Preparation and electrochemical characteristics of new MnO 2V 2O 5 systems as positive materials for rechargeable lithium batteries

Abstract

New binary oxides, MnO 2· xV 2O 5 ( x = 0–0.3), which were formed by heating mixtures of Mn(NO 3) 2·6H 2O and NH 4VO 3 at various V/Mn atomic ratios and at different temperatures in air, have been characterized by X-ray diffraction method, X-ray photoelectron spectroscopy and infrared spectroscopy. The amount of Li + ions inserted into the crystal lattice of the oxide increased with increasing x-value in MnO 2· xV 2O 5, and reached ca 1 Li/mole of the oxide with x = 0.6. Furthermore, the thermodynamic and kinetic studies showed that the standard free energy for the lithium insertion, Δ G 1, is −265 kJ mol −1 in the range of n = 0–1 in Li n MnO 2· xV 2O 5 at 25°C and that the chemical diffusion coefficients of lithium in the oxide matrices are in the range from 10 −9 to 10 −12cm 2s −1 at 25°C and increased with increasing V 2O 5 content in the mixed oxides.