Relieving hydrogen evolution and anodic corrosion of aqueous aluminum batteries with hybrid electrolytes

The lower electro-stripping/plating potential of Al³⁺/Al (-1.68 V) than that of H⁺/H₂ seriously impedes the performance of rechargeable aqueous aluminum-ion batteries (AAIBs). Besides, the Al plate is easily corroded in aqueous electrolytes due to the typical acidic nature of aluminum salt solutions. Exploring appropriate aqueous electrolytes is indispensable to achieve a high-performance AAIB. In this work, we initiate an AlCl₃/lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) electrolyte and find that the addition of an appropriate concentration of LiTFSI can efficiently hinder the hydrogen evolution and corrosion of Al anodes. The full AAIB composed of a vanadium potassium cathode and Al anode exhibits reversible charge/discharge behaviors in 0.5 M AlCl₃@12 M LiTFSI electrolyte. Electrochemical and structural analyses reveal that the vanadium potassium cathode experiences a reversible Al³⁺, H⁺ and Li⁺ co-intercalation/de-intercalation process during cycling. The full AAIB manifests excellent performance in terms of large capacity (223 mA h g^-1 at 1000 mA g^-1), superior rate capability (more than 50% retention from 1000 to 6000 mA g^-1) and outstanding cycling stability (maintains 64.6% after 300 cycles). Moreover, the soft-packed AAIB also manifests good cycling stability and desirable flexibility. The strategy reported in our manuscript may promote the development of rechargeable aluminum-ion batteries based on aqueous electrolytes.