A XANES study of the valence state of vanadium in lithium vanadate phosphate glasses

Bacewicz, R.; Wasiucionek, M.; Twaróg, A.; Filipowicz, J.; Jóźwiak, P.; Garbarczyk, Jerzy E.

doi:10.1007/s10853-005-2827-5

Cited by 18 publications

(13 citation statements)

References 10 publications

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“…Introduction of LiFeP 2 O 7 is detected by the appearance of two sets of IR bands at 762 and 1,180 cm −1 . The band at 762 cm −1 is due to the symmetric stretching mode of P 2 O 7 pyrophosphate groups, while the high-frequency band at 1,180 cm −1 is assigned to the vibration of the PO 3 terminals [17][18][19].…”

Section: Resultsmentioning

confidence: 99%

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Zaghib

Mauger

Giligny

et al. 2007

Ionics

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International audienceThis work is devoted to the study of fundamental properties of LiFePO4 (LFP) olivine in view of the optimization of this material for its use as a positive electrode material in Li-ion batteries. The investigation of the electronic and magnetic properties appears to be successful for the detection of a small amount of impurities. By the combination of X-ray diffraction, optical spectroscopy, and magnetometry, we characterize the local structure and the morphology of LFP particles. The impact of the ferromagnetic clusters (γ-Fe2O3 or Fe2P) on the electrochemical response is examined. The electrochemical performance of the optimized LFP powders investigated at 60 °C is excellent in terms of capacity retention (153 mAh/g at 2 C) as well as cycling life. No iron dissolution was observed after 200 charge–discharge cycles at 60 °C for cells containing Li foil, Li4Ti5O12, or graphite as negative electrode

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Section: Resultsmentioning

confidence: 99%

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Zaghib

Mauger

Giligny

et al. 2007

Ionics

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“…is a decreasing function of V 2 O 5 content in a glass [12], and it can be the reason for the decrease in conductivity with increase of V 2 O 5 for some contents of V 2 O 5 (10% to 20%). Activation energy of samples was obtained from slope of the plot of ln(σ) versus 1/kT.…”

Section: Resultsmentioning

confidence: 97%

“…It means that for higher values of r, the glass network, consisting of vanadate and phosphate polyhedra, is more disrupted. In such cases, the electronic conduction paths are discontinuous [12]. Study on binary V 2 O 5 -P 2 O 5 glasses indicated that the relative abundance of vanadium in V 4+ valence state c¼ V 4þ…”

Section: Resultsmentioning

confidence: 99%

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Activation energy and conductivity of glasses in the P2O5–V2O5–Li2O system

Behzad

Hekmatshoar

Mirzayi

et al. 2009

Ionics

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The conductivity of glasses in the 50P 2 O 5 À xV 2 O 5 À 50 À x ð ÞLi 2 O system was studied as a function of temperature and composition. For all compositions, the conductivity variation as a function of temperature followed an Arrhenius type relationship. Isothermal variation of conductivity as a function of composition showed a minimum for a molar ratio x near 20. Probable mechanisms for decrease of conductivity with decrease of vanadium oxide concentration were explained. The minimum in room temperature was attributed to increase of V 4+ /V 5+ with decrease of vanadium oxide in specific concentrations of vanadium oxide. Activation energy increased with decrease of V 2 O 5 content. This behavior was attributed to increase of average spacing between vanadium ions.

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“…This change in peak intensity is most likely related to the ratio of vanadium sites with 4+ and 5+ oxidation states; in several previous studies it was shown that the intensities of the two vanadium K-edge pre edge peaks in lithium vanadium phosphate glasses were consistent with the V 4+ and V 5+ fraction as determined independently using EPR studies. [49][50][51][52] The crystal structure of Ag 0.48 VOPO 4 has two similar vanadium sites that each have a silver ion in close proximity at a distance of ∼3.7 Å. Depending on whether this silver site is vacant, the neighboring vanadium ions may have initially have either a 4+ or 5+ oxidation state.…”

Section: Electrochemicalmentioning

confidence: 99%

Electrochemical Reduction of Ag_0.48VOPO₄: A Mechanistic Study Employing X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

Kirshenbaum

Menard

Kim

et al. 2015

J. Electrochem. Soc.

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The electrochemical reduction of Ag 0.48 VOPO 4 • 1.9H 2 O is accompanied by vanadium and silver oxidation state changes, characterized with X-ray absorption spectroscopy (XAS), and by structural changes, characterized with X-ray powder diffraction (XRD). The XAS data suggest that the initial reduction process, involving 0 to 0.5 electron equivalents, involved primarily the reduction of vanadium cations, while most of the silver cations are reduced between 0.5 to 1.0 electron equivalents. The XRD data display significant intensity decreases of absorbances associated with the 004 and 006 planes upon electrochemical reduction, consistent with a reduction-displacement of Ag + with insertion of Li + . Retention of intensity of the absorbance associated with the 002 plane, with only minor decrease in interlayer spacing, indicates retention of the VOPO 4 sublattice structure. Uncovering the details of the discharge mechanism of bimetallic cathode materials such as Ag 0.48 VOPO 4 should enable the design of future high current cathodes for secondary batteries displaying an enhanced current capacity based on a reduction-displacement strategy. Polyanionic frameworks form the basis of a number of battery electrode materials with desirable electrochemical properties.1 For example, commercial cells using LiFePO 4 chemistry have found success owing to both high charge and discharge current capability. Unfortunately, these materials can display low electrical and ionic conductivities; fortunately, the use of a conductive additive such as carbon can mitigate these issues. However, the use of conductive additives may increase production costs and negatively affect energy density. 3,4 In addition to conductive additives, low electrical conductivities of electroactive electrode materials can be addressed by exploiting electrode electrochemistries that form conductive metallic networks in situ. Specifically, we established through impedance experiments that the metallic particles formed upon reduction of some bimetallic cathode materials can enhance the conductivity by several orders of magnitude. 5 We successfully extended this strategy to four different members of the material family of silver vanadium phosphorous oxides, Ag 2 VO 2 PO 4 , 21 This strategy should lead to a variety of future battery materials, especially for high current applications.To delineate the discharge process in bimetallic materials, the oxidation state changes associated with the two metal cations as a function of discharge should be obtained. Using X-ray absorption spectroscopy (XAS), the oxidation state as well as the local environment can be measured nondestructively. XAS measurements of LiFePO 4 have been used to show the irreversibility and partial formation of FePO 4 during cycling. 22 There have also been several previous studies on silver vanadium phosphate compounds using XAS to study Ag 2 VO 2 PO 4 , 7 and Ag 2 VP 2 O 8 11 in which the effect of discharge rate on the ratio of V/Ag reduction was determined. * Electrochemical Society Active Membe...

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A XANES study of the valence state of vanadium in lithium vanadate phosphate glasses

Cited by 18 publications

References 10 publications

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Activation energy and conductivity of glasses in the P2O5–V2O5–Li2O system

Electrochemical Reduction of Ag_0.48VOPO₄: A Mechanistic Study Employing X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

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A XANES study of the valence state of vanadium in lithium vanadate phosphate glasses

Cited by 18 publications

References 10 publications

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Relationship between local structure and electrochemical performance of LiFePO4 in Li-ion batteries

Activation energy and conductivity of glasses in the P2O5–V2O5–Li2O system

Electrochemical Reduction of Ag0.48VOPO4: A Mechanistic Study Employing X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction

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Electrochemical Reduction of Ag_0.48VOPO₄: A Mechanistic Study Employing X-Ray Absorption Spectroscopy and X-Ray Powder Diffraction