Suppressing Lithium Migration in a Carbon Fiber Negative Electrode During Atom Probe Tomography Analysis.

Carbon fibers can play dual roles, carrying mechanical load and hosting lithium (Li) simultaneously in multifunctional devices called structural batteries. It is essential to gain a detailed understanding on the interaction between Li and carbon fibers on the nanoscale. Atom probe tomography (APT) can potentially reveal individual Li and C atoms. However, lithiated carbon fibers experience massive Li migration once exposed to the electric field in the APT instrument. We show that a few nanometers of a chromium (Cr) coating on APT specimens can shield the electric field and suppress the massive Li migration. The related effects of the Cr coating, such as introduction of oxygen, enhanced mass resolving power of the mass spectrum, and increased portion of single hits, are also discussed.