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.
Al-based batteries are promising next-generation rechargeable batteries owing to the abundance of raw materials and their high potential energy density. The AlÀ S system has attracted considerable attention because of its high energy density and low cost. However, its low discharge voltage plateau (0.6-1.2 V) hampers its practical application. Herein, eight ionic liquids or deep eutectic solvents were studied as electrolyte candidates for an AlÀ S cell. This was the first study to demonstrate that an AlÀ S cell based on an AlCl 3 /acetamide electrolyte (1.3 molar ratio) showed high discharge voltage plateaus (1.65-1.95 V) and a charging cut-off voltage of 2.5 V in AlÀ S cells. An AlÀ S cell of 0.33 mAh capacity with the AlCl 3 /acetamide electrolyte successfully lit up a red LED (forward voltage 1.6-2.0 V) for around 2 h. This work may help in promoting the development of highperformance and low-cost AlÀ S cells.
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