Preparation and electrochemical characteristics of quaternary Li-Mn-V-O spinel as the positive materials for rechargeable lithium batteries

Quaternary Li-Mn-V-O spinels were prepared by heating mixtures of MnCO3, V2O5 and LiNO3 at 700 °C for 36 h in air. The spinel oxides were characterized by X-ray diffraction, FT-IR spectroscopic, density and electrochemical measurements. The unit cell volume in a cubic cell increased with an increase in V content in LiVxMn2 − xO4 (x = 0–0.2), while the amounts of lithium intercalated into the spinels in a high potential region around 4 V versus Li/Li+ decreased considerably with an increase in V content. Furthermore, the thermodynamics and kinetics of the lithium intercalation process into the spinel LinVxMn2 − xO4 were studied. The standard free energies of lithium intercalation into the spinels were −291 kJ/mol for x = 0 and −264 kJ/mol for x = 0.05 at n = 0–1 and 25 °C. The chemical and self-diffusion coefficients for lithium in LinVxMn2 − xO4 spinels were measured as functions of the n and x values by a current-pulse relaxation method. The diffusion coefficients in the spinel with x = 0.05 in the n-value range from 0.3 to 1 were about one order of magnitude lower than that in LinMn2O4.