  Ion transport across solid solid interfaces is often slower than through the
bulk of a material, impeding the charge and discharge rate of batteries.
Designing highly conductive interfaces is challenging due to the need to probe
ion conduction at individual interfaces and correlate it with the local
structure. In this study, we address this challenge by enabling the
simultaneous measurements of local Li-dominated optical phonons and ion
distributions, using high-energy and high-spatial-resolution spectroscopy in a
scanning transmission electron microscope (STEM). Further, this method allows
for a direct correlation of ion conduction with interfacial structures
identified by STEM imaging. By examining diverse individual interfaces of
LiCoO2, we reveal the sensitivity of ion conduction to interface atomic-scale
structure and chemistry. Our method enables correlative analysis of ion
transport behavior, and atomic and band structures, and can serve as a robust
experimental approach for identifying interface structures that offer high
conductivity and cyclability for batteries.
