Bimetallic Rechargeable Al/Zn Hybrid Aqueous Batteries Based on Al–Zn Alloys with Composite Electrolytes

Abstract Aluminum is abundant and exhibits a high theoretical capacity and volumetric energy density. Additionally, the high safety of aqueous aluminum‐ion batteries makes them strong candidates for large‐scale energystorage systems. However, the frequent collapse of the cathode material and passive oxide film results in the difficult development of aqueous aluminum‐ion batteries. This work provides a novel battery system, namely, Al–Zn/Al(OTF)₃+HOTF+Zn(OTF)₂/Al_xZn_yMnO₂·nH₂O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Al_xMnO₂·nH₂O. Topology transformation alters the structure of the cathode material so that Zn²⁺ can be intercalated into the Al_xMnO₂·nH₂O spinel structure to provide support for the material structure. Regarding the anode, Zn²⁺ in the electrolyte is deposited onto Al of the anode to produce a regional Al–Zn alloy. Zn²⁺ is reduced to Zn metal during discharging, which adds a platform for secondary discharge beneficial for battery capacity enhancement. This system can provide a 1.6 V discharge platform, while the first cycle discharge can reach 554 mAh g^‐1, thereby maintaining a high capacity of 313 mAh g^‐1 after 100 cycles. This study provides a new idea for the further development of aqueous aluminum‐ion batteries (AAIBs).