A robust ultrasonic characterization methodology for lithium-ion batteries on frequency-domain damping analysis

Recently, non-invasive ultrasonic-based detection has emerged as a powerful tool to estimate the state-of-charge (SOC) and state-of-health (SOH) of lithium-ion batteries with a promising accuracy and efficiency. However, the currently available non-invasive methodology is highly sensitive to experimental setups and conditions, leading to unpredictable and unstable results. To this end, from a more fundamental stress wave propagation perspective, we discover that the quantified change of ultrasonic damping can be an intrinsic physical quantity to correlate with the state-of-charge (SOC) of batteries. We employ time-harmonic waves with different frequencies to obtain the steady-state dynamic response of lithium-ion batteries at various SOCs and a quasi-periodic energy gap can be observed. A mesoscale physics-based model of lithium-ion batteries is established to explain the observed energy gap carrying the multiple reflections of ultrasonic waves within the multi-layered structure of the cell. Finally, the change of ultrasonic damping with SOC is quantified for fast and accurate SOC prediction based on the frequency-domain damping analysis. Results underpin a robust and accurate frequency-domain ultrasonic characterization methodology for batteries and highlight the promise of the fundamental understanding of wave propagation for advanced characterization of batteries. • Continuous waves are input as incident signals to conduct in-situ ultrasonic tests. • The wave dissipation mechanism through the pouch cell is revealed. • A meso-scale analytical model of the pouch cell is established. • An acoustic-based methodology for battery SOC estimation is proposed.