Anion Intercalation in Graphite Studied by Electrochemical-Scanning Probe Microscopy: State of the Art and Perspectives

Anion intercalation in graphite was studied since the early 1980s, with the aim of changing the graphite transport properties of a carbon electrode. The Li-ion batteries renewed these researches as well as the interest of low-cost graphene production via (electro-) chemical strategies. In this last case, anion species intercalate inside the stratified graphite crystal structure, expand the layer–layer distance, and facilitate the graphite delamination. Electrochemical-scanning probe microscopy (EC-SPM) offers the possibility of following directly the evolution during the different involved EC processes. In this article, we retrace the main results obtained by the EC-SPM in the characterization of the graphite electrode when immersed in both highly corrosive mineral sulfuric and perchloric acid electrolyte. These are good representatives of the class of mineral acids used for intercalation (such as nitric or phosphoric acids). On the other hand, the rich phenomenology observed can elucidate some processes that can affect the graphite when immersed in other electrolytes. Despite the work done till now, some details of the molecular intercalation model are still under debate. This article tries to summarize the main results and mark possible perspectives in this field.