Patent ID: 7273678
Filing Date: 2007-09-25
Classification: H01M,Y02E,Y02P

Abstract:
1. A secondary cell having an electrode unit ( 4 ) comprising in superposed layers a positive electrode ( 41 ) in the form of a strip, a negative electrode ( 43 ) in the form of a strip and a separator ( 42 ) interposed therebetween, the electrode unit ( 4 ) being housed in a cell can ( 1 ) comprising a bottomed cylinder ( 15 ) and a lid ( 11 ) closing an opening portion of the cylinder, a current collector in the form of a strip forming the positive electrode ( 41 ) or the negative electrode ( 43 ) and having a projecting edge ( 48 ) at at least one of opposite ends of the electrode unit ( 4 ) which one end is opposed to a bottom wall of the cylinder ( 15 ), a current collector plate ( 50 ) covering the edge ( 48 ) and comprising a plate having a plurality of protrusions ( 52 ) extending radially outward from the center of the plate and protruding toward the current collector edge ( 48 ), the protrusions ( 52 ) biting into the current collector edge ( 48 ) and being welded to the current collector edge ( 48 ), the current collector plate ( 50 ) being welded to the bottom wall of the cylinder ( 15 ), the secondary cell being characterized in that a surface of the current collector plate (