Measuring active material compaction
Using the new LVDT distance add-on for the CompreCell, stress/strain curves (right) could be recorded for two high-nickel content NMC samples (one polycrystalline and one single crystal) as they were being pressed in the CompreDrive.
The mechanical properties under applied stress are important both from a processability perspective (calendering etc.) and for the performance of the battery cell. Particle cracking is one of the main degradation pathways, limiting the cycle life.
Disentangling ionic and electronic conductivity
Electrochemical impedance spectroscopy (EIS) was performed on the pure, pristine NMC samples at a range of temperatures and pressures. The single crystal sample spectra exhibited semicircles that allowed distinguishing the electronic from the ionic conductivity (left, middle). The polycrystalline sample, on the other hand, displayed purely resistive/inductive behaviour at room temperature (left, top). At lower temperatures, however, the spectra transitioned to a semicircle, as the ionic conductivity was shifted into the recorded frequency range.
Being able to measure the sample thickness in situ is crucial for obtaining valid conductivity data under pressure. The sample thickness measured at each pressure and temperature was used to calculate the ionic and electronic conductivity from the spectrum fits (left, bottom, single crystal, -30°C).
In collaboration with BASF
The NMC samples analysed here were provided by BASF. A big thank you to Dr. Holger Schneider for the productive discussions in this project!
Read all the details in the application note below!
To cite this application note, please use: “C. Folkers-Karlsson, rhd instruments GmbH & Co. KG, Application Note: Mechanical and Electrical Characterization of Cathode Active Material, February 2026, https://rhd-instruments.de/magazine/cathode-active-material-stress-strain-behaviour-and-electronic-ionic-conductivity”.