Patent ID: 7763377

Claim:
An electrochemical element comprising an electrode assembly that is accommodated in a case with an electrolyte, the electrode assembly including a positive electrode formed of a strip-shaped positive current collector coated with a positive electrode active material and a negative electrode formed of a strip-shaped negative current collector coated with a negative electrode active material, the positive electrode and the negative electrode being wound around a separator interposed therebetween, a positive lead bonded to the positive electrode serving as an external positive connection terminal, a negative lead bonded to the negative electrode serving as an external negative connection terminal, wherein: the positive electrode includes an exposed current collector portion with a predetermined width at least at one end in a width direction where the positive electrode active material has not been coated; the negative electrode includes an exposed current collector portion with a predetermined width at least at the other end in the width direction where the negative electrode active material has not been coated; the separator has a width that is smaller than a width of the positive and negative electrodes, the positive and negative electrodes with the separator interposed therebetween being wound around to form the electrode assembly having an ellipsoidal cross-section; and the exposed current collector portion of the positive electrode protruding beyond the separator from one end being pressed in a shorter side direction of the ellipsoidal cross-section and being welded to form a welding joint, the exposed current collector portion of the negative electrode protruding beyond the separator from an other end pressed in the shorter side direction of the ellipsoidal cross-section being welded to form a welding joint, wherein the positive and negative electrodes form an oval shape on both sides of the welding joint, wherein the positive lead and the negative lead are connected to the positive electrode and the negative electrode, respectively, such that the positive lead is connected to the exposed current collector portion formed on the positive electrode at one end in a lengthwise direction with the positive lead parallel to the end of the positive electrode and extending substantially the entire width of the positive electrode, and the negative lead is connected to the exposed current collector portion formed on the negative electrode at an other end in the lengthwise direction with the negative lead parallel to the end of the negative electrode and extending substantially the entire width of the negative electrode, and wherein the positive lead is connected to the positive electrode at one end of the wound electrode assembly, and the negative lead is connected to an opposite end of the wound electrode assembly.