Carbon acidity. 71. The indicator scale of lithium ion pairs in tetrahydrofuran

1986 ◽  
Vol 108 (22) ◽  
pp. 7016-7022 ◽  
Author(s):  
Scott. Gronert ◽  
Andrew. Streitwieser
Keyword(s):  
Ion Pairs ◽  
Lithium Ion

A Raman spectral study of solvation and ion association in the systems LiAsF6/CH3CO2CH3 and LiAsF6/HCO2CH3

1991 ◽  
Vol 69 (11) ◽  
pp. 1766-1773 ◽  
Author(s):  
Zhongyi Deng ◽  
Donald E. Irish
Keyword(s):  
Methyl Acetate ◽  
Methyl Formate ◽  
Ion Pairs ◽  
Lithium Ion ◽  
Ion Association ◽  
Ion Solvation ◽  
Lithium Cation ◽  
Different Types ◽  
Raman Spectral ◽  
Contact Ion Pairs

The structure of the solvated lithium cation in methyl acetate (MA) solutions has been investigated using Raman spectroscopy. Two bands at 844 and 864 cm−1 have been assigned to two different types of MA: the former is from the bulk solvent and the latter arises from MA molecules solvating the lithium cation. From measurement of changes in intensity of these bands with increasing salt concentration a solvation number of four for Li+ in MA has been inferred. Changes in the Raman bands at ca. 1740 cm−1 suggest that solvation occurs through the carbonyl group. Evidence for contact ion pairing between Li+ and AsF6− is also presented. An equilibrium between solvent-shared ion pairs and contact ion pairs is proposed for which an equilibrium constant is estimated. The system LiAsF6/methyl formate (MF) is similar in structure. Key words: Raman, ion pair formation, lithium and hexafluoroarsenate ions, methyl acetate and formate, lithium ion solvation.

Effet de cation sur la réactivité ambidente des anions: la nette tendance à la O-alkylation manifestée par les énolates de lithium de composés β-dicarbonylés

1980 ◽  
Vol 58 (8) ◽  
pp. 786-793 ◽  
Author(s):  
P. Sarthou ◽  
G. Bram ◽  
F. Guibe
Keyword(s):  
Ion Pairs ◽  
Lithium Ion ◽  
Intrinsic Property ◽  
Alkyl Halides ◽  
Alkyl Sulfonates ◽  
Lithium Enolates ◽  
Leaving Group ◽  
Nucleophilic Reactivity ◽  
Specific Reactivity ◽  
Marked Tendency

The study of the specific reactivity of the ion pairs of alkaline enolates of β-dicarbonyl compounds shows that the lithium enolates, in spite of their characteristically strong enolate–cation interactions display, especially when compared to sodium enolates, a marked tendency towards O-alkylation. This strong O-/C-nucleophilicity of the lithium ion pairs is not very sensitive to changes in medium polarity (from THF or DME to DMF) but depends on the nature of the alkylating agent, being enhanced with moderately electrophilic alkyl sulfonates or sulfate but lessened with alkyl halides or with very electrophilic sulfonates (triflate). It is suggested that the lithium enolate tendency towards O-alkylation is partly the result of a Li+ – leaving group interaction (especially in the case of the sulfonates) and partly an intrinsic property of the enolate–lithium ion pair; this latter property is discussed in terms of the respective solvation abilities towards cations of the C- and O-alkylation transition states.Some of our results about the nucleophilic reactivity of ion pairs in DMF are at variance with previous reports in the literature. The origin of the discrepancy is discussed.

scholarly journals Raman Spectroscopy for Understanding of Lithium Intercalation into Graphite in Propylene Carbonated-Based Solutions

2015 ◽  
Vol 2015 ◽  
pp. 1-5 ◽  
Author(s):  
Yang-Soo Kim ◽  
Soon-Ki Jeong
Keyword(s):  
Spectroscopic Analysis ◽  
Ion Pairs ◽  
Solid Electrolyte Interphase ◽  
Lithium Ion ◽  
Lithium Perchlorate ◽  
Lithium Intercalation ◽  
Graphene Layers ◽  
Raman Spectroscopic ◽  
Contact Ion Pairs ◽  
Raman Spectroscopic Analysis

Electrochemical lithium intercalation within graphite was investigated in propylene carbonate (PC) containing different concentrations, 0.4, 0.9, 1.2, 2.2, 2.8, 3.8, and 4.7 mol dm−3, of lithium perchlorate, LiClO4. Lithium ion was reversibly intercalated into and deintercalated from graphite in 3.8 and 4.7 mol dm−3solutions despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of the graphene layers occurred in other solutions. The results of the Raman spectroscopic analysis indicated that contact ion pairs are present in 3.8 and 4.7 mol dm−3solutions, which suggested that the presence of contact ion pairs is an important factor that determines the solid electrolyte interphase- (SEI-) forming ability in PC-based electrolytes.

scholarly journals Regulating interfacial chemistry in lithium-ion batteries by a weakly-solvating electrolyte

2020 ◽  
Author(s):  
Yu-Xing Yao ◽  
Xiang Chen ◽  
Chong Yan ◽  
Xue-Qiang Zhang ◽  
Wen-Long Cai ◽  
...  
Keyword(s):  
Ion Pairs ◽  
Lithium Ion ◽  
Interfacial Chemistry ◽  
Energy Storage Devices ◽  
Graphite Electrodes ◽  
Storage Devices ◽  
Competitive Coordination ◽  
Fast Charging ◽  
Low Salt

Abstract The performance of lithium-ion battery is highly dependent on its interfacial chemistry, which is regulated by electrolytes. Conventional electrolyte typically contains polar solvents to dissociate Li salts. Here, we report a novel weakly-solvating electrolyte (WSE) that consists of a pure non-polar solvent, which leads to a peculiar solvation structure where ion pairs and aggregates prevail under a low salt concentration of 1.0 M. Importantly, WSE forms unique anion-derived interphases on graphite electrodes that exhibit fast-charging and long-term cycling characteristics. First-principles calculations unravel a general principle that the competitive coordination between anions and solvents to Li ion is the origin of different interfacial chemistries. By bridging the gap between solution thermodynamics and interfacial chemistry in batteries, this work opens a brand-new way towards precise electrolyte engineering for energy storage devices with desired properties.

Local and Translational Motion of the 6Li and 7Li Ions in the Li3Sc2(PO4)3 and Li3In2(PO4)3 Compounds

1990 ◽  
Vol 210 ◽  
Author(s):  
Igor S. Pronin ◽  
Sergei E. Sigaryov ◽  
Andrei A. Vashman
Keyword(s):  
Solid Electrolytes ◽  
Translational Motion ◽  
Ion Pairs ◽  
Lithium Ion ◽  
Spectroscopy Data ◽  
Ionic Radii ◽  
Ion Motion ◽  
Mixed Alkali ◽  
Mixed Alkali Effect ◽  
Li Ion

AbstractBasing on impedance and NMR spectroscopy data it is shown that there are two types of lithium ion motion in the each polymorhic modification of the Li3 Sc2 (P04)3 and Li3 In2 (P04)3 solid electrolytes. First type is a translational motion of these ions which determines the a values, while the second one is Li ion motion within the lithium ion—ion pairs at the distance about the sum of two lithium ionic radii. Substitution of 7Li by 6Li leads to the mixed alkali effect—type behaviour of σ.

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