Development of a novel 1-trifluoroacetyl piperidine-based electrolyte for aluminum ion battery

Highlights: • Ionic liquid analogues based on 1-trifluoroacetyl piperidine was investigated. • The conductivities with different concentrations of TFAP and AlCl3 were obtained. • The electrode.|electrolyte interface exchange current density was measured • The formation of aluminum-containing cations and anions was described. -- Abstract: The first example of chloroaluminate ionic liquids (ILs) analogues based on amides of fluorinated carboxylic acids, namely 1-trifluoroacetyl piperidine (TFAP), has been described. The possibility of applying of this electrolytes has been experimentally evaluated in the series TFAP/AlCl₃; TFAP/LiCl/AlCl₃; TFAP/[EMIm]Cl/AlCl₃; [EMIm]Cl/AlCl₃ for use in an aluminum ion battery. The specific conductivities measured by the method of current interruption and impedance spectroscopy at 30 °C were 0.49, 0.28, 1.37, 20.23 mS cm⁻¹, respectively. The exchange current densities at the two-phase interface aluminium/electrolyte investigated using the impedance spectroscopy method were 0.18, 0.03, 0.42, 1100 μA cm⁻², respectively. TFAP-based electrolytes did not crystallize when cooled down to −60 °C, according to DSC data. The presence of the molecular [AlCl₃(TFAP)], and the ionic AlCl₄⁻, [AlCl₂(TFAP)₄]⁺, and [Al(TFAP)₆]³⁺species is proposed based on the ²⁷Al NMR spectra of the studied new ILs analogues.