Scanning transmission electron microscopy techniques have enables direct visualization and quantification of the structure, chemistry and bonding of interfaces, reconstructions, and defects. So far, most efforts in the physical sciences have focused on room temperature measurements where atomic resolution spectroscopic mapping has been demonstrated. For many materials, including those that exhibit electronic and structural phase transitions below room temperature and systems that involve liquid/solid interfaces, measurements at low temperature are required. Operating close to liquid nitrogen temperature gives access to a range of emergent electronic states in solid materials and allows us to study processes at liquid/solid interfaces immobilized by rapid freezing.
In this talk, I will discuss our approach to study two processes at the anode-electrolyte interface in lithium metal batteries (LMBs), uneven deposition of lithium metal leading to dendrite growth and the breakdown of electrolyte to form a “solid-electrolyte interphase” (SEI) layer, processes which result in capacity fade and safety hazards. By combining cryo-electron microscopy with cryo-FIB lift out, we provide nanoscale compositional information about intact SEI layers in cycled LMBs and track local bonding states at interfaces, leading to new insights into SEI and dendrite formation (Figure right).
We further demonstrate sub-Å resolution imaging of crystalline solids at cryogenic temperature, and map the nature and evolution of incommensurate charge order in a manganites. We measure picometer-scale displacive modulations of the cations, distinct from existing manganite charge-order models, and reveal temperature-dependent phase inhomogeneities in the modulations, such as shear deformations and topological defects. At temperatures well below T c phase coherence emerges (Figure left). Using cryo- STEM, the role of the lattice in a variety of low temperature electronic phases can now be quantified with high resolution and precision.