Electrophoretic NMR measurements of lithium transference numbers in polymer gel electrolytes

Abstract

We describe here our application of electrophoretic NMR (ENMR) to the determination of transference numbers of lithium ions in polymer gel electrolytes. Two types of polymer gel electrolytes were selected for this study: PAN /PC/EC/LiX and Kynar/PC/LiX. Results obtained for the two types of gels are compared and the effects of anion, polymer-ion interactions and ion-ion interactions on lithium transference numbers are discussed.Significant differences in the behavior of transference numbers with salt concentration are observed for the two types of gels. This may be due to the extent of interaction between the polymer and the ions. Implications for solid polymer electrolytes are discussed.

Ionic Conduction Properties of PVDF−HFP Type Gel Polymer Electrolytes with Lithium Imide Salts

“…One is a physical blocking effect of the polymer. The polymer would act as insulating materials and interfere physically with the carrier migration . In this case, the conduction mechanism of the gel would essentially follow the mechanism of the solution.…”

Sensitive and robust electrophoretic NMR: Instrumentation and experiments

“…One may perceive that adopting a truly cylindrical sample cell geometry [4,15,[18][19][20][21][22][23][24][25]40,41] without any lead through the rf-coil-sensitive volume would lead a potential further improvement. Indeed, a change in that direction would eliminate the need for rf filters but would, at the same time, render eNMR less available since then it should be performed in custom-built probes.…”

“…Various types of double concentric or straight tube designs have been tested and used over the years [15,18,19,[21][22][23][24][25]. Although a cylindrical sample geometry intrinsically provides a high filling factor and preserves the sign of the electrophoretic displacement, there are severe practical shortcomings with designs of this family.…”

Ionic Conduction Mechanisms of Polyvinylidenefluoride-Hexafluoropropylene Type Polymer Electrolytes with LiN(CF[sub 3]SO[sub 2])[sub 2]

“…Pulsed field gradient NMR.-Pillar-shaped polymer electrolyte films were inserted into the NMR tube of 3 mm diam, and the measurements were performed on an Alpha-500 NMR apparatus of the JEOL Company using a stimulated echo sequence. 6 The diffusion coefficients of lithium and anion species were determined using the probed species, 7 Li and 19 F, respectively. The data for 7 Li was acquired at a Larmor frequency of 194 MHz, with a 90Њ pulse of 11.50 s; the delay between the two gradient pulses was maintained in the range 650-1500 ms, and the duration of the gradient pulse was fixed on 3 ms.…”

“…6 The diffusion coefficients of lithium and anion species were determined using the probed species, 7 Li and 19 F, respectively. The data for 7 Li was acquired at a Larmor frequency of 194 MHz, with a 90Њ pulse of 11.50 s; the delay between the two gradient pulses was maintained in the range 650-1500 ms, and the duration of the gradient pulse was fixed on 3 ms. The data for 19 F was acquired at a Larmor frequency of 470 MHz, with a 90Њ pulse of 12.5 s; the delay between the two gradient pulses was in the range 500-2200 ms, and the duration of the gradient pulse was maintained between 1 and 1.9 ms.…”