Design of integrated safety vent in prismatic lithium-ion battery

Safety vent is crucial to protect its users from unpredictable explosions caused by the increasing internal pressure of lithium-ion batteries. In order to prevent the explosion of the battery, a safety vent rupture is required when the internal pressure reaches a critical value. In conventional manufacturing, the cap plate and safety vent are fabricated separately and are then welded. In the current study, a manufacturing process, which includes backward extrusion and coining process, is suggested to produce an integrated safety vent, which also has the benefit of increasing the production efficiency. In order to design a backward extrusion process, an upper-bound analysis, which assumed a condition for the end of stroke, is used for the prediction of the forming load. Furthermore, the shape parameters of the coining process were determined as the stress of the notch part with the analytical model, which considers the stress concentration factor. The rupture test was performed to measure the rupture pressure of the safety vent. The results satisfied the required pressure of 8.5±0.5 kgf/cm2. Finally, the results predicted from the analytical models were compared with those of the experiment. It was shown that the predicted rupture pressure was in good agreement with the experimentally measured ones, with a maximum error rate of 3.8 %.