The ac impedance study of electrochemical lithium intercalation into porous vanadium oxide electrode

The electrochemical lithium intercalation into vanadium oxide in LiClO4 propylene carbonate solution has been investigated by using electrochemical impedance spectroscopy as a function of lithium content. Impedance 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 to the charge transfer reaction at the vanadium oxide/electrolyte interface and the low frequency line is associated with the diffusion of lithium ion through single vanadium oxide phase or with the movement of the boundary separating two phases. The chemical and component diffusivities of lithium ion in vanadium oxide were determined from the low frequency 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 intercalated lithium ion and the oxide lattice.