Credit: Brookhaven National Laboratory
Scanning and transmission electron micrographs of the cathode material at different magnifications. These images show that the 10-micron spheres (a) can be hollow and are composed of many smaller nanoscale particles (b). Chemical "fingerprinting" studies found that reactive nickel is preferentially located within the spheres' walls, with a protective manganese-rich layer on the outside. Studying ground up samples with intact interfaces between the nanoscale particles (c) revealed a slight offset of atoms at these interfaces that effectively creates "highways" for lithium ions to move in and out to reach the reactive nickel (d).