Explicit analysis of impedance spectra related to thin films of spinel LiMn2O4

A uniform, dense film of spinel LiMn2O4 (0.1 mum thick) has been prepared b y the electrostatic spray deposition (ESD) technique. The electroanalytical behavior of this electrode is elucidated by application of electrochemical impedance spectroscopy (EIS). The data have been modeled using an equivale nt circuit approach. An excellent fit was found between measured data and a n equivalent circuit, comprising Li+ migration through surface him, potenti al-dependent charge transfer resistance, semiinfinite Warburg-type element, reflecting solid state Li+ ion diffusion and a finite space Warburg-type e lement, describing both diffusion and accumulation of lithium at the very l ow frequency. The apparent chemical diffusion coefficient of lithium in the spinel phase was found within 10(-12) < <(D)over tilde>(Li) < 10(-9) cm(2) s(-1) as a function of electrode potential with minima at the potentials c orresponding to the voltammetric peaks. The intercalation capacitance was f ound 0.7 < C-L < 47 mF cm(-2) exhibiting maxima at the potentials correspon ding to the voltammetric peaks. (C) 2001 Elsevier Science B.V. All rights r eserved.