Solubilization of SEI lithium salts in alkylcarbonate solvents

The SEI (Solid Electrolyte Interphase) at the surface of electrodes in lithium-ion batteries is composed of various lithium compounds, organic or mineral, which have a direct impact on cycling performance. The main lithium species constituting the SEI and selected in this study are lithium fluoride LiF, lithium carbonate Li₂CO₃, lithium hydroxide LiOH, lithium oxide Li₂O, lithium methoxide LiOCH₃ and lithium ethoxide LiOC₂H₅. Their solubilities were determined in ethylene, propylene, dimethyl, diethyl and vinylene carbonates (EC, PC, DMC, DEC and VC) and in one of their mixtures commonly used in lithium-ion batteries (EC/PC/3DMC) by mean of atomic absorption spectroscopy (AAS). These solutions were also investigated by EIS (Electrochemical Impedance Spectroscopy) and conductimetry measurements. Results show that while solubilization properties differ between LiF and other lithium compounds considered, their association pattern in solution is identical and solutions are mainly constituted of quadrupolar aggregates.     

Effect of chain length on nuclear quadrupole interaction of nitrogen-14 in aminated n-alkanes

The ¹⁴N nuclear quadrupole resonance (NQR) spectra of several aminated n-alkanes of the type CH₃(CH₂)_xNH₂(CH₂)_xNH₂ at 77 K are reported and analysed in the framework of a semi-empirical theory. The NQR data presented oscillations for x<6 and reached limiting values for x≥6. The results obtained are discussed in terms of inductive and conjugative effects, as well as the possible contributions of the hydrogen bond network presented in the solid state.     

Alkylammonium-based protic ionic liquids. Part I: Preparation and physicochemical characterization

Novel alkylammonium-cation-based protic acid ionic liquids (PILs) were prepared through a simple and atom-economic neutralization reaction between an amine, such as diisopropylmethylamine, and diisopropylethylamine, and a Br?nsted acid, HX, where X is HCOO-, CH 3COO-, or HF2-. The density, viscosity, acidic scale, electrochemical window, temperature dependency of ionic conductivity, and thermal properties of these PILs were measured and investigated in detail. Results show that protonated alkylammonium such as N-ethyldiisopropyl formate and N-methyldiisopropyl formate are liquid at room temperature and possess very low viscosities, that is, 18 and 24 cP, respectively, at 25 degrees C. An investigation of their thermal properties shows that they present a wide liquid range up to -100 degrees C and a heat thermal stability up to 350 degrees C. Alkylammonium-based PILs have a relatively low cost and low toxicity and show a high ionic conductivity (up a 8 mS cm(-1)) at room temperature. They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media and catalysts as replacements of conventional inorganic acids.     

Synthesis and characterization of new pyrrolidinium based protic ionic liquids. Good and superionic liquids

New pyrrolidinium-cation-based protic acid ionic liquids (PILs) were prepared through a simple and atom-economic neutralization reactions between pyrrolidine and Br?nsted acids, HX, where X is NO 3 (-), HSO 4 (-), HCOO (-), CH 3COO (-) or CF 3COO (-) and CH 3(CH 2) 6COO (-). The thermal properties, densities, electrochemical windows, temperature dependency of dynamic viscosity and ionic conductivity were measured for these PILs. All protonated pyrrolidinium salts studied here were liquid at room temperature and possess a high ionic conductivity (up to 56 mS cm (-1)) at room temperature. Pyrrolidinium based PILs have a relatively low cost, a low toxicity and exhibit a large electrochemical window as compared to other protic ionic liquids (up 3 V). Obtained results allow us to classify them according to a classical Walden diagram and to determinate their "Fragility". Pyrrolidinium based PILs are good or superionic liquids and shows extremely fragility. They have wide applicable perspectives for fuel cell devices, thermal transfer fluids, and acid-catalyzed reaction media as replacements of conventional inorganic acids.