Electrochemical Studies of Spinel LiMn₂O₄ Films Prepared by Electrostatic Spray Deposition

An uniform, dense film of spinel LiMn₂O₄ (thickness, about 0.5 μm) was prepared by the electrostatic spray deposition method onto a Pt film electrode on Si substrate kept at 400 °C. Electrochemical properties of the LiMn₂O₄ film in a solution of 1 M LiClO₄/propylene carbonate were studied by cyclic voltammetry and potential-step chronoamperometry. The oxidation and reduction of the film, which are accompanied by the extraction/insertion of lithium ions, proceeded almost quantitatively around 4 V vs. Li/Li⁺ with excellent coulombic reversibility. The apparent chemical diffusion coefficient of Li⁺ in Li_1-xMn₂O₄ spinel phase varied on the order between 10^-10 and 10^-12 cm² s^-1 as a function of electrode potentials with minima at the potentials corresponding to the voltammetric current peaks.