Multi-scale investigation of thickness changes in a commercial pouch type lithium-ion battery

• The cathode contributes significantly to the thickness change of the battery.
• The cathode expands linearly by 1.8% with the delithiated capacity.
• The anode shows a thickness change of 5.2% within the battery's operating range.
• Structured-light 3D scanning is applied to study the displacement distribution.

The thickness change of a commercial pouch type lithium-ion battery with a graphite anode and a LiCoO2 cathode is investigated at multiple scales. The fraction of anode and cathode expansion in the total thickness change of the battery is derived by dilatometry and 1D battery displacement measurements. The LiCoO2 cathode shows a thickness change of 1.8% and the graphite anode expands by 5.2% within the battery's operating range. Both anode and cathode expansion sum up in an overall thickness change of 2.4% of the pouch battery including the nonactive material. The changes in the differential displacement curve of the battery are related to phase transitions in the graphite anode, which correlate with differential potential curves. Furthermore, the thickness change of the battery is investigated by structured-light 3D scanning. Using this contactless technique, the spatial distribution of the thickness change and the impact of the pouch packaging is visualized. The pouch foil shows to have only a small influence on the displacement distribution. In sum, the results of the applied techniques at different scales correlate well and provide a better understanding of the intercalation-induced volumetric changes in lithium-ion batteries.

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