Rectangular secondary battery

1. A rectangular secondary battery, comprising:

a flat-shaped electrode group;

a current-collecting plate electrically connected to the electrode group;

a battery case accommodating the current-collecting plate and the electrode group;

a battery cover that closes an opening of the battery case;

an electrode terminal disposed along a lower face of the battery cover;

a first insulator that is disposed between the electrode terminal and an upper face of the battery cover;

a second insulator that is disposed between the current-collecting plate and the lower face of the battery cover, wherein the battery cover includes a battery cover side fixing part that engages with the second insulator and fixes the second insulator to the battery cover, and the second insulator includes a current-collecting plate side fixing part that fixes the current-collecting plate;

a current interruption assembly that interrupts electrical connection between the electrode terminal and the current-collecting plate, wherein the current interruption assembly includes:

a connection electrode electrically connected to the electrode terminal,

a conductive plate that includes a dome-shaped diaphragm part having a diameter that gradually increases along an axial direction from a center part to a ring-shaped flange part that is joined with the connection electrode, wherein the dome-shaped diaphragm part includes a first inclined-face part adjacent to the ring-shaped flange part that has an inclination angle that is smaller than 45° with reference of the axial direction of the dome-shaped diaphragm part, and

a fragile part that interrupts the electrical connection between the electrode terminal and the current-collecting plate when an internal pressure of the battery deforms the conductive plate by exceeding a pressure threshold; and

a gasket that is inserted between the electrode terminal and the battery cover for insulating and sealing;

wherein the battery cover is mechanically coupled, via caulk, to the second insulator by at least one first protrusion that protrudes from the battery cover side fixing part into a fixing hole bored at a face of the second insulator in a direction that is orthogonal to the axial direction,

wherein the at least one first protrusion protrudes from a first side of the second insulator through the second insulator and extends past a second side of the second insulator,

wherein the second insulator is coupled to the current-collecting plate via at least one second protrusion, and

wherein the at least one second protrusion is inserted via a through-hole in a base of the current-collecting plate.

2. The rectangular secondary battery according to claim 1 , wherein connection electrode is fixed to the battery cover by caulking the electrode terminal.

3. The rectangular secondary battery according to claim 2 , wherein the electrode terminal is configured so that the second insulator is inserted between the connection electrode and the battery cover, and the connection electrode and the second insulator are integrally fixed to the battery cover.

4. The rectangular secondary battery according to claim 2 , wherein the electrode terminal is configured so that the gasket is inserted between the connection electrode and the battery cover, and the connection electrode and the gasket are integrally fixed to the battery cover.

5. The rectangular secondary batter according to claim 1 , wherein the dome-shaped diaphragm part further includes a second inclined-face part adjacent to the first inclined-face part, wherein the second inclined-face part has an inclination angle that is larger than 180° with reference to the first inclined-face part.

6. The rectangular secondary battery according to claim 5 , wherein as the internal pressure, the diaphragm part is deformed so that the first inclined-face part moves in a direction of increasing the diameter and the second inclined-face part moves to lower a height of the center part.