shown in the drawing each of which consists of a punch and a die as is illustrated in fig8 metal plates 43 of for instance 3 mm thick stainless steel are fed one after another to these punching tools and punched into various shapes as a result of a combination of piercing contour punching and notching the cell electrode plate 42 as illustrated in fig9 is formed having along its length a plurality of notch slits 41 with thorns t and a plurality of retaining holes p arranged at a pitch which corresponds to the width of the collector cells 40 for instance about 20 nm in forming the notch slit 41 four punch dies for punching holes with the cross sectional shape of a short slit for instance a short slit s approximately 7 mm long approximately 1 mm wide and rounded at both ends and one punch die for punching notches with the cross sectional shape of a wedge are prepared the punch dies for punching holes are arranged two each in a straight line separated from one another by a prescribed distance roughly the length of one approximately 7 mm long short slit s and alternately in two rows front and rear the short slits s made by the four punch dies in the metal plate 43 are then combined as illustrated in fig8 to form a long slit ls after which the punch die for punching notches is used to punch out the shape of an isosceles triangle in the strip of the metal plate 43 between its upper edge as illustrated in the drawing and the upper end of the long slit ls also as illustrated in the drawing it should be pointed out that in order to create the.