While developing battery cells, the achievement of fast-charging capability is heavily dependent on avoiding metallic plating on the anode surface (i.e., lithium plating in lithium-ion cells). However, this objective hinges on the effectiveness of plating detection. Currently, measurement techniques are either inadequate in providing spatial, temporal, or causal information, incur high costs when employing, e.g., neutron imaging, or are lengthy due to destructive post-mortem examinations that additionally lack operando data. In this work, we demonstrate an ultrasound imaging method for operando visualization of the interior of a multi-layer pouch battery cell. Here we show that this method can non-invasively visualize the formation and stripping of lithium plating during cycling. Extensive reference electrode studies and ex-situ analysis verify the effectiveness of our method for plating detection. Ultimately, this work enables researchers and industry to significantly accelerate the development of new cell technologies and their optimized utilization.

Ultrasound techniques are increasingly used to probe the internal dynamics of batteries to obtain cost-effective, real-time insights into electrochemical processes. However, prior studies have established only superficial correlations between ultrasound and electrochemical parameters, thus limiting the understanding of signal variations during cycling. In this study, the interpretability of these variations is improved by combining operando ultrasound measurements with synchrotron X-ray diffraction and nanodilatometry measurements during electrochemical cycling and relaxation. We show that at battery states of charge from 10% to 80%, ultrasound signals reflect primarily the change in the graphite electrode, particularly its elastic modulus during lithiation. At battery states of charge between 80% and 100%, the H2 → H3 phase transition in LiNi_0.8Mn_0.1Co_0.1O₂ affects the ultrasound signal. This multimodal approach enhances the understanding of how mechanical and structural battery dynamics influence ultrasound signals, thus marking a step forward in the interpretation of acoustic data in commercial cells via advanced synchrotron techniques.

Active dissipative balancing systems are essential in battery systems, particularly for compensating the leakage current differences in battery cells. This study focuses on using balancing resistors to stimulate battery cells for impedance measurement. The value of impedance spectroscopy for in-depth battery cell diagnostics, such as temperature or aging, is currently being demonstrated and recognized by vehicle manufacturers, chip producers, and academia. Our research systematically explores the feasibility of using existing balancing resistors in battery management systems and identifies potential limitations. Here we propose a formula to minimize hardware requirements through signal processing techniques. A quadrupling of the sampling rate, number of averaging values, or the size of the fast Fourier transform is equivalent, concerning the signal-to-noise ratio, to increasing the analog resolution by one bit or reducing the input filter bandwidth by a quarter.