Tuning the Electrode/Electrolyte Interface Enabled by a Trifunctional Inorganic Oligomer Electrolyte Additive for Highly Stable and High‐Rate Zn Anodes

The practical application of aqueous Zn-ion batteries is still greatly hindered by the unstable Zn anode with severe Zn dendrites growth and side reactions. As it is accessible and economical, the exploitation of electrolyte additives is one of the most promising strategies to stabilize the Zn electrode/electrolyte interface. Herein, the penta-potassium triphosphate (KTPP) as a novel trifunctional electrolyte additive is introduced to tune the electrode/electrolyte interface. First, the KTPP additive can induce an ion-conducting and mechanically robust solid electrolyte interphase film to stabilize the Zn anode. Second, the KTPP can complex with Zn²⁺ ions to reconstitute the dissolution sheath structure of the Zn²⁺ ion. Finally, the K⁺ cations in KTPP adsorb on the tips of the Zn anode surface as a shielding film to regulate Zn²⁺ ion flux. As a result, Zn//Zn symmetric cells can achieve significantly prolonged cycling stability (e.g., from 1077 to 3800 h at 1 mA cm^-2 /1 mAh cm^-2 , from 256 to 2500 h at 2 mA cm^-2 /2 mAh cm^-2 ), and ultrahigh cumulative capacity of 6400/7200 mAh cm^-2 at high current density (40/20 mA cm^-2 ). A four-layer Zn-MnO₂ pouch full cell with a high capacity of 9 mAh can be constructed, showing impressive practical application potential.