## 1 Introduction
In general, a 3D electrode design combines an increased active mass load with a reduced lithium-ion diffusion length, which correlates to an increased energy density and power density, respectively [8]. Several concepts that are based on micro- and nanostructured electrode architectures were proposed for 3D micro-batteries, which could potentially double the energy density by fully utilizing the limited available space [16; 17; 18]. Micro-structuring is a modified approach for nano-sized active material particles. Thereby, the particle itself is not changed, but the particle-electrode-structure is adapted. This can be done by the introduction of 3D electrode architectures while using laser ablation of compact or composite cathode and anode materials [15; 19; 20; 21; 22; 23]. Hereby, a change of the electrode manufacturing process is not necessary. In addition, it is easier to scale-up the process of generation of 3D structures for large footprint areas and layer thicknesses (\(\geq\)100 \(\upmu\)m), which are significantly beyond state-of-the-art batteries. Laser structuring can improve the battery lifetime, cycle stability, and high rate capability. The structuring of the current collector foils can improve the electrode film adhesion, which is a critical aspect for high energy and thick film electrodes [24; 25; 26]. With the direct structuring of thick and thin film electrodes, KIT introduced a new battery concept for achieving large areal energy capacities and power densities [14; 27]. In the case of lithium-ion battery manufacturing, laser processes are already applied for electrode cutting. A high cutting edge quality with no film delamination can be achieved. No tool wear occurs in comparison to mechanical punching and, thus, an exchange of the cutting tool is not necessary [23]. The limit cases of laser processing can be described by either a thermally-driven treatment or a cold laser ablation. Both scenario types could find application in battery manufacturing. For example, the pure laser annealing of compact thin film electrodes was developed as versatile tool for adjusting battery-active crystalline phases [28; 29; 30]. On the other side, cold ablation by ultrafast laser direct writing could be applied to create advanced 3D electrode architectures. It is worth mentioning that, besides improving lithium-ion diffusion kinetics, a tremendous increase in wettability of composite anode and cathode materials with liquid electrolyte can be realized by 3D structured electrodes. It was shown that 3D patterns in electrodes act as capillary structures, which enhances the wettability, reduces cell storage efforts, and improves the electrochemical cell performances [15]. Hereby, a main issue is the laser process up-scaling with respect to large electrode footprint areas, e.g., for batteries in pouch cell design and the laser processing speed, which should be adapted to the standards in battery manufacturing and coating technologies for lithium-ion cells [23]. In this work, ultrashort laser processing was applied to create 3D surface structures in electrodes that were made of LiCoO\({}_{2}\) rich cathodes. Appropriate laser parameters were used to obtain a structure depth within the electrode thickness. An enhanced wetting can be obtained for this dimension [15]. Subsequently, laser-structured cathodes were assembled in Swagelok(r) cells and the capacity retention during galvanostatic cycling (GC) while using different current rates (C rates) were investigated and compared to cells with unstructured cathodes. To compare the lithium-ion transport properties of the cells with different types of cathodes, chemical diffusion coefficients were determined by galvanostatic intermittent titration technique (GITT) as a function of state-of-charge (SOC).