Lithium Spatial Distribution and Split-Off Electronic Bands at Nanoscale V2O5/LiPON Interfaces

• Published in: ACS applied energy materials 2023-05, Vol.6 (9), p.4538-4548
• Main Authors: Levy, Zach, Ferrari, Victoria Castagna, Rosas, Pablo, Walker, Mitchell J., Duddella, Kalpak, Haseman, Micah, Stewart, David, Rubloff, Gary, Brillson, Leonard J.
• Format: Article
• Language: English
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.2c03683

A combination of depth-resolved cathodoluminescence spectroscopy (DRCLS) and X-ray photoemission depth profiling (XPS) measured the pronounced changes in both the electronic density of states and lithium composition near the nanoscale Li x V2O5/LiPON interface. DRCLS studies of electrochemically lithiated bare V2O5 and the sputter-deposited V2O5 plus LiPON overlayer electrochemically lithiated in stages both showed that in the bulk the luminescence intensity of the “split-off” hybridized bonding density of states was anticorrelated with XPS-measured Li content, decreasing as the Li content increased. However, the LiPON overlayer was found to modify the band structure of the underlying Li x V2O5 (LVO) to a depth of at least 30 nm beneath the V2O5 interface. DRCLS spectra near the electrochemically lithiated LiPON/LVO interface showed a significant intensity of the split-off band, implying a low Li content. However, XPS depth profiling revealed a pronounced negative gradient of Li extending from a maximum Li content at the intimate LiPON boundary to its lowest content of ∼30 nm into the V2O5 in the same region, indicating a strong interaction between band structure and Li electrochemical potential near this heterojunction. These results provide evidence for substantial effects on the local band structure near an electrolyte/cathode interface and insights into the electrochemical interface behavior of solid-state batteries in general.