Article

Surface Sensitive Chemical Imaging of Lithium Materials for Battery Applications by Auger Electron Spectroscopy

Surface Analysis Spotlight: AES

by Juergen Scherer     Senior Staff Scientist

In recent years, the interest in all-solid-state batteries (ASSBs) has been increasing due to their higher safety, energy density, and longer lifespan compared to conventional lithium-ion batteries (LIBs). These advantages make ASSBs promising for applications in electric vehicles (EVs), energy storage devices, wearable devices, among others. However, the internal resistance generated at the interface between the solid electrolyte (SE) and the electrode is a challenge for the practical use of ASSBs as it hinders fast charging and discharging. Several studies have been conducted to reduce the internal resistance through various surface modifications between the SE and cathode, which has led to a significant improvement in Li ion transport during charge and discharge. Despite the numerous studies on the SE/cathode interface of ASSBs, the mechanism behind the increase in interfacial impedance remains unclear.

This study focused on lithium chemical mapping of the cross-section of the SE/cathode interface using Auger electron spectroscopy (AES). This technique provides high spatial resolution information on chemical composition and state. The thickness of the anode, SE, and cathode layers in thin-film ASSBs is usually in the range of a few micrometers, making AES an ideal technique for obtaining chemical maps from solid-solid interfaces. Moreover, AES is more sensitive to changes in the lithium chemical state than X-ray photoelectron spectroscopy (XPS).

It is also well-known that SEs are generally vulnerable to electron beam damage, thus there are few reports on the application of AES in lithium mapping on SEIs.

This research examined electron beam damage on the surface of lithium phosphorus oxynitride (LiPON) as a model SE. The goal was to determine optimum conditions for AES lithium chemical mapping and evaluate the impact of electron beam damage on the LiPON surface. Results showed that the intensity of the Li peak was influenced by the beam energy, electron dose, and sample temperature. Optimal conditions for acquiring lithium maps were at room temperature, using 3 keV electrons with a lower beam current.

Despite challenges associated with lithium mapping using an electron beam, the study was successful in differentiating between the distributions of different chemical states of lithium in the form of LiPON and LiCoO₂. The results provide valuable insights into the lithium chemical distributions at the SE/electrode interface and contribute to a deeper understanding of the behavior of ASSBs at this interface.

Fig.1: SEM image and AES Lithium maps from LiPON/LiCoO₂ cross-section

To explore the latest advancements in Auger Electron Spectroscopy and its application to battery materials, don’t miss the upcoming talk by Dr. Juergen Scherer, titled “Surface Sensitive Chemical Imaging of Lithium Materials for Battery Applications by Auger Electron Spectroscopy.” The presentation will take place on Tuesday, September 23, 2025, at 11:30 AM during the AVS 71 Conference in Charlotte, NC.