Secondary battery, battery pack, electric vehicle, electric power storage system, electric tool, and electronic apparatus

A secondary battery comprising:

• a cathode terminal;
• an anode terminal;
• a wound electrode body;
• and
• a step reducing member,
• wherein
• in the wound electrode body,
• a cathode and an anode are provided with a separator interposed between the cathode and the anode while being wound around a winding axis;
• a section intersecting with the winding axis has a flat shape defined by a major axis and a minor axis;
• the cathode includes a cathode current collector and a cathode active material layer provided on a part of the cathode current collector;
• the anode includes an anode current collector and an anode active material layer provided on a part of the anode current collector;
• the cathode includes an end portion on a wound inner side in a wound direction with a first cathode wound portion that extends in a major axis direction and the cathode terminal is attached to the end portion of the cathode;
• and
• the anode includes an end portion on the wound inner side in the wound direction with a first anode wound portion that extends in the major axis direction while facing the first cathode wound portion across the separator, and the anode terminal is attached to the end portion of the anode and the anode terminal does not overlap with the cathode terminal in a minor axis direction,
• wherein the step reducing member is attached to one or both of the first cathode wound portion and the first anode wound portion in one or more of a first region, a second region and a third region,
• wherein the first region is in the major axis direction outside the cathode terminal in the wound direction of the cathode, and the second region is in the major axis direction outside the anode terminal in the wound direction of the anode and the third region between the cathode terminal and the anode terminal,
• wherein the cathode current collector of the first cathode wound portion includes a first cathode exposed portion in which the cathode active material layer is not provided, and the step reducing member is attached to the first cathode exposed portion, and
• wherein a cathode terminal protective member is attached to the first cathode exposed portion and covers the cathode terminal and a periphery of the cathode terminal, and the step reducing member is attached on the cathode terminal protective member.