*2.2. Measurement Procedure*

The cylindrical Li-ion battery cell is subjected to the same measurement procedure at each position around the circumference. An ACT0550 battery tester from PEC Corp. (Leuven, Belgium) is used to cycle the battery cell. The battery cell tester can provide currents up to 50 A per channel and apply a voltage of 5 V maximum. All measurements are performed in a climatic chamber of Memmert GmbH & Co. KG (Schwabach, Germany) at a temperature of *T* = 25 ◦C. To investigate the effect of temperature, a temperature sensor PT100 is attached to the outside of the cell and connected to the battery tester.

The cell is always clamped in the cell holder with the position to be examined facing upwards. The battery cell is first fully charged with a current of *I* = 1C (1C ≡ 2.85 A) and also fully discharged again with *I* = 1C in the voltage range of 2.5 V ≤ *U* ≤ 4.2 V. Charge and discharge period consist of a CC phase and a CV phase as listed in Table 2. The termination criterion for the CV phase is when the current drops below 1/100 C, which corresponds to a current of *I*lim = 28.5 mA. For the following investigations, only this one current rate is used. Willenberg et al. [9] showed that expansions also occur at lower current strengths. The influence of the current strength on the uniformity of the expansion has yet to be shown in subsequent work.

The cell is rotated manually by α = 10◦ after each charge and discharge cycle and measured again. During the measurement, voltage, current, and temperature are logged with one data point per second, averaged from the last 1000 recorded values at a frequency of *f* = 1000 Hz. After a total of 36 cycles, the individual positions can be compared with each other.


**Table 2.** Consistent measurement procedure for each measured position around the circumference of the battery cell.
