James R. Wilson, J. Scott Cronin, Scott A. Barnett, and Stephen J. Harris, “Measurement of 3-dimensional microstructure in a LiCoO2 positive electrode”
LiCoO2 Particle #1 in 3 dimensions (3D) with a Focused Ion Beam (FIB)
A 3D image of the entire LiCoO2 particle.
In this research on lithium battery durability, a three-dimensional serial-sectioning FIB-SEM (Focused Ion Beam-Scanning Electron Microscope) technique was used to reconstruct the microstructure of a fresh LiCoO2 positive electrode from a commercial Li-ion battery. Quantitative analyses revealed highly irregular particle shapes that included significant internal cracking, leading to reduced average Li diffusion lengths and higher surface areas than would be expected from spherical particles with the same volume fraction. Such internal cracks are often associated with battery aging, degradation, and failure. The cracks and grain boundaries observed with the focused ion beam could provide important routes for Li transport within the particles, in which case the commonly used shrinking core model would not be valid. We note that fractured particles usually are not associated with unused batteries, but we expect that changes in the microstructure can lead to lithium battery aging, degradation, and failure.