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

锂离子电池（LIB）快速充电能力的显著提高以及能量和功率密度的提高是当今电池发展的核心挑战之一。除了新材料组合，改善锂离子扩散动力学、循环稳定性和产生的机械应力的方法也在研究中。采用合适的超短脉冲（USP）激光电极结构，可以解决这两个问题，从而在大电流能力和寿命方面显著提高性能。电极的USP结构显著减少了锂离子扩散路径的扭曲，从而提高了性能和寿命，特别是在高充放电电流下。这尤其适用于石墨基电极，由于电极中的颗粒或基面取向，石墨基电极具有明显的Li扩散方向依赖性。“扩大活性面”、“降低压应力”和“适应材料设计”相结合，应能够实现针对各自应用场景在层厚度和层组成方面进行优化的电极结构。在卷对卷（R2R）工艺中USP激光结构的基本可行性已经在KIT上成功演示并在袋状电池（TRL 5）中得到验证。然而，为了实现TRL 7，从而能够在电池生产中以高线速度（> 30m/min）代表电极结构的真正实现，对系统技术的进一步发展提出了巨大的要求。升级将与合作伙伴Fraunhofer ILT合作进行研究，该公司已经开发了使用多光束方法和超快扫描仪提高超短脉冲激光器生产率的技术和系统。因此，可以解决超过1千瓦的激光功率等级，从而实现经济和有竞争力的制造技术。这些进一步发展的基础是FhG-ILT开发的具有256个部分波束的多波束扫描仪系统，并且已经进行了工业测试。这种光束并行化使电极能够在256个周期性排列的部分光束上同时进行处理，与使用单个激光束相比，处理速度提高了200倍。对于电极结构的升级，电极宽度高达30厘米，结构间距在大约的范围内。200 μm，使用面积容量高达4mAh/cm2的现有电池材料（NMC622 vs石墨）建立并评估了工业系统。

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.