FEATURED ARTICLE Laser Processing
BY WILHELM PFLEGING, MELANIE MANGANG, YIJING ZHENG, PETER SMYREK AND JOHANNES PRÖLL
Introduction Thick film anodes and cathodes with thicknesses ranging from 20-300 µm, in state-of-the-art and future lithium-ion cells are complex multi-material systems consisiting of defined material components, grain sizes, porosities and pore size distributions in the micrometer and submicrometer ranges. State-of-the- art cells with pouch cell geometry for high power applications consist of thick film electrode stacks with capacities up to 40-50 Ah.
The development of three-dimensional (3D) cell architectures for electrodes in lithium-ion batteries is a promising approach to overcome problems like 1-dimensional lithium-ion diffusion, inhomogeneous current densities, power losses, high interelectrode ohmic resistances as well as mechanical stresses due to high volume changes resulting from lithium-ion insertion and deinsertion. By applying 3D battery architectures, one can achieve large areal energy capacities while maintaining high power densities at the same time. This feature is important, e.g., for thin film batteries where the lithium-ion diffusion is limited by the thickness of the compact film. A common approach for
Production of Lithium-Ion Batteries
Figure 1. Laser-generated self-organized microstructure in composited electrode cathode material
realization of 3D architectures in electrodes is the structuring of the substrate or current collector. An increased active surface achieved by 3D electrode architectures can induce large areal energy densities. Unfortunately, this approach is in a very early
Figure 2. State-of-the-art processing route for liquid electrolyte filling of lithium-ion cells with time-consuming warm aging (top) and KIT process without warm aging due to laser structured battery materials (bottom)
12 LIATODAY FOCUS: LASERS IN MANUFACTURING MARCH/APRIL 2016
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