Untersuchungen an quaternären Fluoriden LiMIIMIIIF6, Über die Kationenverteilung in Fluortrirutilen

Viebahn, W.; Epple, Philipp

doi:10.1002/zaac.654270107

Cited by 14 publications

(6 citation statements)

References 10 publications

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“…Isomer shift (IS), quadrupole splitting (QS), and line width are given in mm/s.shift of IS = 0.47 mm/s and quadrupole splitting QS = 0.21 mm/s. These parameters are in good agreement with previous reports59 and confirm that Fe 3+ exclusively is present in the as-prepared state and that only one local environment exists for the Fe ions. After milling, the spectrum shows a slight broadening and can be described by a superposition of two doublets with very similar isomer shifts.…”

supporting

confidence: 92%

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Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Lieser

Biasi

Geßwein

et al. 2014

J. Electrochem. Soc.

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To replace common commercial lithium metal oxides or polyanionic cathode materials, lithium transition metal fluorides are of particular interest, as they potentially provide a high energy density, safety, and cyclability. The quaternary fluoride LiMnFeF 6 that crystallizes in the Na 2 SiF 6 -type structure was synthesized without toxic chemicals by a sol-gel process with trifluoroacetic acid as fluorine source. After structural and morphological characterization, the as-synthesized material was ball-milled with carbon. The novel composite cathode material produced in this way was cycled versus lithium. The electrochemical potential range, cycling ability, and rate performance were investigated and the electrochemically active redox couple Fe 3+ /Fe 2+ was confirmed by Mössbauer spectroscopy. Structural changes of the LiMnFeF 6 host structure after Li insertion were investigated by X-ray powder diffraction.Currently, lithium transition metal oxides and phosphates are the most preferred cathode materials for portable and stationary applications. Compared to LiMn 2 O 4 , LiCoO 2 , or LiNiO 2 , positive electrode materials with at least two different transition metal cations like LiNi 0.5 Mn 1.5 O 4 or LiNi 1-x-y Mn x Co y O 2 possess better electrochemical properties like a higher redox potential, increased specific capacity or enhanced cycling performance. 1-3 In general, substitution of oxygen in the cathode host structure by the more electronegative fluorine results in a higher redox potential, leading to an increased energy density of the positive electrode. 4,5 Since the report of Abraham 6 and Arai et al. 7 on metal fluoride-containing positive electrodes, lithium insertion and conversion during cycling of the host material (e.g. FeF 3 , CuF 2 ) has been investigated in great detail. [8][9][10][11] The first lithium transition metal fluoride with an applicable electrochemical performance reported in literature was monoclinic Li 3 FeF 6 . 12 Specific discharge capacities of monoclinic and orthorhombic Li 3 FeF 6 , 13-16 monoclinic Li 3 VF 6 , 17 Li 2 TiF 6 , 18 and LiFeFeF 6 19,20 were reported to be at least 75 mAh/g. Lithium transition metal fluorides were investigated for their Li insertion and extraction potential, Li diffusion properties, and influence of divalent cation doping 21-24 using several theoretical methods. Several patents cover the use of Li 3 FeF 6 , Li 3 VF 6 , Li 2 TiF 6 , Li 2 NiF 4 , and LiFeFeF 6 as positive electrode materials for Li-ion batteries. [25][26][27][28][29] In the last four years, this class of materials attracted increasing attention. Still, lithium transition metal fluorides are not yet competitive with established electrode materials for use in lithium-ion batteries.However, electrochemical properties of ternary Li y MF x or quaternary LiM (1) M (2) F 6 (with M (1) = M (2) , e.g. M = Cr, Mn, Fe, Co, Ni) 3d lithium transition metal fluorides have not yet been studied due to their challenging synthesis process. It usually requires the usage of hazardous chemicals like hydro...

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supporting

confidence: 92%

“…LiNi 1-x Mn x CrF 6 ). 59,60 Lithium transition metal fluorides crystallize in different crystal structures according to the simple geometric formalism of the ratio of metal cation radii r M I I /r M I I I . For cation radii ratios between 1.2-1.5, the Na 2 SiF 6structure type exists and for a ratio below 1.2, the trirutile structure is stable.…”

Section: Mn Fefmentioning

confidence: 99%

Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Lieser

Biasi

Geßwein

et al. 2014

J. Electrochem. Soc.

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“…In the trirutile structural type, three cationic distributions (types 1, 2, and 3) were initially proposed by Viebahn et al in 1976 (Table ). Until now, no compound has adopted type 3, while three other distributions (types 4, 5 and 6) have been revealed. LiFe 2 F 6 , originally announced with disordered Fe 2+ and Fe 3+ (type 1), finally turns out to be perfectly ordered in the P 4 2 nm space group corresponding to type 6 (2a sites (0 0 z)) .…”

Section: Fluoride Materials For Positive Electrodesmentioning

confidence: 99%

Fluorinated Materials as Positive Electrodes for Li- and Na-Ion Batteries

et al. 2022

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Fluorine is known to be a key element for various components of batteries since current electrolytes rely on Li-ion salts having fluorinated ions and electrode binders are mainly based on fluorinated polymers. Metal fluorides or mixed anion metal fluorides (mainly oxyfluorides) have also gained a substantial interest as active materials for the electrode redox reactions. In this review, metal fluorides for cathodes are considered; they are listed according to the dimensionality of the metal fluoride subnetwork. The synthesis conditions and the crystal structures are described; the electrochemical properties are briefly indicated, and the nature of the electron transport agent is noted. We stress the crucial importance of the elaboration processes to induce the presence of cation disorders, of anion substitutions (mainly F–/O2– or F–/OH–) or vacancies. Finally, we show that an accurate structural characterization is a key step to enable enhanced material performances to overcome several lasting roadblocks, namely the large irreversible capacity and poor energy efficiency that are frequently encountered.

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“…Hierzu gehören z.B. LiZnCrF6 [3], LiFeFeF6 [4] und viele andere [1]. Uns ist unklar, warum bislang keine ,Dirutile\ also Rutilvertreter mit gegenüber dem Muttertyp verdoppelter c-Achse, erhalten wurden.…”

unclassified

Zur Rutilverwandtschaft: Zur Kenntnis von LiSrFeF₆[1]/On the Knowledge of LiSrFeF₆

Fleischer

Hoppe

1982

Zeitschrift Für Naturforschung B

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Hitherto unknown LiSrFeF6 was obtained by heating mixtures of binary fluorides [LiF + SrF2 + FeF3; Li:Sr:Fe = 1:1:1] under argon [Au tubes, 500 °C, 2 d or 650 °C, 14d] as a colourless powder or colourless single crystals. LiSrFeF6 crystallizes monoclinicly in P21/c-C52h with a = 5,2972(4), b = 8,7989(8), c = 10,2257(7) Å, β = 92,212(8)°, Z = 4; drö = 3,69 und dpyk = 3,66 g · cm-3, positions are given in the text, R = 9,16% (Rw = 6,83%) for hkl (Mo-Ka, 4-circle diffractometer data).

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Untersuchungen an quaternären Fluoriden LiM^IIM^IIIF₆, Über die Kationenverteilung in Fluortrirutilen

Cited by 14 publications

References 10 publications

Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Fluorinated Materials as Positive Electrodes for Li- and Na-Ion Batteries

Zur Rutilverwandtschaft: Zur Kenntnis von LiSrFeF₆[1]/On the Knowledge of LiSrFeF₆

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Untersuchungen an quaternären Fluoriden LiMIIMIIIF6, Über die Kationenverteilung in Fluortrirutilen

Cited by 14 publications

References 10 publications

Electrochemical Characterization of LiMnFeF6for Use as Positive Electrode in Lithium-Ion Batteries

Electrochemical Characterization of LiMnFeF6for Use as Positive Electrode in Lithium-Ion Batteries

Fluorinated Materials as Positive Electrodes for Li- and Na-Ion Batteries

Zur Rutilverwandtschaft: Zur Kenntnis von LiSrFeF6[1]/On the Knowledge of LiSrFeF6

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Untersuchungen an quaternären Fluoriden LiM^IIM^IIIF₆, Über die Kationenverteilung in Fluortrirutilen

Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Electrochemical Characterization of LiMnFeF₆for Use as Positive Electrode in Lithium-Ion Batteries

Zur Rutilverwandtschaft: Zur Kenntnis von LiSrFeF₆[1]/On the Knowledge of LiSrFeF₆