Patent ID: 7378185

Claim:
A prismatic lithium secondary battery comprising: a prismatic battery can having a bottom, a side wall, and an open top; an electrode assembly; a non-aqueous electrolyte; and a sealing plate covering the open top of said battery can that accommodates said electrode assembly and said non-aqueous electrolyte, wherein said electrode assembly comprises: a positive electrode having a positive electrode active material layer; a negative electrode having a negative electrode active material layer; and a porous heat-resistant layer and a separator that are interposed between the positive and negative electrodes, said porous heat-resistant layer comprises an insulating filler and being in contact with the active material layer of said positive or negative electrode, said side wall of the prismatic battery can has two rectangular main flat portions that are opposed to each other, and a thickness A of said porous heat-resistant layer is 2 to 10 μm, a thickness B of each of said main flat portions is 160 to 1000 μm, and A and B satisfy the relation: 0.005≦A/B≦0.03.