Electrochemically resolved acoustic emissions from Li-ion batteries

New methods of operando non-destructive evaluation (NDE) are needed to better assess the health and safety of Li-ion batteries. Acoustic emission (AE) testing is a widely used NDE technique in structural engineering but has yet to provide reliable assessments in battery applications. Here, we show that various electro-chemo-mechanical processes in battery electrodes (graphite and nickel-manganese-cobalt oxides [NMC]) can be reproducibly identified by electrochemically resolved AEs after eliminating electromagnetic interference and applying wavelet-based signal processing. First, we perform “acousto-voltammetry” to correlate acoustic activity with specific electrochemical processes, such as ethylene gas generation and NMC particle fracture, as confirmed by gas detection and ex situ scanning electron microscopy (SEM) imaging, respectively. Next, we demonstrate that AEs can be distinguished using wavelet-transform features. Electrochemically resolved AEs provide a new window into quantitatively monitoring battery degradation, offering insights into electro-chemo-mechanical processes and potential advantages over conventional methods for the assessing state of health, remaining useful life, and safety risks.