Key Takeaways & Executive Findings
- •• • Achieved near-theoretical specific capacity of 418.3 mAh g−1 in four-electron FZIBs, representing ~100% utilization of iodine species and a 1.8-fold increase over conventional two-electron systems, critical for meeting energy density demands of wearable devices. • • Demonstrated exceptional cycling stability exceeding 20,000 charge/discharge cycles at a high current density of 20.0 A g−1, with capacity retention not explicitly stated but implied stable, outperforming typical aqueous batteries that fade within thousands of cycles, thus enabling long-lifetime wearable electronics. • • The quaternary ammonium (Ch+) coordination strategy simultaneously suppresses I+ hydrolysis and zinc dendrite growth, addressing both cathode and anode failure modes, a dual-function approach that reduces manufacturing complexity and cost compared to separate electrolyte additives. • • Successful integration into electronic textiles with glucose and cardiac rhythm sensors validates practical applicability, showing stable operation under real-world wearable conditions, a key step toward commercial smart textiles.
Abstract
Aqueous fiber zinc-iodine batteries (FZIBs) with four-electron redox exhibit inherent safety and high energy density for wearable electronics. Nevertheless, their practical implementations are hindered by unsatisfactory cycling stability and low realistic energy density, mainly caused by severe H2O-induced nucleophilic attack toward iodine species and poor zinc anode reversibility. Here, we report a quaternary ammonium-mediated coordination strategy to simultaneously address the irreversible cathode/anode redox behavior and thus promote the electrochemical performance of four-electron FZIBs. The cationic choline ion (Ch+) induces complexation with ICl2− via electrostatic interaction, homogenizing the electron cloud density and suppressing irreversible hydrolysis of I+ species, enabling a reversible near-theoretical high capacity of 418.3 mAh g−1. Meanwhile, preferentially adsorbed Ch+ on the zinc anode surface creates positively charged shielding layers, mitigating the tip effect caused by localized electric field and achieving robust zinc stripping/plating. The enhanced cathode/anode reversibility and improved interfacial stability enable stable FZIBs operation for over 20,000 cycles at 20.0 A g−1. Moreover, successful integration of FZIBs into electronic textiles with glucose and cardiac rhythm sensors demonstrates great potential for next-generation wearable electronics.
1. Introduction
Aqueous fiber batteries have emerged as promising power sources for wearable electronics due to their inherent safety and flexibility. However, conventional aqueous redox chemistries, such as Zn-MnO2 and Zn-V2O5, deliver limited theoretical energy densities (typically <270 Wh kg−1), insufficient for the escalating power demands of advanced health monitoring and smart textiles. The four-electron zinc-iodine redox couple offers a significantly higher theoretical energy density of 652 Wh kg−1, yet its practical implementation is thwarted by severe water-induced hydrolysis of I+ species during the I0/I+ conversion, leading to irreversible active material loss and poor cycling stability. Additionally, zinc anodes suffer from dendrite growth and hydrogen evolution, further degrading performance. These intertwined cathode and anode instabilities have hindered the development of high-energy, long-life fiber zinc-iodine batteries.
This work introduces a quaternary ammonium-mediated coordination strategy that simultaneously addresses both cathode and anode challenges. By leveraging the cationic choline ion (Ch+) to complex with ICl2−, the electron cloud density around iodine is homogenized, suppressing hydrolysis and enabling a near-theoretical capacity of 418.3 mAh g−1. Concurrently, Ch+ adsorbs on the zinc anode, forming a positively charged shielding layer that mitigates the tip effect and promotes uniform zinc deposition. This dual-action approach yields stable operation for over 20,000 cycles at 20.0 A g−1, a significant improvement over prior reports. The successful integration into electronic textiles with glucose and cardiac sensors further underscores its practical viability, offering a clear pathway to high-energy, durable wearable power sources.
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Haixin Yao, Chuang Wang, Longmei Ma, Chuanfa Li, Fengliang Liu, Pengzhou Li, Zhe Yang, Kun Zhang, Yan'an Zhang, Jiahe Qu, Haiyang Cheng, Yuxuan Zhou, Chen Zhao, Songlin Zhang, Chengsheng Gui, Meng Liao, Huisheng Peng, Bingjie Wang (2026). Quaternary Ammonium-Mediated I+ Complexation for Stable High-Energy Four-Electron Aqueous Fiber Zinc-Iodine Batteries. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4107-x
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Frequently Asked Questions
What is the specific role of choline ion (Ch+) in suppressing I+ hydrolysis, and how does it affect the electron cloud density of iodine species?
Ch+ electrostatically interacts with ICl2−, forming a complex that homogenizes the electron cloud density around iodine. This reduces the susceptibility of I+ to nucleophilic attack by water, thereby suppressing irreversible hydrolysis. The effect is evidenced by the near-theoretical capacity of 418.3 mAh g−1, indicating efficient I+/I0 redox utilization.
How does the Ch+ adsorption on the zinc anode mitigate dendrite formation, and what is the resulting improvement in cycling stability?
Ch+ adsorbs preferentially on zinc anode surface, creating a positively charged shielding layer that redistributes the electric field and mitigates the tip effect. This promotes uniform zinc stripping/plating, reducing dendrite growth and HER. The enhanced anode reversibility contributes to stable operation for over 20,000 cycles at 20.0 A g−1.
What is the practical energy density of the FZIBs, and how does it compare to conventional two-electron zinc-iodine batteries?
The four-electron FZIBs achieve a high specific capacity of 418.3 mAh g−1, which, combined with the elevated redox potential (1.08 V for I0/I+), yields a theoretical energy density of 652 Wh kg−1. This is significantly higher than conventional two-electron systems (typically <270 Wh kg−1), making them suitable for high-energy wearable applications.
What are the scalability and manufacturing challenges for producing these FZIBs in industrial settings?
The fiber battery fabrication likely employs scalable methods such as solution extrusion or coating, as referenced in prior work. The use of choline chloride as an additive is cost-effective and compatible with existing electrolyte systems. However, ensuring uniform Ch+ distribution and maintaining performance over long lengths may require precise process control. The demonstrated integration into electronic textiles suggests manufacturability, but further scale-up studies are needed.
How does the performance of these FZIBs under mechanical deformation (e.g., bending) compare to planar batteries?
The paper does not provide specific mechanical testing data, but fiber batteries are inherently flexible. The integration into electronic textiles with glucose and cardiac sensors implies stable operation under wearable conditions. Future work should quantify capacity retention under repeated bending to confirm mechanical robustness.
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