Tracking structural evolution in lithium-ion batteries via operando scanning electron microscopy

• An operando SEM workflow has been developed, allowing high-resolution imaging at the full cell level while maintaining practical electrochemical performance. • Both reversible and irreversible changes in electrode thickness have been observed, with electrode expansion potentially mainly resulting from binder deformation. • The synergistic effects of particle cracking and the lithiation/delithiation process contribute to size changes in particle level during cycling. • The proposed workflow is applicable to both Li-ion and next-generation battery systems at cell level, offering valuable insights for battery R&D and manufacturing environment. The comprehensive understanding of structural-performance correlation of lithium-ion batteries is paramount for optimizing their performance, safety, and longevity, which are critical for applications such as portable electronics, electric vehicles, and renewable energy storage systems. Scanning Electron Microscopy (SEM) is instrumental in the examination of lithium-ion batteries, offering high-resolution imaging and detailed insights into the battery microstructure and morphology. Operando SEM analyses are invaluable as they provide precise descriptions of the dynamic phenomena and structural temporal evolution within the battery. However, the application of SEM for operando analyses is hindered by the challenges in the preparation of samples that can deliver practical electrochemical performance within the SEM environment. In this manuscript, we introduce an operando SEM workflow that enables high-resolution analysis of structural evolution in lithium-ion batteries from electrode level to particle level. The efficacy of this system and workflow is demonstrated on lithium nickel manganese cobalt oxide (NMC) and lithium titanium oxide (LTO) battery cells revealing electrode expansion and contraction, as well as grain cracking. Additionally, a graphite-lithium metal system is analyzed, where expansion and cracking of graphite grains were observed. The study delineates a procedure enabling the investigation from entire electrodes change at hundreds of micron level or even larger cell components to submicron changes at the granular level, applicable across various chemistries. We propose that this workflow can offer valuable insights for both fundamental research at the materials development level and cell structure optimization in manufacturing environments.