A Raman spectroscopic study of organic electrolyte solutions based on binary solvent systems of ethylene carbonate with low viscosity solvents which dissolve different lithium salts

Abstract

The ionic structure of organic electrolyte solutions has been investigated, by means of Raman spectroscopy for mixed aprotic solvents that dissolve lithium salts. The solutions consisted of binary solvent systems of a high permittivity solvent (ethylene carbonate, EC) mixed with low viscosity alkyl carbonates (dimethyl carbonate, DMC, and diethyl carbonate, DEC) or a linear alkyl ether (1,2-dimethoxyethane, DME) and of LiCF 3 SO 3 , and as the solute. The Raman shifts based on the solvents varied with the sort of) 2 dissolved lithium salts and their concentration. The ion solvation was estimated from the side-bands of the Raman scattering for the CwO stretch of single bonds of the carbonate groups and for the symmetric ring deformation of EC. The number of EC molecules interacting with the lithium cation (Li`) was higher than that of DMC in a mixed EC ] DMC (50 : 50 by volume) system. The apparent solvation number of Li`in 1.5 mol dm~3 solution was about 2.8 in EC ] DMC, whereas that in 1.5 M solution was LiCF 3 SO 3 LiPF 6 about 3.9. SpeciÐc solvation of Li`was distinguished in EC ] DME (50 : 50), where DME predominantly coordinates to Li`. However, it was also conÐrmed that EC, which has a lower donicity, interacts with Liè ven in the EC ] DME system. That is, the solvation number of EC in remained LiCF 3 SO 3 /(EC ] DME) ca. 1.0 even in high salt concentrations.

Strategies for fast ion transport in electrochemical capacitor electrolytes from diffusion coefficients, ionic conductivity, viscosity, density and interaction energies based on HSAB theory

“…Based on their molecular structures, the ionic radii of TEA + , 12 In the present study, except for LiBF 4 , the orders of magnitude of 26 The r Li /r PC value obtained by our method therefore includes exchange between molecules in the bulk PC and is in good agreement with the assumed value. In the EDLC electrolytes, the values of r TEA /r PC and r TEMA /r PC suggest that the ammonium cations interact weakly with PC and/or the counteranions to form weak solvation structures and ion pairs.…”

Compatibility of quaternary ammonium-based ionic liquid electrolytes with electrodes in lithium ion batteries

“…By Comparison, the FTIR spectra of the graphite anode after having cycled in the two different electrolytes are quite different. In the organic electrolyte, the pronounced peaks of 1518, 1454 and 876 cm −1 are assigned to Li 2 CO 3 salt [20,21]. The bands appeared at 1645(C O, as.)…”

Solution Structure and Magnesium Deposition Electrochemistry of Mixing Alkylmagnesium Halide with Magnesium Sulfonyl Amide/Glyme Solution

“…Raman spectroscopy has been used to elucidate the solution structures of non-aqueous electrolyte for lithium-ion and magnesium batteries. 15,[21][22][23][24][25][26] The magnesium deposition behavior and solution structure of various mixed electrolytes have been compared. Results showing changes in the coordination structure by mixing EtMgBr and Mg(TFSA) 2 might provide information to facilitate the design of electrolyte systems for magnesium secondary batteries.…”