Tailoring micro resistance spot welding parameters for joining nickel tab to inner aluminium casing in a cylindrical lithium ion cell and its influence on the electrochemical performance

Abstract In an automotive battery, a large number of individual cells are electrically connected to meet the energy and power requirement. The choice of suitable welding techniques is critical in terms of mechanical strength and electrical contact resistance of the joint. Although soldering, ultrasonic welding and laser welding are the common joining techniques used in lithium-ion cell fabrication, application of resistance spot welding in the manufacturing of lithium-ion battery for electric vehicles is rather limited due to the difficulties in forming large weld nuggets and electrode sticking to the material. In this work, micro resistance spot welding of nickel anode tab to the one side open inner aluminium casing is carried out in an in-house fabricated cylindrical lithium-ion cell. The welding parameters for high electrical conductive nickel-to-aluminium are optimized using the Taguchi design of experiments. The weld joints are assessed by microstructural, mechanical properties and contact resistance characterization. The optimum weld joint shows a well-defined nugget with a shear strength of 338.4 MPa and the electrical contact resistance of 0.052 mΩ. The cell shows high current rate capability and 2 °C increase in the cell temperature at 2C rate. This work paves the way for the application of spot welding technique for tab welding in one side open casing for the manufacturing of lithium-ion cell.