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Breaking Down a Complex System: Interpreting PES Peak Positions for Cycled Li-Ion Battery Electrodes
journal contribution
posted on 2017-11-16, 00:00 authored by Fredrik Lindgren, David Rehnlund, Ida Källquist, Leif Nyholm, Kristina Edström, Maria Hahlin, Julia MaibachPhotoelectron
spectroscopy (PES) is an important technique for
tracing and understanding the side reactions responsible for decreasing
performance of Li-ion batteries. Interpretation of different spectral
components is dependent on correct binding energy referencing, and
for battery electrodes, this is highly complex. In this work, we investigate
the effect on binding energy reference points in PES in correlation
to solid electrolyte interphase (SEI) formation, changing electrode
potentials, and state of charge variations in Li-ion battery electrodes.
The results show that components in the SEI have a significantly different
binding energy reference point relative to the bulk electrode material
(i.e., up to 2 eV). It is also shown that electrode components with
electronically insulating/semiconducting nature are shifted as a function
of electrode potential relative to highly conducting materials. Further,
spectral changes due to lithiation are highly depending on the nature
of the active material and its lithiation mechanism. Finally, a strategy
for planning and evaluating PES experiments on battery electrodes
is proposed where some materials require careful choice of one or
more internal reference points while others may be treated essentially
without internal calibration.