Ion conductivity of the plastic phase of the organic salt [(C4H9)4N]BF4

Abstract

Based on the thermal and X ray diffraction analysis, NMR spectroscopy, and ion conductivity data it was shown that the organic salt [n Bu 4 N]BF 4 has an orientationally disordered phase with a primitive cubic unit cell (space group unit cell parameter a c = 1.4886(2) nm) in the temperature range 62-161°C. The mobility of molecular fragments and anions increased during the phase transition, and the ion conductivity was relatively high, reaching ~10 -6 S/cm at 150°C.

Hybrid Nanocomposite Solid Electrolytes (n-C4H9)4NBF4–MgO

“…Among quaternary ammonium compounds, tetra-n-butylammonium (Bu 4 N + ) salts are of special interest as they are typical ionic liquids in the molten state and have high-temperature polymorphs which may be attributed to plastic phases. The relatively high ionic conductivity was observed in high-temperature phases of Bu 4 N + salts (n-C 4 H 9 ) 4 NI [ 19 ], (n-C 4 H 9 ) 4 NBF 4 [ 26 ], (n-C 4 H 9 ) 4 NBr [ 27 ].…”

Molecular dynamic simulation of the [N(C4H9)4]BF4 / (110) α-Al2O3 interface

“…The local motions may facilitate ionic transport. A relatively high ionic conductivity of 10 -6 -10 -3 S/cm has been reported for plastic phases of [3][4][5][6][7][8][9][10][11][12][13][14], but the mechanism of the ionic transport in such phases remains unknown.…”

“…are typical ionic liquids in a molten state [15]. On cooling, tetrabutylammonium salts (C4H9)4NX (X = Cl -, Br -, I -, BF4 -, ClO4 -) crystallize with the formation of reorientationally disordered high-temperature plastic phases, which transform into ordered low-temperature modifications under further cooling [12,13,14]. The melting entropy of these salts is lower or comparable that of the solid-state transition indicating a high disordering in the plastic phases [16,17].…”

“…Tetrabutylammonium tetrafluoroborates [R4N]BF4 are promising materials for low-temperature solid-state electrochemical devices due to the high electrochemical stability of both quaternary ammonium cations (R4N) + and BF4-anions. In particular, tetrabutylammonium tetrafluoroborate [(C4H9)4N]BF4 (hereafter, [N4]BF4) exhibit a conductivity of around 10 -6 S/cm in the high-temperature plastic phase at 150 °C [13]. According to 19 F NMR data, the dominant charge carriers in this phase are BF4anions [13].…”

“…In particular, tetrabutylammonium tetrafluoroborate [(C4H9)4N]BF4 (hereafter, [N4]BF4) exhibit a conductivity of around 10 -6 S/cm in the high-temperature plastic phase at 150 °C [13]. According to 19 F NMR data, the dominant charge carriers in this phase are BF4anions [13]. The salt [N4]BF4 has several polymorphic modifications, differing in the degree of conformational disorder in hydrocarbon chains and reorientation disordering of anions [17].…”