Lithium transport through Li1+δ[Ti2−yLiy]O4 (y=0; 1/3) electrodes by analysing current transients upon large potential steps

Lithium transport through Li1+δ[Ti2−yLiy]O4 (y=0; 1/3) electrodes in the coexistence of a Li-poor phase α and a Li-rich phase β was investigated during electrochemical lithium intercalation by using the potentiostatic current transient technique under large potential stepping. For this purpose, the galvanostatic charge–discharge curve and the cathodic current transient were obtained as functions of the lithium content (1+δ) and the lithium injection potential, respectively. The charge–discharge curve showed a potential plateau due to the coexistence of two phases α and β. The values of the quasi-equilibrium potential and the corresponding stoichiometry of the α- and β-phases were determined from the potential plateau. A three-stage current transient was observed as the applied potential step went below the potential plateau, and the second stage of this current was found to be governed by the diffusion-controlled phase boundary movement between the α- and β-phases.