Picosecond laser structuring of graphite anodes—Ablation characteristics and process scaling

Abstract

Laser structuring of graphite anodes substantially improves the electrochemical performance of lithium-ion batteries by facilitating lithium-ion diffusion through the electrode coatings. However, laser structuring is not yet established in industrial battery production due to limited knowledge of its ablation behavior and a low processing rate. This publication addresses these issues with a combination of experimental and theoretical approaches. In a comprehensive process study with picosecond pulsed laser radiation, the influence of various laser parameters on the obtained structure geometries, i.e., the hole diameters and depths, was examined. Wavelengths of 532 and 355 nm combined with pulse bursts and fluences of approximately 10 J cm−2 eventuated in favorable hole geometries with a high aspect ratio. Compared to singlebeam laser structuring, a nearly tenfold reduction in the processing time was achieved by beam splitting with a diffractive optical element without compromising structure geometries or mechanical electrode integrity. The experimental findings were used to model the scalability of electrode laser structuring, revealing the significant influence of the hole pattern and distance on the potential processing rate. Ultrashort pulsed laser powers in the kilowatt regime were found to be necessary to laser-structure electrodes at industrial processing rates resulting in estimated costs of roughly 1.96 $/kWh. The findings support the industrialization of laser electrode structuring for commercial lithium-ion battery production.