An electrolyte cation additive strategy provides a versatile route for developing high‐energy and long‐life aqueous zinc‐ion hybrid capacitors. However, the mechanisms of energy storage and Zn anode protection are still unclear in Zn‐based systems with dual‐ion electrolytes. Here, a dual charge storage mechanism for zinc‐ion hybrid capacitors with both cations and anions adsorption/desorption and the reversible formation of Zn4SO4(OH)6·xH2O enabled by the Mg2+ additive in the common aqueous ZnSO4 electrolyte are proposed. Theoretical calculations verify that the self‐healing electrostatic shield effect and the solvation‐sheath structure regulation rendered by the Mg2+ additive account for the observed uniform Zn deposition and dendrite suppression. As a result, an additional energy storage capacity of ≈50% compared to that in a pure 2 m ZnSO4 electrolyte and an extended cycle life with capacity retention of 98.7% after 10 000 cycles are achieved. This work highlights the effectiveness of electrolyte design for dual‐ion carrier storage mechanism in aqueous devices toward high energy density and long cycle life.

The rampant dendrites and hydrogen evolution reaction (HER) resulting from the turbulent interfacial evolution at the anode/electrolyte are the main culprits of short lifespan and low Coulombic efficiency of Zn metal batteries. In this work, a versatile protective coating with excellent zincophilic and amphoteric features is constructed on the surface of Zn metal (ZP@Zn) as dendrite-free anodes. This kind of protective coating possesses the advantages of reversible proton storage and rapid desolvation kinetics, thereby mitigating the HER and facilitating homogeneous nucleation concomitantly. Furthermore, the space charge polarization effect promotes charge redistribution to achieve uniform Zn deposition. Accordingly, the ZP@Zn symmetric cell manifests excellent reversibility at an ultrahigh cumulative plating capacity of 4700 mAh cm À 2 and stable cycling at 80 % depth of discharge (DOD). The ZP@Zn//V 6 O 13 pouch cell also reveals superior cycling stability with a high capacity of 326.6 mAh g À 1 .

Reversibility and stability are considered as the key indicators for Zn metal anode in aqueous Zn-ion batteries, yet they are severely hindered by uncontrolled Zn stripping/plating and side reactions. Herein,...

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