Comparison of the Small‐Polaron Theory with the Experimental Data of Current Transport in V<sub>2</sub>O<sub>5</sub>

Ioffe, V. A.; Patrina, I. B.

doi:10.1002/pssb.19700400140

Cited by 95 publications

(36 citation statements)

References 5 publications

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“…The high-temperature activation energy deduced from the slope of this curve is W = (0.21 & 0.01) eV. This value is in agreement with those measured in non-stojchiometric V,O, [S], and this suggests that the hopping of free polarons is typically independent of the nature of the defect, An increase of measured activation energy is observed below 225 K. Ioffe and Patrina mentioned that conductivity remains no longer proportional to the number of paramagnetic centres determined by ESR [13]. This suggests that some unpaired electrons remain trapped around the Coulombic field created by Li+ impurities and therefore do not contribute to conductivity.…”

Section: Esrsupporting

confidence: 88%

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Small Polaron Mobility in α‐Li_xO₅

Sánchez

Henry

Morineau

et al. 1984

Physica Status Solidi (b)

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ESR and dc conductivity measurements are performed on a Li,V,O, (z = 0.001) single crystal in the temperature range 4 to 293 K. They suggest that at low temperature, the unpaired electron remains localized in the field of lithium ion and is equally delocalized over four vanadium sites leading to the formation of a bound polaron characterized by a 29 hyperfine lines ESR spectrum. As the temperature is raised bound polarons are freed from the electrostatic field and the electrical properties of the sample above 250 K mainly arise from the hopping of free polarons between the vanadium sites. A comparison with previous measurements on non-stoichiometric V,O, shows that the activation energy corresponding to the hopping process of free polarons does not depend on the nature of the paramagnetic defect, but it appears that the energy needed to extract the bound polaron from the Coulomb field of the defect decreases when the overall radius of the defect increases.EPR und Messungen der Gleichstromleitfilhigkeit werden an einem Li,V,O, (z = 0,00l)-Einkristall im Temperaturbereich 4 bis 293 K durchgefuhrt. Sie zeigen, daB bei tiefen Temperaturen das ungepaarte Elektron lokalisiert bleibt im Feld des Lithiumions und gleichformig delokalisiert ist iiber vier Vanadiumpliitze, was zu der Bildung eines gebundenen Polarons fuhrt, das durch ein EPR-Spektrum mit 29 Hyperfeinlinien charakterisiert ist. Bei Temperaturerhohung werden die gebundenen Polaronen aus dem elektrostatischen Feld befreit und die elektrischen Eigenschaften der Probe oberhalb 250 K ruhren hauptsiichlich vom Hopping-Mechanismus der freien Polaronen zwischen den Vanadiumpliitzen her. Ein Vergleich mit friiheren Messungen an nichtstochiometrischem V,O, zeigt, daB die dem HoppingprozeS freier Polaronen entsprechende Aktivierungsenergie nicht von der Art des paramagnetischen Defekts abhiingt, sondern es scheint, daS die Energie, die zur Befreiung des gebundenen Polarons aus dem Coulombfeld des Defekts notwendig ist, abnimmt, wenn der Gesamtradius des Defekts wiichst.

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Section: Esrsupporting

confidence: 88%

“…This hypothesis was based on several observations : 1. The conductivity appears to be proportional to the number of paramagnetic centres above room temperature, but this relation is no more valid below 300 K[13].…”

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confidence: 96%

Small Polaron Mobility in α‐Li_xO₅

Sánchez

Henry

Morineau

et al. 1984

Physica Status Solidi (b)

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“…The signatures of polaron formation and polaron hopping energies have been predicted theoretically, but direct experimental evidence of polaron formation and the accompanying geometric distortions have hitherto not been examined525262728. Here we present direct evidence of inhomogeneities in charge localization and local structural distortions induced on lithiation using scanning transmission X-ray microscopy (STXM) and corroborate theoretical predictions of a distinctive polaronic state using X-ray absorption near-edge structure and hard-energy X-ray photoemission spectroscopies.…”

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confidence: 99%

Mapping polaronic states and lithiation gradients in individual V2O5 nanowires

et al. 2016

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The rapid insertion and extraction of Li ions from a cathode material is imperative for the functioning of a Li-ion battery. In many cathode materials such as LiCoO2, lithiation proceeds through solid-solution formation, whereas in other materials such as LiFePO4 lithiation/delithiation is accompanied by a phase transition between Li-rich and Li-poor phases. We demonstrate using scanning transmission X-ray microscopy (STXM) that in individual nanowires of layered V2O5, lithiation gradients observed on Li-ion intercalation arise from electron localization and local structural polarization. Electrons localized on the V2O5 framework couple to local structural distortions, giving rise to small polarons that serves as a bottleneck for further Li-ion insertion. The stabilization of this polaron impedes equilibration of charge density across the nanowire and gives rise to distinctive domains. The enhancement in charge/discharge rates for this material on nanostructuring can be attributed to circumventing challenges with charge transport from polaron formation.

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“…At temperatures higher than 300 K, the hyperfine structure in the EPR spectra disappears and, hence, localized states are absent [7,8]. In this temperature range, electrons are free and the activation energy is E a = 0.16 eV.…”

Section: Sensory Properties Of Vanadium Pentoxide Films In Gaseous Mediamentioning

confidence: 99%