Surface Properties‐Performance Relationship of Aluminum Foil as Negative Electrode for Rechargeable Aluminum Batteries

Abstract Rechargeable aluminum batteries with aluminum metal as a negative electrode have attracted wide attention due to the aluminum abundance, its high theoretical capacity and stability under ambient conditions. Understanding and ultimately screening the impact of the initial surface properties of aluminum negative electrodes on the performance and lifetime of the battery cell are of great significance. The purity, surface finishing and degree of hardness of aluminum metal may strongly impact the device's performance, but these properties have not been systematically studied so far. Here, we present an investigation of the underestimated but crucial role of the aluminum foil surface properties on its electrochemical behavior in aluminum battery half‐cells. The results show that commercial aluminum foils with the same purity and degree of hardness but with different thicknesses (from 0.025 to 0.1 mm) exhibit different microstructure and surface roughness, which in turn have an impact on the cyclability. Atomic force microscopy studies show that the aluminum foil is corroded after repeated electrochemical cycling, thus leading to cell failure. The sample with 0.075 mm thickness exhibits the best cycling stability.