Exploring electrochemical dynamics in graphite||LiNi_0.8Mn_0.1Co_0.1O₂ cells via operando ultrasound and multiprobe...

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.