Grant: Collaborative Research and Development Grants

High energy density, low self-discharge, and portability characteristics of automotive Li-ion battery packs make them an indispensable power source that is broadly used in electric, hybrid or plug-in-hybrid electric vehicles. An automotive battery pack consists of a large number of individual cells that are electrically connected. Making the required electrical joints represents several challenges, including welding of highly conductive and dissimilar materials, connecting foil tabs with relatively thick bus bar, and joining of multiple sheets. The joining of cells has two parts: tab-to-tab joining and tab-to-bus bar joining. The latter is most difficult to implement since it assumes joining dissimilar materials (usually Al tabs and Cu bus bar) of different thicknesses and different physical characteristics. The main electrical requirement for such joints is to have low electrical resistance, since lower electrical resistance at the joint results in low energy loss, low heat generation and subsequently, lower joint temperature increases during charging and discharging. Resistance spot welding (RSW) is the most cost-effective and rapid method for joining cells for a wide range of battery types and sizes, using both direct current inverter closed loop and capacitor discharge power supplies. However, direct application of RSW to joining Al tabs and Cu bus bar is difficult because of forming Al-Cu intermetallic compounds (IMCs), which are brittle and have a high electrical resistance. The overall goal of the project is to develop the RSW-based process for forming an electrical interconnection interface, which is IMC free and has low contact resistance between battery electrodes and bus bar. The developed process should also allow for fabrication of scalable battery cell-to-module systems with the partner Ford Motor Company of Canada and Ford Motor Company in collaboration with the University of Windsor and Dr. Roman Maev. Roman Gr. Maev, University of Windsor, [email protected]