Deep eutectic solvent for high-performance aluminum-based hydrated eutectic electrolyte

•A new hydrated eutectic electrolyte was discovered.•Physical and chemical mechanisms of hydrated eutectic electrolytes were confirmed for the first time by Raman, and Molecular Dynamics.•A novel aqueous aluminum-zinc hybrid ion batteries is demonstrated.•Aluminum-zinc hybrid ion batteries with hydrated eutectic electrolyte show a high capacity (177 mAh g−1) and long cycle life (>18,000 cycles). Aqueous multivalent ion batteries, featured by cost-effectiveness, high safety and eco-friendliness, are considered as a preferred alternative to non-aqueous multivalent ion batteries. However, parasitic reactions at the anode (hydrogen precipitation, passivation and dendrite growth) are key factors affecting cell lifespan. Herein, we present a novel aluminum-based hydrated eutectic electrolyte (AHEE) by coupling acetamide, caprolactam, Al(OTF)3 and pure water. Characterization experiments and molecular dynamics theoretical calculations demonstrate that strong interactions between acetamide/caprolactam and water molecules/aluminum ions triggered the construction of a hydrated eutectic network, which significantly suppressed the parasitic reactions at the anode. Moreover, benefiting from the pairing of zinc anode and AHEE, the full battery exhibits high specific discharge capacity (177 mAh g−1) and ultra-long cycle life (18,500 cycles), providing a new technological support for high-performance aqueous multivalent ion batteries.