Connecting battery cells by aluminium ribbon bonding using laser micro welding

Abstract

Battery technology is the basis for the electrification of transportation and the key to a sustainable mobility future. Laser ribbon bonding combines the benefits of a conventional wire bonder and laser micro welding by taking advantage of both the automatic ribbon supply and the robustness of a laser welding process. The key technology to use laser welding for ribbon bonding with high robustness is the use of high brightness fiber laser sources which allows smaller laser spot sizes and high quality keyhole welding. However keyhole welding always produces small seam widths and thus small interconnection cross sections. Spatial power modulation – a linear feed with superposed circular motion – is used to first enlarge the weld width and second to control melt dynamics in laser welding of aluminium and copper materials. By varying additional parameters the weld geometry can be further designed to minimize the contact resistance of the connection area. In addition a temporal power modulation avoids heat accumulation at the edges of the weld as well as it increases the conformity of the weld depth. The presented work contains test results of laser bonding 300 µm thick aluminium ribbons to aluminium usually used for prismatic battery cells. For laser micro welding of the ribbons spatial power modulation is used and the effect on the welding result is presented. As a conclusion the limits of the welding process are pointed out and advice for further investigation is given.