH & Co. KG
Franz Hochwimmer, Battery expert for system technology
Michael Kuran, Battery expert for sensor technology
Koenigbacher Str. 15,
94496 Ortenburg
Germany
Phone: +49 8542 168 0
www.micro-epsilon.com
info@micro-epsilon.com
