A Concentrated AlCl₃–Diglyme Electrolyte for Hard and Corrosion-Resistant Aluminum Electrodeposits

Abstract

A concentrated aluminum chloride (AlCl 3 )−diglyme (G2) electrolyte is used to prepare hard and corrosion-resistant aluminum (Al) electrodeposited films. The Al electrodeposits obtained from the electrolyte with an AlCl 3 /G2 molar ratio x = 0.4 showed a void-free microstructure composed of spherical particles, in stark contrast to flake-like morphologies with micro-voids for lower x. Neutral complexes rarely exist in the x = 0.4 electrolyte, resulting in a relatively high conductivity despite the high concentration and high viscosity. Nanoindentation measurements for the Al deposits with >99% purity revealed that the nanohardness was 2.86 GPa, three times higher than that for Al materials produced through electrodeposition from a well-known ionic liquid bath or through severe plastic deformation. Additionally, the void-free Al deposits had a <100> preferential crystal orientation, which accounted for better resistance to free corrosion and pitting corrosion. Discussions about the compact microstructure and <100> crystal orientation of deposits obtained only from the x = 0.4 concentrated electrolyte are also presented.

Towards Chloride-Free Organic Electrolytes for Rechargeable Aluminum Batteries

“…However, operational organic electrolytes typically comprise of concentrated electrolytes where the effect of free solvent is diminished leading to low volatility. 53 With regards to the flammability of these systems, this hurdle may be overcome by exploring additives that inhibit flammability via routes similar to those investigated for Li-ion 79 and Na-ion 80 electrolytes. We speculate that Al can be electrochemically deposited from organic solvents of similar properties using Al(OTF) 3 .…”

“…The development of an organic electrolyte, however, is a challenging task that requires a fundamental understanding of the solute/solvent ion-dipole and coulombic interactions. 32 Tremendous efforts have been dedicated to electrodeposit Al from a plethora of organic systems including AlCl 3 and lithium hydride(LiH) in diethyl ether, 33 AlCl 3 and lithium aluminum hydride (LiAlH 4 ) in tetrahydrofuran (THF) and benzene mixture, 34 AlCl 3 and LiAlH 4 in THF and toluene, 35 AlCl 3 and LiAlH 4 in THF, [36][37][38][39] aluminum tribromide(AlBr 3 ) in aromatic hydrocarbons, 40,41 AlBr 3 in N,N-dimethylaniline, 42 AlBr 3 and potassium bromide (KBr) in ethylbenzene, 43 AlCl 3 in sulfones, [44][45][46][47][48][49] AlCl 3 in glycol ethers (glymes), [50][51][52][53] AlCl 3 in ethylene carbonate, 54 and AlCl 3 in gamma-butyrolactone (GBL). 55 Unfortunately, these electrolytes are inherently corrosive and the prospects of practically implementing Al-ion batteries as electrochemical energy storage devices is contingent upon active chloride-free systems.…”

Deep eutectics and analogues as electrolytes in batteries

“…205,206 The coordination behavior of AlCl3:G2 was found to be similar to that of AlCl3:amide with the [AlCl 2 • (G2) 2 ] + cations as the active species, paired with the AlCl 4 − anions. 207,208 Finally, mixtures of AlCl3 and γ-butyrolactone (GBL) at different composition were also recently tested for Al deposition. 209 Like AlCl3:amide electrolytes, the molar ratio plays a key role: at relatively low AlCl3 concentration (AlCl3:GBL molar ratio in the range 1:10 to 1:2.…”

Towards Chloride-Free Organic Electrolytes for Rechargeable Aluminum Batteries

“…The development of an organic electrolyte, however, is a challenging task that requires a fundamental understanding of the solute/solvent ion-dipole and coulombic interactions. 32 Tremendous efforts have been dedicated to electrodeposit Al from a plethora of organic systems including AlCl 3 and lithium hydride(LiH) in diethyl ether, 33 AlCl 3 and lithium aluminum hydride (LiAlH 4 ) in tetrahydrofuran (THF) and benzene mixture, 34 AlCl 3 and LiAlH 4 in THF and toluene, 35 AlCl 3 and LiAlH 4 in THF, [36][37][38][39] aluminum tribromide(AlBr 3 ) in aromatic hydrocarbons, 40,41 AlBr 3 in N,N-dimethylaniline, 42 AlBr 3 and potassium bromide (KBr) in ethylbenzene, 43 AlCl 3 in sulfones, [44][45][46][47][48][49] AlCl 3 in glycol ethers (glymes), [50][51][52][53] AlCl 3 in ethylene carbonate, 54 and AlCl 3 in gamma-butyrolactone (GBL). 55 Unfortunately, these electrolytes are inherently corrosive and the prospects of practically implementing Al-ion batteries as electrochemical energy storage devices is contingent upon active chloride-free systems.…”