Bending, breaking, and reconnecting of the electrical double layers at heterogeneous electrodes

In electrochemical systems, the structure of electrical double layers (EDLs) near electrode surfaces is crucial for energy conversion and storage functions. While the electrodes in real-world systems are usually heterogeneous, to date the investigation of EDLs is mainly limited to flat model solid surfaces. To bridge this gap, here we image the EDL structure of an ionic liquid-based electrolyte at a heterogeneous graphite electrode using our recently developed electrochemical 3D atomic force microscopy. These interfaces feature the formation of thin, nanoscale adlayer/cluster domains that closely mimic the early-stage solid-electrolyte interphases in many battery systems. We observe multiple discrete layers in the EDL near the flat electrode, which restructures at the heterogeneous interphase sites. Depending on the local size of the interphase clusters, the EDLs exhibit bending, breaking, and/or reconnecting behaviors, likely due to the combined steric and long-range interaction effects. These results shed light on the fundamental structure and reconfiguration mechanism of EDLs at heterogeneous interfaces.