Abstract: Li/LiClO_4-Propylene Carbonate is one of lithium electrode systems studied often. In this article we present some new findings obtained with a. c. impedance and SEM methods. The variation of R_p×C_p with logarithm of time shows three distinct periods, corresponding to three different stages of growth of the film on lithium surface. In the initial period of film growth R_p×C_p is constant, corresponding to growth of primary compact layer consisting of Li_2CO_3, an ionic conductor. Resistivity of film was callculated to be 1.4×10~8 Ω·cm, and the thickness of film is several hundred angstrons. In the second period of film growth the product of another compact layer, which consists of Li_2CO_3 and organic compounds including organic polymers. Because of inclusion of organic components, the conductivity of the film decreases and it is diffcult to calculate the thickness of film. The third period is charactered by chaotic vibration, which is probably caused by periodic breaking and resealing of the compact layer and the growth of a porous layer. Upon polarization the primary compact layer probably undengoes no significant change and has no effect on the reversibility of the electrode system, while the outer compact layer and porous layer definitely have unfavourable influence on the revesibility of charging and discharging processess.