Preparation and electrochemical characteristics of new LiMnVO system as positive materials for rechargeable lithium batteries

Abstract New quaternary spinels, Li n Mn 2 O 4 ·χV 2 O 5 ( n =0.5–1.5, x =0–0.7), which were formed by heating mixtures of MnCO 3 , NH 4 VO 3 and LiNO 3 at various Li:Mn and V:Mn atomic ratios and at different temperatures (300 to 400 °C) in air, have been characterized by X-ray diffraction method, X-ray photoelectron spectroscopy (ESCA) and infrared spectroscopy. The amount of Li + ions inserted into the crystal lattice of the quaternary oxide by using an electrochemical method increased with decreasing n -value and reaches ∼2Li/mole of the oxide at n =0.5 in Li n Mn 2 O 4 ·0.5V 2 O 5 . But the amount of Li + ions inserted into several LiMn 2 O 4 ·χV 2 O 5 (χ=0.25–0.7) with different x -values were almost constant, being ∼2Li/mole of the oxide, which is double of that for ternary spinel LiMn 2 O 4 not containing V 2 O 5 . When the charge/discharge cyclings with the Li n Mn 2 O 5 ·0.5V 2 O 5 electrode were performed in the n -value range between 0.5 and 0.8 and at a current density of 0.20 mA cm −2 , the electrode could be cycled over 50 cycles at a high mean discharge potential ∼3.5 V versus Li/Li + .