Thermodynamic and kinetic approaches to lithium intercalation into Li[Ti 5/3Li 1/3]O 4 film electrode

Abstract

Lithium intercalation into Li[Ti 5/3Li 1/3]O 4 film electrode in the two-phase coexistence was investigated from the thermodynamic and kinetic viewpoints. The electrode potential versus lithium content curve of the film electrode was theoretically calculated in consideration of the interactions between lithium ions based upon a lattice gas model with the Monte Carlo simulation. According to the model, it was proposed that a wide potential plateau indicating the coexistence of a Li-poor phase α and a Li-rich phase β is due to the repulsive interactions between lithium ions. From the analysis of the ac-impedance spectra in the coexistence of two phases α and β, it was confirmed that the fraction of α phase at the electrode surface and that fraction of β phase continuously decreases and increases, respectively, with increasing lithium content. The analysis of the current transient led to the conclusion that transport of lithium ions subjected to the repulsive interactions within the electrode is governed by the cell-impedance-controlled constraint at the electrode surface during the phase transformation between α and β phases.