| abstract |
To provide secondary batteries, battery packs, electric vehicles, power storage systems, power tools, and electronic equipment that can achieve excellent battery characteristics. The secondary battery includes a wound electrode body having a flat shape defined by a long axis and a short axis, and the ends of the positive and negative electrodes on the inner side of the winding in the winding direction include a first extending in the long axis direction and to which positive and negative terminals are attached. Positive/negative electrode winding part, the first negative electrode winding part is opposite to the first positive electrode winding part through the separator, and the negative electrode terminal does not overlap with the positive electrode terminal in the short axis direction; it also includes one or more step easing parts, in the At least one of the first to third regions is provided on at least one of the first positive electrode winding portion and the first negative electrode winding portion, and the first region is closer to the positive electrode winding than the positive electrode terminal in the direction of the long axis The second region is located on the outer side of the winding direction of the negative electrode in the direction of the major axis, and the third region is located between the positive electrode terminal and the negative electrode terminal. |