To reduce the cost of rechargeable battery technology, materials scientists are exploring the potential of more globally abundant materials, such as iron, manganese, and sodium. Currently, batteries which incorporate these materials into their cathodes do not provide the repeatable rechargeability required for widespread use, so scientists are investigating methods to improve their rechargeability. Recent results from a team composed of members from the Virginia Polytechnic Institute and State University, multiple U.S. Department of Energy (DOE) national laboratories, and Brown University have demonstrated improved recharge capabilities for batteries whose layered cathodes are composed of earth-abundant transition-metal oxides after subjecting said layers to moderate amounts of proton irradiation.

The reasons why proton irradiation may favorably affect a battery's performance are based on the structure of this particular cathode: layers of transition-metal oxides with alkali ions, such as sodium or lithium, inserted between the layers. This insertion is called intercalation and the type of bonding involved allows the sodium ions to move in and out of the layers. When the battery charges, the sodium ions leave the layered structure of the cathode and participate in the reactions which "power" the battery. 

In response to the now-missing ion, the transition-metal oxides undergo several alterations, including structural changes. Ideally, when the cathode's reactions are complete, the sodium ions will return to the layers. However, the layers do not always revert to their initial structure, so during the next discharge of the battery, the cathode performance will decrease. Over many discharge-charge cycles, the ability of the battery to store or release electrons will degrade.

So, how to get the initial layer structure back? Scientists have found that the grain size of a material heavily influences its chemical and physical properties. The dimensions of the domain within a material where atoms share the same crystallographic orientation is the grain size of the material. Previously published research has demonstrated that smaller grain sizes are beneficial for maintaining the reversible structure of some battery materials. But if the grains are too small then the comparatively larger surface area of the material will increasingly react with the battery's electrolyte, diluting the battery's ability to generate charge. 

So, the team asked: could they keep the grain size¾to preserve the good energy density and not increase side reactions¾but create nanodomains within the grains that would allow for the benefits of reversible structural changes? They hypothesized that proton irradiation would create such nanodomains while preserving grain size.

The team chose a transition-metal oxide with composition Na_2/3Fe_1/2Mn_1/2O₂ and experimented with a range of proton irradiation levels. The irradiation process and results are summarized in Figure 1. First, the team took data to characterize the defects created by the proton irradiation. Next, they measured the performance of the battery during discharge-charge cycles for cathodes of both unirradiated and irradiated materials. Additionally, they looked at the discharge capacity as a function of the number of charge-discharge cycles; one irradiation level produced a markedly better discharge capacity retention for more cycles than all the others the team explored. They concluded this moderate amount of irradiation allowed more of the cathode's layered structure to return to its initial state, unlike the amount of reversion in the unirradiated material.

But what is going on within the cathode material itself? To answer this question, the team used beamline 34-ID-C at the Advanced Photon Source, a DOE Office of Science user facility at DOE’s Argonne National Laboratory, to perform Bragg coherent X-ray diffraction on both the moderately-irradiated and unirradiated materials. At the (002) Bragg peak, the moderately-irradiated material showed speckled reflections. These speckled responses represent the interference of reflections from many closely attached small surfaces. The team concluded, both from this response as well as other measured characteristics, that irradiation successfully created crystalline nanodomains within the grains.

To determine if the nanodomains are contributing to structural reversibility in the cathode material, the team used multiple X-ray techniques to characterize the moderately-irradiated material during cycling. They found structural change during charging which reverted to the initial structure on discharge. Additionally, they measured that the peak intensities at both the beginning and end of the cycle were very similar, implying that the structural changes are a reversible process. 

Taken all together, the team concluded that the defects created by the proton irradiation are allowing the cathode material to undergo reversible structural transformation, thus successfully demonstrating a method by which to improve the performance of rechargeable batteries comprised of more globally abundant materials. – Mary Agner

See: M.M. Rahman^1,2, H. Kim³, M. Chancey³, V. Thampey⁴, A. Hu¹, L. Li⁵, L. Ma⁶, E. Hu⁶, S. Sainio⁴, D. Nordlund⁴, S. Hwang⁶, Y. Wang³, X-M. Bai¹, F. Lin^1,7, “Defect formation and microstructure tuning via proton irradiation to control electrochemical and phase reversibility in layered battery materials,” J. Mater. Chem. A, 2026, 14, 5106-5114 (2026)  https://doi.org/10.1039/D5TA05304H

Author affiliations: ¹Virginia Tech; ²Oak Ridge National Laboratory; ³Los Alamos National Laboratory; ⁴SLAC National Accelerator Laboratory; ⁵Argonne National Laboratory; ⁶Brookhaven National Laboratory; ⁷Brown University.

This work was supported by The Thomas F. and Kate Miller Jeffress Memorial Trust, Bank of America, Trustee, and the Jeffress Trust Awards Program in Interdisciplinary Research. The Na cathode was developed based on a project funded by the National Science Foundation (No. CBET-1912885). This research uses beamline 7-BM at the National Synchrotron Light Source II, a US DOE Office of Science user facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract number DE-SC0012704. This work used resources of the Center for Functional Nanomaterials (CFN), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory under Contract No. DE-SC0012704. This work also used beamlines 10-1 and 11-3 at the Stanford Synchrotron Radiation Lightsource, a Directorate of SLAC National Accelerator Laboratory and an Office of Science User Facility. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. This research used beamline 34-ID-C at the Advanced Photon Source; an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The irradiation work was performed at the Center for Integrated Nanotechnologies (CINT) through User Proposal #2019AU0116, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is managed by Triad National Security, LLC for the U.S. Department of Energy's NNSA, under contract 89233218CNA000001.

The U.S. Department of Energy's APS at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. Each year, the APS provides high-brightness X-ray beams to a diverse community of more than 5,000 researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. Researchers using the APS produce over 2,000 publications each year detailing impactful discoveries and solve more vital biological protein structures than users of any other x-ray light source research facility. APS X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC, for the U.S. DOE Office of Science.

The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit the Office of Science website.