Small Crystals, Big Insights: How Electron Diffraction is Transforming Materials, Life Science, and Chemistry Research #5. Revealing Atomic-Level Battery Material Structures with Electron Diffraction

Have you encountered difficult-to-determine crystal structures in battery electrode materials? Knowing the atomic-level crystal structures of battery materials is critical to understanding, and ultimately improving, battery performance. However, battery-grade electrode materials feature small particles and are often poorly crystalline, presenting major challenges for traditional crystallography. Powder diffraction is frequently employed, but often the important structural details cannot be reliably extracted from these data. Micro-ED presents an exciting opportunity in this space, as high-quality single crystal electron diffraction patterns can be collected on individual micro-crystals extracted from working battery electrodes.

Here, we demonstrate the use of micro-ED to study the structural evolution of sodium-ion battery cathode materials for next-generation inexpensive batteries. During charge and discharge, sodium-ion cathodes undergo numerous phase transitions to accommodate sodium ions being removed and added. This crystal structure evolution controls the voltage, usable capacity, and long-term stability of the battery. Subtle superstructures driven by sodium-vacancy ordering and Jahn-Teller effects are especially important, but very difficult to detect with powder X-ray diffraction. We demonstrate the utility of electron micro-ED to determine these structures. Single crystal electron diffraction patterns are collected on individual particles of battery-grade cathode materials, and used to solve sodium-vacancy orderings that were previously unsolved, helping to better understand the performance bottlenecks of sodium-ion battery cathodes.