Tabc Li+ in Sulfolane-and Tetraglyme-based Electrolytes by Very Low Frequency Impedance Spectroscopy (VLF-IS)

Scientific Achievement

A systematic study of the effect of concentration on Li+ transference number under anion-blocking conditions (T_(〖Li〗^+)^abc) in sulfolane (SL) and tetraglyme (G4) using VLF-IS showed that SL is a more superior solvent than G4 for Li+ transport, even though the viscosity of the former is higher but with similar ionic conductivity.

Significance and Impact

Cation-solvent interaction strongly affects cation transport in concentrated systems—the faster Li+ transport in the SL systems is a result of the ion-hopping diffusion mechanism facilitated by the long-range liquid structures of SL molecules and the anions, while the sluggish Li+ transport in the G4 systems is dominated by the vehicular-typed diffusion mechanism resulted from the formation of stable [Li(G4)]+ solvation cages.

Research Details

  • VLF-IS was employed instead of pfg-NMR because the latter assumes no interactions between ions and solvent molecules which is not applicable to concentrated systems.
  • This technique together with the special sample holder with adjustable electrode distance allows salt-diffusion coefficient determination.
  • Frequency from 1 MHz to 0.1 mHz, where the low range captures the diffusion impedance, at 2 mVrms to avoid convective effects.
  • T_(〖Li〗^+)^abc=R_bulk∕(R_bulk+R_diffusion )

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DOI: 10.1002/EEM2.12302

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