Current collector with penetrating holes of complicated shape for use in a secondary battery and manufacturing process thereof

Abstract

There is provided a current collector for use in a secondary battery on which active material coated on both sides of a metal foil are difficult to drop out. The metal foil is provided with a large number of penetrating holes, the periphery of which are formed into a complicated shape, and active material, binder, etc. are intruded on each periphery, whereby the active material, etc. coated on both sides of the current collector consisting of the metal foil are prevented from dropping out. An area S of penetrating holes is in the range of 0.05 to 0.50 mma value M/N is in the range of 1.30 to 100 wherein M is the peripheral length of the penetrating holes and N is the peripheral length of a virtual circle having the area S of the penetrating hole. The current collector having such a large number of penetrating holes is obtained by passing a metal foil without a hole through between a concavo-convex roll having a large number of convex parts and a smoothing roll. If any burr is produced at each periphery edge of the penetrating holes, the current collector is further caused to pass through between a pair of metal smoothing rolls, whereby the burr produced on each periphery edge of the penetrating holes can be removed.