Rectangular secondary battery

1. A rectangular secondary cell comprising:

a cell can housing a winding group and having an opening portion;

an external terminal that is configured as a unitary body;

a lid provided with the external terminal, which is electrically connected to the winding group, and closing the opening portion; and

a gasket having a cylindrical portion through which a shaft portion of the external terminal is adapted to pass and a flange portion radially extending outward from a base end of the cylindrical portion, the flange portion including an interposed portion interposed between the lid and a lower surface of the external terminal, wherein, in the gasket, the interposed portion, which extends radially outward from the cylindrical portion, is thicker than other parts of the gasket interposed between the lid and the lower surface of the external terminal,

wherein the shaft portion is provided at a tip end portion of the external terminal with a swaging portion,

wherein, in the gasket, an external shape of the interposed portion is smaller than an external shape of the lower surface of the external terminal, wherein the external terminal includes a terminal head formed in a rectangular shape and the shaft portion protruded in the cell can and formed in a cylindrical or elliptic cylindrical shape, and wherein, in the gasket, the external shape of the interposed portion has a similarity relationship with an external shape of the shaft portion,

wherein a lower surface of the interposed portion is provided with an abutting surface abutting on the lid, the abutting surface extending continuously from the cylindrical portion to a middle of the flange portion, and a gap is disposed between the lid and the gasket from the middle of the flange portion to a radially outermost end of the gasket,

wherein the abutting surface is coaxially arranged with the cylindrical portion and abutting on the lid, an external shape of the abutting surface is smaller than the external shape of the lower surface, and the external shape of the abutting surface corresponds to a cross-section of the shaft portion, and

wherein, in the gasket, a space between an upper surface of the flange portion and the abutting surface is in a compressed state in a thickness direction due to the swaging portion.

2. The rectangular secondary cell according to claim 1 , wherein, in the gasket, the external shape of the interposed portion is arranged to be equally distant in a radial direction from the external shape of the shaft portion.

3. The rectangular secondary cell according to claim 1 , wherein, in the gasket, the interposed portion is arranged on a recess provided in the lid.

4. The rectangular secondary cell according to claim 1 , wherein a surface of the lid opposed to the interposed portion is provided with a protrusion formed in an annular shape.

5. The rectangular secondary cell according to claim 4 , wherein the protrusion includes a plurality of protrusions.

6. The rectangular secondary cell according to claim 1 , further comprising:

an insulating plate disposed in contact with a bottom surface of the lid such that the lid is interposed between the abutting surface of the interposed portion and an upper surface of the insulating plate; and

an electrode collector plate base portion interposed between the insulating plate and the swaging portion of the external terminal;

wherein the swaging portion of the external terminal includes a recess that is disposed entirely outside of the electrode collector plate base portion.