Inline Thickness Measurement of Coatings on Battery Foils

Battery foils are the main components in lithium-ion battery cells. The continuous monitoring of material parameters – layer thickness and conductivity – is crucial for product quality. We use our terahertz measurement technology to monitor them inline during production. The measurements are carried out inline on single- and multi-layer coatings at various points in the wet or dry process – always contact-free and non-destructive.

Lithium batteries – used in electric vehicles and large battery storage systems – consist of anode and cathode foils that must have different properties depending on their function. Measuring these properties, in particular the conductivity and layer thickness, is essential in the development and production of efficient batteries in terms of energy density and longevity.

Cathodes are characterized by low conductivity. Anodes, on the other hand, have a significantly higher conductivity, which makes them more difficult to measure. Nevertheless, with our photonic terahertz FMCW systems, which have been specially optimized for this application, we are able to generate precise information about the several 10 μm thick foils.

New Sensor Technology Provides Flexibility

Our terahertz technology measures in reflection and thus directly records the thickness of the coating; it takes less than five milliseconds to perform a measurement. The new sensor technology can be flexibly adapted to the respective task in terms of the number and position of the measuring heads and the measuring frequency. Optimization for frequencies between 50 GHz and 1 THz, frequency stabilization through improved driver electronics and adapted signal processing enables precise thickness measurements on thin, highly absorbent and electrically conductive layers.

The inline-capable systems, with measurement speeds of up to 1000 points per second, are also scalable in terms of the number and position of the measuring heads. Their usability with reproducibilities of better than 1 μm has been demonstrated on a wide range of samples and in a pilot plant.

Advantages of our Measurements  

  • Anodes and cathodes can be measured
  • Can be used in both wet and dry processes
  • Continuous monitoring of production
  • Ensure product quality

Technical Specifications  

  • Contactless and non-destructive
  • Measuring range from 10 μm to 300 μm
  • Measurement rate up to 1 kHz
  • Reproducibility better than 1 μm