Nonaqueous electrolyte secondary battery and battery pack

A nonaqueous electrolyte secondary battery, comprising:

• a nonaqueous electrolyte;
• a flat-shaped wound electrode assembly in which, a sheet-shaped positive electrode which comprises a positive electrode active material layer being formed in a strip-like shape along a longitudinal direction on a long positive current collector, a sheet-shaped negative electrode which comprises a negative electrode active material layer being formed in a strip-like shape along the longitudinal direction on a long negative current collector, and a separator which is disposed between the positive electrode and the negative electrode are stacked one on another and wound in the longitudinal direction;
• and
• a square-shaped battery case accommodating the nonaqueous electrolyte and the wound electrode assembly, wherein
• the wound electrode assembly comprises:
• a pair of flat surface parts that are located to be opposed while sandwiching a winding axis;
• and a pair of R parts whose surfaces located between the pair of flat surface parts are curved surfaces, and
• in a state where 4.5 kN restriction pressure is added to restrict from an opposed direction of the flat surface parts onto a whole of the flat surface parts of the wound electrode assembly,
• when a total of an outermost circumferential length of the pair of R parts of the wound electrode assembly on a cross section orthogonal to the winding axis of the wound electrode assembly is treated as a (mm),
• an outermost circumferential length of the wound electrode assembly on the cross section is treated as b (mm),
• a length in a width direction orthogonal to the longitudinal direction of the positive electrode active material layer is treated as c (mm), and
• a height of the wound electrode assembly being a distance between apexes of the pair of R parts on the cross section is treated as d (mm),
• both of conditions:
• 0.282<a/b;
• and c/d<1.91, are satisfied.