Introducing Artificial Solid Electrolyte Interphase onto the Anode of Aqueous Lithium Energy Storage Systems.

Aqueous lithium energy storage systems (ALESSs) offer several advantages over the commercially available nonaqueous systems, and the most noteworthy is that ALESSs have higher ionic conductivity, can be used safely, and are environmental-friendly in nature. The ALESS, however, exhibits faster capacity fading than their nonaqueous counterparts after repeated cycles of charge and discharge, thus limiting their wide-range applications. Excessive corrosion of metallic anodes in the aqueous electrolyte and accelerated growth of dendrites during the charge-discharge process are found to be the main reasons that severely impact the life span of ALESSs. Here, we introduce ultrathin graphene films as an artificial solid electrolyte interface (G-SEI) on the surface of a zinc anode to improve the cycling stability of an aqueous lithium battery system. The G-SEI is fabricated at different thicknesses and areas ranging from ∼1 to 100 nm and ∼1 to 10 cm2, respectively, via a Langmuir-Blodgett trough method and deposited onto the surface of the zinc anode. Electrochemical characterizations show a significant reduction in corrosion current density (0.033 mA cm-2 vs 1.046 mA cm-2 for the control), suppression of dendritic growth (∼50%), and reduction in charge-transfer resistance (222 Ω vs 563 Ω for the control) when the G-SEI is utilized. The aqueous battery system with the G-SEI (100 nm thickness) on the anode exhibits ∼17% improvement in cycling stability (82% capacity retention after 300 cycles) compared to the control system. Comprehensive microscopy and spectroscopy characterizations reveal that the G-SEI not only controls the ion transport between the electrolyte and the anode surface (lower corrosion) but also promotes a uniform deposition (less dendritic growth) of zinc on the anode.