Evaluation of Lithium Ion Insertion Reactivity via Electrochromic Diffraction-Based Imaging

A microscope−CCD setup has been developed as an analytical tool for the detection of diffraction from one-dimensional redox-active transition-metal oxide gratings prepared with a combination of microtransfer molding (μTM) and cathodic electrodeposition. The diffraction efficiencies (DE) of tungsten trioxide, WO₃, and binary molybdenum−tungsten trioxide, Mo_0.6W_0.4O₃, gratings were measured during Li⁺ insertion/deinsertion experiments performed with both cyclic voltammetry and chronoamperometry in 1 M LiClO₄/propylene carbonate. The DE was evaluated in terms of the optical constants of the grating materials determined by spectroscopic ellipsometry (SE) measurements of Li⁺ insertion/deinsertion into unpatterned thin films. The effect of grating thickness and the amount of inserted charge on DE has been analyzed. The diffraction method is used to quantitatively estimate lithium ion diffusion coefficients of electrochemically active metal oxide gratings.