Slurry rheology is influenced by the size, shape, concentration
and charge of dispersed components, hence it is important to
optimize electrode particle properties not just for their individual
electrochemical performance but for the electrode manufacturing
process as a whole 3 . Ultimately it is the performance, and safety, of
the final battery cell which is of critical importance. The most common
tool for measuring the general rheology of battery slurries is a
rotational rheometer, such as Kinexus, although a capillary rheometer
such as the Rosand RH7 or RH10 may better represent the electrode
coating process 4 .
So, what happens to the electrode structure during initial formation,
as well as the repeated charge/discharge cycling of the fabricated
The manufacture of Li-ion battery electrodes is a multi-step process
with each step having potential to influence the electrochemical
performance of the finished device 2
battery cell? The repeated transfer of charge-carrying ions in and
out of the electrode lattice puts strain on the cell structure and can
induce unwanted phase changes, even more so if fast charging and/
or discharging is required. Deterioration in performance is most
commonly due to the build-up of defects within the electrode which
hinders ion mobility. The mechanism of these processes on the
electrode structure can be studied with in operando XRD, using hard
X-rays (Mo or Ag Kα) capable of penetrating a battery cell, ideally (but
not limited to) a pouch cell 5 .
It is then possible to correlate variations in the crystallographic
structure of the electrodes with the amount of Li incorporated in
to them. The spatial resolution of in operando transmission XRD
(approx. 1 mm) also makes it an ideal tool for probing localized wear,
since cells close to the connector tend to degrade faster than those
further away. It can also identify areas within the cell that are not
functioning properly due to ageing or incomplete wetting with
electrolyte. Empyrean equipped with the GaliPIX 3D detector is ideally
suited for this application since it offers the highest resolution data in
the shortest possible time frame.
References
1) Julien, C.M., Mauger, A., Vijh, A., Zaghib, K.; Lithium Batteries: Science and Technology; Springer: Heidelberg, Germany, 2015
2) Bockholt, H. et al. ‘The interaction of consecutive process steps in the manufacture of lithium-ion battery electrodes with regard to structural and
electrochemical properties’; Journal of Power Sources 325 (2016) 140-151
3) White paper: Exploring the impact of particle characteristics on suspension rheology
4) White paper: Establishing an analytical toolkit for the optimization of Li-ion battery electrode manufacturing
5) Application note: High-quality in operando X-ray diffraction analysis of pouch bag lithium-ion batteries