In-Operando Interfacial Electrochemical-Mechanical Coupling Measurements in Thin-Film Batteries Using a Nanoindentation Platform

Solid-state batteries require stress for well-formed interfaces during fabrication and to maintain intimate contact during operation. The interaction between applied and generated stress and electrochemistry significantly impacts performance and degradation. However, accurately measuring the stress-electrochemistry coupling is challenging due to mechanically coupled and irregular interfaces, leading to non-uniform stress distributions. In this work, we use a nanoindenter to apply controlled uniaxial compressive forces to thin-film electrochemical devices and batteries that offer uniform and planar interfaces. This allows us to study the effect of stress on interfacial electrochemistry more directly, with greater quantitative accuracy and control. Using a planar cell with sputter-deposited V₂O₅ electrodes as the working electrode, a NASICON-type LATP solid electrolyte as the substrate, and a Li metal counter electrode with a PEO-LiTFSI interlayer, we can mechanically decouple the electrode interfaces. This setup enables us to measure only the in-operando stress-potential response from the V₂O₅-LATP interface. We further discuss the origins of the observed coupling and its dependence on the lithiation state of the V₂O₅ electrode.<br/><br/>References:<br/>1. Song, Y., Bhargava, B., Stewart, D. M., Talin, A. A., Rubloff, G. W., & Albertus, P. (2023). Electrochemical-mechanical coupling measurements. <i>Joule</i>, <i>7</i>(4), 652-674.<br/>2. Carmona, E. A., Wang, M. J., Song, Y., Sakamoto, J., & Albertus, P. (2021). The Effect of Mechanical State on the Equilibrium Potential of Alkali Metal/Ceramic Single Ion Conductor Systems. <i>Advanced Energy Materials</i>, <i>11</i>(29), 2101355.