S T R U C T U R E O F M A T E R I A L S

S C I E N T I F I C H I G H L I G H T S

1 3 0 H I G H L I G H T S 2 0 2 1 I

PRINCIPAL PUBLICATION AND AUTHORS

Lithium distribution and transfer in high-power 18650-type Li-ion cells at multiple length scales, D. Petz (a,b), M.J. Mühlbauer (b,c), V. Baran (b,d), A. Schökel (b,d), V. Kochetov (a,e), M.Hofmann, (b), V. Dyadkin (f), P. Staron (g), G. Vaughan (f), U. Lienert (d), P. Müller-Buschbaum (a,b), A. Senyshyn (b), Energy Storage Mater. 41, 546-553 (2021); https:/doi.org/10.1016/j.ensm.2021.06.028 (a) Technische Universität München, Garching (Germany) (b) Heinz Maier-Leibnitz Zentrum, Garching (Germany) (c) Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany) (d) Deutsches Elektronen Synchrotron, Hamburg (Germany) (e) Universität Rostock, Rostock (Germany) (f) ESRF (g) Helmholtz-Zentrum Hereon, Geesthacht (Germany)

REFERENCES [1] A. Senyshyn et al., Sci Rep 5, 18380 (2015). [2] M.J. Mühlbauer et al., J. Power Sources 348, 145-149 (2017). [3] M.J. Mühlbauer et al., J. Power Sources 403, 49-55 (2018). [4] D. Petz et al., Batteries & Supercaps 4, 327-335 (2021).

side of the separator. Analysis of the cathode lithiation displayed a more uniform behaviour (Figure 109c), which is attributed to the much weaker susceptibility of the LiFePO4 to local SOC/voltage non-uniformities. Nevertheless, a certain lithium gradient across the electrode thickness was also present in the cathode. The effect was confirmed using operando characterisation of the cathode in a specially designed cell and attributed to the local current density distribution, representing the surface ion flux and reflecting the rates of electrochemical reactions.

It can be concluded that lithium in the Li-ion cell studied is distributed non-uniformly in 3D, where heterogeneities occur on multiple length scales. XRDR and XRD-CT data provide a static snapshot corresponding to the fully-charged state. However, these inhomogeneities are not static but dynamically evolving with the SOC. Further investigations of the complex interplay between different parameters and factors defining battery operation, their interactions on different length scales and their influence on the uniformity of the electrode material are needed. This is important for the development of higher energy- and power-density cells as well as for increasing battery lifetimes.

makes it difficult to study the underlying physics to predict and control the manufacturing process and product quality.

A laser 3D printing machine called the in-situ and operando process replicator (ISOPR, see Figure 110) that works on a synchrotron beamline, has been built to study these ultra-fast dynamics using synchrotron X-ray imaging and diffraction. ISOPR consists of a 200 W laser beam with a scan speed of 4 m/s, and the capability to perform complex multilayer builds. It enables researchers and industrial collaborators to perform 3D printing at a synchrotron beamline whilst monitoring its process dynamics in situ and operando. With beamline ID19 s high-flux and high- brilliance X-rays, ultra-fast imaging was used to unravel

Fig. 110: Schematic of the in-situ and operando process replicator (ISOPR) and (right) a radiograph taken during laser 3D printing at 40 kHz. The radiograph shows the

ability to use a combination of ISOPR and ultra-fast imaging to capture complex process dynamics during

single and multilayer laser 3D printing.

Ultra-fast X-ray imaging of keyhole dynamics during laser 3D printing

Laser 3D printing enables fabrication of complex components by melting powder with a laser beam in a few milliseconds, forming non-equilibrium structures. Beamline ID19 s ultra-fast X-ray imaging captures the mechanisms of microstructure formation, shedding new light on 3D printing.

Laser powder bed fusion (LPBF) is a form of laser 3D printing that enables the fabrication of metallic components with complex geometry that cannot be produced via other manufacturing techniques. The printing process is very complex as it involves laser-matter interaction, multiphase flow, and solidification phenomena, all occurring in 10-3 to 10-6 s. The timescale at which these events take place