Patent ID: 7754375

Claim:
A lithium ion secondary battery comprising: a positive electrode including positive electrode active material layers and a core member carrying said positive electrode active material layers; a negative electrode including negative electrode active material layers and a core member carrying said negative electrode active material layers; and an electrolyte including a non-aqueous solvent, wherein at least one active material layer of at least one electrode selected from said positive electrode and said negative electrode carries a porous insulating layer, a surface of said active material layer carrying said porous insulating layer has (1) a first region in which said porous insulating layer is formed and (2) a second region comprising a plurality of discontinuous deficient hole portions where said porous insulating layer is not formed, and when a given reference deficient hole portion is selected from said plurality of deficient hole portions and when a given circle having an area ten times that of said reference deficient hole portion is set on said surface of said active material layer, an area of a part of said second region that is surrounded by said circle is not less than 10 μm 2 and not more than 100 mm 2 , the ratio of the area of the second region in the total of the first region and the second region being 5 to 30%.