Patent ID: 8481198

Claim:
A wound electrochemical device having a flat wound body formed by winding a multilayer member including a multilayer structure composed of a positive electrode, a separator, and a negative electrode; wherein each of the positive and negative electrodes includes a structure having an active material layer formed on both sides of a current collector; wherein the wound body has a space at a center portion thereof; and wherein the smallest radius of curvature R of a curved part in an innermost circumferential portion of the wound body satisfies the following expression (1): R =α×( T 1 +2 T 2 ) (1) where R is the smallest radius of curvature of the curved part in the innermost circumferential portion of the wound body (unit: μm), α is a value within the range of 3.33 to 7.12, T 1 is a thickness of the current collector of the electrode positioned at the innermost circumference of the wound body (unit: μm), and T 2 is a thickness of the active material layer of the electrode positioned at the innermost circumference of the wound body (unit: μm), T 2 being a value within the range of 8 to 30 (unit: μm).