Investigation of the Anodic Behavior of Al in Room Temperature Ionic Liquid Electrolytes: BMI‐BF₄, PP14‐BF₄ and BMI‐BF₄·PC

Abstract

The anodic polarization behavior of Al, Ta and Nb foil was investigated in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid (BMI-BF 4 ). Compared with that of Ta and Nb foil, it showed that a better passive film was formed on Al foil surface after the anodic polarization in BMI-BF 4 , which could resist the potential up to 94.58 V vs. Ag ＋ /Ag. Besides, similar anodic behavior of Al foil was observed in N-methyl-N-butylpiperidinium tetrafluoroborate ionic liquid (PP14-BF 4 ), which indicated that the anodic polarization behavior of Al foil was independent of the cations of RTIL. In addition, the investigation of anodic polarization behavior of Al foil was carried out in the mixture electrolytes composed of BMI-BF 4 •PC. Differently, two breakdown potential processes of Al foil were presented compared to pure BMI-BF 4 . Further research showed that the passive film on Al foil was mainly composed of AlF 3 and Al 2 O 3 after the first breakdown potential process, while the fluoride film increased with continual anodic polarization, which improved the anodic stability of Al foil and resisted higher breakdown potential. The high breakdown potential properties of Al foil in BMI-BF 4 , PP14-BF 4 and the mixture of BMI-BF 4 •PC during the anodic polarization can be favored for R&D of the high performance electrochemical devices.

Anodic Aluminum Dissolution in Conducting Salt Containing Electrolytes for Lithium-Ion Batteries

“…In case of the salts LiBF 4 and LiPF 6 with readily available F − anions, the formation of AlF 3 as Al protection surface layer, which is investigated via XPS measurements (see section 3.4), is supposed to be the most important factor for a reduced corrosive response according to the literature. 4,18,22 Nevertheless, even in the LiPF 6 mixture L-4 small pitting points can be seen in spite of the fluorine source LiPF 6 . The Al pitting is supposed to arise from the high solubility power of the DMMA-TFSA/PC-mixture which is able to dissolve Al complexes effectively.…”