Laser welded internal terminal of battery cell

Abstract

The battery cell includes a stack including C cathode electrodes, A anode electrodes, and S separators, where C, A, and S are integers greater than 1. The first internal terminal includes a first slot. The external tab of one of the C cathode electrodes and the A anode electrodes is inserted into the first groove. One of edges of an external tab of one of the C cathode electrodes and the A anode electrodes is laser welded in the first groove, and a portion of the external tab of one of the C cathode electrodes and the A anode electrodes extends through the first groove, is folded and laser welded to a surface of the first internal terminal.

Description

Technical Field

[0001] The present disclosure relates to battery cells, and more particularly to laser welded internal terminals for battery cells. Background Art

[0002] The information provided in this section is for the purpose of generally presenting the background of the present disclosure. To the extent described in this section, the work of the presently named inventors, and aspects of the description that may not otherwise constitute prior art at the time of filing, are neither explicitly nor implicitly admitted as prior art to the present disclosure.

[0003] Electric vehicles (EVs), such as battery electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, include one or more motors and a battery system including one or more battery cells, modules, and / or battery packs. A power control system is used to control the charging and / or discharging of the battery system during charging and / or driving. Summary of the invention

[0004] A battery cell includes a stack, the stack including C cathode electrodes, each cathode electrode including a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector; A anode electrodes, each anode electrode including an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and S separators, wherein C, A, and S are integers greater than 1. A first internal terminal includes a first groove. An external tab of one of the C cathode electrodes and the A anode electrodes is inserted into the first groove. Portions of the external tab of one of the C cathode electrodes and the A anode electrodes extend through the first groove, are folded, and are laser welded to a surface of the first internal terminal.

[0005] In other features, the second internal terminal includes a second slot to accommodate an external tab of the other of the C cathode electrodes and the A anode electrodes.

[0006] In other features, a portion of the external tab of the other of the C cathode electrodes and the A anode electrodes that extends through the second slot is folded over and laser welded to a surface of the second internal terminal.

[0007] In other features, the first internal terminal includes N first grooves, where N is an integer greater than 1. External tabs of one of the C cathode electrodes and the A anode electrodes are divided into N groups, respectively inserted through the N first grooves, and folded and laser welded to the surface of the first internal terminal.

[0008] In other features, the N first slots are open-ended. The first slot is open-ended. The external tabs of one of the C cathode electrodes and the A anode electrodes are divided into a first group and a second group, folded along a first direction and a second direction, respectively, and laser welded to the surface of the first internal terminal on opposite sides of the first slot. The first internal terminal is "L"-shaped and includes a first portion and a second portion extending transversely relative to the first portion.

[0009] In other features, a battery cell includes a housing, a first external terminal in contact with the first internal terminal, and a second external terminal in contact with the second internal terminal.

[0010] The battery cell includes a stack comprising C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector; A anode electrodes comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and S separators, wherein C, A, and S are integers greater than zero.

[0011] The first inner terminal includes R grooves, where R is an integer greater than 0. An outer tab of one of the C cathode electrodes and the A anode electrodes is folded and laser welded to an inner surface of the first inner terminal through at least one of the R grooves of the first inner terminal.

[0012] In other features, the second inner terminal includes R grooves. An outer tab of the other of the C cathode electrodes and the A anode electrodes is folded and laser welded to an inner surface of the second inner terminal through at least one of the R grooves of the second inner terminal.

[0013] In other features, R is greater than 1. The outer tab of one of the C cathode electrodes and the A anode electrodes is folded and laser welded to the inner surface of the first inner terminal through at least another of the R grooves of the first inner terminal. The first inner terminal has an "L" shape and includes a first portion and a second portion extending transversely relative to the first portion.

[0014] In other features, the external tabs of one of the C cathode electrodes and the A anode electrodes include a plurality of first external tabs and a plurality of second external tabs, which are folded along a first direction and a second direction and laser welded to the inner surface of the first internal terminal through at least one of the R grooves of the first internal terminal.

[0015] In other features, a battery cell includes a housing, a first external terminal in contact with the first internal terminal, and a second external terminal in contact with the second internal terminal.

[0016] A battery cell includes a stack, the stack including C cathode electrodes, each cathode electrode including a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector; A anode electrodes including an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and S separators, wherein C, A, and S are integers greater than 1. A first internal terminal includes a planar portion and a second portion, the second portion including a central portion connected to the second portion and a first side wall and a second side wall extending from the central portion. The external tab of one of the C cathode electrodes and the A anode electrodes passes through the first side wall and the second side wall of the first internal terminal and is laser welded to the inner surface of the first side wall and the second side wall of the first internal terminal.

[0017] In other features, the second internal terminal includes a planar portion and a second portion, the second portion including a center portion and a first side and a second side extending from the center portion. An external tab of the other of the C cathode electrodes and the A anode electrodes passes through the first side and the second side and is laser welded to the inner surface of the first side wall and the second side wall of the second internal terminal.

[0018] In other features, a battery cell includes a housing, a first external terminal in contact with a planar portion of the first internal terminal, and a second external terminal in contact with a planar portion of the second internal terminal.

[0019] The present invention provides the following technical solutions:

[0020] 1. A battery cell, comprising:

[0021] A stack, the stack comprising:

[0022] C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0023] A anode electrodes, each anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and

[0024] S diaphragms, where C, A, and S are integers greater than 1; and

[0025] comprising a first internal terminal of a first slot, wherein an external tab of one of the C cathode electrodes and the A anode electrodes is inserted into the first slot,

[0026] Part of the external tab of one of the C cathode electrodes and the A anode electrodes extends through the first groove, is folded and laser welded to the surface of the first internal terminal.

[0027] 2. The battery cell according to Option 1 further includes a second internal terminal, which includes a second groove for accommodating an external tab of the other of the C cathode electrodes and the A anode electrodes.

[0028] 3. The battery cell according to claim 2, wherein a portion of the external tab of the other of the C cathode electrodes and the A anode electrodes extending through the second groove is folded and laser welded to a surface of the second internal terminal.

[0029] 4. The battery cell according to claim 1, wherein the first internal terminal includes N first grooves, wherein N is an integer greater than 1.

[0030] 5. A battery cell according to Option 4, wherein the external tabs of the C cathode electrodes and one of the A anode electrodes are divided into N groups, the N groups are respectively inserted through the N first grooves, and are folded and laser welded to the surface of the first internal terminal.

[0031] 6. The battery cell according to claim 4, wherein the N first grooves are open-ended.

[0032] 7. The battery cell of claim 1 , wherein the first groove is open-ended.

[0033] 8. A battery cell according to Option 1, wherein the external tabs of the C cathode electrodes and one of the A anode electrodes are divided into a first group and a second group, folded along a first direction and a second direction, respectively, and laser welded to the surface of the first internal terminal on opposite sides of the first groove.

[0034] 9. The battery cell according to claim 1, wherein the first internal terminal is “L”-shaped and includes a first portion and a second portion extending transversely relative to the first portion.

[0035] 10. The battery cell according to solution 3 further comprises:

[0036] shell;

[0037] a first external terminal in contact with the first internal terminal; and

[0038] A second external terminal is in contact with the second internal terminal.

[0039] 11. A battery cell, comprising:

[0040] A stack, the stack comprising:

[0041] C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0042] A anode electrode, the anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and

[0043] S diaphragms, where C, A, and S are integers greater than zero; and

[0044] a first internal terminal comprising R slots, wherein R is an integer greater than zero,

[0045] The external tab of one of the C cathode electrodes and the A anode electrodes is folded and laser welded to the inner surface of the first internal terminal through at least one of the R grooves of the first internal terminal.

[0046] 12. The battery cell according to claim 11, further comprising:

[0047] A second inner terminal including R slots,

[0048] The external tab of the other of the C cathode electrodes and the A anode electrodes is folded and laser welded to the inner surface of the second internal terminal through at least one of the R grooves of the second internal terminal.

[0049] 13. The battery cell according to claim 11, wherein:

[0050] R is greater than 1; and

[0051] The outer tab of one of the C cathode electrodes and the A anode electrodes is folded and laser welded to the inner surface of the first inner terminal through at least another one of the R grooves of the first inner terminal.

[0052] 14. The battery cell according to claim 11, wherein the first internal terminal has an “L” shape and includes a first portion and a second portion extending transversely relative to the first portion.

[0053] 15. A battery cell according to Option 11, wherein the external tabs of the C cathode electrodes and one of the A anode electrodes include a first external tab and a second external tab, and the first external tab and the second external tab are folded along a first direction and a second direction and laser welded to the inner surface of the first internal terminal through at least one of the R grooves of the first internal terminal.

[0054] 16. The battery cell according to claim 12, further comprising:

[0055] shell;

[0056] a first external terminal in contact with the first internal terminal; and

[0057] A second external terminal is in contact with the second internal terminal.

[0058] 17. A battery cell comprising:

[0059] A stack, the stack comprising:

[0060] C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector;

[0061] A anode electrode, the anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and

[0062] S diaphragms, where C, A, and S are integers greater than zero; and

[0063] A first internal terminal comprising:

[0064] Planar parts; and

[0065] a second portion including a central portion connected to the second portion and a first side wall and a second side wall extending from the central portion;

[0066] The external tab of one of the C cathode electrodes and the A anode electrodes passes through the first and second side walls of the first internal terminal and is laser welded to the inner surfaces of the first and second side walls of the first internal terminal.

[0067] 18. The battery cell according to claim 17, further comprising:

[0068] The second inner terminal comprises:

[0069] Planar parts; and

[0070] a second portion including a central portion and first and second sides extending from the central portion;

[0071] The external tab of the other of the C cathode electrodes and the A anode electrodes passes through the first side and the second side and is laser welded to the inner surfaces of the first side wall and the second side wall of the second internal terminal.

[0072] 19. The battery cell according to claim 18, further comprising:

[0073] shell;

[0074] a first external terminal in contact with the planar portion of the first internal terminal; and

[0075] A second external terminal is in contact with the planar portion of the second internal terminal.

[0076] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] The present disclosure will be more fully understood from the detailed description and accompanying drawings, in which:

[0078] Figure 1 is a side cross-sectional view of an example of a battery cell;

[0079] Figure 2 is a perspective view of an example of a prismatic battery cell according to the present disclosure including a laser welded internal terminal in contact with an external terminal;

[0080] Figure 3 is a perspective view of an example of a prismatic battery cell including electrodes having external tabs laser welded to internal terminals;

[0081] Figure 4 is a perspective view showing laser welding of an outer tab of an electrode to an inner surface of an inner terminal;

[0082] FIG. 5A to FIG. 5D is a perspective view showing an example of an internal terminal having one or more slots and an external tab of an electrode laser welded to the internal terminal in or through the one or more slots according to the present disclosure;

[0083] FIG. 6A to FIG. 6D is a perspective view showing an example of an internal terminal having one or more open-ended slots and an external tab laser welded to an electrode of the internal terminal through the one or more open-ended slots according to the present disclosure;

[0084] Fig. 7A and Figure 7B is a perspective view of another example of an internal terminal laser welded to an external tab of an electrode according to the present disclosure; and

[0085] Fig. 8A and Figure 8B is a perspective view of an example of an internal terminal having a slot and an external tab of an electrode laser welded to an inner surface of the internal terminal through the slot according to the present disclosure.

[0086] Among the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0087] Although battery cells including laser welded internal terminals according to the present disclosure are illustrated in the context of electric vehicles, battery cells including laser welded internal terminals may be used in stationary applications and / or other applications.

[0088] Reference now Figure 1 , the battery cell 10 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32, which are arranged in a predetermined order in a stack 12 in a housing 50, where C, A, and S are integers greater than 1. In some examples, A=C+1. The C cathode electrodes 20-1, 20-2, ..., and 20-C include a cathode active layer 24 arranged on one or both sides of a cathode current collector 26. The A anode electrodes 40-1, 40-2, ..., and 40-A include an anode active layer 42 arranged on one or both sides of an anode current collector 46.

[0089] Reference now Figure 2 , the square battery cell 100 includes a housing 110. In some examples, the housing 110 has a rectangular cross-section. The square battery cell 100 includes external terminals 112 and 114 and a vent cap 116. A stack 115 of C cathode electrodes 20, A anode electrodes 40, and S separators 32 is arranged in the housing 110. As will be further described below, the anode current collector 46 and / or the cathode current collector 26 include external tabs that are laser welded to internal terminals that contact the external terminals 112 and 114 of the battery cell 10.

[0090] Reference now Figure 3 , the square battery cell 200 includes a housing 210 and internal terminals 224 and 226 arranged at opposite ends of the housing 210. A stack 240 of C cathode electrodes, A anode electrodes, and S separators is arranged in the housing 210. The anode current collector and / or the cathode current collector include external tabs 244 and 246 extending therefrom, respectively. The external tabs 244 and 246 are laser welded to the inner surfaces of the internal terminals 224 and 226, respectively.

[0091] exist Figure 4 , the internal terminal 226 includes a first portion 228 and a second portion 230 extending from the first portion 228. In some examples, the first portion 228 is "L" shaped relative to the second portion 230 and forms an angle in the range of 80° to 100° (e.g., 90°). In some examples, the external tabs 246 are laser welded to the inner surface 231 of the internal terminal 226, respectively. It is difficult to laser weld the external tabs 244 and 246 using this method. The internal terminal 226 contacts one of the external terminals 112 and 114 of the battery cell 10 to provide an external connection to the anode electrode or the cathode electrode.

[0092] exist Figures 5A to 5D In the case of a laser welding process, an internal terminal including one or more slots may be used to improve the laser welding process. Figure 5AIn the example, the internal terminal 250 includes a first portion 252 and a second portion 254 extending from the first portion 252. In this example, the second portion 254 of the internal terminal 250 includes a slot 256 extending in the longitudinal direction. In some examples, the slot is a closed-end slot. The longitudinal length of the slot 256 is greater than or equal to the height of the external tab 246, and the width is greater than or equal to the thickness of the stack. The end 260 of the external tab 246 of the anode electrode and / or the cathode electrode is inserted through the slot 256. Figure 5B In the embodiment, the end 260 of the external tab 246 is folded and laser welded to the surface (e.g., the outer surface 251 and / or the edge surface 253) of the internal terminal 250 by the laser 120. In other words, the laser 120 lap welds and / or edge welds the end 260 of the external tab 246 to the internal terminal 250.

[0093] In some examples, the end 260 of the external tab 246 is ultrasonically welded and / or trimmed prior to being inserted through the slot 256. In other examples, the end 260 of the external tab 246 is not ultrasonically welded and / or trimmed prior to being inserted through the slot 256.

[0094] exist Figure 5C , after being inserted through the slot 256, the ends 260 of the external tabs 246 are divided into two groups (the groups may include the same or different numbers of external tabs). The ends 260 of the first group of external tabs 246 are folded in one direction at 260-1 (and laser welded to the outer surface 251 of the inner terminal 250). The ends 260 of the second group of external tabs 246 are folded in another direction at 260-2 (and laser welded to the outer surface 251 and / or edge surface 253 of the inner terminal 250).

[0095] exist Figure 5D In the embodiment, the internal terminal 280 includes N slots 256-1, ..., and 256-N, where N is an integer greater than 1. In some examples, the N slots 256-1, ..., and 256-N extend parallel to each other. Before being inserted through the N slots 256-1, ..., and 256-N, the ends 260 of the external tabs 246 are divided into N groups. The ends 260 of the N groups of external tabs 246 are inserted through corresponding slots in the N slots 256-1, ..., 256-N. All ends of the N groups can be folded in the same direction (for example, Figure 5B The inner terminals 280 are folded inward or outward), folded in different directions (e.g., adjacent pairs are folded toward each other or adjacent pairs are folded away from each other), and / or divided into first and second subgroups folded in opposite directions and laser welded to the outer surface 251 and / or edge surface 253 of the inner terminal 280, such as Figure 5C as shown in .

[0096] exist FIG. 6A to FIG. 6DIn the case of an internal terminal including one or more open ended slots, it is possible to improve the laser welding process. Fig. 6A , the internal terminal 300 includes a first portion 310 and a second portion 312 extending from the first portion 310. In this example, the internal terminal 300 includes an open-ended slot 314 that extends to an edge 317 of the second portion 312 and includes an opening at 316. The end 260 of the external tab 246 of the anode electrode and / or cathode electrode is inserted into the slot 256 (e.g., from the side and / or through the opening 316). Figure 6B In the embodiment, the end portion 260 of the external tab 246 is folded and laser welded to the surface of the internal terminal 300 .

[0097] exist Figure 6C , after being inserted through the open-ended slot 314, the ends 260 of the external tabs 246 can be divided into two groups (having the same or different numbers of external terminals). The ends 260 of the first group of external tabs 246 are folded in one direction and laser welded to the surface of the internal terminal 300. The ends 260 of the second group of external tabs 246 are folded in another direction and laser welded to the surface of the internal terminal 300. As can be appreciated, the ends 320 adjacent to the opening 316 can be tapered to make insertion easier.

[0098] exist Fig.6D In the embodiment, the internal terminal 330 includes N slots 314-1, ..., and 314-N, where N is an integer greater than 1. Before being inserted through the N slots 256-1, ..., 256-N, the ends 260 of the external tabs 246 are divided into N groups. The ends 260 of the N groups of external tabs 246 are inserted through corresponding slots in the N slots 314-1, ..., 314-N. All the ends of the N groups can be folded in one direction and laser welded to the surface of the internal terminal 330, such as Figure 6B All ends of the N groups can be divided into a first subgroup and a second subgroup folded laterally (or transversely) in opposite directions and laser welded to the surface of the internal terminal 330, as shown in FIG. Figure 6C as shown in .

[0099] Reference now Fig. 7A and Figure 7B , the internal terminal 350 includes a planar portion 352 and a second portion 354, the second portion 354 includes side walls 356 and 360 extending from a center portion 364. In some examples, the center portion 364 is arcuate or "U" shaped. The end 260 of the tab 264 is arranged between the side walls 356. In some examples, the side walls 356 bias the end 260 of the external tab 246 (e.g., apply force in an inward direction) to improve electrical contact. In some examples, the side walls 356 are laser welded to the end 260 of the external tab 246 at 357.

[0100] Reference now Fig. 8A and Figure 8B , the internal terminal 400 includes a first portion 410 and a second portion 412 extending laterally relative to the first portion 410. In this example, the internal terminal 400 includes R grooves 414-1, 414-2, ..., and 414-R (where R is an integer greater than zero) extending between the lateral edges of the second portion 412. In some examples, the battery cell stack includes a first external tab 430-1 and a second external tab 430-2 connected to the anode current collector or the cathode current collector. In other words, each of the anode current collector and the cathode current collector includes two external tabs to provide redundant connections, thereby improving reliability. In some examples, the first external tab 430-1 and the second external tab 430-2 are bent in different lateral directions (the first external tab 430-1 is bent in a direction outward from the page, and the second external tab 430-2 is bent in a direction into the page).

[0101] exist Figure 8B , the ends 440 of the first external tab 430-1 and the second external tab 430-2 are positioned to contact the inner surface 441 of the second portion 412, and are laser welded to the inner surface 441 of the second portion 412 through one or more of the R slots 314-1, 314-2, ..., and 314-R. In other words, the laser passes through the R slots 314-1, 314-2, ..., and 314-R.

[0102] The foregoing description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because after studying the drawings, the specification and the appended claims, other modifications will become apparent. It should be understood that one or more steps in the method can be performed in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described as having certain features above, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with each other is still within the scope of the present disclosure.

[0103] The spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "immediately adjacent," "on top of," "above," "below," and "disposed." Unless explicitly described as "direct," when describing a relationship between a first element and a second element in the above disclosure, the relationship may be a direct relationship in which no other intermediate elements exist between the first element and the second element, but may also be an indirect relationship in which one or more intermediate elements (spatially or functionally) exist between the first element and the second element. As used herein, the phrase at least one of A, B, and C should be interpreted to mean a logical (A or B or C) using a non-exclusive logical "or," and should not be interpreted to mean "at least one of A, at least one of B, and at least one of C."

[0104] In the drawings, the direction of the arrows (as indicated by the arrows) generally indicates the flow of information (such as data or instructions) of interest to the diagram. For example, when component A and component B exchange various information, but the information sent from component A to component B is relevant to the diagram, the arrow may point from component A to component B. This unidirectional arrow does not mean that no other information is sent from component B to component A. In addition, for information sent from component A to component B, component B may send a request for the information or a confirmation of receipt of the information to component A.

Claims

1. A battery cell, comprising: A stack, the stack comprising: C cathode electrodes, each cathode electrode comprising a cathode current collector, a cathode active layer disposed on the cathode current collector, and an external tab extending from the cathode current collector; A anode electrodes, each anode electrode comprising an anode current collector, an anode active layer disposed on the anode current collector, and an external tab extending from the anode current collector; and S diaphragms, where C, A, and S are integers greater than 1; and comprising a first internal terminal of a first slot, wherein an external tab of one of the C cathode electrodes and the A anode electrodes is inserted into the first slot, Part of the external tab of one of the C cathode electrodes and the A anode electrodes extends through the first groove, is folded and laser welded to the surface of the first internal terminal. 2 . The battery cell of claim 1 , further comprising a second internal terminal comprising a second groove for accommodating an external tab of the other of the C cathode electrodes and the A anode electrodes.

3. The battery cell according to claim 2, wherein: A portion of the external tab of the other of the C cathode electrodes and the A anode electrodes extending through the second groove is folded and laser welded to a surface of the second internal terminal.

4. The battery cell according to claim 1, wherein: The first inner terminal includes N first grooves, where N is an integer greater than 1.

5. The battery cell according to claim 4, wherein: The external tabs of one of the C cathode electrodes and the A anode electrodes are divided into N groups, and the N groups are respectively inserted through the N first grooves and are folded and laser welded to the surface of the first internal terminal.

6. The battery cell according to claim 4, wherein: The N first slots are open-ended. The battery cell of claim 1 , wherein the first slot is open-ended.

8. The battery cell according to claim 1, wherein: The external tabs of one of the C cathode electrodes and the A anode electrodes are divided into first and second groups, folded in first and second directions, respectively, and laser welded to the surface of the first internal terminal on opposite sides of the first groove.

9. The battery cell according to claim 1, wherein: The first inner terminal is “L” shaped and includes a first portion and a second portion extending transversely relative to the first portion.

10. The battery cell according to claim 3, further comprising: shell; a first external terminal in contact with the first internal terminal; and A second external terminal is in contact with the second internal terminal.

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