Precise 3D maps of arbitrary elements
The copper current collector is a thin copper foil that serves as a substrate for the anode and collects electrons to lead them to the negative terminal. In lithium-metal batteries, lithium can diffuse into the copper current collector during the charge and discharge cycle. “However, it was previously unclear where the lithium ions accumulate,” explains Li. “It is difficult to detect lithium in copper because of a lack of analytical methods for tracing highly reactive and lightweight lithium.”
The research team utilized atom probe tomography, which allows the precise, three-dimensional mapping of any element with sub-nanometer resolution. This revealed that, after just one charge/discharge cycle, lithium is initially incorporated at the grain boundary and boundary junction of the copper foil. After three cycles, the surface of the copper foil becomes nanocrystalline and oxidized. The resulting defects further bind lithium and oxygen beneath the surface, leading to degradation of the copper current collector.
Lithium loss in new battery technology previously overlooked
“All this information is important for understanding how the current collector influences the performance of lithium batteries of the future,” explains Li; lithium-metal batteries (LMBs), and recently zero-excess or anode-free LMBs are seen to be the next significant steps on the path toward even higher energy densities. These far surpass the currently prevailing lithium-ion technology. “The general assumption about zero-excess LMBs is that lithium does not diffuse into or interact with the copper current collector,” says Li. “the loss of lithium to the copper collector has been largely overlooked until now, in discussions about the performance degradation of LMBs.”
Advanced Energy Materials
Observational study
Not applicable
Atomic-Scale Tracing of Lithium Trapped in Copper Current Collectors
10-Jul-2026