Quality assurance in battery production
In order for a lithium-ion battery to be competitive, it must be manufactured inexpensively, have a high energy density and last as long as possible. When manufacturing battery cells in millions of units, high quality is extremely important; because faulty production can, in extreme cases, lead to self-destruction and a fire in the battery. So above all, the battery has to be safe.

Production-integrated test systems – ideally coupled with intelligent data concepts – are increasingly becoming a central element for effective quality assurance and the associated increased cost-effectiveness in battery production. Photothermal coating thickness measurement can make an important contribution to the aspects of cost reduction, resource saving and safety for lithium-ion batteries.

Photothermal coating thickness measurement
Contactless, fast and efficient: The photothermal coating thickness measurement is a contactless measurement method for paints, powder coatings and glazes on metallic and non-metallic substrates. The different thermal properties of the coating and the substrate are used to determine the coating thickness.

The surface of the coating is warmed up by a few degrees using LED or laser light and then cools down again by dissipating the heat into deeper areas. The thinner the coating, the faster the temperature drops. The temperature curve over time is recorded with a highly sensitive infrared sensor and converted into the coating thickness.

New scanning 3D inspection method fulfils all requirements
The newly developed photothermal testing method allows endlessly long surfaces and moving objects to be tested without having to move along with the components. The new technology actively utilises the movement between the workpiece and the sensor instead of compensating for it, as is the case with conventional devices. This makes it possible for the first time to inspect objects of any length, movement and even large surfaces.

The new photothermal scanning system stands for a cost-effective, large area determination of coating thicknesses at high spatial resolution. The system is best suited for real-time monitoring of coil coating processes or for sensing wide and complex coating geometries. For the battery production process, the technology can be used for the entire process chain: From electrode production to cell housing production to module and pack production.

The scanning process, for which a patent application has been filed, means that the extent of the sample in the scanning direction is no longer limited – in principle, infinitely extended samples can be measured with high resolution. The spatial resolution is typically only a few mm. The new solution thus finds coating defects at any point in the scanned area and visualizes the result as a 3D diagram, for example.

Optimized coating thickness measurement of moving objects
While conventional systems generally only allow the measurement of moving objects by means of complex compensation and thus to a limited extent, the new method was developed and optimized for the measurement of moving objects from the outset. This applies to both the underlying measurement algorithms and the general design of the sensor. The method only requires a relative movement between the object and the sensor. In coil coating processes, for example, where the measurement object is already moving due to the process, the sensor can still be installed in a fixed position. This means that no additional motorization is required for the movement; instead, the existing infrastructure can be used.