Effect of Aromaticity in Anion on the Cation-Anion Interactions and Ionic Mobility in Fluorine-Free Ionic Liquids

Ionic liquids (ILs) composed of tetra(n-butyl)phosphonium [P₄₄₄₄]⁺ and tetra(n-butyl)ammonium [N₄₄₄₄]⁺ cations paired with 2-furoate [FuA]⁻, tetrahydo-2-furoate [HFuA]⁻, and thiophene-2-carboxylate [TpA]⁻ anions are prepared to investigate the effects of electron delocalization in anion and the mutual interactions between cations and anions on their physical and electrochemical properties. The [P₄₄₄₄]⁺ cations-based ILs are found to be liquids, while the [N₄₄₄₄]⁺ cations-based ILs are semi-solids at room temperature. Thermogravimetric analysis revealed higher decomposition temperatures and differential scanning calorimetry analysis showed lower glass transition temperatures for phosphonium-based ILs than the ammonium-based counterparts. The ILs are arranged in the decreasing order of their ionic conductivities as [P₄₄₄₄][HFuA] (0.069 mS cm^–1) > [P₄₄₄₄][FuA] (0.032 mS cm^–1) > [P₄₄₄₄][TpA] (0.028 mS cm^–1) at 20 °C. The oxidative limit of the ILs followed the sequence of [FuA]⁻> [TpA]⁻> [HFuA]⁻, as measured by linear sweep voltammetry. This order can be attributed to the electrons’ delocalization in [FuA]⁻ and in [TpA]⁻ aromatic anions, which has enhanced the oxidative limit potentials and the overall electrochemical stabilities.

Comparing the Thermal and Electrochemical Stabilities of Two Structurally Similar Ionic Liquids

Here we focus on the thermal and variable temperature electrochemical stabilities of two ionic liquids (ILs) having a common tributyloctyl phosphonium cation [P_4,4,4,8]⁺ and two different orthoborate anions: bis(mandelato)borate [BMB]⁻ and bis(salicylato)borate [BScB]⁻. The thermo-gravimetric analysis data suggest that [P_4,4,4,8][BScB] is thermally more stable than [P_4,4,4,8][BMB] in both nitrogen atmosphere and air, while the impedance spectroscopy reveals that [P_4,4,4,8][BScB] has higher ionic conductivity than [P_4,4,4,8][BMB] over the whole studied temperature range. In contrast, the electrochemical studies confirm that [P_4,4,4,8][BMB] is more stable and exhibits a wider electrochemical stability window (ESW) on a glassy carbon electrode surface as compared to [P_4,4,4,8][BScB]. A continuous decrease in the ESWs of both ILs is observed as a function of operation temperature.

Synergistic Effect of Blended Components in Nonaqueous Electrolytes for Lithium Ion Batteries

Application of different electrolyte components as blends in nonaqueous electrolyte formulations represents a viable approach towards improving the overall performance and reliability of a lithium ion battery cell. By combining the advantages of different electrolyte constituents, cell chemistry can be optimized and tailored for a specific purpose. In this paper, the current progress on possibilities, advantages, as well as limitations of blended nonaqueous electrolyte formulations, including solvent, salt and additive blends is reviewed and discussed. Emphasis is set on the physicochemical, electrochemical, and safety aspects. In addition, the aim of this review is to provide perspective and possible strategy for further and future development of blended nonaqueous electrolytes with long life, high energy density, high power, and adequate safety at competitive manufacturing costs. The provided overview and perspective on blended nonaqueous electrolyte formulations should encourage researchers to proceed with further and deeper investigations in this promising field of advanced batteries.

Difference in chemical bonding between lithium and sodium salts: influence of covalency on their solubility

The current theoretical study explains the difference in solubility between lithium and sodium salts in ionic liquids due to increased covalency in lithium salts.

Application of functionalized ether in lithium ion batteries

Functionalized ethers have been explored to improve the electrochemical properties of lithium ion batteries (LIBs).

Ion dynamics in halogen-free phosphonium bis(salicylato)borate ionic liquid electrolytes for lithium-ion batteries

Halogen-free and hydrolytically stable phosphonium bis(salicylato)borate ionic liquid electrolytes for enhanced safety and performance of lithium-ion batteries.

New route to carbonate-functionalized imidazolium and pyrrolidinium-based ionic liquids

A new, versatile, and green route to access ionic liquids containing carbonate groups, including 1-[2-(propyloxycarbonyloxy)ethyl]-3-methyl imidazolium and N-methyl-N-[2-(propyl-oxcarbonyl) ethyl] pyrrolidinium associated with a bis(trifluoromethane)sulfonimide anion, [C1(C₂O(CO)OC₃)Im][NTf₂] (4) and [C₁(C₂O(CO)OC₃)Py][NTf₂] (5), has been developed and characterized.