In Situ Mapping of State of Charge of Lithium-ion Battery by Quasi-Static Components of Guided Wave

Abstract

Accurately probing the interaction mechanism between acoustic signals and the state of charge (SOC) in lithium-ion batteries (LIBs) is challenging. This study introduces a novel method based on the quasi-static component of nonlinear guided waves (QSC-NGW) to reveal the evolution of electrode materials during LIB charging and discharging. Utilizing an empirical formula and phase-reversal technique, the method successfully captures high signal-to-noise ratio (SNR) QSC-NGW signals within LIBs. This approach effectively establishes a mapping relationship between the time-frequency domain eigenparameters of the signal and the battery's SOC. Subsequent in-situ characterization techniques, including scanning electron microscopy (SEM), enabled the observation of lithium-ion deintercalation processes within the electrodes. This facilitated precise identification of electrode surface structural evolution and direct extraction of mechanical property variations. These findings corroborate the efficacy of the QSC-NGW method. Compared to conventional linear acoustic techniques for extracting battery state parameters, the QSC-NGW method exhibits superior directivity and strong interpretability. Crucially, it eliminates the need for prior prediction of internal battery material parameters or the construction of complex guided wave dispersion models. The integration of the QSC-NGW method with in-situ characterization effectively captures SOC changes during cycling, demonstrating its broad application potential.