Nanoscale optical imaging of lithium-ion distribution on a LiCoO2 cathode surface

Nanoscale analysis of the local lithium-ion concentration in lithium-ion battery cathode materials is essential for achieving high-performance batteries. We developed a near-field optical technique to visualize the lithium-ion distribution in a lithium-ion battery cathode on a nanometer scale. A plasmonic metallic tip was employed to locally enhance and probe the electric field in close proximity to the LiCoO2 thin film, since it is correlated with the lithium-ion concentration at the surface. We also utilized this technique to map the electrochemically induced ion diffusion at the grain boundaries under the application of a DC voltage to the surface through the plasmonic metallic tip. (C) 2017 The Japan Society of Applied Physics