Digital manufacturing in laser powder bed fusion of aluminium alloy safety feature for EV battery cell

Abstract

Recently, a new way to produce prismatic Li-ion battery cell’s lid part for Battery Electric Vehicles (BEV) was presented, with integrated cell thermal management, based on the Laser Additive Manufacturing (LAM) method. In the solution, the safety vent protects the battery cell from unpredictable explosions caused by the increasing internal pressure. Additive manufacturing allows integrating the feature to the cell lid part and significantly decreases the process steps in manufacturing and increases the production efficiency. Aluminium powder materials for the used Laser Powder Bed Fusion (LPBF) method have relatively high tensile strength, which causes the need for minimum layer thickness for the safety vent. Reliability of producing such a thin layer as a gas tight structure is challenging and several procedures were studied. Material with lower tensile strength and higher elongation ability was tested during the second phase. The challenge is to produce such a thin wall thickness, which breaks at the pressure level of one MPa and opens the valve. The design is based on FEM analysis with constant equivalent strain theory to optimize safety vent dimensions. The pressure test was performed to measure the rupturing pressure of the thin aluminium LPBF layer as materials in normal mode and in annealed mode. The constant equivalent strain theory for estimate rupture pressure was in fine agreement with the experimentally measured ones, even with a maximum error rate. The results show that the manufacturing method is possible for such automotive mass production parts and when comparing different stacking strategies, it showed a great influence in the productivity of such parts’ production.