Process stability in welding of battery cells with ultrasonics
Systems from Herrmann Ultraschalltechnik GmbH & Co. KG reduced the reject rate for CUSTOMCELLS® during the production of a new battery application and thus increased efficiency for this manufacturer.
Image 01: To ensure battery production with the lowest possible reject rates, the ultrasonic welding system must be precisely matched to the application.
As one of the world’s leading developers of customer-specific lithium-ion battery cells, CUSTOMCELLS® pursues the lowest possible reject rate in battery production with maximum process reliability. For the welding of its applications, the development and production company relies on ultrasonic technology in one of their production lines. The ultrasonic welding systems from Herrmann Ultraschall used there minimized the reject rate and optimized production efficiency.
Optimization of the reject rate
In the associated production line, CUSTOMCELLS® performs the pre-welding and main welding on pouch cells. The first step in the pre-welding process is to pre-weld the individual layers of copper foil for the anode and the individual layers of aluminum foil for the cathode. In a second step, the main welding, the so-called tabs are welded to the cathode and anode.
Both pre-welding and main welding require strong, material-to-material connections to ensure the functionality of the battery cells. If individual foil layers are not completely joined together or if there are tears in the foil, which are only a few microns thick, this can lead to rejects and then to the disposal of the entire cell.
The ultrasonic welding machines from Herrmann provide a stable process for these connections. The HiS VARIO B 20 kHz systems have been specially developed for welding battery applications with multilayer foils. They reduce production waste and production costs.
Image 02: As a particularly material-friendly joining process, ultrasonics is perfectly suited to permanently join the thin foils of the cathode and anode to the tabs in a reproducible manner.
Special battery design as a challenge
The special feature of the battery cell developed by CUSTOMCELLS® is the size of the tabs. They are significantly smaller than what is typically used in the industry. In order to ensure a reliable connection between the tab and the anode or cathode, the sonotrodes of the ultrasonic welding machines were adapted to the respective size.
Thanks to ongoing research and development work, Herrmann Ultraschall was able to draw on an existing, special sonotrode design right at the start of the project. This guaranteed a reliable welding process for the CUSTOMCELLS® battery application. After a short time, the appropriate welding parameters were also evaluated in the ultrasonic laboratory. The changeover to Herrmann welding systems could be implemented with virtually no downtime for production.
Image 03: Because of the variable size of the tabs, specially adapted sonotrodes must be used for the main weld.
Both Herrmann welding systems are permanently used for the welding of cell tabs at CUSTOMCELLS®. Within the scope of series production, the ultrasonic welding systems will be integrated into the automated production line in a next step. Ongoing consulting as well as the development of suitable welding solutions by Herrmann Ultraschall enable a smooth process integration.
Image 04: Currently still used as a manual workstation, the ultrasonic welding systems are to be integrated into CUSTOMCELLS’ automated production line in the next step.
Only by using ultrasonic welding systems that meet the demand and requirements, can reject rates in battery production be kept permanently at a low level. Flexible service by the ultrasonic partner is important for the success of a welding project in order to be able to react immediately to changes in the production process if necessary. The interaction of suitable welding solutions and good service forms the basis for safe and efficient production of battery applications with ultrasonics.
CUSTOMCELLS® is one of the leading companies in the field of development and series production of special lithium-ion battery cells. With access to a development and production facility equipped with state-of-the-art electrode and cell manufacturing machines, CUSTOMCELLS® is one of the leading manufacturers of customized battery cells. CUSTOMCELLS® supplies the German automotive industry. CUSTOMCELLS® are technology specialists in aerospace and medical technology, among others, and manufactures series products for autonomous underwater vehicles and battery units for electric aircraft.
Learn more: www.customcells.de
As a specialist in ultrasonic welding, Herrmann has aimed to excite its customers for more than 60 years. For this purpose, Herrmann Engineering was developed which includes a combination of services. It enables more than 600 employees in over 20 countries to successfully implement projects together with their customers. The company’s mission “Bonding – more than materials”, stands for a close and trusting relationship. As a result, more than 2,000 different applications in key industries such as automotive, medical, hygiene and packaging can be solved every year.