Toward the flexible production of large-format lithium-ion batteries using laser-based cell-internal contacting

Lithium-ion battery cells are used for energy storage in many industrial sectors, such as consumer electronics or electromobility. Due to the diversity of these applications, the demand for tailored battery cells is increasing. Consequently, the technical development of the cells leads to numerous coexisting cell variants. Examples of such variants are altering cell materials, formats, and capacities. Different target capacities can be realized by changing the geometrical dimensions of the individual electrodes or the number of electrodes in the cell cores. The increasing quantity of variants poses challenges within battery cell manufacturing, such as the need to adapt the process parameters for the cell-internal contacting of a higher number of electrode sheets in the cell stack. Each new cell variant currently requires elaborate experimental parameter studies for its manufacture. An approach for selecting suitable process parameters for laser-based cell-internal contacting in terms of a modification of the cell properties is presented in this paper. A model was built to determine the weld depth in copper sheets using a millisecond pulsed laser welding strategy. The process parameters for welding stacks of electrode sheets to an arrester tab were calculated on the basis of this model. The necessary weld depth in the arrester tab for achieving suitable mechanical properties of the cell-internal joint was considered. The presented approach was validated by welding different numbers of foils to an arrester tab and varying the thickness of the foils. It was shown that the experimental effort for the selection of the process parameters for laser-based contacting can be reduced significantly.