The carbon/electrolyte interface was characterized during galvanostatic cycling at different current densities by means of impedance spectroscopy, semi-in situ transmission microscopy and Fourier-transform infrared spectroscopy (FT–IR). These techniques, carried-out in an inert atmosphere, showed that the formation rate strongly influences both the chemical nature and thickness of this interface; its growth will be detailed using a rate corresponding to the intercalation of one lithium in 20h.