Constructing an artificial SEI layer rich-AlF3 based on molecular scale in aqueous aluminum batteries to avoid anode passivation and hydrogen evolution reactions

[Display omitted] •The artificial SEI layer rich-AlF3 has been successfully synthesized on the surface of aluminum.•This SEI layer can effectively isolate the hydrogen evolution reaction at the anode.•The SEI make Al deposition smooth and reduce the formation of Al2O3 passivation layer. Serious hydrogen evolution reaction and anodic corrosion in aqueous electrolyte are common problems in aqueous aluminum batteries. In this study, a strategy of electrolyte adjustment based on molecular level is proposed to mitigate side reactions and enhance reaction kinetics. Since some acetonitrile molecules can enter the solvated shell of Al3+ to reshape the solvated structure, some anions and water molecules are replaced from the solvated structure. This promotes the decomposition of anions on the anode surface to form an artificial solid electrolyte interface (SEI) layer rich-AlF3. The SEI layer can effectively isolate water molecules to gain electrons preferentially at the anode to reduce hydrogen evolution reactions. In addition, the deposition behavior of aluminum can be adjusted, and Al3+ can smoothly achieve uniform deposition/stripping on the anode through the protective layer, avoiding the formation of low conductivity Al2O3 passivation layer. On this basis, full batteries composed of different cathode materials also have excellent cycling performance, proving that this electrolyte has universal applicability. The effect of acetonitrile addition on the battery is discussed in detail, which provides insights for the study of efficient energy storage devices.