Second-harmonic electron paramagnetic resonance spectroscopy and imaging reveal metallic lithium depositions in Li-ion batteries

Correlative Electron Paramagnetic Resonance Imaging and Atomic Force Microscopy of Lithium Deposited on Copper

Anode free concepts are gaining traction in battery research. To improve cyclability, a better understanding of the deposition processes and morphologies is necessary. Correlative experiments enable a link between a variety of properties obtained, such as chemical, mechanical or electrochemical data. Here, electron paramagnetic resonance imaging (EPRI) is correlated with atomic force microscopy (AFM) to gain a deeper understanding of the microscopic topography and local stiffness at different intensities of the lithium selective EPRI map. Experiments were carried out on a sample of lithium deposited on copper foil from standard battery electrolyte. The correlation of both methods reveals that EPRI has a high sensitivity towards small lithium structures, while bulk lithium was not detected. The results demonstrate that EPRI can be used for prescreening to identify regions with different properties, which can then be analysed individually by AFM.