Lithium cobalt oxide (LiCoO2, LCO) is one of the most extensively studied/used cathode materials for rechargeable lithium ion batteries. Well-defined, single crystalline LiCoO2 thin films and multilayered structures are highly desirable for fundamental investigations of the charge/discharge processes. In our work, epitaxial LiCoO2 thin films with different orientations and strain states were grown by pulsed laser deposition (PLD). Direct lithium contact was made under a scanning transmission electron microscope (STEM) using an in situ Nanofactory holder. The structural and chemical evolution of the constructed LCO thin film electrode upon lithium contact were studied by STEM, EELS, EDX, and NBD to better understand the reaction products, lithium diffusion pathways, and intercalation induced phase changes, in particular occurring at the interfaces and antiphase boundaries.