Fiber laser welding properties of copper materials for secondary batteries

Abstract

Secondary battery is composed of four main elements: cathodes, anodes, membranes and electrolyte. The cathodes and the anodes are connected to the poles that allow input and output of the current generated while the battery is being charged or discharged. In this study laser welding is conducted for 40 sheets of pure copper material with thickness of 38 μm, which are used in currently manufactured lithium-ion batteries, using pulse-wave fiber laser to compare welded joint to standard bolt joint and to determine optimum process parameters. The parameters, which has significant impact on penetration of the pulse waveform laser to the overlapped thin sheets, is the peak power while the size of the weld zone is mainly affected by the pulse irradiation time and the focal position. It is confirmed that overlapping rate is affected by the pulse repetition rate rather than by the pulse irradiation time. At the cross-section of the weld zone, even with the increased peak power, the width of the front bead weld size does not change significantly, but the cross-sectional area becomes larger. This is because the energy density per pulse increases as the peak power increases.