Electrochemical characteristics of Li2−VTiO4 rock salt phase in Li-ion batteries

Abstract

Li 2-x VTiO 4 /C sample with a disordered rock salt structure was successfully prepared by annealing at a temperature of 850°C. The electrochemical oxidation in the first cycle occurs at voltages above 4 V versus metallic lithium, while the shapes of the electrochemical curves in consequent reduction -oxidation processes show a monotonous change of the potential between the selected cut-off voltages. A linear combination fit of individual XANES spectra was used for the determination of the oxidation states of as prepared sample and intermediate states during oxidation and reduction. In the as-prepared sample, vanadium was found to be in the average oxidation state of V 3.5+ and was additionally oxidized to V 3.8+ by the electrochemical charging. During the discharge process, the vanadium oxidation state was reduced to V 3.0+ . In-situ X-ray diffraction patterns and EXAFS analysis suggest good structural stability during oxidation and reduction, which is also reflected in the cycling stability if batteries were cycled in the voltage window between 2.0 V and 4.4 V. Extension of

Li+ intercalation in isostructural Li2VO3 and Li2VO2F with O2− and mixed O2−/F− anions

“…The charge/discharge performance for Li 2 VO 3 and Li 2 VO 2 F was compared between 4.1 and 1.3 V at 25°C and a rate of C/20 based on their theoretical capacities. 24 These observations suggest that the ligand anions play a predominate role on the electrochemical properties in terms of energy density and energy efficiency. 5a The dQ/dV curves in Fig.…”

A3V2(PO4)3 (A = Na or Li) probed by in situ X-ray absorption spectroscopy

“…3 and 4 show the normalized V XANES spectra of LVP and NVP samples, respectively, during the oxidation and reduction in the first cycle. The spectra were normalized by a standard procedure [14,15]. In the preedge region all spectra exhibit very similar edge profiles with a weak triplet resonance structure, characteristic for octahedrally coordinated vanadium cations, lacking an inversion center [14].…”

“…The valence state of vanadium cations in the sample can be deduced from the energy shifts of the vanadium absorption edge [14,15]. A linear relation between the edge shift and the oxidation state was established for V atoms in different vanadium oxides: the absorption edge shifts for 2.5 eV per valence [14].…”

Lithium-Excess Research of Cathode Material Li2MnTiO4 for Lithium-Ion Batteries

“…Particularly the involved strong Ti–O bond could stabilize the M 3+ /M 2+ and M 4+ /M 3+ transition. The present Li 2 MTiO 4 materials mainly include Li 2 NiTiO 4 , Li 2 FeTiO 4 , Li 2 MnTiO 4 , Li 2 − x VTiO 4 , and Li 2 CoTiO 4 [8,9,10,11,12,13,14,15]. The electrochemical properties indicate that Li 2 NiTiO 4 shows a reversible capacity of 179 mAh g −1 , which is 61.6% of the theoretical value for the exchange of 2 M lithium (290.6 mAh g −1 ).…”