Designing a fluorinated interphase for rechargeable aqueous Al batteries

Abstract

Aqueous aluminum batteries (AABs) have attracted increasing attention as a promising alternative for next-generation large-scale energy storage systems owing to their low-cost, intrinsic safety and high theoretical specific capacity. However, the practical application of AABs is still hindered by side reactions at the anode side, including the hydrogen evolution reaction (HER) and metallic Al corrosion/passivation. Here, we found that an Al anode with a fluorinated interface (FAl) through water and trifluoroacetic acid treatment can accelerate Al anode kinetics with a low overpotential. Meanwhile, the stable and hydrophobic interphase can protect the Al anodes from direct contact with corrosive aqueous electrolytes, achieving a diminished HER and long-term cycling stability. The symmetrical batteries with FAl can cycle reversibly for over 1000 h, nearly 10 times higher than untreated Al. Furthermore, the aqueous Al batteries with PTO (pyrene-4,5,9,10-tetraone) as the cathode achieved a high initial capacity of 350 mAh g⁻¹ that decreased to 237.8 mAh g⁻¹ after 60 cycles. This work provides new insight into design principles of AABs with high safety and long-term stability.