Investigation of LiMn2O4 cathodes for use in rechargeable lithium batteries by linear sweep voltammetry (LSV) Part II.: Experimental study using thin films, single particles and composite electrodes

Thin films, single particles and a composite electrode of the cathode material LiMn2O4 in the lithium battery system were investigated by linear sweep voltammetry (LSV) in 1 M LiClO4 + PC:EC. The experimental data were compared to and analysed by mathematical models described in Part I of this work. Analysis of the measured peak potential. E-p, showed clearly that the larger the characteristic length, the larger is the potential peak shift., at a given sweep rate. From the observations of the measured peak current behaviour, I-p, it seems that the composite electrode and the single particles are semi-infinite diffusion limited at all sweep rates applied. For the thin films, when increasing the sweep rate, a transition from finite to semi-infinite mass transfer limitation is indicated. A model based on solid-phase diffusion, interfacial charge transfer and an external IR-drop could fairly well be fitted to the experimental data measured on a single electrode system at a given sweep rate. It was found that the determined parameter values. i.e. solid-phase diffusion coefficient and the IR-drop, vary greatly with sweep rate and characteristic length. These results indicate that the physical description used is an oversimplification for describing the reaction mechanism in LiMn2O4. (C) 2001 Published by Elsevier Science B,V.