Weakly coordinating anions (WCAs) are used throughout chemistry to minimise cation-anion interactions in the solid and solution states. The ability to suppress ion-pairing has important bearings – or impacts on the properties of materials, on single-site catalysis and on ionic conductivity. Fluorinated alkoxy aluminates (containing [Al(ORF)4]− anions) are an attractive class of WCA owing to their high thermodynamic stability, stemming from strong aluminium-oxygen bonds, and the ability to tailor their steric and electronic properties by changing the organic substituents (R). This work explores the structural and electrochemical properties of sodium tetrakis(hexafluoroisopropyloxy)aluminate, Na[Al(hfip)4] ⋅ xDME (hfip=hexafluoroisopropyloxy, OiPrF, DME=1,2-dimethoxyethane, x=3 or 1). When solvated with one DME molecule, Na[Al(hfip)4] ⋅ DME is a room-temperature solvated ionic liquid, with an activation energy of conduction of 0.4 eV. Both Na[Al(hfip)4] ⋅ 3DME and Na[Al(hfip)4] ⋅ DME have been studied as electrolyte salts for sodium-ion batteries, where sodium-ion cycling proceeds but with low capacity retention.
Sodium Tetrakis(hexafluoroisopropyloxy) aluminates: Synthesis and Electrochemical Characterisation of a Room‐Temperature Solvated Ionic Liquid