Structural Effects of Solvents on Li-Ion-Hopping Conduction in Highly Concentrated LiBF₄/Sulfone Solutions

Abstract

Li-ion-hopping conduction is known to occur in certain highly concentrated electrolytes, and this conduction mode is effective for achieving lithium batteries with high rate capabilities. Herein, we investigated the effects of the solvent structure on the hopping conduction of Li ions in highly concentrated LiBF 4 /sulfone electrolytes. Raman spectroscopy revealed that a Li + ion forms complexes with sulfone and anions, and contact ion pairs and ionic aggregates are formed in the highly concentrated electrolytes. Li + exchanges ligands (sulfone and BF 4 − ) rapidly to produce unusual hopping conduction in highly concentrated electrolytes. The structure of the solvent significantly influences the hopping conduction process. We measured the selfdiffusion coefficients of Li + (D Li ), anions (D anion ), and sulfone solvents (D sol ) in electrolytes. The ratio of the self-diffusion coefficients (D Li /D sol ) tended to be higher for cyclic sulfones (sulfolane and 3-methylsulfolane) than for acyclic sulfones, which suggests that cyclic sulfone molecules facilitate Li-ion hopping. The hopping conduction increases the Li + -transference number (t Li abc + ) under anion-blocking conditions, and t Li abc + of [LiBF 4 ]/[cyclic sulfone] = 1/2 is as high as 0.8.

Ionic Liquid Stabilizes Olefin Facilitated Transport Membranes Against Reduction

“…Previously, Raman spectroscopy has been used to determine anion aggregation. [44][45][46][47][48][49] A series of [hmim][Tf 2 N]/AgTf 2 N and [hmim][NO 3 ]/AgNO 3 solutions containing four different silver salt concentrations were prepared, and the wavelength shifts by Raman scattering were analyzed at room temperature to elucidate changes in the anion structure due to silver ion addition. We focused on the symmetric stretching bands of the SÀ NÀ S bond of Tf 2 N À anions and the NÀ O bonds of NO 3 À anions.…”

A universal strategy for high-voltage aqueous batteries via lone pair electrons as the hydrogen bond-breaker

“…On the time scale of 1000 ps, the almost linear behavior of TMS suggests that it is in a diffusion state throughout the run time, and has a faster diffusion rate compared to that of other components in the electrolyte. Li + possesses the lowest diffusion coefficient because it is solvated by sulfone molecules to form the aggregate [Li(sulfone) x ] + , 37 demonstrating that TMS participates in the interfacial reaction kinetics to form SEI films. The diffusion coefficients (Table S5, ESI†) of different species at different temperatures were extracted using Einstein eqn (1) 38 and Green–Kubo theory eqn (2) as follows:where ν ( t ) is the velocity of the particle at time t .…”

Ionic Liquid Stabilizes Olefin Facilitated Transport Membranes Against Reduction

“…To investigate the differences in hydrogen stability between SILM‐Tf 2 N and SILM‐NO 3 , we probed the molecular structures of the IL mixtures using Raman spectroscopy. Previously, Raman spectroscopy has been used to determine anion aggregation [44–49] . A series of [hmim][Tf 2 N]/AgTf 2 N and [hmim][NO 3 ]/AgNO 3 solutions containing four different silver salt concentrations were prepared, and the wavelength shifts by Raman scattering were analyzed at room temperature to elucidate changes in the anion structure due to silver ion addition.…”