image: The strategy diagram of NC-Nafion artificial SEI structural design is shown in the Figure. The chemically inert protective layer of Nafion ionomer can serve as a Zn2+ ions conductor, as well as isolate solvent water molecules and shield anions to eliminate side reactions. The evenly decorative high-Fermi-level NC in Nafion accelerates the decoupling process of [Zn(H2O)6]2+ outside the inner Helmholtz plane by reducing the charge density of Zn2+, achieving fast desolvation and charge transfer kinetics.
Credit: ©Science China Press
With the growing global demand for energy, safe and efficient energy storage technologies have become crucial for advancing renewable energy development. In recent years, rechargeable aqueous zinc metal batteries (AZMBs) have gained widespread attention due to their high safety, environmental friendliness, abundant zinc resources, and favorable energy density. However, the commercialization of AZMBs still faces significant challenges, with the instability of the zinc anode being a major bottleneck.
In aqueous electrolytes, zinc ions (Zn2+) typically exist in the form of [Zn(H2O)6]2+, which presents several issues. First, when hydrated zinc ions reach the electrode interface, the water molecules directly contact the zinc metal, triggering hydrogen evolution reactions (HER), corrosion, and passivation, which accelerate electrode degradation. Second, the slow desolvation kinetics of Zn2+ result in non-uniform zinc deposition, leading to the formation of zinc dendrites that can puncture the separator, causing short circuits and severe safety risks. Therefore, accelerating the desolvation process of zinc ions, minimizing side reactions, and achieving uniform zinc deposition are essential for improving AZMB performance.
To address these challenges, a research team from the Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, has proposed a novel artificial solid electrolyte interface (SEI) based on non-coordinating charge transfer and developed a composite coating of nitrogen-doped amorphous carbon (NC) and perfluorosulfonic acid polymer (Nafion). This artificial SEI layer optimizes zinc ion transport behavior and effectively suppresses side reactions. Nafion acts as a selective ion channel, blocking anions and water molecules to reduce direct contact with zinc metal, while NC enhances the Fermi-level, enabling non-coordinating charge transfer that accelerates Zn2+ desolvation, thereby promoting more uniform zinc deposition.
Experimental results demonstrate that this artificial SEI layer significantly improves the stability of AZMBs. The NC-Nafion@Zn symmetric battery achieves a lifespan of 3400 hours at 1 mA cm-2 and 2000 hours at 5 mA cm-2, greatly extending the anode’s durability. Additionally, the NC-Nafion@Zn//Mn4O3-carbon nanotube (CNTs) full battery exhibits ultralong cycling stability of 9300 cycles at 2 A g-1, maintaining 91.3% capacity retention, which far surpasses existing technologies. Moreover, the artificial SEI layer effectively suppresses HER, enhancing the battery’s coulombic efficiency (CE) to 99.1%, thereby improving charge-discharge reversibility and energy utilization.
To validate the practical application potential of this technology, the research team tested it in pouch cells, successfully powering an LED array. This confirms its feasibility for use in large-scale energy storage, grid frequency regulation, and portable power devices, highlighting its broad market prospects. This breakthrough not only provides a novel solution for optimizing AZMB performance but also lays a solid foundation for future advancements in energy storage systems.
This study introduces an innovative artificial SEI design based on Fermi-level modulation and non-coordinating charge transfer, effectively addressing the instability of the zinc anode and significantly enhancing the cycle life and safety of AZMBs.