Interface Preconstruction Enables Robust Passivation of the Ah-Level Aqueous Li-ion Batteries

The solid electrolyte interphase (SEI) offers effective passivation on the anode for aqueous lithium-ion batteries (ALIBs). Conventional passivation in ALIBs mainly relies on the LiF-contained SEI originating from anion reduction in the electrolyte. However, such SEI formation is a competitive reaction negatively impacted by the parasitic hydrogen evolution reaction (HER), resulting in high Li⁺ irreversible consumption and imperfect bare flaws. To address this issue, we propose preconstructing an artificial interphase by introducing a multifunctional interface additive CsF to build superior passivation on the anode in ALIBs. CsF first undergoes a displacement reaction with LiTFSI from the fresh electrolyte to form the LiF in situ on the interface of the anode before the cycles, avoiding the extra Li⁺ irreversible consumption. Meanwhile, we uncover that the dissolving Cs⁺ in the electrolyte can destroy the hydrogen bond network of the water to lower water activity on the anode interface and strongly interact with TFSI^- to form the cation-anion complex, facilitating the anion proximity to the anode interface. The anion reduction based on the artificial interphase can finally help achieve the robust SEI in ALIBs. Such passivation stabilizes the aqueous electrolyte, significantly suppressing the side reaction of the HER that allows ALIBs to obtain a superior long life above 2000 cycles. The ampere-hour-level (Ah-level) pouch cell achieves an energy density of 57 Wh/kg and 176 Wh/L with high energy efficiency (∼94%).