Journal article

Li+ ion insertion in TiO2 (anatase). 2. Voltammetry on nanoporous films

Electrochem. properties of Li+ ion insertion in nanoporous TiO2 (anatase) electrodes were studied by voltammetry. Linear and cyclic potential scans were recorded as a function of electrolyte concn., film thickness, and temp. The currents were directly proportional to the inner electrode area of the electrodes. The redn. of Ti4+ and oxidn. of Ti3+ are sluggish and follows irreversible kinetics. The std. rate const. was (3.5 ± 0.5) × 10-10 cm/s. The transfer coeff. was ∼0.5, indicating that the potential drop appears mainly across the Helmholtz layer. The capacitive currents govern largely the shape of the i-v curves, except within a region near the peak potential where diffusion-limited insertion and extn. of Li+ ions in the anatase lattice are dominating. The diffusion coeff. at 25° in the nanoporous structure was ∼2 × 10-17 cm2/s for insertion and 4 × 10-17 cm2/s for extn. The activation energy was 0.4 eV for insertion and 0.5 eV for extn. The max. obtained mole fraction of Li+ in LixTiO2 was x = 0.47.


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