Probing Interfaces in Solid-State Batteries Using Operando X-Ray Tomography

Solid-state batteries (SSBs) with lithium metal anodes offer higher energy density than conventional lithium-ion batteries, but are limited by chemo-mechanical degradation, such as non-uniform deposition through the solid-state electrolyte (SSE) during plating, contact loss during stripping, and decomposition of the SSE to form new phases. These processes occur at the Li/SSE interface, and understanding their underlying mechanisms is critical for enabling commercially viable SSBs. In this work, we used <i>operando</i> synchrotron X-ray tomography to image Li/SSE interfaces in three dimensions during cycling [1]. Leveraging the advantages of synchrotron X-rays, we were able to scan the entire SSB volume in ~7 minutes with a resolution of 1.7 µm. With ~40 scans taken over the course of a single experiment, segmentation of the 3D image datasets allowed us to quantify the amount of each phase present, which could then be linked to the electrochemistry to determine how material changes impacted performance. We found that severe decomposition occurred at the interface due to the electrochemical incompatibility of the SSE (Li₁₀SnP₂S₁₂) with lithium metal, which prevented lithium deposition in favor of side reactions. Additionally, we were able to detect the formation of voids at the Li/SSE interface during lithium stripping. Analysis of these electrochemically formed voids allowed us to reconstruct the contact area of the entire Li/SSE interface at different stages of the experiment. Ultimately, we found that the significant loss of contact during stripping was the cause of cell failure in this experiment, with degradation being exacerbated by current constriction effects that resulted from large contact spots being broken up into smaller, isolated spots.<br/> <br/>[1] J. A. Lewis, F. J. Q. Cortes, Y. Liu, J. C. Miers, A. Verma, B. S. Vishnugopi, J. Tippens, D. Prakash, T. S. Marchese, S. Y. Han, C. Lee, P. P. Shetty, H. W. Lee, P. Shevchenko, F. de Carlo, C. Saldana, P. P. Mukherjee, M. T. McDowell “Linking Void and Interphase Evolution to Electrochemistry in Solid-State Batteries Using Operando X-Ray Tomography”<i> Nat. Mater.</i>, 2021, <b>20</b>, 503–510.