NMR measurements of self diffusion in polymer gel electrolytes

The ion-transport properties of composite electrolytes composed of oligomers of poly͑ethylene glycol͒ dimethyl ether, hydrophobic fumed silica, and Li͑CF 3 SO 2) 2 N ͑LiTFSI͒ are investigated using nuclear magnetic resonance ͑NMR͒, electrophoretic NMR ͑ENMR͒, ac impedance spectroscopy, and rheology. The effects of fumed silica and salt concentration on ionic conductivity, diffusivity of ions and oligomers, and lithium transference number (T Li) are examined at 30°C. The fumed silica forms a selfsupporting network with large pores such that the network, regardless of silica concentration, has little effect on ion-transport characteristics. Examination of the effect of salt on ion transport reveals a maximum ionic conductivity at around 1.06 M, which is attributed to a tradeoff of adding more charge carriers balanced against increased ion-ion interactions and reduced mobilities. T Li with respect to salt concentration surprisingly passes through a minimum around 0.35 M. The increase in T Li at higher concentrations is attributed to the mobilities of cations, anions, and solvating oligomer becoming constrained to the same value due to ''loss of free volume.'' The values of T Li at low salt concentrations ͑Ͻ0.35 M͒ are attributed to the ions existing in either a fully dissociated state or primarily as charged complexes. Results of T Li from ENMR and from estimation via pulse field gradient NMR ͑pfg-NMR͒ are compared showing that pfg-NMR consistently overestimates T Li. Finally, a comparison is presented of measured conductivity with that calculated from the Nernst-Einstein equation and diffusivities found from pfg-NMR measurement; we discuss possible reasons why it is inappropriate to estimate ion-pair formation by this comparison.

show abstract

“…The Nernst-Einstein equation is often used in the literature to write the conductivity as 23,[44][45][46] ϭ…”

Section: Discussionmentioning

confidence: 99%

Ion Transport in Silica Nanocomposite Electrolytes

Walls

Fedkiw

Zawodzinski

et al. 2003

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…NMR diffusion measurements have been proven to be a useful tool in understanding the mobility in polymer gel electrolytes [29,30,31,32,16,33,34]. However, the possibility of multiple diffusive species of both the lithium ions and solvent molecules is discussed in this paper, which has previously been reported by us [18] and also in a publication by Magistris et al [17].…”

Section: Conducting Polymer Electrolyte Research At the University Ofmentioning

confidence: 73%

NMR self diffusion and relaxation time measurements for poly (vinylidene fluoride) (PVDF) based polymer gel electrolytes containing LiBF and propylene carbonate

Richardson

Voice

Ward

2016

Polymer

Self Cite

View full text Add to dashboard Cite

show abstract

“…These studies have not been limited to proton, but have included other nuclei as well (e.g., 13 C, 19 F, 7 Li, etc.) . In the case of oxygen gas, the NMR properties of 17 O (nuclear spin of 5/2 and a quadrupolar moment that leads to very short relaxation times – T 1 , T 2 < 5 ms), coupled with low sensitivity (natural abundance of 0.037%) and paramagnetism hamper the direct detection of its signal.…”

Section: Introductionmentioning

confidence: 99%

“…[27][28][29][30][31][32][33][34][35] These studies have not been limited to proton, but have included other nuclei as well (e.g., 13 C, 19 F, 7 Li, etc.). [ 31,[35][36][37][38][39][40] In the case of oxygen gas, the NMR properties of 17 O (nuclear spin of 5/2 and a quadrupolar moment that leads to very short relaxation times -T 1 , T 2 < 5 ms), coupled with low sensitivity (natural abundance of 0.037%) and paramagnetism hamper the direct detection of its signal. However, the fact that O 2 is paramagnetic causes a reduction of the relaxation times of other nuclei when the gas is present in the sample, due to electron-nuclear dipolar interactions.…”

Section: Introductionmentioning

confidence: 99%

Determination of Oxygen Permeability in Acrylic‐Based Hydrogels by Proton NMR Spectroscopy and Imaging

Compañ

Mollá

Vallejos

et al. 2014

Macro Chemistry & Physics

View full text Add to dashboard Cite

Polymer network membranes with a high capacity for water absorption are obtained by radical polymerization of N‐[2‐(2‐hydroxyethoxy)ethyl]methacrylamide (HEEMAM). The permeability, solubility, and diffusion coefficients of oxygen in hydrogels are determined using nuclear magnetic resonance (NMR) methods based on the paramagnetic effect of dissolved oxygen gas on the proton spin‐lattice relaxation times of water, and the results are compared with those obtained with electrochemical procedures. The results of NMR measurements of oxygen transport coefficients in distilled water show excellent agreement with corresponding literature values. The results of the potentiostatic and NMR oxygen transport measurements in hydrogels are in reasonable agreement and support the viability of the NMR method.

show abstract

NMR measurements of self diffusion in polymer gel electrolytes

Cited by 28 publications

References 14 publications

Ion Transport in Silica Nanocomposite Electrolytes

Ion Transport in Silica Nanocomposite Electrolytes

NMR self diffusion and relaxation time measurements for poly (vinylidene fluoride) (PVDF) based polymer gel electrolytes containing LiBF and propylene carbonate

Determination of Oxygen Permeability in Acrylic‐Based Hydrogels by Proton NMR Spectroscopy and Imaging

Contact Info

Product

Resources

About