(Invited) In Situ Investigation of Interface Evolution and Chemo-Mechanics in Batteries

Abstract

It is critical to understand how energy storage materials transform and degrade within devices to enable the development of next-generation batteries. In my research group, multi-scale in situ techniques are used to reveal reaction mechanisms and interfacial transformations in battery materials. In this talk, I will first present our recent work on understanding and controlling transformations at interfaces between solid-state electrolytes and lithium electrodes within solid-state batteries, where we use interlinked in situ investigations to investigate how these interfacial transformations control chemo-mechanical degradation. In situ X-ray tomography experiments of operating NASICON-based cells reveal that the growth of the interphase causes fracture of the SSE, and quantification of the crack network shows that the extent of fracture with time is directly correlated to impedance increases within the cell. In situ transmission electron microscopy (TEM) shows that the reaction of LAGP with lithium is similar to a conversion reaction, in which lithium insertion causes amorphization and volume expansion of ~130%. The use of structured alloy anodes is shown to be effective for controlling degradation and improving cycle life. Finally, I will discuss results on understanding how chemo-mechanics controls the transformation process of nanocrystal-based battery anodes. Specifically, sufficiently small antimony nanocrystals with native oxide are found to undergo spontaneous and reversible hollowing during delithiation, and this process is found to be driven by the energetic balance between void formation and oxide shell buckling. Together, these findings show the importance of controlling chemo-mechanics in next-generation battery materials, with in situ experiments being critical for understanding these processes.