Sol-gel derived Li-V-Mn-O spinels as cathodes for rechargeable lithium batteries

Nearly stoichiometric ternary Li-V-Mn-O spinels were prepared by a sol-gel method using propionic acid to form the resin framework, and subsequent cal cination of the gel at 600 degreesC. The resulting material was tested as c athode over the voltage range 5.2-2.0 V in lithium cells. The profiles of t he discharge-charge processes were found to be surprisingly similar to that recently reported for thin-film LiMn2O4. The results of X-ray photoelectro n spectroscopy (XPS) and elemental analysis are consistent with an oxidatio n state + 5 for V and with + 3 and + 4 for Mn. Although the spinel preserve s its basic framework across the whole potential window, significant capaci ty fading is observed along the 5.0 and 2.0 V plateaus, the latter effect b eing associated with a reversible cubic-tetragonal phase transition. The be st electrochemical performance of the cell was observed in the potential wi ndow 4.6-2.5 V. Over this voltage range, the cell maintains an acceptable c apacity (105 Ah/K) upon extensive cycling. (C) 2000 Elsevier Science B.V. A ll rights reserved.