The registration of electric vehicles continues to increase worldwide. But the aging of the batteries installed in them poses challenges for the industry. An international team of researchers has now decoded at the atomic level why batteries lose performance. The focus is on a component that was previously considered passive.
In June 2026, electric cars were the best-selling drive type for new car registrations in Germany for the first time. Although in practice vehicles can cover several hundred thousand kilometers on a single battery pack, the storage capacity decreases over time. Scientists from the Ruhr University Bochum, the Helmholtz Institute Ulm and the Karlsruhe Institute of Technology recently examined this aging process in more detail. They published their results in the journal Advanced Energy Materials.
The focus of the research was the current collector of batteries, which is made of copper foil. In the past, engineers only viewed this as an inert conductor track, i.e. one that had no or only minimal chemical reactions.
The new finding: When charging and discharging, lithium ions migrate through the cell, but accumulate on the interfaces of the copper foil after the first cycle. Like tiny microscopic traps, the particles get caught in defects caused by mechanical stress in the material. As a result, the lithium ions remain permanently in the film and are no longer available for energy storage.
How the power loss of batteries occurs at the atomic level
The scientists visualized the structural damage using atomic probe tomography. Using this process, they produced a wafer-thin tip of material that is a thousand times thinner than a human hair. This made it possible to create three-dimensional maps of individual atoms.
After just three charging cycles, there were visible material changes in the top 100 nanometers of the copper foil. The surface crystallized and oxidized. After eight charging cycles, a significantly higher amount of lithium was trapped in the copper than at the start of the process.
In addition to lithium, oxygen and carbon also penetrate the metal. In particular, the oxygen binds additional lithium, which increases the decomposition of the current collector. Tong Li from the Ruhr University Bochum highlighted the significance of the discovery:
Understanding these processes is of great importance for anode-free batteries of the future. However, it was still unclear where exactly the lithium ions were stored. Lithium in copper is difficult to detect due to a lack of analytical capabilities to track highly active and lightweight lithium.
New perspectives for anode-free energy storage
This effect is particularly critical for anode-free systems, so-called zero-excess batteries. Since these battery types work with extremely low lithium reserves, any loss directly leads to a shorter lifespan. Nevertheless, it is precisely these storage media that have the potential for significantly higher energy density.
However, the new findings could significantly increase the range of electric vehicles. A loss-free system also plays a crucial role in the global storage of electricity from wind and solar systems.
Although the study does not yet provide a ready-to-use market solution, the deeper understanding provides a foundation for future developments. Through targeted coating of the copper foil, novel material modifications or adapted charging processes, it may be possible to prevent the ions from getting stuck in the future.
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