Quantitative Interelectrode Talk Analysis using XCT Imaging in All-Solid-State Batteries

Abstract

Understanding the dynamic interplay between mechanical, electrochemical, and morphological changes is essential for realizing high-performance lithium-metal all-solid-state batteries (ASSBs). In this study, we investigate the degradation behavior of pressure-free ASSB configurations using symmetric cells composed of Li–In alloy electrodes and Ta-doped LLZTO garnet-type solid electrolyte. High-resolution X-ray computed tomography (XCT) was employed to capture phase distribution and pore evolution in three dimensions across multiple charge/discharge cycles. Our results reveal that even lithium–indium alloy anodes, previously considered void-suppressing alternatives to lithium metal, exhibit significant pore formation under zero stack pressure. These pores predominantly emerge during lithium stripping following plating, indicating an irreversible redistribution of ionic and mechanical environments. Furthermore, we observe that the nucleation and growth of Li–In phases occur in random, non-uniform domains during alloy formation, and that interfacial depletion of Li-containing phases induces severe kinetic polarization. Digital twin-based phase segmentation allowed us to track electrode morphology and composition in a spatially resolved and quantitative manner. While the study was designed to examine interelectrode “cross-talk,” our analysis found no observable coupling effect between the two electrodes. Specifically, pore formation and phase redistribution in one electrode did not induce measurable morphological or electrochemical changes in the opposing electrode, suggesting that a 500 μm-thick solid electrolyte layer sufficiently buffers interfacial disturbances under low current conditions. This work demonstrates that even in the absence of cross-electrode interactions, Li–In alloy anodes remain vulnerable to internal morphological degradation when operated without stack pressure. These findings emphasize the need to re-evaluate alloy anode stability and interface design strategies in pressure-free ASSB architectures.