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. Monitoring acoustic emissions (AEs) is a popular NDE method in structural engineering, but has not yet provided reliable assessments when applied to batteries. 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 SEM imaging, respectively. Next, we show 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 to improve metrics for state-of-health, remaining useful life, and safety risks.