Controlling the Cathodic Potential of KVPO<sub>4</sub>F through Oxygen Substitution

Wernert, Romain; Nguyen, Long Hoang Bao; Petit, Emmanuel; Camacho, Paula Sanz; Iadecola, Antonella; Longo, Alessandro; Fauth, François; Stievano, Lorenzo; Monconduit, Laure; Carlier, Dany; Croguennec, Laurence

doi:10.1021/acs.chemmater.2c00295

Cited by 30 publications

(64 citation statements)

References 51 publications

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“…The valence variation of the V element of KVPF-P3/C at different charge/discharge statuses is investigated using ex situ XANES, as marked by the representative galvanostatic charging–discharging curves in Figure S31. During the charging process (Figure d), the peak intensity of photon energy at the pre-edge position (∼5470 eV) increases, and the photon energy at the inflection point (∼5480 eV, the normalized intensity is close to 0.5) shifts rightward, which indicates that the valence of V changes from V 3+ to V 4+ . An opposite shift is observed during discharging (Figure e), showing good valence reversibility of V in KVPF-P3/C.…”

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confidence: 86%

“…During the charging process (Figure 4d), the peak intensity of photon energy at the pre-edge position (∼5470 eV) increases, and the photon energy at the inflection point (∼5480 eV, the normalized intensity is close to 0.5) shifts rightward, which indicates that the valence of V changes from V 3+ to V 4+ . 38 An opposite shift is observed during discharging (Figure 4e), showing good valence reversibility of V in KVPF-P3/C. The corresponding k 2 -weighted Fourier-transformed spectra of extended synchrotron X-ray absorption fine-structure (EXAFS) are presented in Figure S32.…”

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confidence: 94%

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Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

Liao

Zhang

et al. 2022

Nano Lett.

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With high theoretical capacity and operating voltage, KVPO 4 F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium−oxalate−phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO 4 F nanoplates. It is found that the V−F−C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO 4 F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO 4 F. The as-synthesized KVPO 4 F/C cathode delivers a reversible capacity of 106.5 mAh g −1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g −1 at the ultrahigh current density of 100 C. In addition, a KVPO 4 F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg −1 .

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confidence: 86%

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confidence: 94%

Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

Liao

Zhang

et al. 2022

Nano Lett.

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“…A Hubbard correction ( U eff = U – J = 5 eV) was applied to take into account the self-interaction error of the strongly correlated 3d electrons , All calculations were spin-polarized with ferromagnetic ordering . The plane-wave cutoff energy was set to 600 eV and a 4 × 4 × 4 k-mesh was used.…”

Section: Methods and Experimentsmentioning

confidence: 99%

“…For example, the preparation of mixed anion phosphates containing O and/or F allows triggering the V 5+/4+ or V 4+/3+ redox couples. Such materials were investigated for Li-ion batteries, Na-ion batteries and even K-ion batteries using, among others, LiVPO 4 F 1– y O y , Na 3 V 2 (PO 4 ) 2 F 3–2 y O 2 y and KVPO 4 F 1– y O y (0 ≤ y ≤ 1). − In these compounds, for the case of oxygen-rich compositions containing only V 4+ , a very short bond of 1.65 Å is formed between V and one of its surrounding oxygen atoms. Such a short bond distance is analogous to the vanadyl VO 2+ ion and is referred to as a “vanadyl bond” depicted as VO.…”

Section: Introductionmentioning

confidence: 99%

“…Remarkably, the combination of all such different theoretical approaches provides a complete picture of the electronic structure of the V atoms, which is directly linked to the distorted coordination geometry and electronic structure of the vanadium cations. Such distortion is hardly detected by extended X-ray absorption fine structure (EXAFS) analysis as the information contained in the spectra is averaged between the different oxygens and the features are less distinct . The approach implemented in Hilbert++, instead, provides a full treatment of the correlation effects.…”

Section: Introductionmentioning

confidence: 99%

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An Original Empirical Method for Simulating V L_2,3 Edges: The Example of KVPO₄F and KVOPO₄ Cathode Materials

et al. 2022

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Reversible chemical reactions are the most common mechanism storing electrochemical energy in M-ion batteries (M = Li, Na, K....). At the positive electrode, these transformations consist in the solid-state oxidation or reduction of transition metal ions going along with the reversible (de)intercalation of an alkali cation from the crystal structure. X-ray spectroscopies are among the most suitable tools to unveil and monitor these reactions. The interpretation of experimental spectra, however, is not trivial. This is particularly true in V-based positive electrodes since the variety of oxidation states of vanadium as well as its coordination and bonding geometries may lead to complex spectroscopic features that call for ab initio modeling to understand the spectra. Here we show not only that V L 2,3 -edge X-ray Raman spectra can effectively be modeled by a full ab initio approach but also that the empirically obtained Hamiltonian parameters can reproduce shape and intensity of the experimental spectra from a given coordination geometry. In a broader context, our study shows that inexpensive empirical calculations provide highly reliable information and help solve the electronic structure of transition metal oxides compounds, which governs the electrochemical behavior in M-ion batteries. The promising results shown here underline the efficiency of this strategy for X-ray spectroscopy data analysis, which can be generalized and extended to the wider family of vanadium phosphate-based polyanionic compounds. Such an approach can in principle be extended to any transition metal-based material.

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K_xVPO₄F (x∼0): A New High‐Voltage and Low‐Stain Cathode Material for Ultrastable Calcium Rechargeable Batteries

Li,

Lee,

Lin

et al. 2024

Advanced Energy Materials

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The utilization of high‐voltage intercalation cathodes in calcium‐ion batteries (CIBs) is impeded by the substantial size and divalent character of Ca2+ ions, which result in pronounced volume alterations and sluggish ion mobility, consequently causing inferior reversibility and low energy/power densities. To tackle these issues, polyanionic K‐vacant KxVPO4F (x∼0, designated as K0VPF) is proposed as high‐voltage and ultra‐stable cathode material in CIBs. The K0VPF demonstrates a decent calcium storage capacity of 75 mAh g−1 at 10 mA g−1 and remarkable capacity retention of 84.2% over 1000 cycles. The average working voltage of the K0VPF is 3.85 V versus Ca2+/Ca, representing the highest value reported for CIB cathodes to date. The combined experimental and theoretical investigations revealed that the low volume changes and hopping diffusion barriers contribute to the extraordinary stability and high‐power capabilities, respectively, of K0VPF. The distribution of Ca ions into polyanionic frameworks with pronounced spatial separation effectively attenuates the Ca2+–Ca2+ repulsive force and thus augmenting the Ca migration kinetics. The high voltage of K0VPF is attributed to the inductive effect from the largely electronegative fluorine. In conjunction with a calcium metal anode and a compatible electrolyte, Ca metal full cells featured a record‐high energy density of ≈300 Wh kg−1.

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Controlling the Cathodic Potential of KVPO₄F through Oxygen Substitution

Cited by 30 publications

References 51 publications

Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

An Original Empirical Method for Simulating V L_2,3 Edges: The Example of KVPO₄F and KVOPO₄ Cathode Materials

K_xVPO₄F (x∼0): A New High‐Voltage and Low‐Stain Cathode Material for Ultrastable Calcium Rechargeable Batteries

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Controlling the Cathodic Potential of KVPO4F through Oxygen Substitution

Cited by 30 publications

References 51 publications

Synthesis of KVPO4F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

Synthesis of KVPO4F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

An Original Empirical Method for Simulating V L2,3 Edges: The Example of KVPO4F and KVOPO4 Cathode Materials

KxVPO4F (x∼0): A New High‐Voltage and Low‐Stain Cathode Material for Ultrastable Calcium Rechargeable Batteries

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Controlling the Cathodic Potential of KVPO₄F through Oxygen Substitution

Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

Synthesis of KVPO₄F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries

An Original Empirical Method for Simulating V L_2,3 Edges: The Example of KVPO₄F and KVOPO₄ Cathode Materials

K_xVPO₄F (x∼0): A New High‐Voltage and Low‐Stain Cathode Material for Ultrastable Calcium Rechargeable Batteries