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Title: Nanosized LiMn{sub 2}O{sub 4} from mechanically activated solid-state synthesis

Abstract

The synthesis of pure and Cr-doped nanosized LiMn{sub 2}O{sub 4} particles has been carried out by solid-state process on high-energy ground mixtures. In situ X-ray analysis demonstrates the spinel forms as single phase at 623 K passing through the Mn{sub 3}O{sub 4} precursor at temperatures as low as 573 K. In the doped high-energy ground mixture Li-rich spinel phase forms at 623 K and Cr ions insert in the spinel octahedral site only at 723 K. A mean particle size value of 60 A, quite independent of the reaction time, is obtained for T<673 K. For higher temperature the growing of the particles as a function of time is observed, independent of doping. The mechanical grinding seems to be the most suitable way to obtain impurity-free spinel phases at lower temperature and with smaller particle size with respect to manually ground mixtures by solid-state reaction and via sol-gel synthesis.

Authors:
 [1];  [2];  [2]
  1. Dipartimento di Chimica Fisica 'M. Rolla' e IENI-CNR, viale Taramelli 16, 27100 Pavia (Italy). E-mail: vincenzo.massarotti@unipv.it
  2. Dipartimento di Chimica Fisica 'M. Rolla' e IENI-CNR, viale Taramelli 16, 27100 Pavia (Italy)
Publication Date:
OSTI Identifier:
20784899
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 179; Journal Issue: 2; Other Information: DOI: 10.1016/j.jssc.2005.11.019; PII: S0022-4596(05)00558-X; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CHROMIUM IONS; DOPED MATERIALS; IMPURITIES; LITHIUM CARBONATES; MANGANESE OXIDES; NANOSTRUCTURES; PARTICLE SIZE; SCANNING ELECTRON MICROSCOPY; SOL-GEL PROCESS; SPINELS; STOICHIOMETRY; SYNTHESIS; TEMPERATURE RANGE 0400-1000 K; X-RAY DIFFRACTION

Citation Formats

Massarotti, V., Capsoni, D., and Bini, M. Nanosized LiMn{sub 2}O{sub 4} from mechanically activated solid-state synthesis. United States: N. p., 2006. Web. doi:10.1016/j.jssc.2005.11.019.
Massarotti, V., Capsoni, D., & Bini, M. Nanosized LiMn{sub 2}O{sub 4} from mechanically activated solid-state synthesis. United States. doi:10.1016/j.jssc.2005.11.019.
Massarotti, V., Capsoni, D., and Bini, M. Wed . "Nanosized LiMn{sub 2}O{sub 4} from mechanically activated solid-state synthesis". United States. doi:10.1016/j.jssc.2005.11.019.
@article{osti_20784899,
title = {Nanosized LiMn{sub 2}O{sub 4} from mechanically activated solid-state synthesis},
author = {Massarotti, V. and Capsoni, D. and Bini, M.},
abstractNote = {The synthesis of pure and Cr-doped nanosized LiMn{sub 2}O{sub 4} particles has been carried out by solid-state process on high-energy ground mixtures. In situ X-ray analysis demonstrates the spinel forms as single phase at 623 K passing through the Mn{sub 3}O{sub 4} precursor at temperatures as low as 573 K. In the doped high-energy ground mixture Li-rich spinel phase forms at 623 K and Cr ions insert in the spinel octahedral site only at 723 K. A mean particle size value of 60 A, quite independent of the reaction time, is obtained for T<673 K. For higher temperature the growing of the particles as a function of time is observed, independent of doping. The mechanical grinding seems to be the most suitable way to obtain impurity-free spinel phases at lower temperature and with smaller particle size with respect to manually ground mixtures by solid-state reaction and via sol-gel synthesis.},
doi = {10.1016/j.jssc.2005.11.019},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 179,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • Mo{sub 2}(O{sub 2}CMe){sub 4} (Mo-{sup 4}Mo) reacts with neat ethylenediamine (en) to form (Mo{sub 2}(O{sub 2}CMe){sub 2}(en){sub 4})((O{sub 2}CMe){sub 2}) {times} en (1) in high yield. The Mo{sub 2}(O{sub 2}CMe){sub 2}(en){sub 4}{sup 2+} ion in 1 contains a quadruply bonded Mo{sub 2}{sup 4+} center (Mo-Mo = 2.125 (1) {angstrom}) supported by two axial and two spanning en ligands in addition to two spanning acetates. The complex exists as an ion pair in which the displaced acetates are separated from the Mo{sub 2} coordination sphere by the two spanning en ligands. The acetate counterions are hydrogen bonded to the spanning enmore » ligands (N-O = 2.86 (2) {angstrom} (av)). Compound 1 converts back to Mo{sub 2}(O{sub 2}CMe){sub 4} at 120{degree}C in the solid state. NMR studies show that dissociated and coordinated acetate ligands are present in neat en whereas, in D{sub 2}O, only dissociated en and acetate are observed. Crystal data for 1 (20{degree}C) is reported. 35 refs., 3 figs., 4 tabs.« less
  • Ru{sub 2}(O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}){sub 4} (1a) is soluble in both coordinating (THF, CH{sub 3}OH, CH{sub 3}CN) and noncoordinating solvents (benzene, toluene, cyclohexane, CH{sub 2}Cl{sub 2}), allowing its solution properties to be investigated by {sup 1}H and {sup 13}C NMR spectroscopy, UV/visible spectroscopy, resonance Raman spectroscopy, and cyclic voltammetry. In noncoordinating solvents, 1a exists as an oligomer, presumably by way of axial intermolecular -(--[Ru{sub 2}]--O--){sub n}-interactions. {sup 1}H NMR studies of 1a and [Ru{sub 2}(O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}){sub 4}]{sup +}[X]{sup {minus}}([1a]{sup +}[X]{sup {minus}}), where X = Cl, BF{sub 4}, or O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}, indicate that bothmore » dipolar and contact mechanisms contribute to the paramagnetic shifts of the protons. Resonances for axial and equatorial ligands are shifted upfield and downfield, respectively, by a dipolar mechanism. Aromatic ligands in the axial sites, e.g. pyridine and pyrazine, experience an enhanced upfield shift by direct {pi}-delocalization. Comparison of the {sup 1}H NMR signals for M{sub 2}(O{sub 2}CR){sub 4} compounds where M = Ru and O{sub 2}CR = benzoate, toluate, butyrate, crotonate, and dimethylacrylate with those where M = Mo indicates that the equatorial carboxylate ligands in the diruthenium species also experience {pi}-contact shifts. Variable-temperature studies and calculated estimates of dipolar shifts indicate a significant zero-field splitting contribution to the dipolar shift. The arrangements of the toluate rings in Ru{sub 2}(O{sub 2}C -p-tolyl){sub 4}-(THF){sub 2}, Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(CH{sub 3}CN){sub 2}, and [Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(THF){sub 2}]{sup +}[BF{sub 4}]{sup {minus}} deviate by 15(1), 2.3(2), and 7.3{degrees}, respectively, form alignment with the Ru-Ru axis.« less
  • Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn{sub 2}O{sub 4} particles in air and water vapor atmospheres as model reactions; LiMn{sub 2}O{sub 4} is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO{sub 3} precursor impregnated with LiOH, LiMn{sub 2}O{sub 4} spheres with a hollow structure were obtained in air, while angulated particlesmore » with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn{sub 2}O{sub 4} particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.« less
  • The nature of the phases obtained by acid digestion of LiMn{sub 2}O{sub 4} phases prepared at 800 C from a mixture of MnO{sub 2} (EMD) and Li{sub 2}CO{sub 3} was investigated. The authors found that the complete transformation toward {alpha}-MnO{sub 2} and then {gamma}-MnO{sub 2} observed for LiMn{sub 2}O{sub 4} treated in 2.5 M H{sub 2}SO{sub 4} for 24 h at 95 C is highly dependent on the amount of water in the reaction medium. The {lambda} {yields} {alpha}/{gamma} transformation was found to be the result of a dissolution-crystallization mechanism that can be completely avoided by adding a soluble Bi,more » Pb, or Tl salt to the reaction medium. By coupling energy dispersive spectroscopy analysis, infrared spectroscopy, and potentiometric titration, the authors demonstrated the presence of Bi species adsorbed at the surface of the {lambda}-MnO{sub 2} oxide thus modifying its reactivity. In addition, the kinetics of the {lambda} {yields} {alpha}/{gamma} phase transformation was found to depend on the amount of added Bi salt, suggesting the complexing role of Bi toward Mn (Bi-Mn complexes), thereby affecting the crystallization step of the reaction. The same treatment was applied to LiMn{sub 2}O{sub 4} in the presence of a Bi salt in anhydrous electrolyte (LiPF{sub 6}/ethylene carbonate/dimethyl carbonate). In this case, the spinel oxide dissolution slows down and BiF{sub 3} precipitates. With respect to recent findings about the mechanisms involved in the electrochemical capacity failure at elevated temperature in Li-ion LiMn{sub 2}O{sub 4} cells, these results open new alternatives to solve this recurrent problem.« less
  • Two new organic-inorganic hybrid compounds, [Ga(phen)(H{sub 1.5}PO{sub 4}){sub 2}].H{sub 2}O (1) and [Ga(phen)(HPO{sub 4})(H{sub 2}PO{sub 4})].1.5H{sub 2}O (2) (phen=1,10-phenanthroline), have been synthesized by hydrothermal methods and structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and solid-state NMR spectroscopy. Their structures consist of 1-D chains of strictly alternating GaO{sub 4}N{sub 2} octahedra and phosphate tetrahedra. The phen ligands in both compounds bind in a bidentate fashion to the gallium atoms and the 1-D structures extend into 3-D supramolecular arrays via {pi}-{pi} stacking interactions of phen ligands and hydrogen bonds. {sup 2}H MAS NMR spectroscopy was applied to study themore » deuterated sample of 1 which contains very short hydrogen bonds with an O-O distance of 2.406(2) A. Crystal data for 1: monoclinic, space group C2/c (No. 15), a=11.077(1) A, b=21.496(2) A, c=7.9989(7) A, {beta}=127.211(2){sup o}, and Z=4. The crystal symmetry is the same for 2 as for 1 except a=27.555(2) A, b=6.3501(5) A, c=21.327(2) A, {beta}=122.498(1){sup o}, and Z=8.« less