Efficient Mineralization of Lithium Bis(pentafluoroethanesulfonyl)imide and Related Electrolyte Fluorochemicals Using Superheated Water

Lithium bis(pentafluoroethanesulfonyl)imide, Li[N(SO2C2F5)2], a typical fluorochemical aimed at better electrochemical performance of battery electrolytes, in superheated water was studied for its waste treatment. When Li[N(SO2C2F5)2] was reacted in pure superheated water at 300 °C, little F- ions were produced. In contrast, complete mineralization of the fluorine, sulfur, and nitrogen atoms in Li[N(SO2C2F5)2] was achieved when the reaction was performed in the presence of KMnO4. Specifically, when Li[N(SO2C2F5)2] was treated for 18 h with 158 mM of KMnO4, the F- and SO42- yields were 101 and 99%, respectively, and the sum of the NO3- and NO2- yields was 101%. In the gas phase, trace CO2 was detected and no CHF3, which has high global warming potential, was formed. Furthermore, the fluorine, sulfur, and nitrogen atoms in the analogues K[N(SO2C4F9)2] and K[N(SO2CF2)2CF2] also underwent complete mineralization using the same approach.

Molecular Design of Organic Ionic Plastic Crystals Consisting of Tetracyanoborate with Ultralow Phase Transition Temperature

Organic ionic plastic crystals (OIPCs) are a ductile soft material where the composing ions are in isotropic free rotation, while their positions are aligned in order. The rotational motion in its plastic phase promotes ion conduction by decreasing the activation energy. Here, we report novel OIPCs comprised of tetracyanoborate ([TCB]-) and various organic cations. In particular, the OIPC composed of [TCB]- and spiro-(1,1')-bipyrrolidinium ([spiropyr]+) cations can transform into its plastic phase at ultralow temperature (Tp = -55 °C) while maintaining a high melting point (Tm = 242 °C). Replacement of the cation with either tetraalkylammonium or phosphonium and comparing their phase behavior, the high Tm was attributed to the relatively small interionic distance between [spiropyr]+ and [TCB]-. At the same time, the low Tp was realized by the restricted vibrational mode of the spirostructure, allowing the initiation of isotropic rotational motion with less thermal energy input.

Insights into structure-property relationships in ionic liquids using cyclic perfluoroalkylsulfonylimides

Room temperature ionic liquids of cyclic sulfonimide anions ncPFSI (ring size: n = 4-6) with the cations [EMIm]+ (1-ethyl-3-methylimidazolium), [BMIm]+ (1-butyl-3-methylimidazolium) and [BMPL]+ (BMPL = 1-butyl-1-methylpyrrolidinium) have been synthesized. Their solid-state structures have been elucidated by single-crystal X-ray diffraction and their physicochemical properties (thermal behaviour and stability, dynamic viscosity and specific conductivity) have been assessed. In addition, the ion diffusion was studied by pulsed field gradient stimulated echo (PFGSTE) NMR spectroscopy. The decisive influence of the ring size of the cyclic sulfonimide anions on the physicochemical properties of the ILs has been revealed. All ILs show different properties compared to those of the non-cyclic TFSI anion. While these differences are especially distinct for ILs with the very rigid 6cPFSI anion, the 5-membered ring anion 5cPFSI was found to result in ILs with relatively similar properties. The difference between the properties of the TFSI anion and the cyclic sulfonimide anions has been rationalized by the rigidity (conformational lock) of the cyclic sulfonimide anions. The comparison of selected IL properties was augmented by MD simulations. These highlight the importance of π+-π+ interactions between pairs of [EMIm]+ cations in the liquid phase. The π+-π+ interactions are evident for the solid state from the molecular structures of the [EMIm]+-ILs with the three cyclic imide anions determined by single-crystal X-ray diffraction.

Organic Crystalline Solid Electrolytes with High Mg-Ion Conductivity Composed of Nonflammable Ionic Liquid Analogs and Mg(TFSA)2

The development of solid electrolytes with Mg-ion conductivity at room temperature is an important issue to achieve all-solid magnesium batteries. We focus on organic ionic crystals with Mg-ion conduction paths in addition to nonflammable and nonvolatile features as an innovative candidate of solid electrolytes with Mg-ion conductivity. Herein, we show the development of novel organic ionic crystals, [N(CH₃)_4-n(CH₂CH₃)_n][Mg{N(SO₂CF₃)₂}₃] (n = 0 or 2), using analogs of ionic liquids, [N(CH₃)₄][N(SO₂CF₃)₂] (N₁₁₁₁TFSA) and [N(CH₃)₂(CH₂CH₃)₂][N(SO₂CF₃)₂] (N₁₁₂₂TFSA), and magnesium salt, Mg{N(SO₂CF₃)₂}₂ (Mg(TFSA)₂). We also report the crystal structures of the obtained crystals and the high Mg-ion conductivity of 10^-4 S cm^-1 under mild conditions of 80 °C in the solid state. These results indicate that organic ionic crystals with ion conduction paths have significant potential as safe solid electrolytes and provide insights into developing innovative Mg-ion conductors.

Synthesis of an Adduct-Type Organic Ionic Crystal with Solid-State Ionic Conductivity from A Thiocyanate-Based Ionic Liquid and B(C6F5)3

We synthesized the novel adduct-type organic ionic crystal [C3mim][SCN·B(C6F5)3] (1) by the reaction of 1–methyl–3–propylimidazolium thiocyanate ([C3mim][SCN]), which is a room temperature ionic liquid, and B(C6F5)3, a bulky Lewis acid. The formation of a coordinative B–N bond between the SCN anion and the B(C6F5)3 in 1 was revealed by single-crystal X-ray diffractometry. We showed that 1 displays ionic conductivity in the crystalline state and that doping 1 with sodium thiocyanate and B(C6F5)3 results in a dramatic increase in ionic conductivity compared to that of 1.

Synthesis of pyrrolidinium-based plastic crystals exhibiting high ionic conductivity at ambient temperature

Pyrrolidinium-based plastic crystals were synthesised with various anions to investigate the effect of the anion structure on the properties.

Paramagnetic ionic plastic crystals containing the octamethylferrocenium cation: counteranion dependence of phase transitions and crystal structures

Octamethylferrocenium salts with various anions exhibit paramagnetic plastic phases at or above room temperature.