Spike laser welding for the electrical connection of cylindrical lithium-ion batteries

The transition toward renewable energies implicates decentralized and time-dependent ways of energy generation. To compensate for the resulting fluctuation in energy supply, local storage systems are necessary. Larger systems may consist of thousands of battery cells. Therefore, the reliable interconnection between the individual battery cells is a prerequisite for the economic production of these systems. Laser beam welding is a suitable process to contact batteries. Due to the high requirements regarding the heat input and the reproducibility of the joining process, thorough investigations are necessary. Experiments on pulsed laser beam welding of cylindrical lithium-ion cells were conducted by applying a strategy named spike welding. Suitable process parameters were identified and tested with regard to their impact on the reproducibility of the welded joint. For the measurement of the heat input during the welding process, the temperature rise inside the battery case was determined. Results indicate that a pulsed welding strategy with discrete weld seams is preferable in order to minimize the heat input and to maximize the flexibility during the welding process. Finally, battery cells were contacted and electrical properties of the cell compound were determined. The pulsed laser welding process proved to be superior compared to conventional resistance spot welding since no negative influence on the electrical properties could be observed and the heat input was kept at a minimum.