Potential of ultrasonic time-of-flight and amplitude as the measurement for state of charge and physical changings of lithium-ion batteries

Lithium-ion battery is an electrochemical energy storage device with high reliability safety and efficiency requirements, it is necessary to obtain and evaluate the battery performance in time. In this study, ultrasound is applied as a timely measuring method for the state-of-charge (SoC) of lithium-ion battery. In experimental presentation, the ultrasonic measurement is performed on commercial pouch cell, to identify the relationship between its SoC and the ultrasonic signals. The ultrasonic time-of-flight (ToF) and amplitude are sensitive to changes in physical properties of cell's layers during charging and discharging. Analyses of ultrasonic ToF signals present that sound velocity is influenced by the cell's temperature, the charging/discharging current and voltage, as well as the changing in layered materials. Analysis of ultrasonic amplitude shows that amplitude is properly correlated with physical (volume) changing in anode and cathode layers, as a function of the SoC. This ultrasonic amplitude measurement shows the potential application as one real-time diagnostic technique for lithium-ion battery. • Time-of-flight showed to be obviously influenced by its temperature. • Ultrasonic amplitude demonstrated as potential indicator for state of charge. • Amplitude is correlated with volume changes of electrode layers in charging.