Presented are electrical interconnect board (ICB) assemblies with multilayer current collectors, methods for making/using such ICB assemblies, battery systems employing such ICB assemblies, and vehicles equipped with such ICB assemblies. An ICB assembly includes an electrically insulative ICB board frame that mounts to a battery case, an electrically conductive busbar assembly mounted to the board frame, and one or more end terminal assemblies mounted to the board frame adjacent opposing ends of the busbar assembly. The busbar assembly includes one or more busbar tracks that electrically interconnect a group of battery cells. Each end terminal assembly includes a bottom current collector plate that attaches to the ICB board frame and electrically connects to the battery cells and busbar track, a dielectric separator attached to the bottom current collector plate, and a top current collector plate attached to the dielectric separator and electrically connected to the bottom current collector plate.