Accurate monitoring of thickness changes in lithium-ion batteries during operation is essential for understanding cell swelling and its impact on performance and lifetime. This is particularly relevant for high-energy-density electrode materials such as silicon-rich anodes, which exhibit pronounced volume expansion during cycling.

In this work, two in-operando swelling measurement approaches for small-format pouch cells are compared: (1) pneumatic cell presses operating under constant force conditions and (2) a compact printed circuit board (PCB)-based system using eddy-current displacement sensors combined with a quasi-constant preload force applied through compression pads.

While pneumatic presses enable precise swelling measurements under controlled force, their size, cost, and complexity limit their widespread application. The PCB-based setup provides a compact and cost-effective alternative that enables long-term, high-resolution thickness monitoring during formation and cycling.

The system was further optimized for long-term experiments by analyzing the relaxation behavior of the compression pads and its influence on thickness measurements. In addition to applying mechanical preload, the compression pad was found to positively influence electrochemical performance, highlighting its dual role in the experimental setup.

Overall, the results demonstrate that the PCB-based system represents a practical alternative to pneumatic presses for in-operando swelling measurements of lithium-ion pouch cells.