Lithium insertion into mesoscopic and single-crystal TiO2 (rutile) electrodes

Electrochemical behavior of single-crystal and mesoscopic TiO2 (rutile) was studied in propylene carbonate solutions at potentials negative to the fla tband potential. In electrolytic solutions containing sodium or tetrabutyla mmonium (Bu4N+), the injected charge is compensated by protonization of the surface and/or by adsorption of cations in the double layer In electrolyti c solutions containing Li+, the insertion into the rutile lattice occurs at potentials below 1.5 V (Li/Li+). At higher potentials, the charge is compe nsated mainly by a nonfaradaic process. Lithium insertion into rutile proce eds at a potential ca. 0.4 V more negative than the insertion potential int o anatase. The maximum insertion capacity of rutile is also lower than that of anatase. The insertion of lithium into rutile is accompanied by an incr ease of the electrode mass, while the mass/charge relations show hystereses between anodic and cathodic potential sweeps. This behavior is explained i n terms of a free convection in the electrode vicinity. (C) 1999 The Electr ochemical Society. S0013-4651(98)08-025-2. All rights reserved.