Constructing Water‐Lean Inner Helmholtz Plane Stabilizes Solid Electrolyte Interphase for Zinc Anode Longevity

The Zn anode stability is greatly influenced by the interface property between the Zn anode and electrolyte, which is almost determined by the electrical double layer (EDL) structure. Tailoring the EDL structure to enhance Zn anode stability is one effective solution. In this work, the water-lean inner Helmholtz plane (IHP) of EDL structure is experimentally realized via betaine (Bet) and diethylene glycol (DEG) into the ZnSO₄ electrolyte. DEG (Bet) preferentially adsorbs on the Zn surface to construct a water-lean IHP of EDL. It can adjust the local environment of the electrolyte on the Zn anode to suppress the parasitic reactions. What is more, DEG and Bet tend to decompose in situ to form the organic/inorganic hybrid solid electrolyte interphase, which can hinder the dendrite growth. Consequently, the Zinc anode maintains an ultra-long cycle life of over 1700 cycles and a superior Coulombic efficiency of 99.8% at 1 mA cm^-2 and 1 mAh cm^-2. The symmetric cell can cycle over 280 h under a high current density of 10 mA cm^-2 and a high depth of discharge of 50%. This work is helpful for the development of a longevity Zn anode in AZIBs.