THERMODYNAMIC AND KINETIC-STUDIES OF ELECTROCHEMICAL LITHIUM INSERTION INTO QUATERNARY LI-MN-V-O SPINEL AS POSITIVE MATERIALS FOR RECHARGEABLE LITHIUM BATTERIES

The thermodynamics and kinetics of the lithium insertion process into the quaternary spinel LixMn2O4 . yV2O5 (x = 0.5 to 3, y = 0.25 to 0.5) have been studied. The partial molar quantities DELTAG(Li(x))BAR, DELTAH(Li(x))BAR, and DELTAS(Si(x))BAR of lithium in the quaternary spinels have been determined from electromotive force-temperature measurements performed using 1M LiClO4 solution of propylene carbonate in the temperature range from 298 to 330 K. These thermodynamic functions varied with the lithium concentration in the oxide structure and a major variation was observed around x = 1 in LixMn2O4 . yV2O5. The chemical diffusion coefficient for lithium D in the spinel oxides has been measured as functions of the lithium composition and temperature by a current-pulse relaxation technique. The values of D, obtained in the x value range from 0.5 to 1.0 at 298 K, were found to be several orders of magnitude higher than those in the x value range from 1.3 to 2.5. The lithium self-diffusion coefficient D(Li), partial lithium-ion conductivity and activation energy for lithium diffusion have been calculated.