Quasi-Solid Cathode Additive Enables Highly Reversible Four-Electron I⁻/I⁰/I⁺ Conversion in Aqueous Zn-I₂ Batteries

Date

2025

Authors

Wu, H.
Zhang, S.-J.
Vongsvivut, J.
Jiang, Y.
Hao, J.
Qiao, S.-Z.

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Advanced Materials, 2025; e11680-1-e11680-10

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Han Wu, Shao-Jian Zhang, Jitraporn Vongsvivut, Yunling Jiang, Junnan Hao, Shi-Zhang Qiao

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Abstract

Aqueous zinc-iodine (Zn-I₂) batteries with four-electron (4e) I⁻/I⁰/I⁺ conversion (4eZIBs) offer high energy density but face both-step I⁻/I⁰ and I⁰/I⁺ challenges, including the polyiodide shuttle effect, sluggish I⁰/I⁺ conversion kinetics, and severe I⁺ hydrolysis. To mitigate these issues, a quasi-solid additive composed of 1-butyl-3-methylimidazolium chloride (BMICl) and carbon nanotubes (CNTs) is introduced into the cathode. Specifically, by co-grinding BMICl with CNTs, a homogeneous quasi-solid additive is formed due to the π–π stacking interactions between CNTs and imidazole rings. This additive not only suppresses the shuttle effect by binding with polyiodides in the first-step I⁻/I⁰ conversion, but also enhances I⁺ conversion kinetics by immobilizing Cl⁻ inside the electrode and curbs I⁺ hydrolysis through forming a BMI-ICl₂ complex in the second-step conversion. This innovative approach enables the 4eZIBs to achieve a near-theoretical specific capacity of 418.9 mA h g¯¹ at 0.5C, while maintaining a robust lifespan of over 600 cycles with a capacity retention of 93.4% at 1C. Moreover, pouch cells under a high areal capacity of 7.1 mA h cm¯² for each side of the cathode demonstrate a high-capacity retention of 95.8% after 150 cycles at 6.3 mA cm¯² (≈0.5C).

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© 2025 The Author(s). Advanced Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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