Patent ID: 7335448

Claim:
A lithium ion secondary battery including: (a) a positive electrode plate comprising a positive electrode active material part and a positive electrode current collector carrying said positive electrode active material part, said positive electrode active material part comprising a positive electrode active material capable of absorbing or desorbing a lithium ion during charge and discharge; (b) a negative electrode plate comprising a negative electrode active material part and a negative electrode current collector carrying said negative electrode active material part, said negative electrode active material part comprising a negative electrode active material capable of absorbing or desorbing a lithium ion during charge and discharge; (c) a separator interposed between said positive electrode plate and said negative electrode plate; (d) an electrolyte; and (e) a battery case accommodating said positive electrode plate, said negative electrode plate, said separator, and said electrolyte, wherein said positive electrode plate and said negative electrode plate are wound around an axis with said separator interposed therebetween, thereby to form an electrode plate assembly, said electrode plate assembly is so configured that each lengthwise edge of said positive electrode current collector is positioned on an outer side of each lengthwise edge of said negative electrode active material part, and said electrode plate assembly is so configured that each lengthwise edge of said negative electrode active material part is positioned on an outer side of each lengthwise edge of said positive electrode active material part, wherein lengthwise directions of said positive electrode active material part, positive electrode current collector, and negative electrode active material part are perpendicular to the axis of winding of the electrode plate assembly.