An investigation of intercalation-induced stresses generated during lithium transport through Li1-δCoO2 film electrode using a laser beam deflection method

The stress change, Deltasigma, generated during lithium transport through the rf sputter-deposited Li1-deltaCoO2 film was exactly determined as a function of the lithium stoichiometry, (1 - delta), 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. Deltasigma varied remarkably with (1 - delta) in the single-ci-phase region as well as in the two-phase region, but it remained almost constant in the single-beta-phase region. Deltasigma generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by (1 - delta). The value of Deltasigma coincided well with that value derived from the Deltasigma versus (1 - delta) curve (stress transient) measured simultaneously along with the galvanostatic intermittent titration discharge curve. From the comparison between the values of Deltasigma, measured experimentally and calculated theoretically, it was suggested that Deltasigma in the single-et-phase region and the two-phase region originate from the molar volume change of the alpha-phase and from the lattice parameter mismatch between the alpha-phase and beta-phase, respectively. (C) 2004 Elsevier Ltd. All rights reserved.