Now showing 1 - 10 of 16
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    Reversible Li insertion studies on V4O3(PO4)3 as high energy storage material for Li-Ion battery applications
    (01-01-2017)
    Satyanarayana, M.
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    Rao, R. S.
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    Pralong, V.
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    Li-insertion studies were performed on V4O3(PO4)3 that belongs to the libscombite/lazulite family. Availability of multiple oxidation states and vacancies in crystal structure allows for the insertion of more than 7 lithium ions per formula unit. We will show that in the voltage window of 1-4 V vs. Li+/Li, 6.0 Li-ions could be inserted leading to a reversible capacity of 195 mAh/g at a C/5 rate. A structural transformation is observed from ex-situ XRD patterns after the insertion of 2 lithium at 2.4 V vs. Li+/Li, consistent with the available crystallographic sites in the structure. Interestingly we show that from this phase Li2V4O3(PO4)3, further lithium insertion lead to an amorphous material but the structure is completely recovered on charge.
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    New layered hydrogenophosphate, protonic conductor: Mn(H2PO 4)2
    (07-07-2008)
    Baies, R.
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    Pralong, V.
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    Caignaert, V.
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    Saradhi, M. P.
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    Raveau, B.
    A new hydrogenophosphate Mn(H2PO4)2 has been synthesized from an aqueous solution. Its ab initio structure resolution shows that the original layered structure of this phase consists of PO 2(OH)2 tetrahedra and MnO5OH octahedra, sharing corners to form [MnP2O8H4]∞ layers, whose cohesion is ensured through hydrogen bonds. The excitation and emission spectra of this phase are characteristic of Mn2+ species. This phosphate is shown to be a good protonic conductor with a conductivity of 10-4.4 S/cm at 90°C (363 K). © 2008 American Chemical Society.
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    Crystallite size constraints on lithium insertion into brookite TiO2
    (23-06-2008)
    Anji Reddy, M.
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    Pralong, V.
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    Raveau, B.
    We demonstrate lithium insertion into brookite TiO2 in the nanophase regime. The extent of lithium insertion is significantly influenced by the crystallite size. A maximum of 0.95 Li/ TiO2 can be inserted into 10 nm size crystallites and the extent of lithium insertion is low (0.23 Li) in 33 nm crystallites. The reversibility decreases with an increase in crystallite size. The contrasting behavior of brookite and rutile TiO2 suggests that the structural features of brookite TiO2 may play an important role in determining Li insertion behavior. © 2008 The Electrochemical Society.
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    Lithium intercalation into nanocrystalline brookite TiO2
    (08-01-2007)
    Reddy, M. Anji
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    Kishore, M. Satya
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    Pralong, V.
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    Raveau, B.
    Lithium intercalation in phase-pure nanocrystalline brookite TiO2 is demonstrated for the first time. Galvanostatic studies show that 0.9 Li per formula unit can be intercalated into this phase in initial discharge. Ex situ X-ray diffraction studies on the electrodes at different levels of lithium intercalation show that the structure is stable toward lithium intercalation and deintercation. In the initial charge, an irreversible capacity loss is observed. However, on further cycling, the phase shows excellent cycling behavior. A reversible capacity of 170 mAhg-1 is observed even after 40 cycles. © 2006 The Electrochemical Society.
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    Synthesis and electrochemical properties of a new vanadyl phosphate: Li4VO(PO4)2
    (01-10-2006)
    Kishore, M. Satya
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    Pralong, V.
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    Caignaert, V.
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    Raveau, B.
    The exchange of lithium for proton in VO(H2PO4)2 has been studied. Beside the continuous exchange from VO(H2PO4)2 to Li2H2VO(PO4)2, a new cathode material Li4VO(PO4)2 has been synthesized, whose structure is closely related to that of VO(H2PO4)2. The electrochemical evaluation of Li4VO(PO4)2 vs. Li shows that it undergoes reversible lithium deintercalation/intercalation at high voltage, ∼4.0 V with a reversible capacity of ∼70 mAh/g. © 2006 Elsevier B.V. All rights reserved.
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    Electrochemical Li insertion studies on WNb12O33-A shear ReO3 type structure
    (01-05-2010)
    Saritha, D.
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    Pralong, V.
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    Raveau, B.
    Electrochemical lithium insertion studies on WNb12O33 synthesized by solid state reaction (SSR) are carried out in the voltage range 1.0-3.2 V. During first discharge 15.6 Li are inserted with a specific capacity of 221 mAh/g. WNb12O33 is also synthesized by sol-gel (SG) technique with a view to enhance the rate capability and cycling properties. The SSR and SG samples are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic cycling. Electrochemical cycling performance of SG samples is superior to that of the SSR sample at high 'C' rates. The sample synthesized by SG method exhibits high specific capacity of 142 mAh/g after 20 cycles at 20C rate. © 2010 Elsevier Inc. All rights reserved.
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    A new form of LiNbO3 with a lamellar structure showing reversible lithium intercalation
    (12-04-2011)
    Pralong, V.
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    Reddy, M. Anji
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    Caignaert, V.
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    Malo, S.
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    Lebedev, O. I.
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    Raveau, B.
    The exchange of lithium for univalent copper in CuNbO3 has been investigated. A new form of LiNbO3 with a lamellar structure has been synthesized from the topotactic reaction between CuNbO3 and a molten salt corresponding to the eutectic "LiCl/LiNO3". This compound crystallizes in the P21/a space group with a = 9.433 Å, b = 8.226 Å, c = 6.213 Å, and β = 90.2°. This new phase intercalates one lithium on the first discharge and shows reversibility of 0.7 lithium through a first-order transformation leading to a capacity of 120 mAh/g at a potential of 1.65 V vs Li+/Li. © 2011 American Chemical Society.
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    Electrochemical intercalation of lithium in the titanium hydrogeno phosphate Ti(HPO4)2·H2O
    (20-06-2007)
    Kishore, M. Satya
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    Pralong, V.
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    Caignaert, V.
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    Raveau, B.
    The electrochemical reactivity of the layered titanium hydrogeno phosphate Ti(HPO4)2·H2O versus lithium has been studied. Lithium intercalation occurs at ∼2.5 V with low polarization, leading to a new lithiated Ti(III) phase, LiTi(HPO4)2·H2O. Ti(HPO4)2·H2O exhibits a reversible capacity of 80 mAh g-1 in the voltage window 1.8-3.5 V at C/10 rate. The stable reversible capacity reveals that the presence of H2O lattice is not affecting the electrochemical reaction. The reversibility of the reaction is demonstrated by extracting lithium from LiTi(HPO4)2·H2O and the host structure is intact. The electrochemical behaviour of dehydrated phases Ti(HPO4)2 and TiP2O7 has also been investigated. © 2007 Elsevier B.V. All rights reserved.
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    A new lithium vanadyl diphosphate Li2VOP2O7: Synthesis and electrochemical study
    (01-10-2008)
    Kishore, M. Satya
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    Pralong, V.
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    Caignaert, V.
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    Raveau, B.
    A new vanadium diphosphate, Li2VOP2O7, has been synthesized by ion exchange from Na2VOP2O7, using an eutectic mixture of {0.4LiOH·H2O-0.6LiNO3} at 200 °C. It crystallizes in space group P21/c, with the lattice parameters a = 7.4674(8) Å, b = 12.442(2) Å, c = 6.2105(7) Å and β = 97.79(1)°. The crystal structure of Li2VOP2O7, refined by powder X-ray diffraction data, shows that the structure of the parent Na-phase is retained but a prominent decrease in the layer spacing is observed. Li2VOP2O7 has been tested as a cathode material for Li-ion battery. One lithium is deintercalated by charging to 4.6 V, however, on discharge only about 0.5 Li is re-intercalated. © 2007 Elsevier Masson SAS. All rights reserved.
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    Facile chemical insertion of lithium in Eu0.33Zr2(PO 4)3-An elegant approach for tuning the photoluminescence properties
    (12-05-2009)
    Saradhi, M. P.
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    Pralong, V.
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    Raveau, B.
    The synthesis of a mixed valent LixEuIIxEuIII0.33-xZr2(PO4) 3 with the NZP structure, using soft chemistry was reported. Stoichiometric amounts of starting materials Eu2O3 and ZrOCl2.8H2O were dissolved in 2 N HNO3, addition of NH4H2PO4 to the metal nitrate solution under constant stirring resulted in a colorless gel. Electrochemical lithium insertion studies were carried out by using Swagelok type cells with lithium metal as the negative electrode. The mixture was pressed onto a stainless steel plate to form the electrode. The photoluminescence (PL) spectrum of the reduced phase shows signature of both Eu3+ and Eu 2+ excitation and emission bands. It was observed that The CIE coordinates are significantly changed upon Li insertion and shift towards the white region as the concentration of Li increases in the host.