Composite current collector, electrode sheet, battery, and electrical device

A composite current collector includes an insulating substrate and a conductive layer. the conductive layer is the one provided at both sides of the insulating substrate in a thickness direction of the insulating substrate; in a direction perpendicular to a thickness of the composite current collector, the composite current collector includes an active material support region and a tab connection region, a thickness of an insulating substrate of the tab connection region is less than that of an insulating substrate of the active material support region; and a thickness of a conductive layer of the tab connection region is greater than that of a conductive layer of the active material support region.