Storing renewable energy remains one of the central challenges of the clean-energy transition. Solar panels and wind turbines can generate electricity without burning fossil fuels, but their output rises and falls with weather and time of day. Batteries must therefore absorb surplus electricity and release it when demand increases. Lithium-ion technology dominates many applications because it is compact, efficient and powerful, yet concerns about flammability, cost and the availability of lithium and other critical materials are driving researchers to explore safer and more abundant alternatives.
A research team from several Chinese universities has reported a strategy for improving aqueous zinc-ion batteries, or AZIBs, by modifying an industrial form of manganese dioxide. The researchers found that mechanical treatment known as ball milling can remove oxygen atoms from the manganese dioxide crystal lattice, creating oxygen vacancies that significantly alter the material’s electronic and chemical behavior. Their findings suggest that a relatively inexpensive manufacturing process could transform commercially produced manganese dioxide into a more effective cathode for next-generation energy-storage systems.
Unlike lithium-ion batteries, AZIBs use positively charged zinc ions as the charge-carrying species. Zinc is abundant, inexpensive and already suitable for large-scale manufacturing. The batteries also employ water-based electrolytes containing mild acids or neutral salts rather than volatile organic solvents. This makes them far less prone to ignition and potentially safer for stationary storage installations, where batteries may be deployed in large numbers. However, the technology has been held back by the difficulty of developing cathodes that can rapidly and repeatedly accommodate zinc ions without suffering structural damage.
The team investigated electrolytic manganese dioxide, or EMD, an industrially manufactured material that is relatively cheap, abundant and capable of storing substantial amounts of energy. Manganese dioxide has long attracted attention as a battery electrode, but its limited electrical conductivity can slow electrochemical reactions. During repeated charging and discharging, the material may also undergo phase changes and structural distortion. These processes can promote manganese dissolution into the electrolyte, gradually reducing the battery’s reversible capacity and shortening its useful lifetime.
To address these limitations, the researchers subjected EMD powders to ball milling. In this process, heavy balls repeatedly collide with and shear the powder inside a rotating or vibrating container. The impacts can reduce particle size, introduce defects and modify the arrangement of atoms. In the researchers’ experiments, the mechanical energy was sufficient to drive lattice oxygen out of the manganese dioxide structure. The resulting oxygen vacancies left behind additional electrons and changed the local chemical environment around manganese atoms.
Measurements indicated that the oxygen content of the treated material declined from 68.93 percent to 61.17 percent, while the measured manganese content increased from 31.07 percent to 38.83 percent. The researchers interpreted this shift as evidence that oxygen vacancies had formed within the EMD lattice. These vacancies can improve electronic transport by creating pathways through which electrons move more readily. The modified material also displayed induced half-metallic behavior, in which electrons with one spin orientation conduct like those in a metal while electrons with the opposite spin experience insulating behavior.
The electronic changes were important because they affected how the cathode interacts with both zinc ions and protons. According to the study, oxygen vacancies shifted the energy positions of manganese d-bands and oxygen p-bands. These orbitals determine how strongly atoms bind incoming ions and how easily electrons move through the solid. By adjusting the balance between these interactions, the modified EMD reduced the tendency of zinc ions and hydrogen ions to become trapped at specific sites. That could allow the ions to enter and leave the cathode more smoothly during battery operation.
The researchers also calculated adsorption energies and migration barriers, which describe how strongly ions bind to a material’s surface and how much energy they need to move through its crystal structure. The ball-milled EMD showed more favorable ion-transport characteristics than untreated material, including lower barriers for zinc-ion and proton migration. Faster ion movement can accelerate charging and discharging, while more balanced binding energies can reduce the buildup of chemically immobile species. At the same time, the altered lattice appeared to limit the structural distortions that normally develop as EMD cycles between different chemical states.
The study, published in Nano Research Energy, presents defect engineering as a practical route for upgrading an existing industrial material rather than replacing it with a costly, laboratory-only compound. The researchers argue that the combination of oxygen vacancies and d- and p-band modulation addresses several weaknesses at once: poor conductivity, sluggish ion diffusion, ion trapping and structural instability. Although further work will be needed to evaluate long-term cycling, large-scale production and performance under commercial conditions, the ball-milling approach is attractive because it uses established mechanical processing and does not require elaborate synthesis. The results could help bring safer zinc-based batteries closer to use in grid storage, where affordability, material availability and fire safety may matter more than extreme energy density.
Subject of Research: Oxygen-vacancy engineering in industrial electrolytic manganese dioxide for aqueous zinc-ion battery cathodes
Article Title: Unveiling the action mechanism of synergistic d/p-band center modulation on the zinc storage capability of industrial-grade MnO2 cathode
News Publication Date: 15-Jul-2026
Web References: https://doi.org/10.26599/NRE.2026.9120255
References: Nano Research Energy, “Unveiling the action mechanism of synergistic d/p-band center modulation on the zinc storage capability of industrial-grade MnO2 cathode,” DOI: 10.26599/NRE.2026.9120255
Image Credits: Nano Research Energy, Tsinghua University Press
Keywords
Aqueous zinc-ion batteries, manganese dioxide, oxygen vacancies, ball milling, energy storage, battery cathodes, zinc-ion transport, defect engineering, renewable energy, grid-scale batteries
