ELECTRODE TERMINAL FOR A CYLINDRICAL BATTERY CELL

Abstract

ELECTRODE TERMINAL FOR A CYLINDRICAL BATTERY CELL The disclosure herein generally relate to a battery and more particularly to an electrode terminal in a cylindrical battery cell (10) for firmly clamping an insulating gasket (300) against a cylindrical can (400) of cylindrical battery cell (10) thereby hermetically sealing the cylindrical can (400) at its corresponding end. The electrode terminal (100, 200) includes a main body (102, 202), a first flange (104, 204) and a second flange (106, 206). The second flange (106, 206) of the electrode terminal (100, 200) is one of a tapered flange configuration or a stepped flange configuration. Positive fitting or clamping of electrode terminal (100, 200) with cylindrical can (400) via insulating gasket (300) in a riveted state of electrode terminal (100, 200). Prevent entry of contaminants into cylindrical battery cell (10). The electrode terminal (100, 200) is reliable and is easy to manufacture. Fig. 2

Specification

Description:TECHNICAL FIELD
[001] The embodiments herein generally relate to a battery and more particularly to an electrode terminal (terminal rivet) in a cylindrical battery cell for firmly clamping (pressing) an insulating gasket (rivet gasket) against a cylindrical can of the cylindrical battery cell thereby hermetically sealing the cylindrical can at its corresponding end.
BACKGROUND
[002] Generally, cylindrical lithium-ion batteries are widely used in consumer electronics, electric vehicles and energy storage applications. Typically, cylindrical battery cell mainly includes a cylindrical can and an electrode assembly. The cylindrical can is usually made of steel or aluminum, which serves as both the container and one of the electrodes (negative terminal) of the cylindrical battery cell. Usually, the electrode assembly is provided in the form of a jelly roll configuration which is formed by tightly winding the positive and negative electrodes (cathode and anode) with a separator in between, and the electrode assembly is placed inside the cylindrical can. An electrolyte is introduced in the jelly roll for facilitating movement of ions between the electrodes during charge and discharge cycles. The separator which is made from a microporous polymer isolates the two electrodes from each other while allowing the flow of ions. The cylindrical battery cell further includes current collectors which are connected to the electrodes to ensure efficient electron flow in and out of the cylindrical battery cell.
[003] Typically, in a large format cylindrical battery cell, a terminal rivet acts as an electrode terminal which is connected to electrode tabs of the jelly roll through the current collector. An insulating gasket is inserted into a through hole formed in the cylindrical can such that the insulating gasket is interposed between the cylindrical can and the electrode terminal to isolate the terminal rivet from the cylindrical can. The terminal rivet is riveted against the cylindrical can via the insulating gasket to prevent electrolyte leakage from the cylindrical cell. During use, the cylindrical battery cell is subject to repeated temperature and pressure fluctuations as a result of charging, discharging and also because of varying ambient temperatures. The repeated temperature and pressure fluctuations inside the cylindrical battery cell may weaken the mechanical contact between the terminal rivet, the insulating gasket and the cylindrical can. For example, a crimp region of the terminal rivet may deform such that the contact surface between terminal rivet and the insulating gasket may be spaced apart from each other. This increases the possibility of electrolyte leakage from the cylindrical battery cell thereby decreasing the safety and lifetime of the cylindrical battery cell as well as causes contamination of the electrolyte due to entry of foreign contaminants into the cylindrical battery cell which is undesirable.
[004] Therefore, there exists a need for electrode terminal (terminal rivet) for the cylindrical battery cell which obviates the aforementioned drawbacks.
OBJECTS
[005] The principal object of embodiments herein is to provide electrode terminals (terminal rivet) in a cylindrical battery cell for firmly clamping (pressing) an insulating gasket (rivet gasket) against a cylindrical can of the cylindrical battery cell thereby hermetically sealing the cylindrical can at its corresponding end.
[006] Another object of embodiments herein is to enhance crimping (riveting/ tight fitting) of the electrode terminal against the cylindrical can via the insulating gasket thereby providing hermetic contact of the insulating gasket against the cylindrical can of the cylindrical battery cell.
[007] Another object of embodiments herein is to enhance the sealing interface between the insulating gasket and the cylindrical can of the cylindrical battery cell to restrict leakage of electrolyte from the cylindrical battery cell thereby enhancing safety of the cylindrical battery cell.
[008] Another object of embodiments herein is to ensure a secure mechanical connection between the electrode terminal and the insulating gasket during long time use, and repeated temperature and pressure fluctuations inside the cylindrical battery cell.
[009] Another object of embodiments herein is to prevent entry of contaminants into the cylindrical battery cell.
[0010] Another object of embodiments herein is to provide a positive fitting/ clamping of the electrode terminal with the cylindrical can via the insulating gasket in a riveted state of the electrode terminal.
[0011] Another object of embodiments herein is to provide the electrode terminal which is reliable and is easy to manufacture.
[0012] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0014] Fig. 1 depicts an exploded view of a cylindrical battery cell, according to first and second embodiments as disclosed herein;
[0015] Fig. 2 depicts sectional view of the cylindrical battery cell with detailed view of an electrode terminal, an insulating gasket and a cylindrical can of the cylindrical battery cell in assembled condition, according to first and second embodiments as disclosed herein;
[0016] Fig. 3 depicts perspective view of the cylindrical battery cell, according to first and second embodiments as disclosed herein;
[0017] Fig 4a, 4b and 4c illustrates the electrode terminal before performing crimping (riveting) operation of the electrode terminal with respect to the cylindrical can and the insulating gasket, according to first and second embodiments as disclosed herein;
[0018] Fig. 5 depicts sectional view of the electrode terminal with detailed view of flanges, according to first embodiments as disclosed herein; and
[0019] Fig. 6 depicts sectional view of the electrode terminal with detailed view of flanges, according to second embodiments as disclosed herein.
DETAILED DESCRIPTION
[0020] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0021] The embodiments herein achieve electrode terminals (terminal rivet) in a cylindrical battery cell for firmly clamping (pressing) an insulating gasket (rivet gasket) against a cylindrical can of the cylindrical battery cell thereby hermetically sealing the cylindrical can at its corresponding end. Referring now to Figs. 1 to 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0022] Fig. 1 depicts an exploded view of the cylindrical battery cell (10), according to first and second embodiments as disclosed herein. Fig. 2 depicts sectional view of the cylindrical battery cell (10) with detailed view of the electrode terminal (100, 200), the insulating gasket (300) and the cylindrical can (400) of the cylindrical battery cell in assembled condition, according to first and second embodiments as disclosed herein. In an embodiment, the cylindrical battery cell (10) includes an electrode terminal (100, 200) (terminal rivet), an insulating gasket (300) (rivet gasket), a cylindrical can (400), a current collector lid (500), a battery cell jelly roll (600), a closing pin (700), a sealing plug (800), a top current collector (900) and an insulator (1000). For the purpose of this description and ease of understanding, the electrode terminal (100, 200) is explained herein with below reference to be provided in a large format cylindrical battery cell. The electrode terminal (100, 200) is adapted to facilitate access terminal and to hold the insulating gasket (300). The insulating gasket (300) is inserted into a through hole (402H) (as shown in fig. 1) provided on a terminal holding portion (402) (as shown in figs. 1, 2, 3, 5 and 6) of the cylindrical can (400). The insulating gasket (300) (as shown in figs. 2 and 3) is interposed between the cylindrical can (400) and the electrode terminal (100, 200) to insulate the electrode terminal (100, 200) from the cylindrical can (400) thereby preventing short circuit since the cylindrical can (400) is welded to the current collector lid (500). Further, the insulating gasket (300) is configured to provide a sealing between the electrode terminal (100, 200) and the cylindrical can (400) to prevent electrolyte leakage as the insulating gasket (300) is compressed to 30 to 40% between the electrode terminal (100, 200) and the cylindrical can (400). The jelly roll (600) is formed by tightly winding the positive and negative electrodes (cathode and anode) with a separator in between. The cylindrical can (400) is adapted to house the jelly roll (600). The sealing plug (800) is received by a central hollow tubular section (not shown) of the current collector lid (500) to prevent leakage of electrolyte from a core (600C) (as shown in fig. 2) of jelly roll (600). The closing pin (700) is pressed against the current collector lid (500) and the sealing plug (800) after filling the electrolyte into the core (600C) of the jelly roll (600). The insulator (1000) is interposed between the top current collector (900) and the cylindrical can (400) to prevent short circuit. The top current collector (900) is adapted to be connected to electrode tabs of the jelly roll (600) and the electrode terminal (100, 200).
[0023] In one embodiment, the electrode terminal (100, 200) is configured to act as a positive terminal (cathode terminal) of the cylindrical battery cell (10) when the top current collector (900) is connected to positive electrode tabs of the jelly roll (600), and the cylindrical can (400) is configured to act as a negative terminal (anode terminal) of the cylindrical battery cell (10) when the current collector lid (500) is connected to negative electrode tabs of the jelly roll (600). In another embodiment, the electrode terminal (100, 200) is configured to act as the negative terminal (anode terminal) of the cylindrical battery cell (10) when the top current collector (900) is connected to negative electrode tabs of the jelly roll (600), and the cylindrical can (400) is configured to act as the positive terminal (cathode terminal) of the cylindrical battery cell (10) when the current collector lid (500) is connected to positive electrode tabs of the jelly roll (600).
[0024] In the first and second embodiments, the electrode terminal (100, 200) includes a main body (102, 202), a first flange (104, 204) and a second flange (106, 206) (as shown in figs. 2, 5 and 6). The main body (102, 202) of the electrode terminal (100, 200) is inserted into the insulating gasket (300). The first flange (104, 204) of the electrode terminal (100, 200) is adapted to radially extend outward from the main body (102, 202) near its first end. The first flange (104, 204) of the electrode terminal (100, 200) is engaged with a first insulating flange (302) (as shown in figs. 2, 5 and 6) of the insulating gasket (300).
[0025] The second flange (106, 206) of the electrode terminal (100, 200) is configured to radially extend outward from the main body (102, 202) near its second end. The second flange (106, 206) of the electrode terminal (100, 200) is adapted to clamp a second insulating flange (304) (as shown in figs. 2, 5 and 6) of the insulating gasket (300) against an inner surface of the terminal holding portion (402) of the cylindrical can (300) thereby facilitating hermetic sealing of the cylindrical can (300) at its corresponding end. At least a portion of the second flange (106, 206) of the electrode terminal (100, 200) is parallel and spaced away from the first flange (104, 204). In the first and second embodiments, the second flange (106, 206) of the electrode terminal (100, 200) is configured to have variable thickness from an inner circumference of the second flange (106, 206) towards an outer circumference of the second flange (106, 206).
[0026] Fig. 5 depicts sectional view of the electrode terminal (100) with detailed view of flanges (104, 106), according to first embodiments as disclosed herein. In the first embodiment, the thickness of the second flange (106) of the electrode terminal (100) is configured to progressively (gradually) taper from the inner circumference of the second flange (106) towards the outer circumference of the second flange (106). In the first embodiment, the second flange (106) of the electrode terminal (100) is a tapered flange configuration having a first flange portion (106A) and a second flange portion (106B). In an embodiment, the first flange portion (106A) and the second flange portion (106B) of the second flange (106) of the electrode terminal (106) are formed by a single stage pressing operation or a multi-stage pressing operation. The first flange portion (106A) of the second flange (106) is configured to radially extend outward from the main body (102) near its second end. The second flange portion (106B) of the second flange (106) is configured to radially extend outward from the first flange portion (106A) at a predefined angle (A) with respect to a bottom surface of the first flange portion (106A), wherein the predefined angle (A) is in the range of 0.5 to 30 degree. It is also within the scope of the invention to vary the value of predefined angle (A) between second flange portion (106B) and the bottom surface of the first flange portion (106A). A radial distance from an inner circumference of the first flange portion (106A) of the second flange (106) to an outer circumference of the first flange portion (106A) is greater than 0.1 mm. A thickness of the first flange portion (106A) of the second flange (106) is in the range of 0.5 to 1 mm. A thickness of the second flange portion (106B) of the second flange (106) near its outer circumference is in the range of 0.2 to 0.7 mm.
[0027] Fig. 6 depicts sectional view of the electrode terminal (200) with detailed view of flanges (204, 206), according to second embodiments as disclosed herein. In the second embodiment, the thickness of the second flange (206) of the electrode terminal (200) is configured to progressively (gradually) decrease from the inner circumference of the second flange (206) towards the outer circumference of the second flange (206). In the second embodiment, the second flange (206) of the electrode terminal (200) is a stepped flange configuration having a base flange portion (206A) and a plurality of stepped flange portions (206B, 206C, 206D). In an embodiment, the base flange portion (206A) and the stepped flange portions (206B, 206C, 206D) of the electrode terminal (206) are formed by a single stage pressing operation or a multi-stage pressing operation. The base flange portion (206A) of the second flange (206) is configured to radially extend outward from the main body (102) near its second end. The plurality of stepped flange portions (206B, 206C, 206D) of the second flange (206) includes a first step flange portion (206B), a second step flange portion (206C) and a third step flange portion (206D). The first step flange portion (206B) is configured to radially extend outward from the base flange portion (206A). The second step flange portion (206C) is configured to radially extend outward from the first step flange portion (206B). The third step flange portion (206D) is configured to radially extend outward from the second step flange portion (206C). A thickness of the first step flange portion (206B) is lesser than a thickness of the base flange portion (206A). A thickness of the second step flange portion (206C) is lesser than the thickness of the first step flange portion (206B). A thickness of the third step flange portion (206D) is lesser than the thickness of the second flange portion (206C). A radial distance between the outer circumference of the second flange (206) and an outer circumference of the second insulating flange (304) of the insulating gasket (300) is in the range of 0.3 to 0.7 mm. A radial distance from an inner circumference of the base flange portion (206A) of the second flange (206) to an outer circumference of the base flange portion (206A) is in the range of 0.7 to 0.11 mm. A radial distance from an inner circumference of the first step flange portion (206B) of the second flange (206) to an outer circumference of the first step flange portion (206B) is in the range of 0.2 to 0.6 mm. A radial distance from an inner circumference of the second step flange portion (206C) of the second flange (206) to an outer circumference of the second step flange portion (206C) is in the range of 0.2 to 0.6 mm. A radial distance from an inner circumference of the third step flange portion (206D) of the second flange (206) to an outer circumference of the second step flange portion (206D) is in the range of 0.4 to 0.9 mm. A thickness of the base flange portion (206A) of the second flange (206) is in the range of 0.5 to 0.7 mm. A thickness of the first step flange portion (206B) of the second flange (206) is in the range of 0.4 to 0.6 mm. A thickness of the second step flange portion (206C) of the second flange (206) is in the range of 0.3 to 0.5 mm. A thickness of the third step flange portion (206D) of the second flange (206) is in the range of 0.2 to 0.4 mm.
[0028] Fig 4a, 4b and 4c illustrates the electrode terminal (100, 200) before performing crimping (riveting) operation of the electrode terminal (100, 200) with respect to the cylindrical can (400) and the insulating gasket (300), according to first and second embodiments as disclosed herein. In the first and second embodiments, the main body (102, 202) of the electrode terminal (100, 200) includes a first portion (102A, 202A), and a second portion (102B) coaxially extending from the first portion (102A, 202A) in a direction towards the top current collector (900) and is disposed below the first flange (104, 204). The second portion (102B, 202B) of the main body (102, 202) is configured to be deformed to facilitate formation of the second flange (106, 206) adapted for clamping the second insulating flange (304) of the insulating gasket (300) against the inner surface of the terminal holding portion (402) of the cylindrical can (300) during crimping of the electrode terminal (100, 200) with respect to the insulating gasket (300) and the cylindrical can (400). An overall height of the electrode terminal (100, 200) is in the range of 2 to 4 mm. An outer diameter of the first flange (104, 204) is in the range of 18 to 22 mm. An outer diameter of the second flange (106, 206) is in the range of 15 to 20 mm. A thickness of the first flange (104, 204) is in the range of 0.5 to 1.5 mm.
[0029] Further, in the first and second embodiments, the electrode terminal (100, 200) includes a first cavity (108, 208), a second cavity (110, 210) and a dividing wall (112, 212). The first cavity (108, 208) is provided in the first portion (102A, 202A) of the main body (102, 202). An outer diameter of the first cavity (108, 208) is in the range of 8 to 12 mm. An inner diameter of the first cavity (108, 208) is in the range of 7 to 11 mm. The second cavity (110, 210) is provided in the second portion (102B, 202B). An outer diameter of the second cavity (110, 210) is in the range of 10 to 14 mm. An inner diameter of the second cavity (110, 210) is in the range of 9 to 13 mm. A depth of the second cavity (110, 210) is in the range of 0.3 to 0.7 mm. The dividing wall (112, 212) is defined between the first cavity (108, 208) and the second cavity (110, 210). A portion of the top current collector (900) is adapted to be received by the second cavity (110, 210) and the dividing wall (112, 212) is fixedly connected (welded) to the top current collector (900). A thickness of the dividing wall (112, 212) is in the range of 0.5 to 1 mm.
[0030] The technical advantages of the electrode terminal (100, 200) are as follows. The electrode terminal (100, 200) is adapted to firmly clamp (press) the insulating gasket (rivet gasket) against the cylindrical can of the cylindrical battery cell thereby hermetically sealing the cylindrical can at its corresponding end. The electrode terminal (100, 200) enhances the sealing interface between the insulating gasket and the cylindrical can of the cylindrical battery cell to restrict leakage of electrolyte from the cylindrical battery cell thereby enhancing safety of the cylindrical battery cell. Enhance crimping (riveting) of the electrode terminal against the cylindrical can via the insulating gasket thereby providing hermetic contact of the insulating gasket against the cylindrical can of the cylindrical battery cell. Ensure a secure mechanical connection between the electrode terminal and the insulating gasket during long time use, and repeated temperature and pressure fluctuations inside the cylindrical battery cell. Positive fitting/ clamping of the electrode terminal with the cylindrical can via the insulating gasket in a riveted state of the electrode terminal. Prevent entry of contaminants into the cylindrical battery cell. The electrode terminal (100, 200) is reliable and is easy to manufacture.
[0031] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.
, Claims:We claim:
1. An electrode terminal (100, 200) for a cylindrical battery cell (10) having a cylindrical can (400) and an insulating gasket (300) inserted into a through hole (402H) provided on a terminal holding portion (402) of the cylindrical can (400), the electrode terminal (100, 200) having:
a main body (102, 202) inserted into the insulating gasket (300);
a first flange (104, 204) radially extending outward from the main body (102, 202) near its first end, wherein the first flange (104, 204) is engaged with a first insulating flange (302) of the insulating gasket (300); and
a second flange (106, 206) configured to radially extend outward from the main body (102, 202) near its second end, wherein the second flange (106) is adapted to clamp a second insulating flange (304) of the insulating gasket (300) against an inner surface of the terminal holding portion (402) of the cylindrical can (300) thereby facilitating hermetic sealing of the cylindrical can (300) at its corresponding end.
2. The electrode terminal (100, 200) as claimed in claim 1, wherein the second flange (106, 206) of the electrode terminal (100, 200) is configured to have variable thickness from an inner circumference of the second flange (106, 206) towards an outer circumference of the second flange (106, 206).
3. The electrode terminal (100) as claimed in claim 2, wherein the thickness of the second flange (106) is configured to progressively taper from the inner circumference of the second flange (106) towards the outer circumference of the second flange (106).
4. The electrode terminal (200) as claimed in claim 2, wherein the thickness of the second flange (206) is configured to progressively decrease from the inner circumference of the second flange (206) towards the outer circumference of the second flange (206).
5. The electrode terminal (100) as claimed in claim 1, wherein the second flange (106) of the electrode terminal (100) is a tapered flange configuration having:
a first flange portion (106A) configured to radially extend outward from the main body (102) near its second end; and
a second flange portion (106B) configured to radially extend outward from the first flange portion (106A) at a predefined angle (A) with respect to a bottom surface of the first flange portion (106A), wherein the predefined angle (A) is in the range of 0.5 to 30 degree.
6. The electrode terminal (200) as claimed in claim 1, wherein the second flange (206) of the electrode terminal (200) is a stepped flange configuration having:
a base flange portion (206A) configured to radially extend outward from the main body (102) near its second end; and
a plurality of stepped flange portions (206B, 206C, 206D), wherein the stepped flange portions (206B, 206C, 206D) includes:
a first step flange portion (206B) configured to radially extend outward from the base flange portion (206A);
a second step flange portion (206C) configured to radially extend outward from the first step flange portion (206B); and
a third step flange portion (206D) configured to radially extend outward from the second step flange portion (206C),
wherein
a thickness of the first step flange portion (206B) is lesser than a thickness of the base flange portion (206A);
a thickness of the second step flange portion (206C) is lesser than the thickness of the first step flange portion (206B); and
a thickness of the third step flange portion (206D) is lesser than the thickness of the second flange portion (206C).
7. The electrode terminal (100, 200) as claimed in claim 1, wherein the main body (102, 202) of the electrode terminal (100, 200) includes:
a first portion (102A, 202A); and
a second portion (102B, 202B) coaxially extending from the first portion (102A, 202A) in a direction towards a top current collector (900) of the cylindrical battery cell (10) and is disposed below the first flange (104, 204),
wherein
the second portion (102B, 202B) of the main body (102, 202) is configured to be deformed to facilitate formation of the second flange (106, 206) adapted for clamping the second insulating flange (304) of the insulating gasket (300) against the inner surface of the terminal holding portion (402) of the cylindrical can (300) during crimping of the electrode terminal (100, 200) with respect to the insulating gasket (300) and the cylindrical can (400).
8. The electrode terminal (100, 200) as claimed in claim 7, wherein the electrode terminal (100, 200) includes:
a first cavity (108, 208) provided in the first portion (102A, 202A) of the main body (102, 202);
a second cavity (110, 210) provided in the second portion (102B, 202B); and
a dividing wall (112, 212) defined between the first cavity (108, 208) and the second cavity (110, 210), wherein a portion of the top current collector (900) is adapted to be received by the second cavity (110, 210) and the dividing wall (112, 212) is fixedly connected to the top current collector (900),
wherein
a thickness of the dividing wall (112, 212) is in the range of 0.5 to 1 mm;
a depth of the second cavity (110, 210) is in the range of 0.3 to 0.7 mm;
an outer diameter of the first cavity (108, 208) is in the range of 8 to 12 mm;
an inner diameter of the first cavity (108, 208) is in the range of 7 to 11 mm;
an outer diameter of the second cavity (110, 210) is in the range of 10 to 14 mm;
an inner diameter of the second cavity (110, 210) is in the range of 9 to 13 mm;
an overall height of the electrode terminal (100, 200) is in the range of 2 to 4 mm;
an outer diameter of the first flange (104, 204) is in the range of 18 to 22 mm;
an outer diameter of the second flange (106, 206) is in the range of 15 to 20 mm; and
a thickness of the first flange (104, 204) is in the range of 0.5 to 1.5 mm.

9. The electrode terminal (100) as claimed in claim 5, wherein a radial distance from an inner circumference of the first flange portion (106A) of the second flange (106) to an outer circumference of the first flange portion (106A) is greater than 0.1 mm;
a thickness of the first flange portion (106A) of the second flange (106) is in the range of 0.5 to 1 mm; and
a thickness of the second flange portion (106B) of the second flange (106) near its outer circumference is in the range of 0.2 to 0.7 mm.

10. The electrode terminal (200) as claimed in claim 6, wherein a radial distance between the outer circumference of the second flange (206) and an outer circumference of the second insulating flange (304) of the insulating gasket (300) is in the range of 0.3 to 0.7 mm;
a radial distance from an inner circumference of the base flange portion (206A) of the second flange (206) to an outer circumference of the base flange portion (206A) is in the range of 0.7 to 0.11 mm;
a radial distance from an inner circumference of the first step flange portion (206B) of the second flange (206) to an outer circumference of the first step flange portion (206B) is in the range of 0.2 to 0.6 mm;
a radial distance from an inner circumference of the second step flange portion (206C) of the second flange (206) to an outer circumference of the second step flange portion (206C) is in the range of 0.2 to 0.6 mm;
a radial distance from an inner circumference of the third step flange portion (206D) of the second flange (206) to an outer circumference of the second step flange portion (206D) is in the range of 0.4 to 0.9 mm;
a thickness of the base flange portion (206A) of the second flange (206) is in the range of 0.5 to 0.7 mm;
a thickness of the first step flange portion (206B) of the second flange (206) is in the range of 0.4 to 0.6 mm;
a thickness of the second step flange portion (206C) of the second flange (206) is in the range of 0.3 to 0.5 mm; and
a thickness of the third step flange portion (206D) of the second flange (206) is in the range of 0.2 to 0.4 mm.

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