stage of development and in general it is not feasible for state- of-the-art electrodes.


At the Karlsruhe Institute of Technology (KIT), a new process for the generation of 3D electrode designs has been created by developing two processes; 1.) Laser-assisted self-organized structuring (Fig. 1) and 2.) direct structuring of tape cast electrodes [1-3]


.


In each case, the laser structured electrodes exhibit a significant improvement in liquid electrolyte wetting as well as in electrochemical performance after laser treatment. During the manufacturing process of lithium-ion cells, liquid electrolyte filling is a cost- and time-consuming process. Insufficient electrolyte wetting in turn can lead to unexpected cell failure under challenging cycling conditions. At KIT, a cost efficient laser-based technology for the realization of 3D architectures in thick-film tape-cast electrodes was developed to accelerate the wetting process and to also shorten the time-span for cell manufacturing (Fig. 2).


In addition, an improved cell operation with extended life- time and increased capacity retention at high charging and discharging currents could be achieved. For the development of advanced laser processes in battery manufacturing, a complete lithium-ion cell manufacturing process cycle has been built-up which includes electrochemical characterization of lithium-ion cells (Fig. 3).


consist of active material, carbon black, graphite and binder. All lithium-ion cells were assembled either in an argon-filled glove box or in a dry room. An ultrafast fiber laser system (Tangerine, Amplitude Systèmes, France), a ns fiber laser system (YLPM, IPG Photonics, Germany), or an excimer laser system (ATLEX- 1000-I, ATL Lasertechnik GmbH, Germany) were used to manufacture 3D architectures into the thin or thick film electrode layers.


The Results In general, electrolyte filling of lithium-ion cells is realized by time and cost consuming vacuum and storage processes at elevated temperatures. Nevertheless, by applying state-of-the- art electrolyte filling processes, insufficient wetting of electrode and separators is one drawback resulting in a certain production failure rate accompanied with a lowered cell capacity or a reduced cell life-time. Laser structuring has been developed for the formation of capillary micro-structures in thick film tape- cast electrodes which resulted in the acceleration of electrolyte wetting in comparison to unstructured electrodes (Fig. 4). The removal of the complete electrode material from the ablation zone delivers the most efficient capillary transport [4]


.


Figure 3. Process chain for cell fabrication and testing including laser processing of battery materials


(C) and LiFePO4


Experimental Setup Different types of electrode materials were already investigated such as LiCoO2 doped SnO2


(FTO), Li(NiMnCo)O2 (LCO), LiMn2 O4 (LMO), SnO2 (SnO), fluorine (NMC), silicon (Si), graphite (LFP). Thin films as well as thick films were applied. Thick film electrodes are composite materials which (Continued on page 14) www.lia.org 1.800.34.LASER 1.800.34.LASER 13


For ns-laser radiation (λ =1064 nm, pulse length 200 ns) the laser beam energy is absorbed at the material surface and,


Figure 4. Rapid wetting of laser structured electrodes


For the formation of capillary structures, ns-laser ablation as well as ultrafast laser processing was investigated.


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