Sophia Suarez

There is increasing interest in studying molecular motions in ionic liquids to gain better insights into their transport properties and to expand their applications. In this study, we have employed the fast field cycling relaxometry and pulsed field gradient nuclear magnetic resonance techniques to investigate the rotational and translational dynamics of fluorinated imide-based ionic liquids (ILs) at different temperatures. We have studied a total of six ILs composed of the 1-butyl-3-methylimidazolium cation ([BMIM]⁺) combined with chemically modified analogs of the bis((trifluoromethyl)sulfonyl)imide anion ([NTf₂]⁻ or [TFSI]⁻). The primary objective of this paper is to broaden the understanding of how the anion's conformational flexibility, fluorination, and mass affect the molecular dynamics of cations and anions. Our results indicate that flexibility has the most significant impact on the rotational and translational motions of ions. Meanwhile, the effect of fluorination and mass is only relevant when conformational flexibility does not change significantly between the ILs being compared.

Zinc ion batteries are a niche alternative for battery applications. Their implementation is however afflicted by several factors, one of which is the need for more efficient electrolytes. Deep eutectic solvent (DES) electrolytes based on ZnCl₂salt offer many attributes including, including improved stability and reduced dendrite formation. In this work we will present a molecular level understanding of the ion dynamics in electrolyte mixtures based on ZnCl₂ and various co-solvents including organic carbonates and water. Focus is on the ion dynamics as interrogated by ¹H NMR spin-lattice relaxation times (T₁ ) combined with ionic conductivity, viscosity and density measurements. As shown in Figure 1, preliminary T₁ results infers multiple ionic coordinated species with varying rates of mobilities that are co-solvent dependent. Additionally, data shows selective interaction sites between the hydrogen bond donors and acceptors, as well as the co-solvents. Figure 1. ¹H T₁ for the null and AcN co-solvent mixtures of (a) 1ZnCl₂:4EtG and (b) 1ChCl:1ZnCl₂:6EtG. Figure 1

Nuclear Magnetic Resonance (NMR) spin relaxation times have been an instrumental tool in deciphering the local environment of ionic species, the various interactions they engender and the effect of these interactions on their dynamics in conducting media. Of particular importance has been their application in studying the wide range of electrolytes for energy storage, on which this review is based. Here we highlight some of the research carried out on electrolytes in recent years using NMR relaxometry techniques. Specifically, we highlight studies on liquid electrolytes, such as ionic liquids and organic solvents; on semi-solid-state electrolytes, such as ionogels and polymer gels; and on solid electrolytes such as glasses, glass ceramics and polymers. Although this review focuses on a small selection of materials, we believe they demonstrate the breadth of application and the invaluable nature of NMR relaxometry.

NMR spin relaxation times have been an instrumental tool in deciphering the local en-vironment of ionic species, the various interactions they engender and the effect of these interactions on their dynamics in conducting media. Of particular importance has been their application in studying the wide range of electrolytes for energy storage, on which this chapter is based. Here we highlight some of the research carried out on electrolytes in recent years using NMR relaxometry techniques. Specifically, studies on liquid electro-lytes, such as ionic liquids and organic solvent; on semi-solid-state electrolytes, such as ionogels and polymer gels, and solid electrolytes such as glasses, glass ceramics and polymers. Although this chapter focuses on a small selection of materials, we believe they demonstrate the breadth of application and the invaluable nature of NMR relaxometry.

In the market of medium- and large- scale energy supplies, sodium (Na⁺) ion batteries are considered a possible alternative to current technologies. This is because sodium is naturally more abundant and cheaper than the ubiquitous lithium. Room temperature Na⁺ batteries typically employ organic solvents such as propylene carbonate. However, room temperature ionic liquids – while more viscous – are safer, and because of this attention is being paid towards their partial or complete replacement of organic solvents. Towards this endeavor, we investigated ions dynamics in mixtures of varying concentrations of sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) or sodium bis(fluorosulfonyl)imide (NaFSI) salts, combined with the 1-butyl-1-methylpyrrolidinium (PYR_1,4) FSI and PYR_1,4 TFSI ionic liquids. We used variable-temperature ¹H and ²³Na Nuclear Magnetic Resonance (NMR) spin-lattice relaxation times (T₁) and self-diffusion coefficients (D) measurements to investigate the short- and long- range ions dynamics and a preview of or results are shown in Figure 1. Both T₁ (¹H and ²³Na) and ¹H D data show greater short- and long- range dynamics for mixtures containing the FSI salt or ionic liquid. A more comprehensive discussion will be presented. Figure 1. Variable-temperature Na⁺ spin-lattice relaxation times (left) and ¹H self-diffusion coefficients (right) for mixtures of various mol% of NaFSI or NaTFSI salt with PYR_1,4 based ILs. Figure 1