Aqueous zinc-iodine batteries with ultra-high loading and advanced performance

Abstract

Aqueous zinc-iodine (Zn-I₂) batteries, leveraging abundant resources and inherent safety, face commercialization challenges due to low cathode loading and iodine sublimation in traditional fabrication methods. We introduce a dry electrode preparation technique that significantly enhances the areal capacity to 15.8 mA h cm⁻² (ZnI₂ loading >100 mg cm⁻²), far exceeding previous Zn-I₂ and commercial Li-ion batteries (∼3–5 mA h cm⁻²). This method not only increases cathode loading but also reduces polyiodides' shuttle effects and self-discharge rates, achieving a low discharge rate of 11.16% over 168 h. To address zinc-related issues at high loadings, 1,3,5-trioxane is added to the electrolyte to form a flexible polymer solid electrolyte interphase, preventing zinc dendrite formation. Our approach enables an A h-level pouch cell with remarkable cycling stability, maintaining 88.6% capacity after 750 cycles at 1 C at a high areal capacity of 15.8 mA h cm⁻², demonstrating potential applicability to other aqueous and halogen-based battery systems.