ELECTROCHEMICAL CHARACTERISTICS OF MNO2-V2O5 COMPOSITES SERVING AS POSITIVE MATERIAL FOR SECONDARY LITHIUM BATTERIES

MnO2-V2O5 composites formed by heating mixtures of MnO2 and NH4VO3 under various conditions are evaluated as positive material for secondary lithium batteries. The charge/discharge characteristics of the composites are dependent on the type of MnO2 used, the heat-treatment temperature, the discharge rate, and the depth-of-discharge. A composite formed by heating a mixture of EMD and NH4VO3 (V/Mn atom ratio = 1.0) at 350-degrees-C for 4 h in air exhibits the best cycling characteristics, and gives a discharge capacity of 250-350 A h/kg-oxide over 10 cycles at a current density of 0.20 mA cm-2 at 25-degrees-C in 1 M LiClO4-Propylene carbonate. X-ray diffraction, X-ray photoelectron spectroscopic, and SEM studies of the composite reveal that the charge/discharge characteristics may be determined by the structure of a surface layer formed on the MnO2 particles.