Operando 2D Acoustic Characterization of Lithium-Ion Battery Spatial Dynamics

Spatially sensitive operando characterization techniques provide fundamental insights into dynamic and complex electrode phase behaviors of electrochemical cells during operation. However, real-time characterization of cell-level phase behavior during fast-charging has primarily been limited to synchrotron tools. We demonstrate a significant advance in the use of acoustic characterization for batteries by enabling spatially resolved operando scanning to detect local variations in phase behavior for the entire cell area during charging at all practical rates. Amplitude attenuation during fast-charge is shown to arise from localized lithium metal plating near the welded tab locations. Differential amplitude analysis takes advantage of the electrochemical-mechanical coupling of graphite staging dynamics to visualize the varying extent of graphite lithiation at different locations on the pouch cell. These time-domain modalities are coupled with frequency-domain images from Fourier transforms. Analyzing anode-free lithium metal pouch cells demonstrates that rapid and spatially heterogeneous attenuation in suboptimal electrolytes is because of electrolyte consumption initiating from electrode edges after deposition of an initial porous layer.