Coordination-Escorted Organo-Interhalogen Conversion Enables Durable Dual-Deposition Zn||I2 Batteries with High Areal Capacities

Abstract

Dual-deposition aqueous Zn||I2 batteries, via reversible Zn plating/stripping and four-electron (4e-) iodine redox, represent promising high-energy systems. However, their practical application is hindered by low areal capacity and limited cycle life, stemming from severe shuttling, hydrolysis, the insulating nature of iodine species, and Zn corrosion. Here, we introduce a coordination-escorted organo-interhalogen conversion strategy employing choline cation (Ch+) and 2-acetbromamide (BrAce) as coregulators to address these challenges. Ch+ coordinates strongly with key intermediates (I3-, I2, and organo-interhalogen complexes), effectively suppressing the shuttle effect and stabilizing organo-interhalogen complexes. This coordination induces a smooth semiliquid iodine deposition/dissolution process during the 4e- conversion, significantly improving electrical contact and redox kinetics. Simultaneously, the interface shielding effect of Ch+ effectively protects the deposited Zn anode. Markedly outperforming existing systems, this battery achieves a well-balanced capacity between the I-/I0 and I0/I+ steps, a threefold increase in iodine utilization (∼70%), and a tenfold longer cycle life (exceeding 12,000 cycles) at 20 mA cm-2 under a practical areal capacity of 2.5 mA h cm-2. A dual-deposition configuration also delivers 800 cycles with nearly 100% retention. This approach concurrently addresses critical issues in 4e- iodine redox and Zn anode chemistry, offering a universal paradigm to explore other dual-deposition high-energy systems.