4D-STEM Imaging of The Evolution and Performance Relevance of Microstructures in Cathode Nanoparticles

In this talk, I will discuss our recent efforts on utilizing four-dimensional scanning transmission electron microscopy (4D-STEM) to image the microstructures in cathode nanoparticles in rechargeable multivalent-ion batteries. We use metal oxide nanoparticles, either single-crystalline or defect-laden ones, as the cathodes, which undergo electrochemically driven phase transformation during charge and discharge cycles. The phase transformation induces the emergence of complex microstructures in the nanoparticles, such as phase orientation domains, domain boundaries, and defects such as stacking faults and dislocations. These microstructures ultimately change the energy barriers associated with ion diffusivity, the capacity, and cyclability of the battery systems. Our work demonstrates the prospect of “microstructure” engineering in energy storage materials, where spatiotemporal heterogeneity from the atomic to the nanoscale can impact macroscopic performances.