Self-Separating Biphasic Electrolyte Enables High-Performance Aqueous Zinc-Ion Batteries via Electron-Enriched Interphase Engineering

Abstract Aqueous Zn-ion batteries encounter significant challenges, including unstable electrolyte interfaces and dendrite formation, which curtail their cycle life and metal utilization. Here, we present a self-separating biphasic electrolyte through phase separation of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonic acid) (PEDOT:PSS) conductive polymers in Zn sulfate solution driven by a mechanical shear-ionic crosslinking process. The negatively charged sulfonic groups in PSS disrupt the hydrogen-bonding network of bulk electrolyte and remodel solvation structure of Zn 2+ ions, enhancing ionic transfer kinetics and facilitating desolvation. Meanwhile, the insoluble PEDOT fibers with continuous conjugated thiophene ring together with sulfonic groups in PSS spontaneously adhere to the electrode surface, establishing a robust electron-rich interphase that regulates electric double layer thickness, promotes uniform Zn deposition and repels sulfate ions. Consequently, this electrolyte allows Zn anodes to achieve exceptional stability and longevity even at larger depths of discharge (68.4% and 94.1%) and delivers outstanding cyclability exceeding 10,000 cycles in Zn||V 2 O 5 full cells.