Abstract: A lithium-ion rechargeable battery includes an electrode body rolled about a roll axis to be low-profile. In a cross section orthogonal to the roll axis, the electrode body includes a planar flat portion pressed to have a low profile and two semicircular rod-shaped bent portions bent and formed on opposite ends of the flat portion. Combined resistance of reaction resistance caused by an inter-electrode distance with solution resistance caused by air permeance of the separator in site, longitudinally extending from center to a peripheral surface of each bent portion, equals combined resistance of the reaction resistance with the solution resistance in site, extending from straight line to a peripheral surface of the flat portion in a thickness-wise direction, to obtain uniform resistance of the electrode body, thereby limiting deposition of lithium metal caused by non-uniform current density.

Abstract: The present teaching provides a highly durable lithium ion secondary battery including a flat shape wound electrode body, with which a high capacity retention ratio and suppression of resistance rise are realized, and also provides a battery pack constructed by using the secondary battery as a unit battery. The lithium ion secondary battery (unit battery) provided in accordance with the present teaching has a flat-shaped wound electrode body 20, and in a state in which a constraint pressure is applied in the direction toward the flat surface of the wound electrode body under the same conditions as the conditions when the battery pack is constructed, the condition of a D/B ratio being 1.01 or more and 1.

Abstract: The present teaching provides a highly durable lithium ion secondary battery including a flat shape wound electrode body, with which a high capacity retention ratio and suppression of resistance rise are realized, and also provides a battery pack constructed by using the secondary battery as a unit battery. The lithium ion secondary battery (unit battery) provided in accordance with the present teaching has a flat-shaped wound electrode body 20, and in a state in which a constraint pressure is applied in the direction toward the flat surface of the wound electrode body under the same conditions as the conditions when the battery pack is constructed, the condition of a D/B ratio being 1.01 or more and 1.