Lithium insertion into pyrochlore WO3

Hernán, L.; Macı́as, M.; Morales, J.; Sánchez, L.; Tirado, J.L.

doi:10.1016/0167-2738(91)90037-c

Cited by 44 publications

(44 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The precursors used for the Ni-substituted spinels were Mn(ac) 3 • 2H 2 O and Ni͑ac) 2 • 4H 2 O (ac ϭ acetate). The starting materials were thoroughly mixed and heated in air at 500°C for 4 h or at 800°C for 6 h. Samples were reground by hand and annealed at 500 or 800°C for 24 h. The three sample series were designated M500 or M800, depending on their synthesis temperature, M being the substituting transition metal.…”

Section: Methodsmentioning

confidence: 99%

“…The starting materials were thoroughly mixed and heated in air at 500°C for 4 h or at 800°C for 6 h. Samples were reground by hand and annealed at 500 or 800°C for 24 h. The three sample series were designated M500 or M800, depending on their synthesis temperature, M being the substituting transition metal. A Cr-substituted spinel of similar composition was also prepared by using a sol-gel procedure 15 involving the reaction between Mn͑acac) 3 and Li 2 CO 3 in boiling propionic acid under vigorous stirring, and the addition of Cr͑acac) 3 to obtain the doped form. Solutions were heated to dryness at 140°C.…”

Section: Methodsmentioning

confidence: 99%

“…Three series of cation-substituted lithium manganese spinels of nominal composition LiM 0.2 Mn 1.8 O 4 (M ϭ Cr,Ni,Cu) were prepared from appropriate amounts of Li 2 CO 3 ͑Merck͒ and freshly prepared Mn͑acac) 3 , Cr͑acac) 3 , or Cu͑acac) 2 (acac ϭ acetylacetonate) by using a conventional ceramic method at two different temperatures ͑500 and 800°C͒. The precursors used for the Ni-substituted spinels were Mn(ac) 3 • 2H 2 O and Ni͑ac) 2 • 4H 2 O (ac ϭ acetate).…”

Section: Methodsmentioning

confidence: 99%

“…1 LiM x Mn 2Ϫx O 4 spinels (M ϭ V 5ϩ , 2 Cr 3ϩ , 3 Fe 3ϩ , 4 Co 3ϩ , 5 Ni 2ϩ , 6 Cu 2ϩ , 7 and Al 3ϩ 8 ͒, in addition to LiMn 2 O 4 itself, 9 have been found to exhibit this peculiar behavior. While the oxidation of M may account for the electrochemical reaction yielding the plateau, that of V 5ϩ , Al 3ϩ , or even LiMn 2 O 4 is not so clearly associated with this phenomenon.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Caballero

Hernán

Melero

et al. 2005

J. Electrochem. Soc.

View full text Add to dashboard Cite

The origin of the overcharge in the 5 V region observed in lithium-substituted LiM x Mn 2Ϫx O 4ϩ␦ spinels (M ϭ Cr, Ni, Cu; x Ϸ 0.2) prepared at 500°C was analyzed by using accurate analytical spectroscopic techniques ͑mass spectroscopy, nuclear magnetic resonance͒ to examine the electrolyte behavior. The spectra revealed organic solvents to be stable as no decomposition products were detected, thus excluding the electrolyte oxidation as a side reaction accounting for the cell overcharge. However, these spinels contain excess oxygen in an amount that was quantified from thermogravimetric data. The excess oxygen plays a prominent role in the electrochemical response of the spinel. The cyclic voltammetry and galvanostatic results support the assumption that the excess oxygen can be released above 4.5 V. The additional capacity obtained and that required to release the oxygen were quite consistent. This must be the origin of both the overcharge and the poor performance of the cells compared with spinels of similar composition but synthesized at higher temperatures ͑800°C͒, the excess of oxygen in which was smaller. The ability of some Li-Mn based spinels to exhibit high-voltage plateaus at about 5 V has opened up new prospects for lithium batteries such as the possibility of manufacturing high-voltage batteries capable of supplying highly specific energy.1 LiM to Mn 5ϩ or Mn 6ϩ hypothesized for the undoped spinel has not yet been confirmed. Two alternative side reactions can be considered: ͑i͒ electrolyte oxidation above 4.6 V and (ii) a redox process undergone by the oxygen lattice of the spinel framework involving release of oxygen. This latter model can be related with theoretical computations based on either first-principles calculations 10 or the DV-X␣ molecular orbital model.11 Based on such models, when M is substituted by Mn ions, a new O 2p band at a low energy is responsible for the high electrochemical cell voltage observed. Simultaneously, evolved oxygen may oxidize organic solvents. These unwanted side reactions can lead to a premature cell capacity loss. Three recent reports 12-14 have insisted on the origin of the electrochemical activity above 4.5 V. Thus, Wang et al. 12 claim that the high voltage capacity of Li 1ϩx Mn 2Ϫx O 4Ϯz originates from the extraction of Li ϩ at 16d sites, whereas Shin and Manthiram 13,14 ascribe it to the involvement of O 2Ϫ -2p in the redox process. The aim of this work was to help clarify the processes taking place in the high-potential region of 5 V in cation-substituted lithium manganese spinels. For this purpose, Cr-, Ni-, and Cusubstituted spinels containing the doping elements in various oxidation states and prepared at two different temperatures ͑500 and 800°C͒ were examined. The electrolyte decomposition was analyzed using mass spectrometry ͑MS͒ and nuclear magnetic resonance ͑NMR͒ measurements. These measurements, together with thermogravimetric ͑TG͒ data, confirmed the central role played by the excess oxygen ion in the spinel lattice. ExperimentalThree series ...

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Caballero

Hernán

Melero

et al. 2005

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…In order to overcome the capacity fade caused by the Jahn-Teller distortion, many authors have suggested substituting some of the manganese with trivalent or divalent cations in order to reduce the resultant Mn (III) content 6,7 . There are number of reports on the influence of substitutions with many 3d transition and non transition metal ions [8][9][10] . However, the reduction of the amount of the active Mn (III) species decreases the maximum value of the capacity that can be reached in the 3.5-4.2 V range.…”

Section: Introductionmentioning

confidence: 99%

Effect of Si(iv) substitution on electrochemical, magnetic and spectroscopic performance of nanosized LiMn2−xSixO4

et al. 2013

View full text Add to dashboard Cite

We report a simple and cheap process for the synthesis of Si substituted LiMn 2 O 4 . The resulting materials are composed of partially sintered particles of 80 nm average size, corresponding to single crystalline phases with cubic spinel structures. The substitution of Mn(IV) by Si(IV) in the crystal framework changed the cell parameter and volume, and was confirmed by the evolution observed in the XPS and ESR measurements. A complete magnetic study was carried out. Due to the in-built magnetic frustration within the spinel structure and the competition between different exchange pathways, the insertion of different quantities of Si(IV) causes significant differences in the properties. The electrochemical study revealed that introducing a small amount of Si (IV) enhances the electrochemical performance of the spinel. The highest specific capacity and rate discharge capability were obtained for LiMn 1 . 95 Si 0.05 O 4 , while insertion of a higher amount of the tetravalent dopant caused deterioration of the electrochemical behavior.

show abstract

Semiempirical calculations on WO ₃ and M _X WO ₃ crystals (M = H, Li, Na)

Stashans

Lunell

1997

Int J of Quantum Chemistry

View full text Add to dashboard Cite

ABSTRACT:The monoclinic structure of tungsten trioxide WO has been studied by 3 Ž . combining a modified intermediate neglect of differential overlap INDO method and the supercell model. The fitted semiempirical parameters describe very well the features of the band structure and crystal structure. Calculations of H, Li, and Na impurities in a WO crystal have been performed to study the absorption spectra and the equilibrium 3 geometries of intercalated impurities.

show abstract

Lithium insertion into pyrochlore WO3

Cited by 44 publications

References 9 publications

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Effect of Si(iv) substitution on electrochemical, magnetic and spectroscopic performance of nanosized LiMn2−xSixO4

Semiempirical calculations on WO ₃ and M _X WO ₃ crystals (M = H, Li, Na)

Contact Info

Product

Resources

About

Lithium insertion into pyrochlore WO3

Cited by 44 publications

References 9 publications

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Oxygen Lattice Instability as a Capacity Fading Mechanism for 5 V Cathode Materials

Effect of Si(iv) substitution on electrochemical, magnetic and spectroscopic performance of nanosized LiMn2−xSixO4

Semiempirical calculations on WO 3 and M X WO 3 crystals (M = H, Li, Na)

Contact Info

Product

Resources

About

Semiempirical calculations on WO ₃ and M _X WO ₃ crystals (M = H, Li, Na)