Electrochemical properties of chromium oxyfluoride CrO2−xFx with 0 ≤ x ≤ 0.3

Mukai, Kazuhiko; Uyama, Takeshi; Yamada, Ikuya

doi:10.1039/c9qi00765b

Cited by 3 publications

(3 citation statements)

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“…properties. The reason to select the HP/HT method was that the high concentration of F − ions and the stabilization of the rock-salt structure are achievable under HP/HT conditions (12 GPa and ~1000 °C) as reported in CrO 2−p F p (p ≤ 0.3) 14 and Li-Co-Mn oxides 15 , respectively, and the high crystallinity of the compounds is maintained. We successfully synthesized highcrystallinity Li 3 VO 3 F and Li 4 WO 4 F and revealed that their electrochemical reactions involving a decomposition reaction.…”

Section: Syntheses Of LImentioning

confidence: 99%

“…Li x MO 1+x−y F y (M = Fe, Mn, V, Nb, Mo, and W) was synthesized using the HP/HT method with a Walker-type apparatus installed at Osaka Prefecture University. 14,15 1000 °C for 30 min. The procedure has been described in further detail elsewhere.…”

Section: Sample Preparation and Phase Identificationmentioning

confidence: 99%

“…The procedure has been described in further detail elsewhere. 14,15 Hereafter, the retrieved powdery samples are denoted by HP(M, y), as listed in Table 1.…”

Section: Sample Preparation and Phase Identificationmentioning

confidence: 99%

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High-Pressure Synthesis of Cation-Disordered Rock-Salt Oxyfluorides with High Crystallinity

2021

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Lithium-excess transition metal (M) oxyfluorides, Li x MO 1+x−y F y , have received considerable attention as positive electrode materials for lithium-ion batteries. Little is known about the relationship between the crystallinity and electrochemical reactivities although this offers further understanding and improvement of Li x MO 1+x−y F y , because conventionally ball-milled Li x MO 1+x−y F y exhibits limited crystallinity, i.e., amorphous-like nanoparticles. We herein adapted a high-pressure/high-temperature method at 12 GPa and 1000 °C to synthesize highcrystallinity Li x MO 1+x−y F y (M = Fe, Mn, V, Nb, Mo, and W) and investigated the electrochemical properties of this series. Rietveld analyses based on X-ray diffraction (XRD) and cross-sectional elemental mapping clarified that Li 3 VO 3 F and Li 4 WO 4 F crystalized as an almost-single-phase rock-salt structure with homogenous cation/anion distributions and formed well-faceted particles with sizes of 1-20 μm. Their rechargeable capacities over 1.8-5.0 V vs. Li + /Li were ~40 mAh g −1 and ~10 mAh g −1 , respectively. According to ex situ XRD measurements of the cycled Li 3 VO 3 F electrodes, these partial rechargeable capacities were caused by a decomposition reaction during the initial charge, which differed from the topotactic reaction proposed for the low-crystallinity phases. This information is helpful for designing the microstructure of Li x MO 1+x−y F y to improve its performance now that both crystal and amorphous Li x MO 1+x−y F y phases are attainable.

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Section: Syntheses Of LImentioning

confidence: 99%

Section: Sample Preparation and Phase Identificationmentioning

confidence: 99%

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High-Pressure Synthesis of Cation-Disordered Rock-Salt Oxyfluorides with High Crystallinity

2021

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Electronic band structures and optical properties of 2D XOF (X = Ga or In) oxyfluoride monolayers using density functional theory and GW approximation

2023

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Critical overview of polyanionic frameworks as positive electrodes for Na-ion batteries

Deb

Gautam

2022

Journal of Materials Research

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Na-ion batteries (NIBs) are increasingly looked at as a viable alternative to Li-ion batteries due to the abundance, low cost, and thermal stability of Na-based systems. To improve the practical utilization of NIBs in applications, it is important to boost the energy and power densities of the electrodes being used, via discovery of novel candidate materials. Thus, we explore the chemical space of transition metal containing oxyfluorides (TMOFs) that adopt the perovskite structure as possible NIB electrodes. Our choice of the perovskite structure is motivated by the 'large' cationic tunnels that can accommodate Na + , while the chemistry of TMOFs is motivated by the high electronegativity and inductive effect of F − , which can possibly lead to higher voltages. We use density functional theory based calculations to estimate the ground state polymorphs, average Na (de)intercalation voltages, thermodynamic stabilities and Na + mobility on two distinct sets of compositions: the F-rich NaxMOF2, and the O-rich Na1+xMO2F where x = 0-1 and M = Ti, V, Cr, Mn, Fe, Co, or Ni. Upon identifying the ground state polymorphs in the charged compositions (i.e., MOF2 and NaMO2F), we show that F-rich perovskites exhibit higher average voltages compared to O-rich perovskites. Also, we find six stable/metastable perovskites in the F-rich space, while all O-rich perovskites (except NaTiO2F) are unstable. Finally, our Na-ion mobility calculations indicate that TiOF2-NaTiOF2, VOF2-NaVOF2, CrOF2, and NaMnOF2 can be promising compositions for experimental exploration as NIB cathodes, primarily if used in a strained electrode configuration and/or thin film batteries. Our computational approach and findings provide insights into developing practical NIBs involving fluorine-containing intercalation frameworks.

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Electrochemical properties of chromium oxyfluoride CrO_2−xF_x with 0 ≤ x ≤ 0.3

Abstract: To overcome the limitations of graphite as a negative electrode material for lithium-ion batteries (LIBs), transition metal oxyfluorides are under active development.

Cited by 3 publications

References 44 publications

High-Pressure Synthesis of Cation-Disordered Rock-Salt Oxyfluorides with High Crystallinity

High-Pressure Synthesis of Cation-Disordered Rock-Salt Oxyfluorides with High Crystallinity

Electronic band structures and optical properties of 2D XOF (X = Ga or In) oxyfluoride monolayers using density functional theory and GW approximation

Critical overview of polyanionic frameworks as positive electrodes for Na-ion batteries

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