Laminated tin-aluminum anodes to build practical aqueous aluminum batteries

Aqueous aluminum metal batteries (AAMBs) have emerged as promising energy storage devices, leveraging the abundance of Al and their high energy density. However, AAMBs face challenges such as unsuccessful Al deposition during charging or poor anode reversibility, passivation layer formation, and the competing hydrogen evolution reaction (HER). A promising approach to alleviate these issues is introducing foreign metals to interact with Al. In this study, Sn is selected for its appropriate standard reduction potential (-0.13 V), work function (4.42 eV), and compatibility with Al, facilitating Al underpotential deposition and enhancing anode reversibility. We first determine the feasibility of Al deposition on Sn substrate after three-electrode testing, which, however, results in low capacity. To increase the contact interface between Sn and Al and thereby improve capacity, we employ a scalable folding and rolling method to prepare Sn-Al laminate electrodes (Sn@Al). The Sn@Al heterostructure can effectively facilitate Al stripping/plating, reducing internal resistance. The Sn@Al electrodes demonstrate stable cycling for over 900 h in symmetric cells and superior performance in full cells when coupled with AlxMnO2 or KNHCF cathodes. To further enhance Sn@Al anodes, a polymer coating is applied to suppress HER. After 700 cycles, the p-Sn@Al||KNHCF cell shows 82 % capacity retention compared to the 10th cycle. This study presents a strategy for designing effective and low-cost anodes for AAMBs and may provide insights into developing metal anodes for other aqueous batteries.