Ionic liquid dynamics and electrical conductivity under confinement within micro and nanocellulose ionogels

Abstract

To investigate the effect of cellulose matrix on the diffusion and conductivity properties of the ionogels formed with the BMIMCl ionic liquid (IL), two types of samples were made with micro (CMC) and nano (CNC) cellulose. The cellulose interactions with IL were studied by 1H and 13C NMR solid-state spectroscopy. The cation [BMIM]+ self-diffusion coefficient was calculated based on Fast Field Cycling 1H NMR relaxation measurements. The ionic conductivity was measured by the thermal scanning conductometry method. The NMR spectra at room temperature revealed that cation in the CNC-based ionogel interacts more strongly with the cellulose chain than in the CMC-based ionogel through the methyl group at the end of the alkyl chain. Despite this, the cellulose matrix's influence on the cations' dynamics and electrical conductivity are comparable in both ionogels. The diffusion coefficient is reduced by about two times and the conductivity by about 30% compared with bulk IL.

Nuclear Magnetic Resonance Relaxation Pathways in Electrolytes for Energy Storage

“…FFC-NMR relaxometry studies about confined liquid electrolytes have been mostly concentrated on ILs without [103,106,119,121,[142][143][144][145] and with lithium salt [60], and few of them on aqueous electrolyte solutions [146]. Most of them have been focused on the dynamics of the cation ( 1 H NMR) [119,121,142,143,145,146] and only few of them have studied both cation and anion dynamics ( 1 H and 19 F NMR) [60,103,106,108,144].…”

“…FFC-NMR relaxometry studies about confined liquid electrolytes have been mostly concentrated on ILs without [103,106,119,121,[142][143][144][145] and with lithium salt [60], and few of them on aqueous electrolyte solutions [146]. Most of them have been focused on the dynamics of the cation ( 1 H NMR) [119,121,142,143,145,146] and only few of them have studied both cation and anion dynamics ( 1 H and 19 F NMR) [60,103,106,108,144]. Many of these works have shown that the confinement causes a slight slowing-down of the ion dynamics, which is consistent with the fact that the ionic conductivity of the confined electrolyte is usually smaller compared to the corresponding value for the pure IL [119].…”

Broadband NMR Relaxometry as a Powerful Technique to Study Molecular Dynamics of Ionic Liquids

“…% was added. Kaszyńska et al [49] and Kowalczuk et al [65] explored how dissolving cellulose at 10 wt. % in [BMIM][Cl] affected the cation dynamics and ionic conductivity.…”

“…Confinement of ILs in polymeric systems has also been explored by FFC NMR relaxometry [34,49,53,[63][64][65]68,69] and some of these studies are mentioned very briefly herein. Neves et al [63] and Martins et al [64] investigated ionic mobility and level of confinement, in addition to the effect of temperature and water content on the molecular structure and dynamics of the IL cations BMIM, DTA (n-dodecyltrimethylammonium) and TMPA (phenyltrimethylammonium) in Nafion membranes.…”

“…Confinement can modify the molecular dynamics of ions in the IL in a complex way depending on the chemical structure of the ions, the nature of the confining matrix and how they interact with each other. Broadband NMR relaxometry has proven to be a promising technique to investigate molecular dynamics of IGs [22,29,30,34,47,49,53,62−65] and, in order to emphasize the potentiality of this technique, a few studies are highlighted in this section. FFC NMR can clearly evidence the effect of confinement on ILs by a well‐pronounced dispersion in the relaxation profiles in the low frequency range (in general below 1 MHz) in contrast to the low/almost no frequency dependence at the same frequencies for the IL in bulk.…”