An investigation of intercalation-induced stresses generated during lithium transport through Li 1 − δCoO 2 film electrode using a laser beam deflection method

Abstract

The stress change, Δ σ, generated during lithium transport through the rf sputter-deposited Li 1 − δ CoO 2 film was exactly determined as a function of the lithium stoichiometry, (1 − δ), using a laser beam deflection method (LBDM) combined with cyclic voltammetry, galvanostatic intermittent titration technique and potentiostatic current transient technique. Tensile and compressive stresses were generated during the lithium intercalation and deintercalation, respectively. Δ σ varied remarkably with (1 − δ) in the single-α-phase region as well as in the two-phase region, but it remained almost constant in the single-β-phase region. Δ σ generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by (1 − δ). The value of Δ σ coincided well with that value derived from the Δ σ versus (1 − δ) curve (stress transient) measured simultaneously along with the galvanostatic intermittent titration discharge curve. From the comparison between the values of Δ σ measured experimentally and calculated theoretically, it was suggested that Δ σ in the single-α-phase region and the two-phase region originate from the molar volume change of the α-phase and from the lattice parameter mismatch between the α-phase and β-phase, respectively.