A new strategy for protecting zinc metal in aqueous zinc-ion batteries could address one of the most persistent obstacles facing low-cost, large-scale energy storage: the unstable behavior of the zinc anode. Researchers at Hubei University have developed a hydrated network interphase that forms directly on zinc during battery operation, creating a dynamic protective layer designed to suppress dendrites, corrosion, hydrogen evolution, and other reactions that gradually damage the electrode. In tests, the modified zinc anode supported thousands of hours of stable cycling and enabled a zinc–iodine battery to retain most of its capacity over 12,000 cycles.
Aqueous zinc-ion batteries have attracted intense interest because they combine several advantages that are difficult to achieve simultaneously with lithium-ion technology. Their electrolytes are water-based, making them safer and less flammable, while zinc is relatively abundant, inexpensive, and compatible with simple manufacturing processes. These properties make the technology especially attractive for stationary storage systems that could help balance renewable electricity grids. Yet the zinc anode remains a major weakness. During charging, zinc ions can accumulate unevenly and form needle-like dendrites. At the same time, the electrode may undergo corrosion and parasitic hydrogen evolution, consuming electrolyte and active material while increasing internal resistance and reducing battery life.
The team’s solution is a hydrated network interphase, or HNI, created through monomer-induced in situ interface engineering. Instead of preparing a polymer coating separately and transferring it onto the electrode, the researchers allow the protective structure to assemble at the zinc–electrolyte boundary during electrochemical cycling. This approach is intended to improve contact between the electrode and the protective layer while avoiding the processing complexity and potential defects associated with prefabricated films. Because the interphase forms under operating conditions, it can adapt to the changing chemical environment and may be renewed as the battery continues to cycle.
The formation process begins with acrylamide molecules dispersed in the aqueous electrolyte. According to the researchers’ calculations, acrylamide interacts more strongly with the zinc surface than water does. Its calculated adsorption energy on the Zn (002) crystal plane is −0.828 electronvolts, compared with −0.325 electronvolts for water. This preference enables the monomer to concentrate at the zinc interface, where it creates a localized environment favorable for polymerization. The process is then activated by the combined presence of zinc ions and sulfate ions during battery operation, rather than by a conventional external chemical initiator.
Zinc ions play a dual role in this interfacial reaction. They coordinate with the polymer-forming species and help lower the energy barrier for polymerization, promoting the generation of reactive intermediates that link acrylamide molecules into a network. Sulfate ions contribute a different function through a salting-out effect. By reducing the hydration of the polymer chains, sulfate encourages them to contract and assemble into a denser structure. The result is a hydrated polymer network containing dynamic negatively charged microregions, described by the researchers as DNCM. These sulfate-rich regions remain electrostatically associated with the network and help regulate the movement of zinc ions near the electrode.
The protective layer controls zinc deposition through three connected mechanisms. First, carbonyl groups in the polymer coordinate with Zn²⁺, creating preferential nucleation sites where incoming zinc ions can be reduced and deposited. The calculated binding energy for the C=O···Zn²⁺ interaction is −8.45 electronvolts, indicating a strong affinity that can guide the initial stages of metal growth. Rather than allowing zinc to nucleate randomly at isolated points, the interphase distributes deposition across chemically favorable locations. This reduces the probability that a small number of protrusions will grow rapidly into unstable dendrites.
Second, the negatively charged microregions influence ion transport through long-range electrostatic interactions. Because the DNCM regions repel sulfate and other negatively charged species while affecting the local distribution of positively charged zinc ions, they help smooth variations in zinc-ion flux near the electrode. A more uniform ion supply reduces concentration polarization, a condition in which certain areas become starved of ions while others receive an excessive flow. By moderating this imbalance, the interphase supports more even plating and stripping across the zinc surface. Third, the polymer network forms extensive hydrogen bonds with water. The calculated C=O···H–O–H interaction has a binding energy of −0.46 electronvolts, allowing the network to immobilize a portion of the water molecules near the interface. Limiting the activity of free water suppresses hydrogen evolution and other parasitic reactions that would otherwise accelerate electrode degradation.
The electrochemical results indicate that these mechanisms translate into a substantial improvement in zinc stability. Symmetric cells containing two HNI-modified zinc electrodes operated for 8,650 hours at a current density of 1 milliampere per square centimeter with an areal capacity of 0.5 milliampere-hours per square centimeter. That is more than 360 days of repeated zinc plating and stripping under the reported conditions. At the same current density and a higher areal capacity of 1 milliampere-hour per square centimeter, the cells continued operating for 6,700 hours. They also remained stable for 2,740 hours at 5 milliamperes per square centimeter and 1,600 hours at 10 milliamperes per square centimeter. Compared with unprotected zinc, the reported lifetimes improved by approximately 90-fold, 20-fold, and 45-fold under the corresponding test conditions. The nucleation overpotential also fell from 42.8 millivolts for bare zinc to 36.5 millivolts with the interphase, suggesting that zinc deposition became energetically more favorable and more uniform.
Additional tests examined how efficiently zinc could be deposited and removed in asymmetric cells, an important measure of whether a zinc anode can operate with limited loss of active material. In zinc–titanium cells, the HNI-modified electrode delivered an average Coulombic efficiency of 99.71 percent at 5 milliamperes per square centimeter for more than 1,150 cycles. Zinc–copper cells achieved an average efficiency of 99.68 percent over 2,000 cycles at 1 milliampere per square centimeter. Coulombic efficiency describes the fraction of zinc that can be recovered during stripping after it has been deposited; values approaching 100 percent indicate that fewer side reactions and irreversible losses are occurring at the interface.
The technology also performed in full zinc–iodine batteries, where the modified zinc anode was paired with an iodine-based cathode. The cell delivered a specific capacity of 356.27 milliampere-hours per gram at a current density of 1 ampere per gram and retained 89.15 percent of its capacity after 12,000 cycles. In rate tests, the battery provided 539.89 milliampere-hours per gram at 0.1 ampere per gram and 231.75 milliampere-hours per gram even at 10 amperes per gram, while maintaining recognizable charge and discharge platforms across the tested range. Although laboratory demonstrations do not by themselves establish commercial readiness, the combination of long cycle life, high efficiency, and a water-based electrolyte highlights why dynamic interphase engineering is attracting attention in the development of safer grid-scale batteries. The researchers argue that the same principle could be extended to other aqueous metal batteries by using electrochemical ion enrichment to trigger protective networks directly where they are needed.
Subject of Research: Aqueous zinc-ion batteries and in situ interfacial engineering for stabilizing zinc anodes
Article Title: Hydrated Network Interphase with Dynamic Negatively Charged Microregion Enables Ultra‑Stable Aqueous Zinc‑Ion Batteries
News Publication Date: 29-Jun-2026
Web References: https://doi.org/10.1007/s40820-026-02262-0
References: Nano-Micro Letters, DOI: 10.1007/s40820-026-02262-0
Image Credits: Yin Yang, Xiaofang Wang, Xin Chen, Jia Yao, Daigan Wang, Luyang Ge, Fei Wang, Lin Lv, Li Tao, Hao Wang, Houzhao Wan
Keywords
Aqueous zinc-ion batteries, zinc anodes, hydrated network interphase, dendrite suppression, hydrogen evolution, zinc deposition, zinc–iodine batteries, energy storage, electrochemistry, battery materials
