Synthesis and Use of Zwitterion Bearing Sulfonyl(trifluoromethane sylfonyl)imide Anion as Additive for Polymer Electrolytes

In order to improve the electrochemical properties of poly(ethylene oxide), a well-known-solid polymer electrolyte, by adding zwitterion molecules, the synthesis of a new zwitterion (ZN) having imidazolium cation and sulfonyl(trifluoromethane sulfonyl)imide anion is investigated. The addition of different amounts of ZN to the mixture of lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) and poly(ethylene glycol)dimethyl ether (PEGDM) of 1000 g mol−1 does not significantly affect the transition temperature of PEGDM but causes a slight decrease in ionic conductivity of the electrolyte mixtures. However, even with the presence of only 0.05 mole fraction of ZN, the anodic stability of LiTFSI/PEGDM based electrolytes is improved to over 4.5 V vs. Li+/Li at 25 °C. This makes the new synthesized zwitterion a promising electrolyte’s additive for high voltage batteries.

Ionic Liquid Electrolytes for Safer and More Reliable Sodium Battery Systems

Na+-conducting, binary electrolytic mixtures, based on 1-ethyl-3-methyl-imidazolium, trimethyl-butyl-ammonium, and N-alkyl-N-methyl-piperidinium ionic liquid (IL) families, were designed and investigated. The anions were selected among the per(fluoroalkylsulfonyl)imide families. Sodium bis(trifluoromethylsulfonyl)imide, NaTFSI, was selected as the salt. The NaTFSI-IL electrolytes, addressed to safer sodium battery systems, were studied and compared in terms of ionic conductivity and thermal stability as a function of the temperature, the nature of the anion and the cation aliphatic side chain length. Room temperature conductivities of interest for sodium batteries, i.e., largely overcoming 10−4 or 10−3 S cm−1, are displayed. Similar conduction values are exhibited by the EMI-based samples even below −10 °C, making these electrolyte mixtures potentially appealing also for low temperature applications. The NaTFSI-IL electrolytes, with the exception of the FSI-ones, are found to be thermally stable up to 275 °C, depending on the nature of the cation and/or anion, thus extending their applicability above 100 °C and remarkably increasing the reliability and safety of the final device, especially in the case of prolonged overheating.

Temperature effects on the spatial distribution of electrolyte mixtures at the aqueous liquid–vapor interface

Monte Carlo simulations indicate that an anion's propensity for interfacial adsorption increases with its size and is associated with an enthalpic gain and entropic cost for the largest anion.

Carbonate Solvents and Ionic Liquid Mixtures as an Electrolyte to Improve Cell Safety in Sodium-Ion Batteries

Ionic liquid-based electrolytes proved to be effective in terms of alleviating the safety problems associated with lithium/sodium ion batteries, especially for large-scale applications, due to their superior thermal stability and nonflammability. The main disadvantage of ionic liquids is their relatively high viscosity. Adding a suitable amount of organic “thinning” solvents could be a potential solution for this problem: while the electrolyte viscosity is greatly reduced, the electrochemical properties and thermal stability remain almost as good as those of pure ionic liquid. In this study, electrolyte mixtures based on 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) (EMI-TFSI) and carbonate solvents (EC-PC) were prepared. The electrochemical compatibility in half-cell configuration with respect to sodium metal anode of various electrode materials, including SnS/C, hard carbon (HC), and Na0.44MnO2, was evaluated. Moreover, the thermal stability, the flammability, and the conduction mechanism of such electrolyte mixtures were also explored and discussed.