Effects of Additives Containing Cyanopyridine on Electrodeposition of Bright Al Coatings from AlCl3-EMIC Ionic Liquids

Abstract

The Al coatings were electrodeposited on the Cu substrate from AlCl3-EMIC ionic liquid (AlCl3:EMIC = 2:1 molar ratio) containing three cyanopyridine additives with different positions of the substituent group on the pyridine ring, which were 2-cyanopyridine, 3-cyanopyridine, and 4-cyanopyridine. The effects of cyanopyridine additives on the deposition potential, morphology, brightness, and corrosion properties of Al coatings were investigated. It was considered that the deposition potential of Al shifted to more negative overpotentials, the quality of Al coatings was promoted, and the corrosion property was improved by the cyanopyridine additives to a varying degree. Especially in the presence of 4-cyanopyridine, the flattest mirror bright Al coating was obtained, which had the smallest homogeneous nanocrystal grain size and strongest Al (200) crystallographic orientation. The average roughness Ra value was as low as 31 nm compared to that in the absence of cyanopyridine additives, which was 417 nm. Furthermore, the corrosion current density of the bright Al coating was three orders of magnitude lower than the rough Al coating, which resulted from the dense nanocrystal structure.

Solvation Structure Regulation for Highly Reversible Aqueous Al Metal Batteries

“…In fact, the reduction of solvated water cannot be restrained by sufficient metal salt additives; therefore, ideal alternative additives are necessary to replace the H 2 O in the Al 3+ -solvation sheath without sacrificing Al 3+ -ions transfer kinetics . Brightener is a kind of organic material that was widely utilized to improve the quality of Al plating in electroplating industry, while the underlying mechanism is still mysterious. , Particularly, pyridine derivatives have excellent coating modification effects because of their stronger polarization and leveling effect in a water bath. Therefore, introducing the typical pyridine derivative into AAMB electrolyte should be an effective approach for the optimization of Al 3+ -solvation sheath in electrolyte, which is radically different from the other reports targeting the modification of the electrode interface in AAMBs.…”