Development of an All Kapton-Based Thin-Film Thermocouple Matrix for In Situ Temperature Measurement in a Lithium Ion Pouch Cell

Based on the design of a lithium ion battery cell and the resulting thermophysical properties, considerable temperature gradients may form within the cell not only during abusive scenarios. While the temperature gradients during normal operation are mostly negligible for small cells, which are commonly employed in mobile applications, the discrepancy between the temperature inside a battery cell and the cell´s surface can be significant for larger scaled cells, which are employed, e.g., in automotive applications. Battery management systems that rely on a monitoring of the cell´s surface temperature may consequently lead to an unfavorable operation of the whole battery in terms of aging and safety aspects. Thus, we hereby present an approach of designing, producing, and incorporating an all Kapton-based temperature sensor for an in situ temperature monitoring of lithium ion pouch cells. First prototypes are developed as a proof of concept when using a common potential for a thermocouple matrix that will later allow for a spatially resolved temperature monitoring within a lithium ion pouch cell. The interactions between the sensor and the cell are investigated and further design steps for improvements in functionality are elaborated.