Manuel Rubio Gomez

Temperature monitoring of Lithium-Ion Batteries (LIBs) and Sodium-Ion Batteries (SIBs) is essential for safe operation, as excessive temperature can trigger a Thermal Runaway (TR) event. Although surface temperature sensors have traditionally been used, their limitations have led to the exploration of alternative methods. Notably, estimating temperature based on pulse resistance (RDC) has emerged as a promising approach. Nonetheless, this method has not yet been investigated at temperatures exceeding the cell’s safety specifications, highlighting a research gap for its application in TR early detection. In this study, the RDC-temperature relationship was characterized at temperatures exceeding the cell’s safety limits for two different LIB technologies and a SIB. The results revealed a turning point in the RDC-temperature relationship between 60 °C and 70 °C for both LIB technologies and at approximately 110 °C for the SIB. From this turning point, RDC increases with increasing temperature. This contradicts the loss of sensitivity of RDC to temperature variations predicted by the Arrhenius model at temperatures typically encountered during a TR event. Finally, a novel TR early detection approach based on the characterized RDC behavior during a TR event is proposed. The strength of the method lies in the combination of two monitored RDC properties changing during TR.

This study presents a method to analyze the electrical resistance of planar contacts. The method can determine whether the contact resistance of the joint exhibits linear or non-linear behavior. By analyzing the current distribution over a planar contact, it can be determined whether an area-based contact resistance is justified or if other parameters define the contact resistance. Additionally, a quantitative evaluation of the factors that affect the measurement accuracy, including the positioning, the measurement equipment used, and the influence of the current injection on the sense pin was conducted. Based on these findings, the electrical contact resistance and the mechanical ultimate tensile force of a silver-filled epoxy-based adhesive are analyzed and discussed. The layer thickness and the lap joint length were varied. Overall, the investigated adhesive shows a low contact resistance and high mechanical strength of the same magnitude as that of well-established joining techniques, such as welding, press connections, and soldering. In addition to evaluating the mechanical and electrical properties, the electric conductive adhesive underwent an economic assessment. This analysis revealed that the material costs of the adhesive significantly contribute to the overall connection costs. Consequently, the effective costs in mass production are higher than those associated with laser beam welding.