In Situ Transmission Electron Microscopy of the Electrochemical Intercalation of Graphite in Concentrated Sulfuric Acid

Graphite intercalation compounds, where some atom or molecule is inserted between the carbon layers of the host graphite, are attractive materials for charge storage. In commercial, rechargeable lithium ion batteries, for instance, the graphite anode intercalates and de-intercalates lithium as the battery is cycled [1]. In this work we present our in situ scanning transmission electron microscopy (STEM) observations of a model electrochemical intercalation system, namely graphite and concentrated sulfuric acid (98% mass fraction H2SO4). We cycle the potential between two graphite/gold electrodes that are immersed in the sulfuric acid and sealed in a fluid cell designed for in situ TEM. The construction of the fluid cell and the graphite transfer process have been described previously [2].