Aqueous Aluminum Cells: Mechanisms of Aluminum Anode Reactions and Role of the Artificial Solid Electrolyte Interphase

Abstract

Electrochemical cells with aluminum (Al) as the active material offer the benefits of high energy density, low cost, and high safety. Although several research groups have assembled rechargeable Al//M x O y (M = Mn, V, etc) cells with 2 m aqueous Al trifluoromethanesulfonate as an electrolyte and demonstrated the importance of the artificial solid electrolyte interphase (ASEI) on the Al anode for realizing high rechargeable capacity, the reactions of the Al anode in such cells remain underexplored. Herein, we investigate the effects of the ASEI on the charge/discharge cycling stability and activity of Al cells with the abovementioned aqueous electrolyte and reveal that this interphase provides chloride anions to induce the corrosion of Al rather than to support the transportation of Al3+ ions during charge/discharge. Regardless of the ASEI presence/absence, the main reactions at the Al anode during charge/discharge cycling are identified as oxidation and gas evolution, which suggests that the reduction of Al in the employed electrolyte is irreversible. The simple introduction of chloride anions (e.g., 0.15 m NaCl) into the electrolyte is shown to allow the realization of an Al//MnO2 cell with superior performance (discharge working voltage ≈ 1.5 V and specific capacity = 250 mA h/g). Thus, the present work unveils the mechanisms of reactions occurring at the Al anode of aqueous electrolyte Al cells to support their further development.

Relieving hydrogen evolution and anodic corrosion of aqueous aluminum batteries with hybrid electrolytes

“…This phenomenon is similar with the results in previous reports. 20,36 On the other hand, a reversible redox peak is observed in the CV curve, which is different with above-mentioned references that only presented oxidization peak in the CV curve. The reversible redox peak (Fig.…”

H2‐Inhibited Organic Anodes for Fast and Long‐Life Aqueous Aluminum Ion Batteries with a 3.5‐Month Calendar Life

“…As shown in Figure 2a, in AlCl 3 (1 M) solution, the discharge plateau around −1.21 V (vs Hg/HgSO 4 ) is according to electrochemical H 2 evolution (−0.565 V vs SHE) and the charge plateau is the reaction of Al dissolution which is accompanied by H 2 generation (H 2 evolution from corrosion of Al). [17,18] During the immersion of Al metal in an aqueous AlCl 3 electrolyte, Al corrosion and H 2 evolution constantly occurred. In contrast, the PI-0.6 anode exhibits a typical charge-discharge curve.…”

“…[1,11,14] In addition, the reactions of Al metal in aqueous Al(OTf) 3 solution [15,16] were also revealed to be the dissolution of Al and electrochemical H 2 evolution. [17,18] Alternatively, other anode materials either faced with small capacity or relatively positive potential (Table S1, Supporting Information), accompanied by poor rate capability and unreversible structural degradation. [19][20][21][22][23] The main obstacle of Al anode in aqueous electrode, relating to the formation of passive oxide and the voltage degradation, the hydrogen evolution reaction as well as the uneven erosion of aluminum, drives the development of other anodes which can eliminate the H 2 evolution in ordinary aluminum ion solutions.…”

Recent progress of flexible aqueous multivalent ion batteries

“…However, it is noteworthy that the mechanisms of aluminum anode reactions in aqueous electrolytes are still controversial. 44,45 The FAMIBs with metal foil anodes were reported to have high capacity retention under different bending angles. Paired with a flexible cathode and a hydrogel electrolyte, a Zn foil was incorporated as a part of a flexible quasi solid-state V 2 O 5 -Zn battery by Liang et al 46 The as-prepared battery was tested under different mechanical conditions, such as hammering, weight loading, drilling, sewing, cutting, and bending (Figure 1A), which could retain a high capacity retention above 80% compared to its original state, indicating the excellent potentially practical use of metal foil anodes in reliable and tailorable FAMIBs.…”

“…Thin Zn foils 23,24,33–41 and Al foils 42,43 were sometimes adopted as anodes of FAMIBs due to their moderate flexibility. However, it is noteworthy that the mechanisms of aluminum anode reactions in aqueous electrolytes are still controversial 44,45 . The FAMIBs with metal foil anodes were reported to have high capacity retention under different bending angles.…”