In Operando Nanoscale Imaging for Lithium and Sodium Intercalation Compounds

Coherent x-ray diffractive imaging (CXDI), a lensless form of microscopy capable of discerning electron density and strain with 20 nm resolution, is used to map the strain evolution of a single cathode particle in a functional battery as it is cycled in-situ. The evolution of compressive/tensile strain reveals a number of interesting phenomena. For instance, a strain front nucleates and propagates inward/outward during discharge/charge. Strain can be quantitativley correlated to the Lithium amount in the initial cycles, eventually becoming uncorrelated upon longterm cycling. We demonstrate that CXDI is a powerful diagnostic tool to reveal correlation between strain and electrochemistry at the single particle level and offers valuable information for electrode/battery modeling and future battery design. Scanning electron microsocpy and electron energy loss spectroscopy (STEM/EELS) offers unprecendented spatial resolution, which has enabled nanoscale imaging and chemical anslysis of the interfaces, ground boundaries and phase boundaries. By combinign electron based and X-ray based novel imaging techniques, we showcase the state-of-the-art diagnostic tools developed for probling functional battery materials in operando.