Lithium ion transport through nonaqueous perfluoroionomeric membranes

Abstract

The transport properties of lithiated perfluorinated ionomers imbibed with nonaqueous solvents and solvent mixtures were studied. Polymeric ion‐exchange membranes have potential use in the next generation single‐ion secondary lithium polymer batteries, where the lithiated form of the membrane is used as a polymer electrolyte. The novelty of the approach for lithium battery applications lies in the advantage offered by a transference number of unity, no additional salt (e.g., LiPF6) is needed, and the excellent physical and chemical stability of the fluoropolymers. Ion‐exchange membranes were converted to the Li+ salt form and analyzed for total conversion using FT‐IR. Nonaqueous solvents and solvent mixtures were imbibed into the membranes in a glove box, and the uptake was measured over time. A four‐point probe was used to determine the ionic conductivity based on impedance measurements performed over a frequency range of 10 to 35,000 Hz. Conductivities exceeding 10−4 S/cm with transference numbers of unity were achieved making these ionomeric membranes potentially useful in rechargeable lithium polymer batteries.

Molecular Dynamics Modeling of the Conductivity of Lithiated Nafion Containing Nonaqueous Solvents

“…26,[31][32][33] Conductivity was generally observed to increase with solubility parameter, dielectric constant, and amount of solvent, and decrease with the equivalent weight (EW) of the ionomer. However, many exceptions were observed and large variations in performance were found from the many different solvents, necessitating an understanding of how individual solvent properties contribute to overall performance.…”

Study of lithiated Nafion ionomer for lithium batteries

“…As shown in spectra B and C, the band at 1052 cm )1 shifts to 1065 cm )1 , the bands at 1702, 1415 and 924 cm )1 disappear and a new band appears at 1636 cm )1 . These indicate [11] that hydrolysis has been carried out completely in the ethanol solution as well as DMSO solution.…”

“…However, DMSO is very difficult to remove completely. The residue DMSO will cause a mixed solvent effect and influence the electrochemical properties of the membrane [11]. Here, ethanol was used as swelling agent as developed by Sachan et al [11].…”

“…The residue DMSO will cause a mixed solvent effect and influence the electrochemical properties of the membrane [11]. Here, ethanol was used as swelling agent as developed by Sachan et al [11]. By comparison, the membrane was also hydrolyzed in a solution of 0.5 M LiOH in a 1:1 volume ratio of DMSO and deionized H 2 O for 2 h at 60°C.…”

“…The ionic conductivity of lithiated Nafion Ò 117 ionomer reaches 1.00 · 10 )4 S cm )1 if it is swollen with a mixture of propylene carbonate and ethylene carbonate without the use of a lithium salt. Sachan et al [11] proposed that perfluoro ionomers may be used in rechargeable lithium polymer batteries if the ionic conductivity exceeds 1 · 10 )4 S cm )1 . The aim of this work is to study lithiated Nafion Ò 112 ionomer for use as a polymer electrolyte in rechargeable lithium batteries.…”