Electrochemical Reduction of Al2Cl7  −  Ions in Chloroaluminate Melts

Abstract

The electrodeposition of aluminum at glassy carbon, platinum, and tungsten electrodes in slightly acidic chloroaluminate melts has been studied using cyclic voltammetry, chronopotentiometry, chronoamperometry, and related techniques. The reduction of Al2Cl7− ions involves a nucleation process at glassy carbon electrodes and to a lesser extent, at the platinum and tungsten electrodes. At platinum electrodes alloy formation is also involved. The discrepancies in the values of diffusion coefficients obtained by three different methods may be attributed to the nucleation effect.

Electrocrystallization of Pb and Pb assisted Al on aluminum electrode from molten salt (AlCl3–NaCl–KCl)

“…During the charging of a rechargeable battery based on aluminum anodes, it has been found that [17,18] both aluminum dendrites and spongy deposits form under certain circumstances. As previously demonstrated [19], spongy deposits of aluminum could be prevented with the addition of MnCl 2 and codeposition of Al and Mn.…”

Electrodeposition of Al, Mn, and Al–Mn Alloy on aluminum electrodes from molten salt (AlCl3–NaCl–KCl)

“…During the charging of a rechargeable battery based on aluminum anodes, Hjuler et al [17,18] found that both aluminum dendrites and spongy deposits can be formed under certain circumstances. As previously demonstrated [19], spongy deposits of aluminum may be prevented by the addition of MnCl 2 and co-deposition of Al and Mn.…”

Electrodeposition of aluminum from molten AlCl3–NaCl–KCl mixture

“…Aluminum can be electrodeposited from three types of non-aqueous solution: (i) mixtures of AlX 3 (X = Br or Cl) with alkali metals or various organic halide salts or with aromatic hydrocarbon solvents [3], (ii) mixtures of aluminum hydrides such as LiAlH 4 and AlCl 3 dissolved in ethers [4], and (iii) mixtures of Al(C 2 H 5 ) 3 +NaF in toluene at 80°C [5]. Low temperature haloaluominate molten salts [6][7][8][9][10] fall into the first category. In this category, numerous reports describing the electrodeposition of aluminum from the Lewis acidic molten salt systems AlCl 3 -(Bupy)Cl orMe(Etim)Cl have appeared [11][12][13][14][15].…”

“…Most of these studies are concerned with the kinetics and mechanism of aluminum electrodeposition and/or stripping of aluminum off the inert electrodes such as glassy carbon, mercury, platinum, and tungsten. Fewer reports have appeared for alkali metal molten salt studies [6][7][8][9][10].…”

“…During the charging of a rechargeable battery based on aluminum anodes, Hejuler et al [6][7][8] found that aluminum dendrites and spongy deposits can be formed under certain circumstances. The spacing between the electrodes in batteries is usually very small; hence, the density of the deposits is of importance for the capacity and life of the batteries.…”