Dielectric elastomer sensors adapted for monitoring compression load of clamped battery cells

Condition monitoring of Li-ion cells in battery packs for electric vehicles is becoming increasingly important, not only in terms of safety, but also with respect to predictive maintenance and recycling applications of the battery. Parameters already monitored by the battery management system are the pack temperature and electrical properties such as cell voltage and current flow. The compression load in a stacked battery pack, which changes not only during charging and discharging but also during aging, would provide valuable information about the health condition of the cell. This work shows the development of a dielectric elastomer sensor (DES) system especially adapted for monitoring the compression load of clamped Li-ion cells. By attaching special elastomer-based structures on both sides of an elastomer film, a thin and soft compression load sensor is realized. Various sensor configurations were investigated in order to increase the sensor performance in the required pressure range of the battery cell. The sensor design was varied by using different structures or by modifying the elastomer material or the electrodes of the intermediate elastomer film. The sensor characterization was performed by applying a controlled compression load and simultaneously recording the capacitance signals of the sensor. First cycling experiments using a sensor array in a clamped setup with the battery cell showed that the sensor capacitance depends on the compression load as the cell is charged and discharged. This result demonstrates the great potential in the field of condition monitoring of Li-ion battery cells.