Impact of NMC 811 electrode porosity on GHz burst laser ablation characteristics

Significant improvements in lithium-ion battery performance such as lifetime, fast charging, and high-power capability can be achieved by using three-dimensional (3D) electrode architectures in comparison to state-of-the-art two-dimensional (2D) electrodes. To establish such an advanced 3D electrode concept, high-power ultrafast laser ablation has proven to be a precise and efficient approach. The production of 3D electrodes with laser ablation needs to be integrated into an already established and complex processing chain for battery production. This requires efficient coordination and harmonization of these processing steps with regard to diverse aspects in electrode manufacturing such as the selected composite material system, its targeted micro- and nano-structures, processing speed, and process reliability. In particular, electrode calendering is an established processing step, which holds great importance as it has a significant impact on the structural properties of the electrode on the micro- and nano-scale, including porosity, composite density, and layer cohesion and adhesion to the current collector. In this study, the impact of laser structuring using GHz bursts on LiNi0.8Mn0.1Co0.1O2 (NMC 811) cathodes with porosities between 10% and 40% is investigated. Distinct ablation characteristics are observed depending on electrode porosity and laser burst length, revealing a clear interplay between both parameters. Shorter bursts significantly increase ablation efficiency for electrodes with higher porosities, whereas for lower porosities, ablation efficiency is higher for longer bursts. Morphological analysis shows that shorter burst lengths lead to minor visible modification, indicating that the ablation process is dominated by binder removal. In contrast, longer burst lengths produce more homogeneous, layer-like surface structures, suggesting an additional temperature-driven contribution due to cumulative heating effects. A processing rate of 1.67 cm2/s is achieved for a burst length of 500 ns at a burst fluence of 20.2 J/cm2, demonstrating the potential for industrial upscaling, for example, by using higher laser power in combination with beam splitting. These results highlight the potential of GHz burst laser ablation for the structuring of 3D lithium-ion battery electrodes and provide a basis for further process optimization.