Harnessing solvent regeneration to spontaneously engineer a multifunctional interphase for high-energy-density flexible zinc batteries

Gel electrolytes hold considerable promise for flexible aqueous zinc batteries, yet simultaneously achieving mechanical robustness, ultrathin form factors, and dendrite-free zinc deposition remains a formidable challenge. Here, we report a cellulose-based gel electrolyte featuring a spontaneously self-assembled functional interfacial layer (FIL) that forms in situ during a single-step solvent regeneration process, requiring no additional fabrication procedures. The FIL consists of zinc hydroxide sulfate, with a deep eutectic solvent adsorbed on its surface, serves as an artificial solid–electrolyte interphase that displaces interfacial water, lowers the Zn 2+ desolvation energy barrier from 31.59 to 14.26 kJ mol −1 , and directs uniform ion flux to promote (002)-textured planar zinc deposition. Concurrently, Zn 2+ -mediated crosslinking of the cellulose network decouples mechanical strength from electrolyte thickness, yielding ultrathin (60 μm) membranes with enhanced tensile strength. The resulting electrolyte exhibits a high Zn 2+ transference number of 0.84, a widened electrochemical stability window of 1.89 V, and markedly suppressed interfacial corrosion. These attributes enable Zn||Zn symmetric cells to cycle stably for over 1200 h, Zn||Cu cells to maintain a Coulombic efficiency exceeding 98.5% over 600 cycles, and Zn||V 2 O 5 full cells to retain 77.1% capacity after 1000 cycles. When assembled into a flexible pouch configuration, the device delivers energy densities of 184.5 Wh L −1 and 143.2 Wh kg −1 while withstanding bending, puncturing, and cutting without thermal runaway. This work establishes a scalable paradigm for engineering multifunctional interphases through gel regeneration, offering a generalizable route toward safe, high-performance flexible aqueous batteries.