Lithiation Diagnostics by Measuring Electrochemodynamics in Solid-State Batteries

Abstract

A significant challenge in solid-state batteries remains the need to understand and control electrochemomechanical phenomena arising from the complex interplay between electrochemical reactions and mechanical stress within the cell. In this study, we investigate the relationship between mechanical stress and lithium reaction dynamics under varied conditions, including stack pressure, substrate materials, and negative-to-positive electrode ratios. Using dual operando pressure measurements and side-view optical microscopy, we examine how these factors govern horizontally and vertically preferred lithiation. Analysis of pressure dynamics reveals that high stack pressures favor horizontally preferred reactions, minimizing vertical expansion and dendritic formation, which supports stable mechanical responses and enhances cycle life. Conversely, lower stack pressures or negative-to-positive electrode ratios below 1 induce a shift from the horizontally to vertically preferred reaction, leading to dendritic growth, uneven stress distribution, and potential short-circuit risks. This electrochemodynamic insight provides a comprehensive framework for designing durable solid-state batteries with improved safety and longevity.