Electronic structure of transition-metal chalcogenides and their intercalation compounds

McKinnon, W. R.

doi:10.1007/978-1-4757-9649-0_9

Cited by 14 publications

(3 citation statements)

References 33 publications

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“…This process shifts the resonance peak by some ppm to lower frequencies from that for Li + in solution (LiCl). This result cannot be compared to the shift of 240 ppm for Li in Li metal [17]. It indicates that the electronic density in the Li + ion environment increases as intercalation occurs.…”

Section: LI Nmrmentioning

confidence: 79%

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy

Eméry

Bohnké

Fourquet

et al. 1999

J. Phys.: Condens. Matter

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The long-range and short-range motion of lithium ions into an electrochemically intercalated Li3xLa2/3-xTiO3 (LLTO) sintered pellet has been studied by ac impedance spectroscopy and 7Li solid state nuclear magnetic resonance (NMR). The temperature dependence of the dc conductivity and the intercalation ratio dependence of the chemical shift, the relative intensity of the resonance line, the spin-lattice and the spin-spin relaxation times of 7Li NMR experiments are indicative of polaron formation at the initial stage of intercalation. The total dc conductivity measured in the temperature range 45-600 K and the shape of the impedance diagrams show that after intercalation the conductivity is both ionic and electronic in nature. However for temperatures lower than 300 K the total conductivity is mainly dominated by the electronic one and for temperatures higher than 400 K the total conductivity is dominated by the ionic one. Moreover at low temperatures, when electronic conductivity dominates, the temperature dependence of the conductivity agrees well with a polaron model for conduction in these intercalated oxides. The NMR experiments clearly show that the resonance peak decreases strongly as intercalation occurs. This is explained by a coupling between the electronic and the Li+ nuclear spins leading to an unobservability of some Li+ nuclei in NMR. The other Li+ nuclei, which do not interact directly with the electronic spins, are responsible for the observed NMR signal. If the static effect of the intercalation is weak and leads to a very small chemical shift variation, variable temperature 7Li NMR spin-lattice and spin-spin relaxation measurements show that the presence of electrons acts essentially on the dynamics of the Li+ nuclei through the lattice modification induced by the polaron formation. At the beginning of the intercalation the inverse of the relaxation time T1 of the observed Li+ nuclei decreases by one order of magnitude. At the same time the linewidth of the resonance peak (1/T2) decreases abruptly. The motion of the lithium ions is sharply enhanced. For further intercalation, 1/T1 decreases and the linewidth of the central peak increases indicating that the variations of the relaxation times are mostly governed by the variations of the spectral densities of the Li+ motion. Consequently, the lithium motion decreases gradually as intercalation proceeds. These results are in good agreement with a lattice modification due to polaron formation during intercalation.

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Section: LI Nmrmentioning

confidence: 79%

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy

Eméry

Bohnké

Fourquet

et al. 1999

J. Phys.: Condens. Matter

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“…In layered solids, the interaction between guest intercalants and the host layers is defined by the match of energy level, which has roots in the chemical structure. [4][5][6]108 As shown in Figure 2c, three major types of the layered materials are identified according to the surface chemistry, namely, (i) the graphitelike materials that feature the nonpolar surface and π-electrondominated van der Waals gaps; 4,108 (ii) TMDs-like layered solids that are also built on weak interlayer van der Waals interactions but with polar covalent bonds (therefore they own the ability to be electrically doped); 5 (iii) clay-like layered materials that consist of high electron negativity elements on the surface (e.g., -O/-OH/-F) and a neutral/intrinsically charged skeleton. 2,3,6 Graphite could be intercalated by both electron donors and acceptors (such as alkali metal and halogen); 108,109 in these two cases electrons either flow into or are lost from the conduction band in graphite.…”

Section: Mxenes and Their Intercalation Behaviorsmentioning

confidence: 99%

Host–Guest Intercalation Chemistry in MXenes and Its Implications for Practical Applications

Chen

2021

ACS Nano

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The ever-increasing demand on developing layered materials for practical applications, such as electrochemical energy storage, responsive materials, nanofluidics, and environmental remediation, requires the profound understanding and artful exploitation of interlayer engineering or intercalation chemistry. The past decade has witnessed the massive exploration of a recently discovered 2D materialtransition metal carbides, carbonitrides, and nitrides (referred to as MXenes), which began to take hold of a myriad of applications owing to the abundant possibilities on their compositions and intercalation states. However, application-targeted manipulation of the material performance of MXenes is constrained by the dearth of deep comprehension on fundamental intercalation chemistry/physics. To this end, the aim of this review is to provide a holistic discussion on the intercalation chemistry in MXenes and the physical properties of MXene intercalation compounds. On the basis of this, potential solutions for the challenges confronted in the synthesis, tuning of material properties, and practical applications are proposed, which are also expected to reinvigorate the exploration of layered materials that are similar to MXenes.

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“…For that reason, TiS 2 and also other lamellar transition-metal dichalcogenides have attained considerable attention. [1][2][3] The first polarized Ti K absorption of TiS 2 was studied by Antonangeli et al, 4 however, their theoretical results do not match well the experiment and cannot reliably explain and interpret observed features in spectra. Quite recently Wu et al [5][6][7] presented unpolarized experimental and theoretical studies of x-ray-absorption near-edge structure ͑XANES͒ of Ti K and S K edges for TiS 2 .…”

Section: Introductionmentioning

confidence: 99%

Unoccupied electron states ofTiS2studied by means of polarized x-ray absorption

et al. 1997

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Using polarized x-ray-absorption spectroscopy along with band-structure and real-space multiple-scattering calculations, we have studied unoccupied states of TiS 2 . With respect to titanium and sulfur sites, the local angular momentum projections of the density of states are presented for states up to 25 eV above the Fermi level. Good agreement between experiment and theory suggests that quadrupole (1s→d) transitions in Ti K absorption are negligible compared to dipole (1s→p) transitions. We have applied a new technique for construction of pseudopotentials adapted to the chemical bond and found that previous calculation of electronic states with energies higher than 10 eV above Fermi level was not correct.

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Electronic structure of transition-metal chalcogenides and their intercalation compounds

Cited by 14 publications

References 33 publications

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy

Host–Guest Intercalation Chemistry in MXenes and Its Implications for Practical Applications

Unoccupied electron states ofTiS2studied by means of polarized x-ray absorption

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Electronic structure of transition-metal chalcogenides and their intercalation compounds

Cited by 14 publications

References 33 publications

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by7Li NMR and impedance spectroscopy

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by7Li NMR and impedance spectroscopy

Host–Guest Intercalation Chemistry in MXenes and Its Implications for Practical Applications

Unoccupied electron states ofTiS2studied by means of polarized x-ray absorption

Contact Info

Product

Resources

About

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy

Polaronic effects on lithium motion in intercalated perovskite lithium lanthanum titanate observed by⁷Li NMR and impedance spectroscopy