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 LiNO{sub 3}, MnCO{sub 3}, and NH{sub 4}VO{sub 3} around 350{degree} have been characterized by electrochemical measurement, X-ray photoelectron spectroscopy, X-ray diffractometry, {sup 7}Li-NMR, and magnetic susceptibility measurements. These results were compared with those for ternary Li-Mn-O spinels prepared at 350 and 850 C. The compositions of the quaternary and ternary spinels formed at 350 C were shown to be x(Li{sub 2}O)Mn{sub 2}O{sub 4} {center_dot} yV{sub 2}O{sub 5} (x = 0.5 {approximately} 1, y = 0 {approximately} 0.4). The cubic a{sub 0}-lattice parameter and specific density of the quaternary spinels increased with increasing vanadium content in the spinel structure. The {sup 7}Li-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 C had a large Knight shift of 490 {approximately} 535 ppm in reference to LiCl. Furthermore, the measurement of the magnetic susceptibility indicated that the ternary and quaternary spinels formed at 350 C are paramagnetic and the ternary LiMn{sub 2}O{sub 4} prepared at 850 C is antiferromagnetic.