(A) study on the electrochemical lithium intercalation reaction into transition metal oxide electrodes such as vanadium, cobalt and nickel oxides

Abstract

The present work is concerned with the electrochemical lithium intercalation reaction into anodic vanadium oxide film, porous $V_2O_5$, $LiNiO_2$ and $LiCoO_2$ electrodes. In chapter III, the electrochemical lithium intercalation reaction into anodic vanadium oxide films in 1 M $LiClO_4$ propylene carbonate solution has been investigated by using the galvanostatic intermittent titration technique and electrochemical impedance spectroscopy(EIS) as a function of electrode potential. Measured impedance spectra were analysed using the complex non-linear least-squares(CNLS) fitting method. The impedance spectra measured in the potential range of 3.6 to 2.6 $V_{Li/Li+}$ showed that the electrochemical intercalation reaction of lithium ions into the anodic oxide film consists of three consecutive steps of charge transfer at the electrolyte/oxide film interface, lithium ion incorporation into the oxide film and diffusion through the oxide film. The charge transfer reaction at the electrolyte / anodic vanadium oxide film interface is mainly affected by the valence change of vanadium ion of the oxide film. In the electrode potential range from 3.0 to 3.6 $V_{Li/Li+}$, intercalated lithium ions are highly accumulated in the near-surface region of the anodic vanadium oxide film. The component diffusivity of lithium in the oxide film was determined to be $10^{-12}$ to $10^{-14}$ ㎠ s^{-1}$ in the lithium content range investigated, due to the increased interaction between intercalated lithium ions. Also the lithium transport through anodic vanadium oxide film electrode was investigated by using potentiostatic current transient technique. The chemical diffusivities of lithium ion in the fresh anodic vanadium oxide film electrode specimens of various thicknesses were determined as a function of lithium charging potential. The cathodic current transient curves obtained from the fresh anodic oxide film electrode are divided into two stages. The first stage is due to the lithiu...