Polymer Gel Electrolytes: Conduction Mechanism and Battery Applications

The Journal of Chemical Physics

2013

Longitudinal relaxation (T1) measurements of (19)F, (7)Li, and (1)H in propylene carbonate/LiBF4 liquid electrolytes are reported. Comparison of T1 values with those for the transverse relaxation time (T2) confirm that the measurements are in the high temperature (low correlation time) limit of the T1 minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T1 from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

Section: B T 1 Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

NMR T1 relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF4 and propylene carbonate

The Journal of Chemical Physics

2013

“…Following the pioneering research of Wright [1] and Armand [2] into solid polymer electrolytes and their potential for use in lithium batteries, thermo-reversible polymer gel electrolytes (PGEs) [3,4] have been studied at the University of Leeds with the introduction of solvents [5,6]. These gel electrolytes combine the high ionic mobility of conventional liquid electrolytes with the mechanical advantage of incorporating a polymer.…”

Section: Introductionmentioning

confidence: 99%

Pulsed-Field Gradient NMR Self Diffusion and Ionic Conductivity Measurements for Liquid Electrolytes Containing LiBF4 and Propylene Carbonate

2014

Electrochimica Acta

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Page 1 of 42A c c e p t e d M a n u s c r i p t 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 AbstractLiquid electrolytes have been prepared using lithium tetrafluoroborate (LiBF 4 ) and propylene carbonate (PC). Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) measurements were taken for the cation, anion and solvent molecules using lithium ( 7 Li), fluorine ( 19 F) and hydrogen ( 1 H) nuclei, respectively. It was found that lithium diffusion was slow compared to the much larger fluorinated BF 4 anion likely resulting from a large solvation shell of the lithium. Ionic conductivity and viscosity have also been measured for a range of salt concentrations and temperatures. By comparing the measured conductivity with a ideal predicted conductivity derived from the Nernst-Einstein equation and self diffusion coefficients the degree of ionic association of the anion and cation was determined and was observed to increase with salt concentration and temperature. Using the measured viscosity and self diffusion coefficients the effective radius of each of the species was determined for various salt concentrations.

“…Due to easy fabrication by an extrusion lamination process [6], there is no need for external casing or a polymer separator to stop electrodes shorting [7]. For these reasons PGEs have become the focus of a significant amount of research by many groups worldwide [8,9,10,11,12,13].…”

Section: Introductionmentioning

confidence: 99%

Two distinct lithium diffusive species for polymer gel electrolytes containing LiBF4, propylene carbonate (PC) and PVDF

International Journal of Hydrogen Energy

2014

Polymer gel electrolytes have been prepared using lithium tetrafluoroborate (LiBF 4 ), propylene carbonate (PC) and polyvinylidene fluoride (PVDF) at 20% and 30% concentration by mass. Self diffusion coefficients have been measured using pulse field gradient nuclear magnetic resonance (PFG-NMR) for the cation and anion using 7 Li and 19 F resonant frequencies respectively. It was found that lithium ion diffusion was slow compared to the much larger fluorine anion likely resulting from a large solvation shell of the lithium. Lithium ion diffusion measurements exhibited two distinct diffusive species, whereas the fluorine ions exhibited only a single diffusive species.