THE AC-IMPEDANCE STUDY OF ELECTROCHEMICAL LITHIUM INTERCALATION INTO POROUS VANADIUM-OXIDE ELECTRODE

The electrochemical lithium intercalation into vanadium oxide in LiClO 4 propylene carbonate solution has been investigated by using electroc hemical impedance spectroscopy as a function of lithium content. Imped ance spectra measured in the lithium content range investigated (delta = 0-0.8 in LideltaV2O5) consist of a high frequency depressed are and a low frequency straight line. The high frequency are is attributed t o the charge transfer reaction at the vanadium oxide/electrolyte inter face and the low frequency line is associated with the diffusion of li thium ion through single vanadium oxide phase or with the movement of the boundary separating two phases. The chemical and component diffusi vities of lithium ion in vanadium oxide were determined from the low f requency line combined with coulometric titration curve. The variation of the chemical and component diffusivities with lithium content has been discussed in relation to the coulombic interaction between the in tercalated lithium ion and the oxide lattice.