Self-Stratifying Electrolyte Enables Triple-Interface Regulation for Highly Reversible Zn Metal Batteries

Aqueous zinc metal batteries (AZMBs) are challenged by the incompatibility between cathode kinetic demands and Zn-anode interfacial stability in homogeneous electrolytes. Biphasic electrolytes can spatially decouple the two electrode environments, yet the accompanying liquid/liquid interface often suffers from active-water crossover and sluggish interfacial ion transport. Herein, a self-stratifying electrolyte is developed to realize triple- interface regulation across the cathode/electrolyte, liquid/liquid, and Zn/electrolyte interfaces. In this design, dimethyl carbonate (DMC) serves as a salt-solvating solvent to facilitate Zn²⁺ transfer and regulate solvation evolution across the biphasic interface, whereas methyl (2,2,2-trifluoroethyl) carbonate (FEMC) acts as a water-excluding solvent to suppress active-water crossover and stabilize Zn-side interfacial chemistry. Together, they disrupt the hydrogen-bond network of free water, induce a water-shielding electrical double layer, and promote a robust organic-inorganic gradient interphase on the Zn anode. Consequently, highly reversible Zn plating/stripping and markedly improved full-cell performance are achieved, including over 2500 h cycling in Zn||Zn cells and enhanced stability in Zn||PANI and Zn||MnO₂ full cells. This work establishes a triple-interface regulation strategy for highly reversible AZMBs and provides a new design principle for advanced biphasic electrolytes.