Regulating the inner Helmholtz plane structure at the electrolyte-electrode interface for highly reversible aqueous Zn batteries

The development of aqueous Zn batteries is limited by parasitic water reactions, corrosion, and dendrite growth. To address these challenges, an inner Helmholtz plane (IHP) regulation method is proposed by employing low-cost, non-toxic maltitol as the electrolyte additive. The preferential adsorption behavior of maltitol can expel the water from the inner Helmholtz plane, and thus hinder the immediate contact between Zn metal and H2O. Meanwhile, strong interaction between maltitol and H2O molecules can restrain the activity of H2O. Besides, the "IHP adsorption effect" along with the low LUMO energy level of maltitol-CF3SO3- can promote the in-situ formation of an organic-inorganic complex solid electrolyte interface (SEI) layer. As a result, the hydrogen/oxygen evolution side reaction, corrosion, and dendrites issues are effectively suppressed, thereby leading to highly reversible and dendrite-free Zn plating/stripping. The Zn||I2 battery with hybrid electrolytes also demonstrates high electrochemical performance and ultralong cycling stability, showing a capacity retention of 75% over 20000 charge-discharge cycles at a large current density of 5 A g−1. In addition, the capacity of the device has almost no obvious decay over 20000 cycles even at −30 °C. This work offers a successful electrolyte regulation strategy via the IHP adsorption effect to design electrolytes for high-performance rechargeable Zn-ion batteries.