A short overview concerning the nature of lithium ＇passivity＇ and the use of in situ techniques in lithium research will be given in order to emphasize the important role of the properties of the phase-boundary metal/electrolyte. The electrochemical behaviour of lithium is strongly influenced by the formation of a surface layer due to the reduction of the solvent and of the electrolyte. A kinetic model for the layer formation at uncovered lithium surfaces will be suggested.