Design of dual-electrode interfacial kinetics regulator for long-lasting Ah-level zinc-iodine batteries

Zinc-iodine (Zn-I 2 ) batteries hold great promise for large-scale applications, yet their practical deployment is constrained by uncontrollable iodine conversion, polyiodide shuttling, and unpredictable zinc (Zn) depositional morphology. Furthermore, the mismatched kinetics of its interfacial reactions demand significant attention. Herein, we introduce a betaine (Bet) additive as a dual-electrode interfacial regulator to synergistically address the challenges faced at both the anode and cathode interface. Specifically, the hydrophilic group (–COO) of Bet preferentially adsorbs on the Zn anode surface, modulating Zn 2+ solvation and electrodeposition dynamics to enable highly uniform Zn plating, extending the Zn-Zn symmetric cell lifespan beyond 7,000 h at 1 mA cm −2 . Moreover, Bet’s lipophilic group (–N–R 3 ) interacts with polyiodides, suppressing their migration and accelerating iodine redox kinetics, thereby mitigating cathodic side reactions. Consequently, Zn-I 2 full-cell demonstrates exceptional cycle life, maintaining capacity with an ultralow decay rate of 0.007‰ per cycle over 15,500 cycles at 10 mA cm −2 . Furthermore, an Ah-level pouch cell of ∼1.15 Ah can deliver a competitive capacity retention of 92.1% after 600 cycles, highlighting the scalability of this approach. This cost-effective and efficient interfacial modulation strategy offers a new perspective for realizing long-cycle Zn-I 2 batteries and advancing their practical applications.