article · eScience
Zinc-iodine batteries are promising candidates for large-scale energy storage, but their real-world use is hindered by uncontrolled iodine conversion, polyiodide shuttling, uneven zinc growth, and mismatched reaction speeds at the electrodes. Researchers have addressed these dual-electrode challenges using betaine as an electrolyte additive. The hydrophilic portion of betaine binds to the zinc anode, adjusting zinc ion solvation and electrodeposition to produce uniform zinc plating, allowing symmetric cells to operate past 7,000 hours. Concurrently, betaine's lipophilic group binds polyiodides at the cathode, suppressing unwanted migration and speeding up iodine conversion reactions. As a result, zinc-iodine full cells achieved an ultralow capacity loss rate across 15,500 cycles. The strategy was also validated in practical pouch cells delivering 1.15 ampere-hours, which retained over 92 percent of their initial capacity after 600 cycles.
Widespread transition to renewable power demands durable, safe, and inexpensive grid-scale energy storage. Zinc-iodine batteries offer an attractive alternative to lithium systems, but short lifespans and chemical instability have prevented practical use. By demonstrating that a low-cost additive can resolve degradation at both electrodes and function reliably in ampere-hour pouch cells, this approach brings long-lasting aqueous batteries closer to everyday implementation.
This work is relevant to battery manufacturers and energy storage developers targeting grid-scale applications. Because the approach relies on a cost-effective additive and has been tested in a working 1.15 ampere-hour pouch cell, it sits at an applied, laboratory-validated stage rather than purely basic research. Further scaling to multi-ampere-hour commercial formats and extended industrial cycling tests will be necessary before full market deployment can occur.
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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. • A dual-electrode interfacial kinetics regulator Betaine is proposed for shuttle-free and dendrite-free zinc-iodine batteries. • The retricted shuttle effect and facilated cathode kinetics contribute to batteries with an ultralow decay rate of 0.007‰ per cycle over 15,500 cycles. • The optimized solvation structure and electronic double layer ensures Zn-Zn symmetrical cells with 7,000 h cycle life at 1 mA cm −2 . • The interfacial remodeling enables a realization of pouch cells with a capacity of 1.15 Ah, and retaining 92.1% capacity after 600 cycles.
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DOI: 10.1016/j.esci.2025.100455
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