Synthesis and Characterization of Bromoaluminate Ionic Liquids

Abstract

Twelve bromoaluminate based ionic liquids (ILs) were synthesized and characterized by IR, Raman, and NMR spectroscopy, as well as single crystal X-ray diffraction in part. Their principal physicochemical properties including melting points, conductivities, viscosities, and densities were determined and compared with related ILs. The influence of the cation and anion on the physicochemical properties are discussed. The [AlBr ] based salts are-with one exception-solid at room temperature, while the compounds based on the anion [Al Br ] are liquid at room temperature. The liquid salts show low viscosities (49-139 mPa s), medium to high conductivities (0.76-3.53 mS cm ) and high densities (1.82-2.04 g cm ) at 28 °C. Furthermore, we showed aluminum electrodeposition from Lewis acidic ILs based on AlBr and 1-hexyl-3-methylimidazolium bromide and investigated the stability range of various formulations.

An Investigation of the Symmetric and Asymmetric Cleavage Products in the System Aluminum Trihalide/1‐Butylimidazole

“…The room-temperature potentiostatic electrodeposition of Al was carriedo ut at ap otentialo fÀ400 mV for 18 ho naCu substrate. [46] The AlCl 3 /BuIm system AlCl 3 -basedm ixturesw ere synthesized to investigate the influence of the aluminumh alide on the symmetric and asymmetric cleavage products and hence the differences between the two systems. The energydispersive X-ray (EDX) spectrum shows peaks of the electrodepositeda luminuma nd small amounts of carbon,o xygen, and copper( see Figure 14 ca nd Figure S37 of the Supporting Information).I nc onclusion, microcrystallinea luminum can be depositede lectrochemically from an eat Lewis acidic mixture of the system AlBr 3 /BuIm {x(AlBr 3 ) = 0.60}.…”

First Investigations Towards the Feasibility of an Al/Br2 Battery Based on Ionic Liquids

“…The melting point of the [AlBr 4 ] − salts are usually the highest for all four anions. Thus, we synthesized and characterized a series of bromoaluminate ILs with the cations ethyl‐dimethyl‐propyl‐ammonium ([N 1123 ] + ), butyl‐dimethyl‐propyl‐ammonium ([N 1134 ] + ), butyl‐diethyl‐methyl‐ammonium ([N 1224 ] + ), triethyl‐pentyl‐ammonium ([N 2225 ] + ), triethyl‐pentyl‐phosphonium ([P 2225 ] + ) and 1‐hexyl‐3‐methyl‐imidazolium ([C 6 MIm] + ) in previous work . Unfortunately, all cations – with the exception of [C 6 MIm] + – led to solid [AlBr 4 ] − salts with melting points between 35 and 117 °C.…”

“…Unfortunately, all cations – with the exception of [C 6 MIm] + – led to solid [AlBr 4 ] − salts with melting points between 35 and 117 °C. However, we could potentiostatically electrodeposit microcrystalline Al on a Cu substrate from the IL [C 6 MIm][Al 2 Br 7 ] . In addition, chronoamperometric experiments of [C 6 MIm][Br 9 ] and [C 6 MIm][Br 3 ] showed that the ILs conduct continuous current at positive potentials and cyclic voltammetry revealed an immediate increase of current without a defined oxidation peak at positive potentials.…”

“…Thus, both ILs seem to have a semiconducting behavior and accept charge immediately . A drawback of the therefore selected [C 6 MIm] + is its chemical stability, as it reacts with a combination of dibromine and [Al 2 Br 7 ] − to mono‐ and dibrominated imidazolium cations and HBr . Despite that problem, we used [C 6 MIm] + as standard cation for first proof of principle battery measurements as the cation degradation reactions are slow enough for orienting measurements and all four electrolytes with this cation are liquid at room temperature.…”

“…However, such cations could suffer from high molar masses, high viscosities and low conductivities. Additions of molecular solvents as liquefier were unfortunately unsuccessful in earlier work, due to the strict requirements of these chemically very reactive anolytes and catholytes.…”