ANALYSIS: E-MOBILITY g


– the productivity of the processing, the complexity of the defined geometry or the quality of the joint. For this reason, a combination of process acceleration and high- performance systems will be necessary to process at higher area rates. To ensure the surface quality under industrial manufacturing conditions, an efficient quality assurance for the pre-treatment and the joining process is necessary. Integrable measuring systems, whose inline measurements enable process control, are an elegant approach in this case.


Additive manufacturing using laser metal deposition (LMD) with coaxial wire feeding In science and industry, additive manufacturing of metals to apply protective coatings, to build up complex, lightweight structures and to repair worn or damaged components, is currently the subject of intensive R&D. For e-mobility, the ability to produce lightweight structural components is of particular interest.


Commonly, powder or wire


is continuously and locally fed to a substrate into a laser- induced molten pool. Areas of application are still emerging through specialised additive manufacturing processes, such as wire-based coaxial LMD, as shown in figure 2b. One advantage of using wire as feedstock is a 100 per cent usage of the material. Additionally, the effort required to protect the operator and the environment is significantly reduced compared to a powder- based LMD process. Recent developments in laser optics that enable coaxial wire feeding in the centre of an annular laser beam profile14-16


represent


a relevant step towards an industrial relevance of wire- based LMD.


One of the main challenges of the process is that the implementation of a new system, as well as changes in influencing parameters, for example, through the use of


26 LASER SYSTEMS EUROPE AUTUMN 2021


Figure 3: (top) a battery pack demonstrator welded using green laser radiation and (bottom) laser-contacted cell-cab of a lithium-ion battery


a different material, require extensive parameter studies to achieve a stable process. For this reason, suitable closed- loop control approaches are currently an important part of R&D in LMD processes17


. In


this context, the qualification of sensor technologies for the real-time monitoring of process variables is crucial. Considering the TRL


evaluation, theoretical fundamentals of the beam- matter interaction were investigated, along with feasibility studies of the process. Further investigations are needed to increase the process reliability, as well as the automation of LMD and to integrate prototypes into a series of applications to reach a standardised industrial use.


Battery cell and module production Within the context of battery production, laser materials processing can be used as a versatile tool to improve production steps or modify components. In lithium-ion cell-based battery storages, up to several thousand electrical contacts have to be manufactured18


. LBW – with its advantageous


properties such as a high degree of automation, a low


“Laser materials processing is indispensable for e-mobility. Long-term it will be essential to production”


cycle time and a precise local energy input – is a promising technology19


. However,


LBW of highly electrically and thermally conductive materials, such as aluminium and copper, is challenging20


sources, challenging material combinations and an inline quality assurance need to be investigated more deeply. Additionally, laser processes


are promising with respect to the cell-internal contacting of LIBs19


. In this production step,


an arrester tab is welded to the uncoated parts of the metallic current collector foils of the electrodes, as shown in figure 3b. The weld seam ensures the mechanical and electrical connection. Commonly, ultrasonic welding is used for joining the electrodes. In comparison, laser welding enables novel product designs by a higher degree of geometric flexibility and thus improved seam properties23


. LBW, with its . In


several publications, the high reflectivity of copper using near-infrared laser radiation and the advantages of laser beams with wavelengths in the visible spectrum were discussed21, 22


high welding speed, contributes to an industrially-scalable process. In previous studies, laser


. A battery pack


demonstrator welded using green laser radiation is shown in figure 3a. From the evaluated TRL it can be concluded that LBW for the joining of LIBs and cell connectors is about to achieve the technological maturity to enter serial or mass production. However, process windows for novel beam


beam sources emitting in the infrared and visible wavelength spectrum, as well as different welding strategies, for example, CW and pulsed welding, were investigated24, 25


. The


evaluation of the TRL showed that further investigations on suitable process parameters for a varied number of foils and the analysis of the thermal cell load during joining have to be carried out. Verifying the technology on large-format


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Geiger et al.


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