Lithium-rich anti-perovskites (LiRAPs) have attracted a great deal of attention as they have been praised as another superior group of solid electrolytes that can be used to realize all-solid-state ...batteries free of flammable liquids. Despite several studies that have reported on the properties of LiRAPs, many questions remain unanswered. In particular, these include fundamental ones concerning the structure, stability, and Li-ion conductivity and diffusivity. Moreover, it is not clear whether some of the previously reported compounds do really exist. To untangle the current picture of LiRAPs, we synthesized “Li3OCl” and Li2OHCl polymorphs and applied a wide spectrum of methods, such as powder X-ray diffraction (PXRD), powder neutron diffraction (PND), nuclear magnetic resonance spectroscopy, and impedance spectroscopy to carefully shed some light on LiRAPs. Here we self-critically conclude that the cubic polymorph of the two compounds cannot be easily distinguished by PXRD alone as the lattice metrics and the lattice parameters are very similar. Furthermore, PXRD suffers from the difficulty of detecting H and Li. Even Rietveld refinement of our PND data turned out to be complicated and not easily interpreted in a straightforward way. Nevertheless, here we report the first structural models for the cubic and a new orthorhombic polymorph containing also structural information about the H atoms. In situ PXRD of “Li3OCl”, intentionally exposed to air, revealed rapid degradation into Li2CO3 and amorphous LiCl·xH2O. Most likely, the instability of “Li3OCl” explains earlier findings about the unusually high ion conductivities as the decomposition product LiCl·xH2O offers an electrical conductivity that is good enough for some applications, excluding, of course, those that need aprotic conditions or electrolytes free of any moisture. Considering “H-free Li3OCl” as well as Li5(OH)3Cl2, Li5(OH)2Cl3, Li3(OH)2Cl, and Li3(OH)Cl2, we are confident that Li4(OH)3Cl and variants of Li3–x (OH x )Cl, where x > 0, are, from a practical point of view, so far the only stable lithium-rich anti-perovskites.
Li oxide garnets are among the most promising candidates for solid-state electrolytes in novel Li ion and Li metal based battery concepts. Cubic Li7La3Zr2O12 stabilized by a partial substitution of ...Zr4+ by Bi5+ has not been the focus of research yet, despite the fact that Bi5+ would be a cost-effective alternative to other stabilizing cations such as Nb5+ and Ta5+. In this study, Li7-xLa3Zr2-xBixO12 (x = 0.10, 0.20, ..., 1.00) was prepared by a low-temperature solid-state synthesis route. The samples have been characterized by a rich portfolio of techniques, including scanning electron microscopy, X-ray powder diffraction, neutron powder diffraction, Raman spectroscopy, and 7Li NMR spectroscopy. Pure-phase cubic garnet samples were obtained for x ≥ 0.20. The introduction of Bi5+ leads to an increase in the unit-cell parameters. Samples are sensitive to air, which causes the formation of LiOH and Li2CO3 and the protonation of the garnet phase, leading to a further increase in the unit-cell parameters. The incorporation of Bi5+ on the octahedral 16a site was confirmed by Raman spectroscopy. 7Li NMR spectroscopy shows that fast Li ion dynamics are only observed for samples with high Bi5+ contents.
Li-oxide
garnets such as Li
7
La
3
Zr
2
O
12
(LLZO) are among the most promising candidates for
solid-state electrolytes to be used in next-generation Li-ion batteries.
The garnet-structured cubic ...modification of LLZO, showing space group
Ia
-3
d
, has to be stabilized with supervalent
cations. LLZO stabilized with Ga
3+
shows superior properties
compared to LLZO stabilized with similar cations; however, the reason
for this behavior is still unknown. In this study, a comprehensive
structural characterization of Ga-stabilized LLZO is performed by
means of single-crystal X-ray diffraction. Coarse-grained samples
with crystal sizes of several hundred micrometers are obtained by
solid-state reaction. Single-crystal X-ray diffraction results show
that Li
7–3
x
Ga
x
La
3
Zr
2
O
12
with
x
> 0.07 crystallizes in the acentric cubic space group
I
-43
d
. This is the first definite record
of this
cubic modification for LLZO materials and might explain the superior
electrochemical performance of Ga-stabilized LLZO compared to its
Al-stabilized counterpart. The phase transition seems to be caused
by the site preference of Ga
3+
.
7
Li NMR spectroscopy
indicates an additional Li-ion diffusion process for LLZO with space
group
I
-43
d
compared to space group
Ia
-3
d
. Despite all efforts undertaken to
reveal structure–property relationships for this class of materials,
this study highlights the potential for new discoveries.
Mixed transition metal oxides have emerged as promising electrode materials for electrochemical energy storage and conversion. To optimize the functional electrode properties, synthesis approaches ...allowing for a systematic tailoring of the materials’ composition, crystal structure and morphology are urgently needed. Here we report on the room‐temperature electrodeposition of a ternary oxide based on earth‐abundant metals, specifically, the defective cubic spinel ZnMnO3. In this unprecedented approach, ZnO surfaces act as (i) electron source for the interfacial reduction of MnO4− in aqueous solution, (ii) as substrate for epitaxial growth of the deposit and (iii) as Zn precursor for the formation of ZnMnO3. Epitaxial growth of ZnMnO3 on the lateral facets of ZnO nanowires assures effective electronic communication between the electroactive material and the conducting scaffold and gives rise to a pronounced 2‐dimensional morphology of the electrodeposit forming – after partial delamination from the substrate – twisted nanosheets. The synthesis strategy shows promise for the direct growth of different mixed transition metal oxides as electroactive phase onto conductive substrates and thus for the fabrication of binder‐free nanocomposite electrodes.
Lateral facets of wurtzite ZnO nanowires serve as precursor and substrate for the epitaxial growth of defective cubic spinel ZnMnO3 via a room‐temperature, one‐step electrodeposition process from aqueous KMnO4 solution.
Small single crystals of NASICON-type LiTi2(PO4)3 of high quality were grown by means of long-term annealing of polycrystalline specimens synthesized using conventional solid state reaction. A ...thorough study of their structural properties and vibrational dynamics was carried out by means of an integrated experimental and theoretical approach. A single-crystal X-ray diffraction analysis at room temperature allowed us to determine the precise crystal structure and the anisotropic displacement parameters of all atoms. In addition, all the 25 independent components of the polarizability tensor, expected on the basis of the group theory for the LiTi2(PO4)3 crystal, were observed using polarized Raman spectroscopy in backscattering geometry on a microcrystal, properly oriented by a micromanipulator. Thus, all the expected Raman modes have been unambiguously identified by determining both their wavenumber and symmetry throughout an accurate analysis of the spectral profiles observed in the different polarization configurations. Finally, these experimental findings were fully corroborated by the results of first-principles calculations performed to determine Raman and infrared vibrational modes.
Amphibole asbestos is related to lung fibrosis and several types of lung tumors. The disease-triggering mechanisms still challenge our diagnostic capabilities and are still far from being fully ...understood. The literature focuses primarily on the role and formation of asbestos bodies in lung tissues, but there is a distinct lack of studies on amphibole particles that have been internalized by alveolar epithelial cells (AECs). These internalized particles may directly interact with the cell nucleus and the organelles, exerting a synergistic action with asbestos bodies (AB) from a different location. Here we document the near-atomic- to nano-scale transformations induced by, and taking place within, AECs of three distinct amphiboles (anthophyllite, grunerite, "amosite") with different Fe-content and morphologic features. We show that: (i) an Fe-rich layer is formed on the internalized particles, (ii) particle grain boundaries are transformed abiotically by the internal chemical environment of AECs and/or by a biologically induced mineralization mechanism, (iii) the Fe-rich material produced on the particle surface does not contain large amounts of P, in stark contrast to extracellular ABs, and (iv) the iron in the Fe-rich layer is derived from the particle itself. Internalized particles and ABs follow two distinct formation mechanisms reaching different physicochemical end-states.
Li
La
Zr
O
(LLZO) is one of the potential candidates for Li metal-based solid-state batteries owing to its high Li
conductivity (≈10
S cm
) at room temperature and large electrochemical stability ...window. However, LLZO undergoes protonation under the influence of moisture-forming Li
CO
layers, thereby affecting its structural and transport properties. Therefore, a detailed understanding on the impact of the exchange of H
on Li
sites on structural alteration and kinetics under the influence of wet environments is of great importance. The present study focuses on the Li
/H
exchange in single-crystal and polycrystal Li
La
ZrTaO
(LLZTO) garnets prepared using the Czochralski method and solid-state reactions subjected to weathering in air, aqueous solutions at room temperature, and in aqueous solution at 363 K using X-ray diffraction (XRD) and neutron diffraction (ND) techniques. Based on 36 single-crystal diffraction and 88 powder diffraction measurements, we found that LLZTO crystallizes with space group (SG)
3̅
with Li located in 96
(Li(2)) and 24
(Li(1)) sites, whereas the latter one is displaced toward the general position 96
forming shorter Li(1)-Li(2) jump distances. The degradation in air, wet air, water, and acetic acid leads to a Li
/H
exchange that preferably takes place at the 24
site, which is in contrast to previous reports. Higher Li
/H
was observed for LLZTO aged in water at 363 K that reduced the symmetry to SG
4̅3
from SG
3̅
. This symmetry reduction was found to be related to the site occupation behavior of Li at the tetrahedral 12
site in SG
4̅3
. Moreover, Li
is exchanged by H
preferably at the 48
site (equivalent to 96
site). We also found that the equilibrium H
concentrations in all media tested remains very similar, which is related to the H
diffusion in the LLZTO-controlled exchange process. Only the increase in temperature led to a significant increase in the exchange capacity as well as in the Li
/H
exchange rate. Overall, we found that the exchange rate, exchange capacity, site occupation behavior of Li
and H
, as well as the structural stability of LLZTO, strongly depend on the composition. These findings suggest that measurements on a single LLZTO variant sample do not lead to a general conclusion for all garnets to guide the field toward better materials. In contrast, each composition has to be analyzed exclusively to understand the interplay of composition, structure, and exchange kinetic properties.
Orthorhombic β-LiScGe2O6 single crystals were compressed hydrostatically up to 10.35 GPa using a diamond anvil cell and investigated in situ by means of X-ray diffraction and Raman spectroscopy. ...Crystal-structure investigations at ambient conditions and at high pressure show a structural transition from an orthopyroxene-type Pbca structure (a ≈ 18.43 Å, b ≈ 8.85 Å, and c ≈ 5.34 Å at 8.6 ± 0.1 GPa) to a postorthopyroxene type P21/c structure of the new dense γ-LiScGe2O6 (a ≈ 18.62 Å, b ≈ 8.85 Å, c ≈ 5.20 Å, and β ≈ 93.1° at 9.5 ± 0.1 GPa). The structure refinements reveal displacive shifts of O atoms associated with a rotation of every other tetrahedral-chain unit from the O- to S-type position similar to the postorthopyroxene-type MgSiO3. As a consequence of the oxygen displacement, the coordination number of Li atoms is changing from 5 + 1 to a proper 6-fold coordination. The transition around P c = 9.0 ± 0.1 GPa is associated with a volume discontinuity of ΔV = −1.6%. This orthopyroxene (OEn-Pbca) to postorthopyroxene (pOEn-P21/c) transition is the second example of this type of transformation. Precise lattice parameters have been determined during isothermal compression. The fit of the unit-cell volumes of β-LiScGe2O6, using a third-order Birch–Murnaghan equation of state, yields V 0 = 943.63 ± 0.11 Å3, K 0 = 89.8 ± 0.6 GPa, and dK/dP = 4.75 ± 0.18 as parameters. Evaluation of the data points beyond the critical transition pressure using a second-order Birch–Murnaghan equation suggests V 0 = 940.6 ± 4.4 Å3 and K 0 = 82.4 ± 4.8 GPa. A series of high-pressure Raman spectra confirm the symmetry-related structural transition, with band positions shifting in a noncontinuous manner, thus confirming the proposed first-order transition.
Amphibole asbestos is related to multiple diseases, mainly those targeting the lungs. Asbestos-related malignancies can also be caused by non-regulated asbestiform minerals and some elongated mineral ...particles (EMPs). In particular, the role of nano- and micro-sized EMPs internalized by lung epithelial cells must be clarified. This is of major importance when considering that EMPs to which humans are exposed are likely a highly heterogeneous mix of different mineral types, shapes, and sizes. Here, we document that particles smaller than 4.54 µm in length and smaller than 0.89 µm in width (e.g., particles that do not fit the regulatory categories to be identified as asbestos) are easily internalized because of their specific dimensions, surface charge, and shape (mostly dictated by the aspect ratio L/w). Once internalized, these particles can be found in proximity to the cell nucleus, in vesicles, and in the cytoplasm. Examining the localization of particles in cells provides important information, which helps in determining the physicochemical environment found inside the biological compartment, thus allowing for a better comprehension of the mineralogical transformation that might happen after internalization by cells.
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