Physical and electrochemical characterization of quaternary Li-Mn-V-O spinel as positive materials for rechargeable lithium batteries

Quaternary Li-Mn-V-O spinels formed from heating mixtures of LiNO3, MnCO3, and NH4VO3 around 350 degrees have been characterized by electrochemical measurement, x-ray photoelectron spectroscopy, x-ray diffractometry, Li-7-NMR, and magnetic susceptibility measurements. These results were compared with those for ternary Li-Mn-O spinels prepared at 350 and 850 degrees C. The compositions of the quaternary and ternary spinels formed at 350 degrees C were shown to be x(Li2O)Mn2O4 . yV(2)O(5)(x = 0.5 similar to 1, y = 0 similar to 0.4). The cubic a(0)-lattice parameter and specific density of the quaternary spinels increased with increasing vanadium content in the spinel structure. The Li-7-NMR measurements revealed that the quaternary spinels did not show any Knight shift, while the ternary Li-Mn-O spinels formed at 350 and 850 degrees C had a large Knight shift of 490 similar to 535 ppm in reference to LiCl. Furthermore, the measurement of the magnetic susceptibility indicated that the ternary and quaternary spinels formed at 350 degrees C are paramagnetic and the ternary LiMn2O4 prepared at 850 degrees C is anti-ferromagnetic.