Dynamic Adaptive Interfaces Enable Zn-Iodine Hydrogel Batteries with High Areal Capacity and Low Self-Discharge

Serious self-discharge due to side reactions and the shuttle effect has been formidable limits for liquid zinc-iodine batteries. Hydrogel electrolytes can reduce self-discharge in certain degree and induce new properties of biocompatibility and mechanical flexibility. However, without a proper interface, chemical welding, most hydrogel ZIBs suffer from poor interfacial robustness, particularly under deformation, compromising the battery cycle life. To mitigate this issue, we deploy an in situ integration strategy to construct chemo-mechanical dynamically adaptive interfaces to enable high-iodine-loading hydrogel batteries. On the anode side, the interfacial polycatecholamine accommodates surface evolution via robust adhesion, induces a stable hybrid interphase, and functions as an ion sieve. Simultaneously, the hydrogel permeates the dry-processed cathode, forming a low-tortuosity ion transport pathway that adapts to volume fluctuations and chemically immobilizes polyiodides. This dual-role strategy enables low self-discharge (∼20% loss after 200 h) and unlocks the potential for high areal capacity (∼12.5 mAh cm^-2) in thick cathodes. At an areal capacity of ∼5 mAh cm^-2 (>40 mg cm^-2 iodine loading), the hydrogel battery can sustain over 2200 cycles with a negligible capacity decay of 0.0063% per cycle.