Transport studies of NaPF6 carbonate solvents-based sodium ion electrolytes. (1st May 2021)

• Record Type: Journal Article
• Authors: Morales, Daniel; Chagas, Luciana Gomes; Paterno, Domenec; Greenbaum, Steve; Passerini, Stefano; Suarez, Sophia
• Is Part Of: Electrochimica acta. Volume 377(2021)
• Publication Date: 2021-05-01
• Subjects: Ion-association -- NMR diffusometry -- Sodium electrolytes -- Walden products -- Salt dissociation; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.138062
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Preferential solvation of sodium ions by propylene carbonate. Walden Product classification of electrolytes as 'solvent-co-solvent'. The inclusion of FEC enhanced the ionic conductivity of the lower polarity solvent electrolyte. Abstract: Characterizing fundamental ion transport is necessary for the modification and development of electrolytes. In this study, we investigated the local and bulk transport properties of 1 M NaPF6 in the binary EC:PC (1:1), and ternary 5EC:3PC:2DEC (5:3:2) solvents, as well as their 2 wt.% FEC modulated versions. We determined 1 H, 19 F and 23 Na Nuclear Magnetic Resonance (NMR) spin-lattice relaxation time ( T1 ), self-diffusion coefficient ( D ), linewidth and chemical shift. These were complimented with density, viscosity and ionic conductivity measurements, all as a function of temperature. Both the viscosity and ionic conductivity displayed VFT behavior and their Walden products showed a dependence on temperature. This coupled with their having the lower Walden products indicated less salt dissociation in the 5EC:3PC:2DEC and 5EC:3PC:2DEC + 2 wt.% electrolytes. NMR D 19 F and 23 Na values for these electrolytes were also similar at 298K indicating cation-anion association, but diverged with increasing temperatures, with that for the anion being greater than the cation. The addition of the FEC provides greater local dynamics for the individual solvents in the less polar electrolyte but appeared to impede that of the ions.