Lithium ion secondary battery

A lithium ion secondary battery comprising:

• a battery can:
• an electrode assembly in the battery can formed by rolling up a positive electrode, a separator, and a negative electrode;
• an organic electrolyte solution in the battery can;
• a positive electrode tab in the battery can connected to the positive electrode;
• a negative electrode tab in the battery can connected to the negative electrode;
• an overcharge preventer in the battery can;
• a cap body sealing the battery can;
• a positive electrode terminal fixed to the cap body and connected to the positive electrode tab;
• and
• a negative electrode terminal fixed to the cap body and connected to the negative electrode tab,
• wherein the overcharge preventer comprises:
• a temperature-sensitive deformation member configured to detect the internal temperature of the electrode assembly to undergo shape change;
• a switch member configured to be driven by the shape change of the temperature-sensitive deformation member;
• a fuse member connected in series between the positive electrode terminal and the positive electrode or the negative electrode terminal and the negative electrode;
• and a short circuit configured to connect the electrode assembly, the fuse member, and the switch member, and when the switch member is driven and turned on by the shape change of the temperature-sensitive deformation member, the short circuit becomes a closed circuit, and the fuse member is melted down by electrical energy accumulated in the electrode assembly to shut off a charging current path,
• wherein the switch member comprises at least one of a positive electrode lead member and a negative electrode lead member,
• the positive electrode lead member is connected to the positive electrode tab,
• the negative electrode lead member is connected to the negative electrode tab,
• when the short circuit is not closed before the shape change of the temperature-sensitive deformation member, the positive electrode lead member and the negative electrode lead member are not connected to the battery can,
• when the switch member is driven and turned on by the shape change of the temperature-sensitive deformation member, and the positive electrode lead member and the negative electrode lead member are connected to the battery can forced by the shape change of the temperature-sensitive deformation member, the short circuit becomes a closed circuit, and the fuse member is melted down by electrical energy accumulated in the electrode assembly to shut off a charging current path.