Process upscaling of laser-structured thick-film electrodes in high performance Li-ion batteries

• Applicant: Professor Dr. Wilhelm Pfleging
• Subject Area: Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 519141407

The significant improvement in fast charging capability and the increase in energy and power density of Li-ion batteries (LIB) is one of the central challenges in battery development today. In addition to new material combinations, approaches about improving lithium-ion diffusion kinetics, cycle stability and the mechanical stresses generated are also being investigated. With a suitable ultra-short pulse (USP) laser structuring of the electrodes, both issues can be addressed and thus significant increases in performance in terms of high-current capability and lifetime can be achieved. The USP structuring of the electrodes significantly reduces the tortuosity of the lithium-ion diffusion paths, which leads to an increase in performance and lifetime, especially at high charging/discharging currents. This applies in particular to graphite-based electrodes, which have a pronounced directional dependency of the Li diffusion due to the particle or basal plane orientation in the electrode. The combination of "enlargement of the active surface", "reduction of the compressive stress" and "adaptation of the material design" should enable the realization of an electrode architecture optimized in terms of layer thickness and layer composition with regard to the respective application scenario. The basic feasibility of USP laser structuring in the roll-to-roll (R2R) process has already been successfully demonstrated at KIT and verified in pouch cells (TRL 5). However, in order to achieve TRL 7 and thus be able to represent a real implementation of the electrode structuring in battery production with high line speeds (> 30m/min), enormous demands are placed on the further development of the system technology. The upscaling will be investigated in cooperation with the partner Fraunhofer ILT, which has developed technologies and systems to increase the productivity of ultrashort pulse lasers using multi-beam approaches and ultrafast scanners. As a result, laser power classes of more than 1 kW can be addressed, so that economical and competitive manufacturing technologies can be achieved. The basis of these further developments is a multi-beam scanner system with 256 partial beams that was developed at the FhG-ILT and has already been industrially tested. This beam parallelization enables the electrodes to be processed simultaneously on 256 periodically arranged partial beams, which leads to a 200-fold increase in processing speed compared to processing using a single laser beam. For the upscaling of the electrode structuring on an electrode width of up to 30 cm with a structure spacing in the range of approx. 200 μm, an industrial system is set up and evaluated using established battery materials (NMC622 vs graphite) with areal capacities up to 4mAh/cm2.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: EAS Batteries GmbH; MOEWE Optical Solutions GmbH; Pulsar Photonics GmbH
• Cooperation Partner: Professor Dr.-Ing. Arnold Gillner