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

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 /Alx Zny MnO2 ·nH2 O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Alx MnO2 ·nH2 O. Topology transformation alters the structure of the cathode material so that Zn2+ can be intercalated into the Alx MnO2 ·nH2 O 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).