Alkali Metal Hyperfine Structure in the ESR Spectra of Biphenyl Mononegative Ions

Nishiguchi, Hiroaki; Nakai, Yoshio; Nakamura, Kazuo; Ishizu, Kazuhiko; Deguchi, Yasuo; Takaki, Hideo

doi:10.1063/1.1724877

Cited by 40 publications

(3 citation statements)

References 8 publications

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“…As displayed in Figure a and formula , Na-Bp solution can be simply synthesized by mixing equal amounts of biphenyl and sodium metal in dimethoxyethane (DME) solvent. Because of the strong electron affinity of biphenyl, electron donation from Na metal to the conjugated biphenyl rings occurs spontaneously at room temperature, resulting in the formation of the Bp – radical anion . Electron paramagnetic resonance (EPR) spectra given in Figure b show a set of sharp Dysonian peaks that belong to biphenyl free radicals, further demonstrating the electron-transfer from Na to Bp rings.…”

Section: Resultsmentioning

confidence: 98%

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Liu

Zhang

Guo

et al. 2020

ACS Appl. Mater. Interfaces

116

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Hard carbon (HC) is an attractive anode material for low-cost and high-energy density sodium-ion batteries (SIBs); however, its low initial Coulombic efficiency (ICE) limits its practical battery application. To overcome this problem, we reported a facile strategy to compensate the irreversible capacity loss of HC anodes simply by a chemical presodiation reaction of the HC electrode with a sodiation reagent (sodium biphenyl, Na-Bp). Benefiting from the strong sodiation ability of Na-Bp, HC anodes can be presodiated rapidly in a very short time and the presodiated HC (Na x HC) is found to have a desirable ICE of 100%. When coupled with the Na3V2(PO4)3 cathode to build a SIB full cell, the Na x HC||Na3V2(PO4)3 cell exhibits a high ICE of ∼95.0% and an elevated energy density of 218 W h kg–1, which are far superior to those of the control cell using a pristine HC anode (50% ICE and 120 W h kg–1, respectively), suggesting great advantages brought about by the chemical presodiation process. More importantly, this presodiation reaction is very mild and highly efficient and can be widely extended to a variety of Na-storage materials, offering a new route to develop high-performance Na-storage materials for practical battery applications.

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Section: Resultsmentioning

confidence: 98%

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Liu

Zhang

Guo

et al. 2020

ACS Appl. Mater. Interfaces

116

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“…Due to the strong electron affinity of Bp, electron transfer from Na metal to conjugate Bp rings occurs spontaneously, which forms Bp − radical anion and Na + ions (Equation (1)). [ 34 ] Subsequently, the NVP electrodes were immersed in the 0.5 M Na‐Bp solution. Because the reduction potential of Bp/Bp − (≈0.12 V vs Na/Na + ) is much lower than the open circuit potential (≈2.8 vs Na/Na + ) and the Na intercalation potential of NVP (≈1.65 vs Na/Na + ), the NVP electrodes receive electrons from Bp − anion to accommodate Na ions, spontaneously forming Na‐rich NVP, that is, Na 4 VP (Equation (2)).…”

Section: Resultsmentioning

confidence: 99%

Na‐Rich Na₃V₂(PO₄)₃ Cathodes for Long Cycling Rechargeable Sodium Full Cells

Liu

Moeez

et al. 2022

Advanced Energy Materials

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NASICON‐type sodium vanadium phosphate (Na3V2(PO4)3, or NVP) cathode materials have great potential for fast charging and long cycling sodium‐ion batteries (SIBs) similar to lithium iron phosphate (LiFePO4, or LFP) cathode materials used in lithium‐ion batteries (LIBs). However, the cycle life and energy density in the full cell using NVP materials need to be significantly improved. This paper investigates the degradation mechanisms of NVP‐based SIBs and identifies the Na loss from the cathode to the anode solid electrolyte interphase (SEI) reactions as the main cause of capacity degradation. A new Na‐rich NVP cathode (e.g., Na4V2(PO4)3, or Na4VP) is developed to address the Na loss problem. Conventional NVP can be easily transformed into the Na4VP by a facile and fast chemical solution treatment (30 s). Na‐free‐anode Na4VP and hard carbon‐Na4VP full cells are assembled to evaluate the electrochemical properties of the Na‐rich NVP cathode. The Na4VP cathode provides excess Na to compensate for the Na loss, resulting much longer cycle life in the full cells (>400 cycles) and a high specific energy and power density. Good low‐temperature performance is also observed.

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“…spectra of solutions of aromatic radical anions in solvents of low dielectric constant is accepted as evidence for ion-association. [1][2][3][4][5][6] The principal interest has generally been the electronic structure of the anion, and there have been relatively few explicit studies of ion-association by e.s.r. It is apparent, however, that e.s.r.…”

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confidence: 99%

E.s.r. studies of ion association. Part 1.—Rate of the intramolecular cation exchange in sodium-pyrazine ion-pairs

Atherton¹,

Goggins²

1965

Trans. Faraday Soc.

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The line-width alternation effect observed in the e.s.r. spectra of sodium-pyrazine ion-pairs in dimethoxyethane, tetrahydrofuran, and mixtures of the two, is due to an intra-molecular cation exchange. The rate constant in mixed solvent containing 0.72 mole fraction of tetrahydrofuran is measured as 1013.3 exp (-7400/RT) from comparing observed and calculated spectra. A similar value for the energy of activation has been obtained from line-breadth measurements in the region of rapid exchange, and this method has been used to measure energies of activation over a range of solvent composition. The values are higher in mixed solvents than in pure. The results are discussed in terms of a model for the ion-pairs.

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Alkali Metal Hyperfine Structure in the ESR Spectra of Biphenyl Mononegative Ions

Cited by 40 publications

References 8 publications

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Na‐Rich Na₃V₂(PO₄)₃ Cathodes for Long Cycling Rechargeable Sodium Full Cells

E.s.r. studies of ion association. Part 1.—Rate of the intramolecular cation exchange in sodium-pyrazine ion-pairs

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Alkali Metal Hyperfine Structure in the ESR Spectra of Biphenyl Mononegative Ions

Cited by 40 publications

References 8 publications

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Chemically Presodiated Hard Carbon Anodes with Enhanced Initial Coulombic Efficiencies for High-Energy Sodium Ion Batteries

Na‐Rich Na3V2(PO4)3 Cathodes for Long Cycling Rechargeable Sodium Full Cells

E.s.r. studies of ion association. Part 1.—Rate of the intramolecular cation exchange in sodium-pyrazine ion-pairs

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Product

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Na‐Rich Na₃V₂(PO₄)₃ Cathodes for Long Cycling Rechargeable Sodium Full Cells