The use of laser beam welding (LBW) for joining dissimilar metals in the battery systems of newly emerging electric vehicles is gaining popularity. Recently developed beam shaping technologies are being studied and are considered beneficial in many aspects of dissimilar metal LBW applications, which include reduction in intermetallic compounds (IMCs), modifying weld pool profiles, and reducing porosity and spatters. This study utilises various beam profiles by tailoring power ratios between core and ring laser beams for the welding of aluminium to Ni-coated steel. The use of beam shaping for the joining of aluminium to Ni-coated steel in the application of joining the aluminium busbar to the cylindrical battery cells has not been studied before. High-resolution electron microscopy was performed in horizontal and transverse cross sections of the weld seams in order to quantify various microstructural parameters, which covered, spatters and seam quality, metal-mixing and subsequent IMC formation (as well as type), and weld defects such as cracking, and cavitation. Lap-shear mechanical testing as well as electrical resistivity testing was also used to assess key performance indicators. Results revealed that lower power ratios (core-dominant laser beam) increased the formation of brittle Al-rich IMCs and reduced mechanical properties as well as electrical conductivity. In comparison at the same total power, higher power ratios (ring-dominant beam) reduced the melting of the metals, however, increased the surface area of the metallurgical bond. Consequently, metal-mixing and IMC formation was reduced, which in turn improved the mechanical properties of the weld as well as electrical conductivity.