Graphite dual-ion batteries represent a potential battery concept for large-scale stationary storage of electricity, especially when constructed free of lithium and other chemical elements with ...limited natural reserves. Owing to their non-rocking-chair operation mechanism, however, the practical deployment of graphite dual-ion batteries is inherently limited by the need for large quantities of electrolyte solutions as reservoirs of all ions that are needed for complete charge and discharge of the electrodes. Thus far, lithium-free graphite dual-ion batteries have employed moderately concentrated electrolyte solutions (0.3-1 M), resulting in rather low cell-level energy densities of 20-70 Wh kg
. In this work, we present a lithium-free graphite dual-ion battery utilizing a highly concentrated electrolyte solution of 5 M potassium bis(fluorosulfonyl)imide in alkyl carbonates. The resultant battery offers an energy density of 207 Wh kg
, along with a high energy efficiency of 89% and an average discharge voltage of 4.7 V.
Metal trifluoroacetates (TFAs) are commonplace precursors for bulk and nanostructured metal fluorides and oxides obtained usually through their thermal decomposition. Very little, however, is known ...about the atomistic mechanism of such a thermal conversion, or even the crystal structure of the precursors. In this study, we detail the structural evolution of Fe(TFA)3 upon its thermal decomposition into rhombohedral iron(III) fluoride. Several distinct structural motifs have been identified in the temperature range of 250–350 °C. In particular, Fe(TFA)3, Fe2F(TFA)5, and FeF(TFA)2 are composed of infinite chains. In addition, several volatile molecular species with ring structureFe n F n (TFA)2n (n = 6–10)have been characterized both by single-crystal X-ray diffraction and by mass spectrometry. Further conversion of TFA groups into fluoride ions leads to a layered FeF2(TFA). All these compounds feature bridging TFA ligands and octahedral fluoro- or oxo-coordination of Fe. The retention of the +3 oxidation state is confirmed by 57Fe Mössbauer spectroscopy. Magnetization measurements point to the ferrimagnetic ordering in FeF2(TFA) at T ≤ 150 K, unlike Fe(TFA)3, which remains paramagnetic at as low as 10 K. This study highlights the potential of metal TFAs for the rational synthesis of molecular and solid-state hybrid compounds by their versatile thermal decomposition into fully inorganic materials.
Pyrochlore‐type iron (III) hydroxy fluorides (Pyr‐IHF) are appealing low‐cost stationary energy storage materials due to the virtually unlimited supply of their constituent elements, their high ...energy densities, and fast Li‐ion diffusion. However, the prohibitively high costs of synthesis and cathode architecture currently prevent their commercial use in low‐cost Li‐ion batteries. Herein, a facile and cost‐effective dissolution–precipitation synthesis of Pyr‐IHF from soluble iron (III) fluoride precursors is presented. High capacity retention by synthesized Pyr‐IHF of >80% after 600 cycles at a high current density of 1 A g−1 is obtained, without elaborate electrode engineering. Operando synchrotron X‐ray diffraction guides the selective synthesis of Pyr‐IHF such that different water contents can be tested for their effect on the rate capability. Li‐ion diffusion is found to occur in the 3D hexagonal channels of Pyr‐IHF, formed by corner‐sharing FeF6–x(OH)x octahedra.
In this research article, the authors report a facile and cost‐effective synthesis of pyrochlore iron (III) hydroxy fluoride (Pyr‐IHF), enabling to produce Pyr‐IHF at a low cost. Pyr‐IHF‐containing cathodes show superior capacity retention of >80% after 600 cycles at a high current density of 1 A g−1.
Colloidal nanoparticles
(NPs) with myriads of compositions and
morphologies have been synthesized and characterized in recent years.
For wüstite Fe
x
O, however, obtaining
phase-pure NPs with ...homogeneous morphologies have remained challenging.
Herein, we report the colloidal synthesis of phase-pure Fe
x
O (
x
≈ 0.94) popcorn-shaped
NPs by decomposition of a single-source precursor, Fe
3
(μ
3
-O)(CF
3
COO)(μ-CF
3
COO)
6
(H
2
O)
2
·CF
3
COOH. The popcorn shape and multigrain structure had been reconstructed
using high-angle annular dark-field scanning transmission electron
micrograph (HAADF-STEM) tomography. This morphology offers a large
surface area and internal channels and prevents further agglomeration
and thermal tumbling of the subparticles. Fe
3
(μ
3
-O)(CF
3
COO)(μ-CF
3
COO)
6
(H
2
O)
2
·CF
3
COOH behaves as
an antiferromagnetic triangle whose magnetic frustration is mitigated
by the low symmetry of the complex. The popcorn-shaped Fe
x
O NPs show the typical wüstite antiferromagnetic
transition at approximately 200 K, but behave very differently to
their bulk counterpart below 200 K. The magnetization curves show
a clear, unsymmetrical hysteresis, which arises from a combined effect
of the superparamagnetic behavior and exchange bias.
We report a simple one-pot synthesis of uniform transition metal difluoride MF
(M = Fe, Mn, Co) nanorods based on transition metal trifluoroacetates (TMTFAs) as single-source precursors. The ...synthesis of metal fluorides is based on the thermolysis of TMTFAs at 250-320 °C in trioctylphosphine/trioctylphosphine oxide solvent mixtures. The FeF
nanorods were converted into FeF
nanorods by reaction with gaseous fluorine. The TMTFA precursors are also found to be suitable for the synthesis of colloidal transition metal phosphides. Specifically, we report that the thermolysis of a cobalt trifluoroacetate complex in trioctylphosphine as both the solvent and the phosphorus source can yield 20 nm long cobalt phosphide nanorods or, 3 nm large cobalt phosphide nanoparticles. We also assess electrochemical lithiation/de-lithiation of the obtained FeF
and FeF
nanomaterials.
Colloidal nanoparticles (NPs) with myriads of compositions and morphologies have been synthesized and characterized in recent years. For wüstite Fe x O, however, obtaining phase-pure NPs with ...homogeneous morphologies have remained challenging. Herein, we report the colloidal synthesis of phase-pure Fe x O (x ≈ 0.94) popcorn-shaped NPs by decomposition of a single-source precursor, Fe3(μ3-O)(CF3COO)(μ-CF3COO)6(H2O)2·CF3COOH. The popcorn shape and multigrain structure had been reconstructed using high-angle annular dark-field scanning transmission electron micrograph (HAADF-STEM) tomography. This morphology offers a large surface area and internal channels and prevents further agglomeration and thermal tumbling of the subparticles. Fe3(μ3-O)(CF3COO)(μ-CF3COO)6(H2O)2·CF3COOH behaves as an antiferromagnetic triangle whose magnetic frustration is mitigated by the low symmetry of the complex. The popcorn-shaped Fe x O NPs show the typical wüstite antiferromagnetic transition at approximately 200 K, but behave very differently to their bulk counterpart below 200 K. The magnetization curves show a clear, unsymmetrical hysteresis, which arises from a combined effect of the superparamagnetic behavior and exchange bias.
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