Exploring Inductive Behavior of Lithium-Ion Batteries in the High-Frequency Domain : Using Physical Modeling and Simulation

Sammanfattning

In recent years, lithium-ion batteries (LIBs) have become the most popular battery type for various industries and applications, ranging from small electronics in the home to the automotive industry. With this increase in use comes a need for better understanding; the thesis investigates how the inductance, a measurement of the resistance to current change, is affected by the frequency of the current in the high-frequency domain (1 kHz – 1 MHz). Furthermore, methods to model the inductance are explored, and some dependence on the battery's geometry and the measurement setup were also investigated. Studies from other researchers were gathered and used to explain the inductive behavior. Both numerical methods and simulation using an equivalent circuit model (ECM) were employed to model the inductive behavior and evaluate which model works best. The results were compared to measurements taken from a battery cell to verify the models. The largest contributor to inductance within the investigated frequency range was the current traveling radially through the battery at higher frequencies instead of along the LIB plates as in lower frequencies. The study also revealed that tab positions influence inductance, with the lowest inductance observed when tabs are positioned at the same end of the LIB. The measurement setup can significantly impact the measured inductance if caution is not taken, with one impact being the connection wires' inductance. Finally, comparing the numerical simulation and the ECM results showed that the ECM was more accurate in predicting the inductance at higher frequencies. Moreover, the results from the ECM were more consistent with the measurements than those from the numerical simulation.