Lithium NMR

G��nther, Harald

doi:10.1002/9780470034590.emrstm0273

Cited by 8 publications

(8 citation statements)

References 147 publications

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“…The ion binding environment was also examined using 7 Li and 19 F NMR. An NMR capillary setup was used for 7 Li NMR (see the Experimental Section) and the data referenced to a 1 M LiClO 4 in acetonitrile internal standard (−2.80 ppm) . Within the FTriEG family, as one moves from MME to DME to DEG, an upfield shift is observed (Figure e), which could be due to stronger ion solvation or an increase in ion-pairing; unfortunately Figure e alone is insufficient to distinguish between the two as both phenomena will lead to upfield shifts. − Figure f shows the 19 F chemical shift where a downfield trend is observed for FSA – as one increases the ether length.…”

Section: Resultsmentioning

confidence: 99%

A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability

et al. 2020

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Increasing battery energy density is greatly desired for applications such as portable electronics and transportation. However, many next-generation batteries are limited by electrolyte selection because high ionic conductivity and poor electrochemical stability are typically observed in most electrolytes. For example, ether-based electrolytes have high ionic conductivity but are oxidatively unstable above 4 V, which prevents the use of high-voltage cathodes that promise higher energy densities. In contrast, hydrofluoroethers (HFEs) have high oxidative stability but do not dissolve lithium salt. In this work, we synthesize a new class of fluorinated ether electrolytes that combine the oxidative stability of HFEs with the ionic conductivity of ethers in a single compound. We show that conductivities of up to 2.7 × 10– 4 S/cm (at 30 °C) can be obtained with oxidative stability up to 5.6 V. The compounds also show higher lithium transference numbers compared to typical ethers. Furthermore, we use nuclear magnetic resonance (NMR) and molecular dynamics (MD) to study their ionic transport behavior and ion solvation environment, respectively. Finally, we demonstrate that this new class of electrolytes can be used with a Ni-rich layered cathode (NMC 811) to obtain over 100 cycles at a C/5 rate. The design of new molecules with high ionic conductivity and high electrochemical stability is a novel approach for the rational design of next-generation batteries.

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Section: Resultsmentioning

confidence: 99%

A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability

et al. 2020

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“…5 to −5 ppm). [37] Wagemaker et al [35] concluded that conduction, rather than paramagnetism, is the dominant interaction in anatase. Distributions of quadrupole interactions and chemical shifts due to disordered environments and interactions with electrons in the conduction band then account for the line broadening and the intense spinning sidebands.…”

Section: Resultsmentioning

confidence: 99%

Exploiting cationic vacancies for increased energy densities in dual-ion batteries

Koketsu

Morgan

et al. 2020

Energy Storage Materials

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Dual-ion Li-Mg batteries offer a potential route to cells that combine desirable properties of both single-ion species. To maximize the energy density of a dual-ion battery, we propose a strategy for achieving simultaneous intercalation of both ionic species, by chemically modifying the intercalation host material to produce a second, complementary, class of insertion sites. We show that donor-doping of anatase TiO 2 to form large numbers of cationic vacancies allows the complementary insertion of Li + and Mg 2+ in a dual-ion cell with a net increase in cell energy density, due to a combination of an increased reversible capacity, an increased operating voltage, and a reduced polarization. By tuning the lithium concentration in the electrolyte, we achieve full utilization of the Ti 4+ /Ti 3+ redox couple with excellent cyclability and rate capability. We conclude that native interstitial sites preferentially accommodate Li + ions, while Mg 2+ ions occupy single-vacancy sites. We also predict a narrow range of electrochemical conditions where adjacent vacancy pairs preferentially accommodate one ion of each species, i.e., a [Li Ti +Mg Ti ] configuration. These results demonstrate the implementation of additional host sites such as cationic sites as an effective approach to increase the energy density in dual-ion batteries.

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“…The whole sample preparation process was done inside an argon-filled glovebox (O 2 , H 2 O < 1 ppm). The reference solution peak of 7 Li NMR spectra was calibrated to −2.80 ppm, 42 and the reference peak of 19 F NMR spectra was calibrated to −62.5 ppm. 43 Raman Spectroscopy.…”

Section: ■ Conclusionmentioning

confidence: 99%

Effect of Building Block Connectivity and Ion Solvation on Electrochemical Stability and Ionic Conductivity in Novel Fluoroether Electrolytes

Mirmira

Amanchukwu

2021

ACS Cent. Sci.

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Novel electrolytes are required for the commercialization of batteries with high energy densities such as lithium metal batteries. Recently, fluoroether solvents have become promising electrolyte candidates because they yield appreciable ionic conductivities, high oxidative stability, and enable high Coulombic efficiencies for lithium metal cycling. However, reported fluoroether electrolytes have similar molecular structures, and the influence of ion solvation in modifying electrolyte properties has not been elucidated. In this work, we synthesize a group of fluoroether compounds with reversed building block connectivity where ether moieties are sandwiched by fluorinated end groups. These compounds can support ionic conductivities as high as 1.3 mS/cm (30 °C, 1 M salt concentration). Remarkably, we report that the oxidative stability of these electrolytes increases with decreasing fluorine content, a phenomenon not observed in other fluoroethers. Using Raman and other spectroscopic techniques, we show that lithium ion solvation is controlled by fluoroether molecular structure, and the oxidative stability correlates with the “free solvent” fraction. Finally, we show that these electrolytes can be cycled repeatedly with lithium metal and other battery chemistries. Understanding the impact of building block connectivity and ionic solvation structure on electrochemical phenomena will facilitate the development of novel electrolytes for next-generation batteries.

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Lithium NMR

Cited by 8 publications

References 147 publications

A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability

A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability

Exploiting cationic vacancies for increased energy densities in dual-ion batteries

Effect of Building Block Connectivity and Ion Solvation on Electrochemical Stability and Ionic Conductivity in Novel Fluoroether Electrolytes

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