In certain aspects, electrolytic deposition and electroless displacement deposition methods are provided to form bimetallic structures that may be used as a bipolar current collector in a battery or a substrate for forming graphene sheets. In other aspects, bipolar current collectors for lithium-ion based electrochemical cells are provided. The bimetallic current collector may have an aluminum-containing surface and a continuous copper coating. In other aspects, a flexible substrate may be coated with one or more conductive materials, like nickel, copper, graphene, aluminum, alloys, and combinations thereof. The flexible substrate is folded to form a bipolar current collector. New stack assemblies for lithium-ion based batteries incorporating such bipolar current collectors are also provided that can have cells with a tab-free and/or weld-free design.