Phenomenological Transition of an Aluminum Surface in an Ionic Liquid and Its Beneficial Implementation in Batteries

Abstract

Aluminum (Al) electrochemical dissolution in organic nonaqueous media and room temperature ionic liquids (RTILs) is partially hampered by the presence of a native oxide. In this work, Al activation in EMIm(HF)2.3F RTIL is reported. It was confirmed that as a result of the interaction of Al with the RTIL, a new film is formed instead of the pristine oxide layer. Aluminum surface modifications result in a transformation from a passive state to the active behavior of the metal. This was confirmed via the employment of electrochemical methods and characterization by XPS, AFM, and TEM. It was shown that the pristine oxide surface film dissolves in EMIm(HF)2.3F, allowing an Al-O-F layer to be formed instead. This newly built up layer dramatically restricts Al corrosion while enabling high rates of Al anodic dissolution. These beneficial features allow the implementation of Al as an anode in advanced portable power sources, such as aluminum-air batteries.

Hybrid Ionic Liquid Propylene Carbonate-Based Electrolytes for Aluminum–Air Batteries

“…Recently, the incorporation of RTILs in Al-based batteries gained increasing interest. , The RTIL-based electrolytes usually utilized for Al-based cells are composed of an ionic liquid [M + X – ], where M + is an organic cation like pyrrolidinium or imidazolium and X – is a halogen anion such as Cl – , Br – and I – , and AlCl 3 . Most of the studies in this field focus on the use of RTILs composed of imidazolium cation bearing different alkyl side chains, such as 1-butyl-3-methyl­imidazolium (BMIm) or 1-ethyl-3-methyl­imidazolium (EMIm), and a chloride anion. ,− In recent works, promising results were also obtained when EMIm­(HF) 2.3 F ionic liquid was utilized as the electrolyte in Al–O 2 battery systems . Accordingly, the activation of the Al surface due to the presence of the H 2 F 3 – species enabled the dissolution of the anode, resulting in high anodic currents. − …”

“…Most of the studies in this field focus on the use of RTILs composed of imidazolium cation bearing different alkyl side chains, such as 1-butyl-3-methyl­imidazolium (BMIm) or 1-ethyl-3-methyl­imidazolium (EMIm), and a chloride anion. ,− In recent works, promising results were also obtained when EMIm­(HF) 2.3 F ionic liquid was utilized as the electrolyte in Al–O 2 battery systems . Accordingly, the activation of the Al surface due to the presence of the H 2 F 3 – species enabled the dissolution of the anode, resulting in high anodic currents. − …”

Suppression of byproduct accumulation in rechargeable aluminum–air batteries using non-oxide ceramic materials as air cathode materials

“…Shvartsev et al exhibited that this newly built up layer restricts Al corrosion while enabling high rates of Al anodic dissolution. 20,21 Nevertheless, byproducts are still observed with the use of ionic liquid based electrolytes on the air cathode, which inhibit further electrochemical reactions. [13][14][15][16][17][18][19] On the other hand, non-oxide ceramic materials, e.g., nitride, carbide, oxynitride, and carbonitride, have been applied for use as cathodic materials for PEFCs (polymer electrolyte fuel cells) as well as Li-air and Zn-air batteries, due to their oxygen reduction reaction catalytic effect.…”

“…Peak 1 was located at a binding energy of 74.3-74.4 eV which was attributed to Al 2 O 3 and Al x (OH) y species. 21 This fact indicates that even byproducts such as Al 2 O 3 and Al x (OH) y species were not detected by XRD measurements, and they exist on the TiC air cathode aer the electrochemical reaction. Peak 2 indicates that carbon exists as carbon atoms.…”

Paving the Path toward Reliable Cathode Materials for Aluminum‐Ion Batteries

“…Surprisingly, the reconstructed aluminum oxide no longer blocks the Al‐ion migration as pristine oxide film does, and further explanation will be present in our future works. Herein the solid electrolyte interface (SEI) emerges as an essential factor for anode reactions, of which the component, thickness and structure are the basic information . So far, the further modification of aluminum electrode is still lacking in RABs, merely reported in the dual‐ion battery system .…”