Tuning the Aluminum–Water Interface in Aqueous Aluminum Metal Batteries

Abstract

Metallic aluminum-based aqueous batteries have emerged as promising energy storage devices due to the abundance of metallic aluminum and its high theoretical capacity (gravimetric: 2980 mAh g^–1; volumetric: 8056 mAh cm^–3). Despite this potential, challenges in the utilization of these batteries arise from the narrow potential window of water and the passivating effects of the high-electrical band gap aluminum oxide (Al₂O₃) film, hindering the realization of their full potential. A prospective solution involves the development of an electrolyte for aqueous aluminum systems that not only widens the stability window but also effectively removes the passivating oxide layer. In this context, this study investigates the impact of a highly concentrated electrolyte based on Al(ClO₄)₃ on the performance of an aluminum metal anode. The elevated concentration of the ClO₄^– anion (maintained via periodic electrolyte replenishment) is found to be highly effective in removing the passivating Al₂O₃ oxide layer, thereby enabling the facile plating and stripping of aluminum ions from the anode. These findings present a strategic step forward in designing improved electrolytes for aluminum-ion batteries, opening up possibilities for the utilization of aluminum metal anodes in aqueous battery systems.