A Hydro-Organo Biphasic Gel Electrolyte for Decoupled Interfacial Stability and Fast Ion Transport in Zinc Metal Batteries.

Organic and aqueous electrolytes offer complementary advantages in electrochemical stability and ion transport, but integrating both within a single electrolyte remains challenging. In this study, it is discovered that a distinct interphase can be spontaneously formed between the aqueous and organic phases through the synergy of amphiphilic monomers, Hofmeister effects, and phase partitioning. This aqueous-organic, mixed-solvent region boosts ion transfer by smoothing solvation change across phases, resulting in an order-of-magnitude increase in overall conductivity over biphasic counterparts without such an interphase. Meanwhile, compartmentalized organo- and hydrogel domains decouple anodic and cathodic interfacial chemistries. Demonstrated in zinc metal batteries, this biphasic gel electrolyte thermodynamically stabilizes zinc metal anodes and inhibits parasitic ion crossover, while also enabling high-rate operation comparable to aqueous systems. Accordingly, Zn||Zn symmetric cells demonstrate >3,600 h stable cycling at 5 mA cm-2 and 5 mAh cm-2, and MnO2||Zn full cells show high capacity retention after >3,000 cycles at 10 A g-1. Overall, the findings establish organizing phase and solvation chemistry as a general materials design principle toward advanced electrolyte systems for high-power, long-duration electrochemical energy storage.