An in situ electrochemical atomic force microscopy (EC-AFM) cell was developed to study surface and dimensional changes of individual Li x CoO2 crystals during lithium de-intercalation. Discrete Li2CO3 particles having 50–250nm in diameter and 5–15nm in height were observed on the surface of stoichiometric LiCoO2 crystals and they were shown to gradually dissolve into the LiPF6-containing electrolyte. The dimensional change of individual Li x CoO2 crystals along the c hex. axis was monitored in situ during lithium de-intercalation. Evidence of surface instability or structural instability was not found in Li x CoO2 single crystals upon de-intercalation to 4.2V versus Li.