DETERMINATION OF THERMODYNAMIC, KINETIC AND INTERFACIAL PROPERTIES FOR THE LI//LIXMN2O4 SYSTEM BY ELECTROCHEMICAL TECHNIQUES

Thermodynamic, kinetic and impedance studies of the Li/LixMn2O4 (spinel phase) have been carried out using a polymer-based electrolyte system. There appear to be three voltage ranges for the reversible lithium intercalation reaction, centered around 4, 2.9 and 1.1 V versus Li/Li+. A cell utilizing all three ranges shows good coulombic reversibility but also relatively high cell impedance at the lower cell voltage. The upper voltage range shows excellent reaction kinetics, good coulombic reversibility and low cell impedance. A third and previously unidentified structural or electronic modification in the spinel phase has been found at about 3.9 V versus Li/Li+. The 2.9 V plateau is characterized by reasonable coulombic reversibility, slower reaction kinetics and higher cell impedance than the upper voltage region. The voltage region around 1.1 V versus Li/Li+ is considered too low for practical application.