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Vol. 18 (2026)

A Synchronous Strategy to Zn-Iodine Battery by Polycationic Long-Chain Molecules

https://doi.org/10.1007/s40820-025-01854-6
Da‑Qian Cai
Interdisciplinary Graduate Programme ‑ Collaborative Initiative, Graduate College, Nanyang Technological University, Singapore 637371, Singapore
Hengyue Xu
Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China
Tong Xue
School of Materials Science and Engineering, North Minzu University, Yinchuan 750021, People’s Republic of China
Jin‑Lin Yang
School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
Hong Jin Fan
School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore

Corresponding Author: Hong Jin Fan

fanhj@ntu.edu.sg

Nano-Micro Letters, Vol. 18 (2026), Article Number: 3

Abstract

Aqueous Zn-iodine batteries (ZIBs) face the formidable challenges towards practical implementation, including metal corrosion and rampant dendrite growth on the Zn anode side, and shuttle effect of polyiodide species from the cathode side. These challenges lead to poor cycle stability and severe self-discharge. From the fabrication and cost point of view, it is technologically more viable to deploy electrolyte engineering than electrode protection strategies. More importantly, a synchronous method for modulation of both cathode and anode is pivotal, which has been often neglected in prior studies. In this work, cationic poly(allylamine hydrochloride) (Pah+) is adopted as a low-cost dual-function electrolyte additive for ZIBs. We elaborate the synchronous effect by Pah+ in stabilizing Zn anode and immobilizing polyiodide anions. The fabricated Zn-iodine coin cell with Pah+ (ZnI2 loading: 25 mg cm−2) stably cycles 1000 times at 1 C, and a single-layered 3 × 4 cm2 pouch cell (N/P ratio ~ 1.5) with the same mass loading cycles over 300 times with insignificant capacity decay.


Highlights:
1 A long chain polycation (Pah⁺) is propos ed to simultaneously regulate Zn anode deposition , mitigate side reactions and stabilize iodine cathode chemistry.
2 The iodophilic and low diffusivity nature of Pah enables effective polyiodide immobilization, suppressing the shuttle effect and ensuring a stable redox environment.
3 The Zn iodine battery delivers high areal capacity (~4 mAh cm−2 at 1 C) and excellent durability, with 95% capacity retained over 1000 cycles.

Keywords

Polyiodide shuttle effect Halogen battery Conversion cathode Dendrites Polycation molecule
Cai, Da‑Qian, Hengyue Xu, Tong Xue, Jin‑Lin Yang, and Hong Jin Fan. 2025. “A Synchronous Strategy to Zn-Iodine Battery by Polycationic Long-Chain Molecules”. Nano-Micro Letters 18 (July):3. https://doi.org/10.1007/s40820-025-01854-6.
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