IMPEDANCE STUDY OF THE INTERFACES BETWEEN LITHIUM, POLYANILINE, LITHIUM-DOPED MNO2 AND MODIFIED POLY(ETHYLENE OXIDE) ELECTROLYTE

Impedance study was carried out for the interfaces between lithium, po lyaniline (PAn), lithium-doped MnO2 and modified poly(ethylene oxide) (PEO) electrolyte under various' conditions. The interfacial charge-tr ansfer resistances R(ct) on PEO/PAn, R(ct) on PEO/LiMn2O4 increase wit h depth-of-discharge and decrease after the charge of the cell contain ing modified PEO as electrolyte. The charge-transfer resistance R(ct) on PEO/PAn is higher than R(ct) on PEO/LiMn2O4 under the same conditio n, since inserted species and mechanism are different for both cases. In the case of PAn, an additional charge-transfer resistance might be related to the electronic conductivity change in discharge/charge pote ntial range, as it was evident from a voltammetry curve. With increasi ng cycle numbers, the charge-transfer resistance increases gradually. The impedance results also have shown that at low frequency the diffus ion control is dominant in the process of the charge and discharge of Li/PEO/PAn or Li/PEO/LiMn2O4 cell. The diffusion coefficients have bee n calculated from impedance data.