In-situ X-ray absorption spectroscopy analysis of capacity fade in nanoscale-LiCoO2

The local structure of nanoscale (similar to 10 similar to 40 nm) LiCoO2 is monitored during electrochemical cycling utilizing in-situ X-ray absorption spectroscopy (XAS). The high surface area of the LiCoO2 nanoparticles not only enhances capacity fade, but also provides a large signal from the particle surface relative to the bulk. Changes in the nanoscale LiCoO2 metal-oxide bond lengths, structural disorder, and chemical state are tracked during cycling by adapting the delta mu (Ay) technique in complement with comprehensive extended X-ray absorption fine structure (EXAFS) modeling. For the first time, we use a AL/ EXAFS method, and by comparison of the difference EXAFS spectra, extrapolate significant coordination changes and reduction of cobalt species with cycling. This combined approach suggests Li-Co site exchange at the surface of the nanoscale LiCoO2 as a likely factor in the capacity fade and irreversible losses in practical, microscale LiCoO2. Published by Elsevier Inc.