US Patent 7794872 Secondary battery

A secondary battery includes an electrode assembly having a separator interposed between a positive plate and a negative plate. Each of the positive and negative plates has a portion that is not coated with active material. The uncoated regions of the positive and negative plates are respectively fixed to positive and negative collector plates by welding. A plurality of first weld lines are formed on the positive collector plate at predetermined angles from one another. A plurality of second weld lines are formed on the negative collector plate also at predetermined angles from one another. The plurality of first weld lines and the plurality of second weld lines are offset from one another.