A recent study published in Advanced Science reports a strategy to improve aqueous zinc-iodine (Zn-I2) batteries. These batteries are valued for their low cost, safety, and long cycle life. Despite these advantages, poor iodine conductivity and the shuttle effect limit their practical use.
Researchers addressed these challenges by developing nitrogen-doped porous carbon materials derived from metal-organic frameworks (MOFs) to improve structural and electrochemical performance.
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Background
Zn-I2 batteries have gained attention due to their safety and affordability, but performance issues remain. The poor electrical conductivity of iodine restricts efficiency, while the shuttle effect causes self-discharge and capacity loss. Porous carbon materials have been used to immobilize iodine species and improve conductivity, but conventional carbons often lack strong interactions with iodine.
MOFs offer a solution due to their customizable structures, high surface areas, and porosity. Nitrogen doping further enhances chemical interactions with iodine, making MOF-derived carbons a promising material for Zn-I2 battery cathodes.
Study Overview
This study synthesized a zinc-based metal-organic framework (Zn-MOF) with a cubic morphology as a precursor for nitrogen-doped porous carbon (NC). Hexadecyl trimethyl ammonium bromide (CTAB) was used as a surfactant and capping agent to promote the formation of ordered porous structures. The material underwent thermal pyrolysis at different temperatures to optimize pore size distribution.
Characterization methods included scanning electron microscopy (SEM) for morphology, X-ray diffraction (XRD) for structural analysis, and X-ray photoelectron spectroscopy (XPS) to confirm nitrogen doping. Adsorption experiments and density functional theory (DFT) calculations were conducted to study iodine interactions with different nitrogen doping configurations.
Results and Discussion
The nitrogen-doped carbon derived from the Zn-MOF, specifically the S3-1000 sample, showed strong electrochemicalperformance as a Zn-I2 battery cathode. It achieved a high iodine loading of 43.7 wt%, contributing directly to increased energy density.
The material maintained a discharge capacity of 112.4 mAh g⁻¹ over 10,000 cycles at a current density of 2 A g⁻¹, demonstrating excellent cycle stability. In-situ analysis indicated that pyridinic-N and graphitic-N sites served as effective anchoring points for iodine species, suppressing the polyiodide shuttle effect and improving redox kinetics.
The study also highlighted the importance of balancing nitrogen content and structural stability. Excessive nitrogen doping reduced surface area, while insufficient doping weakened iodine retention. These results emphasize the need for precise control of synthesis conditions to optimize nitrogen doping and enhance electrochemical performance.
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Conclusion
MOF-derived nitrogen-doped porous carbons improve iodine immobilization and conductivity in Zn-I2 batteries. The developed material delivers high iodine loading, enhanced ion/electron transport, and stable cycling performance.
Future work will focus on further optimizing synthesis parameters to improve material performance and support the development of more efficient, scalable aqueous battery systems.
Journal Reference
Li Y., Guo X., et al. (2025). Nano/micro metal-organic framework-derived porous carbon with rich nitrogen sites as efficient iodine hosts for aqueous zinc-iodine batteries. Advanced Science, 2502563. DOI: 10.1002/advs.202502563, https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202502563