Lithium manganese oxide spinel electrodes

Batteries based oil intercalation eletrodes are currently being considered for a variety of applications including automobiles. This thesis is concerned with the simulation and experimental investigation of one such system: spinel Li_yMn₂O₄.; A mathematical model simulating the behavior of an electrochemical cell containing all intercalation electrode is developed and applied to Li _yMn₂O₄ based systems. The influence of the exchange current density oil the propagation of the reaction through the depth of the electrode is examined theoretically. Galvanostatic cycling and relaxation phenomena on open circuit are simulated for different particle-size distributions. The electrode with uniformly sized particles shows the best performance when the current is on, and relaxes towards equilibrium most quickly. The impedance of a porous electrode containing a particle-size distribution at low frequencies is investigated with all analytic solution and a simplified version of the mathematical model. The presence of the particle-size distribution leads to an apparent diffusion coefficient which has all incorrect concentration dependence.; A Li/1 M LiClO₄ in propylene carbonate (PC)/ Li_yMn ₂O₄ cell is used to investigate the influence of side reactions oil the current-potential behavior of intercalation electrodes. Slow cyclic voltammograms and self-discharge data are combined to estimate the reversible potential of the host material and the kinetic parameters for the side reaction. This information is then used, together with estimates of the solid-state diffusion coefficient and main-reaction exchange current density, in a mathematical model of the system. Predictions from the model compare favorably with continuous cycling results and galvanostatic experiments with periodic current interruptions.; The variation with respect to composition of' the diffusion coefficient of lithium in Li_yMn₂O₄ is estimated from incomplete galvanostatic discharges following open-circult periods. The results compared favorably with those available in the literature. Dynamic Monte Carlo simulations were conducted to investigate the concentration dependence of the diffusion coefficient fundamentally. The dynamic Monte Carlo predictions compare favorably with the experimental data.