We are excited to share our newest paper in Nature Materials where we study surface lithium ion mobility in a solid-state electrolyte using extreme ultraviolet second-harmonic generation spectroscopy (XUV-SHG)! In this work, we investigated a prototypical solid-state electrolyte using linear and nonlinear extreme ultraviolet spectroscopies.
By leveraging the surface sensitivity of XUV-SHG, we obtained a direct spectral signature of surface lithium ions, showing a distinct blueshift relative to bulk absorption spectra. First-principles simulations attributed the shift to transitions from the lithium 1s state to hybridized Li-s/Ti-d orbitals at the surface. Our calculations further suggest a reduction in lithium interfacial mobility due to suppressed low-frequency rattling modes, which is the fundamental origin of the large interfacial resistance in this material. Our findings pave the way for new optimization strategies to develop these electrochemical devices via interfacial engineering of lithium ions.
This work was done in collaboration with CISI researchers from UC Berkeley and UC San Diego alongside external collaborators from the University of Tokyo, Argonne National Laboratory, and the University of Nevada Las Vegas. The measurements were conducted at the SACLA free-electron laser at RIKEN in Japan.
Open-access to the research paper at Nature Materials:
https://www.nature.com/articles/s41563-023-01535-y
College of Chemistry press release:
https://chemistry.berkeley.edu/news/search-nonflammable-lithium-battery-technology