Electrolyte Additive Molecule Disassembly to Reveal the Roles of Individual Groups in Zn Electrode Stabilities in Aqueous Batteries

Zn metal anodes experience dendritic growth and hydrogen evolution reactions (HER) in aqueous batteries. Herein, we propose an interface regulation strategy with a trace (1.4 × 10-4 mol kg-1) all-in-one epicatechin (EC) electrolyte additive to solve the above issues and reveal the roles of individual functional groups. By the disassembly of EC into simple molecules combined with entire molecule investigations, we show that phenol and ether sites preferentially anchor on the Zn surface, while the hydroxyl group pointing outward enters Zn2+ solvation shells at the interface. It modifies the following desolvation path, which not only enables uniform deposition with the thermodynamically favored plate morphology but also inhibits HER. With these synergistic effects of trace EC additive, the lifespan of symmetric cells extends to 8.5 times that of the baseline ZnSO4 electrolyte. The capacity retention of Zn//MnO2 full batteries with N/P = 3 also increases from 59.1 to 85.6% after 500 cycles.