INSERTION OF LITHIUM INTO MESOSCOPIC ANATASE ELECTRODES - AN ELECTROCHEMICAL AND IN-SITU EQCM STUDY

The insertion of Li+ into mesoscopic TiO2 (anatase) electrodes was stu died using cyclic voltammetry combined with the in situ gravimetric mo nitoring of the electrode mass in LiClO4 and Li(CF3SO2)(2) N/propylene carbonate (PC)-based solutions. The insertion of Li+ takes place at p otentials less than 2.0 V vs Li/Li+. The cathodic process is associate d with a mass uptake; the subsequent oxidation process is associated w ith a mass decrease. The apparent molar mass of the inserted/extracted material is, however, remarkably different from that expected for the simple insertion/extraction of unsolvated Li+ ions. For a more accura te description of the behaviour of the mesoscopic anatase electrodes, we consider them as gold electrodes modified with a porous film. Thus, the mesoscopic anatase electrode behaves similarly to a polymer-modif ied electrode, i.e. the overall process includes coupled electron/ion transfer (insertion of Li+) and a transfer of neutral species. Analysi ng the EQCM (electrochemical quartz crystal microbalance) data, one ca n conclude that the controlling step of the insertion/extraction of Li + into/from anatase electrodes is a coupled electron/ion transfer or t he transfer of neutral species in solutions containing ClO4- and (CF3S O2)(2)N- respectively.