Department Interface Design

Hard XAS for probing bulk processes in coin cells

Probing bulk redox by operando hard XAS

•The modified coin cell with a Kapton window allows for probing bulk redox reaction by hard XAS in operating conditions.

•Example: Study of the Na intercalation into the anatase structure of TiO₂

•Sodiation proceeds with amorphization of the anatase TiO₂ during the first dis/charging  cycle. 0.6 Na+ ions are intercalated in total per unit formula (0.2 irreversible, 0.4 reversible)

•Desodiation leads to the distortion of the octahedral structure towards a five-fold coordinated structure.

1.Pristine: Typical anatase features (peaks A1, A2, A3, B)

2.1st Sodiation: Main edge shift (Ti^4-x) and dissapareance of anatase features

3.1st Desodiation: Edge shift to higher energies and pre-edge peaks intensity increases

4.After first sodiation: Reversible spectral changes

15 nm NP of TiO2 + PVDF + C65 carbon black  WE , Na metal CE, 1M NaClO4  in EC/PC 1:1

you can find more information in this paper:

A. Siebert, X. Dou, R. Garcia-Diez, D. Buchholz, R. Félix, E. Handick, G. Greco, I. Hasa, R.G. Wilks, S. Passerini, M. Bär, Monitoring the Sodiation Mechanism of Anatase TiO2 Nanoparticle-Based Electrodes for Sodium-Ion Batteries by Operando XANES Measurements, ACS Applied Energy Materials, 4 (2021) 164-175.https://doi.org/10.1021/acsaem.0c02025