Operando Investigation of Energy Storage Material Across Multiple Length Scale by Electron Microscopy

Lithium-ion battery is one of the most needed energy storage technologies and being used from portable electronics to electric vehicles. However, the capacity and energy density of current battery materials cannot meet the requirement for long lasting applications or long-range driving. In order to impove the performence and understand the fading mechanism of energy storage materials, various charicterizations were employed to study the working mechanism of the energy storage materials in real time. <i>In situ</i> characterization methods such as X-ray diffraction, X-ray absorption spectroscopy, coherent X-ray diffraction imaging and analytical scanning/transmission electron microscopy (S/TEM) were used to monitor materials evolution during electrochemical cycling. In the assembled battery device, the dimensions of the materials ranges from nanometers (single primary particles) to micrometers (secondary particles and some single crystal Si, Ge and ternary cathode material). The investigation at each length scale provides valuable insights about the battery materials. Electron microscopy is a versatile tool to study materials in wide range of length from atomic scale (S/TEM) to mesoscale (Scanning Electron Microscopy). We employed TEM and FIB-SEM to study structure and composition evolution of single particle Li-ion battery during electrochemical cycling. The all-solid state single particle battery was built in FIB-SEM. The morphology changes of micrometer-sized single particles during lithiation and delithiation was directly observed. The crystal structure transformation was investigated by S/TEM for fundamental understanding of how the materials fail from atomic level. The lithium dendrite evolution on electrolyte, electrodes and the mechanical contact between the electrolyte and electrodes along with electrochemical testing were studied to provide constructive solution for building battery with better performance.<br/> <i>This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, and supported by the U.S. Department of Energy, Office of Science, under Contract No. </i><i>DE-AC</i><i>02</i><i>-</i><i>06</i><i>CH</i><i>11357</i><i>.</i>