Composite metal tab and single cell test structure

Abstract

This application relates to the field of battery technology, and more particularly to a composite metal connector and a single-cell testing structure. The composite metal connector and single-cell testing structure provided in this application aim to solve the problems of large contact resistance increments and excessive heat generation in long-term performance testing of traditional hard aluminum busbar connectors. The connector consists of a first conductive busbar and a second conductive busbar connected together. The first conductive busbar is a hard aluminum busbar with positioning holes for positioning with the cell terminals. The second conductive busbar has a conductivity ≥45% IACS and higher fatigue strength, and has connection holes for connecting test wiring harnesses. This structure, by introducing a second conductive busbar with good conductivity and fatigue resistance, significantly improves the fatigue resistance and connection reliability of the connector, reducing or avoiding excessive heat generation due to excessive contact resistance increments during testing, thereby ensuring the accuracy and safety of long-term performance test data.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a composite metal connector and a single cell testing structure. Background Technology

[0002] In existing technologies, the commonly used connecting pieces for testing individual battery cells are mostly rigid aluminum busbars. These busbars have positioning holes near one end and connection holes near the other. The rigid aluminum busbars are positioned with the terminals of the individual battery cells via the positioning holes and are then bolted to the test wiring harness via the connection holes.

[0003] In practical applications, during long-term performance testing of individual battery cells, such as cycle life and calendar life tests, the contact resistance at the connection between the hard aluminum busbar and the test harness increases significantly after a period of testing, generating a large amount of heat. When this heat is transferred into the individual battery cell, it affects the accuracy of the test data and the lifespan of the individual battery cell, which is detrimental to the assessment of the individual battery cell's performance. Utility Model Content

[0004] To address the technical problem of significant heat generation due to large increases in contact resistance at the connection between the hard aluminum busbar and the test harness during long-term performance testing of individual battery cells, this application provides a composite metal connector and a single-cell testing structure.

[0005] The technical solution of this application is as follows:

[0006] In a first aspect, this application provides a composite metal connector, which includes a first conductive bus and a second conductive bus connected to each other. The first conductive bus is a hard aluminum bus, and a positioning hole is provided on the hard aluminum bus, which is positioned with the terminal post of the single cell.

[0007] The second conductive bus has a conductivity ≥45% IACS and a fatigue strength greater than that of the first conductive bus. The second conductive bus is provided with connection holes for connecting the test harness via threaded fasteners.

[0008] The composite metal connector of this application adds a second conductive busbar with excellent conductivity and better fatigue resistance to the traditional connector (hard aluminum busbar), thereby improving the fatigue resistance of the connector. In the long-term performance testing of individual cells, this improvement helps to enhance the connection reliability between the connector and the test harness, effectively avoiding the problem of excessive heat generation due to excessive increase in contact resistance during the test, thus ensuring the accuracy and security of long-term performance test data.

[0009] In one possible design, the second conductive bus is a copper bus with a silver or nickel layer on its surface. The first and second conductive buses are welded together by ultrasonic welding or diffusion welding.

[0010] Based on the composite metal connector provided in this embodiment, using a copper busbar as the second conductive busbar can improve the fatigue resistance of the connector. Simultaneously, a silver or nickel layer is deposited on the surface of the copper busbar, which reduces the formation of brittle compounds with poor conductivity between the first and second conductive busbars under high temperatures. Furthermore, the first and second conductive busbars are ultrasonically welded or diffusion welded. Since ultrasonic welding and diffusion welding operate at lower temperatures, the formation of brittle compounds between the first and second conductive busbars is further avoided, ensuring the conductivity and connection reliability of the first and second conductive busbars.

[0011] In one possible design, the thickness of the silver or nickel layer is 6-15 μm.

[0012] Based on the composite metal connector provided in this embodiment, by controlling the thickness of the silver and nickel layers to be between 6-15 μm, costs can be reduced. Furthermore, when the nickel layer thickness is between 6-15 μm, the resulting increase in resistance is far less than that of a thick copper-aluminum brittle compound layer.

[0013] In one possible design, the copper busbar is made of annealed oxygen-free copper, annealed TAg0.1 silver copper, or Cu T2-Y2.

[0014] Based on the composite metal connector provided by this embodiment, during the cycle performance test of a single battery cell, the contact resistance increment after 1000 cycles is ≤20%, and the bolt preload decay is ≤10%, which effectively reduces the increase in contact resistance and improves the connection reliability between the connector and the test harness.

[0015] In one possible design, the first conductive bus includes a first sub-segment and a second sub-segment of integral structure, with a positioning hole disposed in the first sub-segment.

[0016] The second conductive bus includes a third sub-segment and a fourth sub-segment with an integral structure. The third sub-segment is overlapped with the second sub-segment, and the connection hole is located in the fourth sub-segment.

[0017] Based on the composite metal connecting piece provided in this embodiment, the third segment overlaps with the second segment, which helps to improve the connection reliability between the first conductive busbar and the second conductive busbar.

[0018] In one possible design, the end of the first conductive bus is connected to the end of the second conductive bus. This helps to reduce material usage and save costs.

[0019] In one possible design, a bend is formed on the composite metal connector.

[0020] When transporting or storing a battery cell with a composite metal connector welded to this structure, the second conductive busbar can be bent towards the first conductive busbar via a bending section. This reduces the length of the composite metal connector and the likelihood of contact with other conductive objects. Furthermore, it facilitates the use of insulating tape to wrap the composite metal connector, improving the electrical insulation of the battery cell from the external environment.

[0021] In one possible design, the bend is arched.

[0022] Based on the composite metal connector provided in this embodiment, the bent portion is arched and has a certain supporting force. When the second conductive busbar is bent towards the first conductive busbar, the bent portion ensures a stable distance between the two conductive busbars. This distance provides installation space for threaded fasteners. Thus, test harnesses can be connected without changing the bending state, which helps improve testing efficiency. Furthermore, it saves testing space.

[0023] Secondly, based on the same inventive concept, this application also provides a single-cell test structure, which includes a single-cell battery, a test harness, a metal connecting piece, and threaded fasteners.

[0024] Each individual battery cell includes a terminal post. The test harness includes an electrical connector ring disposed at one end of the test harness. The connector is any of the composite metal connectors described above, with positioning holes positioned with the terminal post and connection holes aligned with the electrical connector ring.

[0025] The threaded fasteners include bolts and nuts. The bolts pass through the electrical connection ring and the connection hole, and the nuts are threadedly connected to the bolts to secure the second conductive busbar to the test harness.

[0026] The beneficial effects of the single-cell test structure provided in the second aspect and the various possible designs of the second aspect can be found in the first aspect and the various possible implementations of the first aspect, and will not be repeated here. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the connecting piece used for testing existing single-cell batteries.

[0028] Figure 2 for Figure 1 Top view.

[0029] Figure 3 For use Figure 1 The diagram shows a single-cell test structure for the connecting piece.

[0030] Figure 4This is a schematic diagram of the structure of the connecting piece for testing a single battery cell provided in an embodiment of this application.

[0031] Figure 5 for Figure 4 Top view.

[0032] Figure 6 For use Figure 4 The diagram shows a single-cell test structure for the connecting piece.

[0033] Figure 7 This is a schematic diagram of another composite metal connector provided in an embodiment of this application.

[0034] Figure 8 This is a schematic diagram of another single-cell test structure provided in an embodiment of this application.

[0035] The reference numerals in the prior art are:

[0036] 1′, Single cell; 11′, Terminal post;

[0037] 2′ Test harness; 21′ Electrical connector ring;

[0038] 3′, connecting piece; 311′, positioning hole; 321′, connecting hole;

[0039] 4′ Threaded fasteners;

[0040] The reference numerals in the embodiments of this application are as follows:

[0041] 1. Individual battery cell; 11. Terminal posts;

[0042] 2. Test harness; 21. Electrical connector ring;

[0043] 3. Composite metal connecting piece; 31. First conductive bar; 311. Positioning hole; 312. First sub-segment; 313. Second sub-segment; 32. Second conductive bar; 321. Connecting hole; 322. Third sub-segment; 323. Fourth sub-segment; 33. Bending part;

[0044] 4. Threaded fasteners; 41. Bolts; 42. Nuts. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and drawings of this application are intended to cover non-exclusive inclusion.

[0047] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0048] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0049] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0050] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, "connection" or "joining" in mechanical structures can refer to a physical connection. A physical connection can be a fixed connection, such as a connection secured by spacers, screws, bolts, or other spacers. A physical connection can also be a detachable connection, such as a snap-fit ​​or interlocking connection. A physical connection can also be an integral connection, such as a connection formed by welding, bonding, or integral molding. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0051] The present application will be described in detail below with reference to the accompanying drawings.

[0052] Figure 1 This is a schematic diagram of the structure of the connecting piece used for testing existing single-cell batteries. Figure 2 for Figure 1 Top view, Figure 3 For use Figure 1 The diagram shows a single-cell test structure for the connecting piece.

[0053] Please combine Figures 1 to 3 In existing technologies, the commonly used connecting piece 3' for testing individual battery cells 1' is mostly made of hard aluminum busbar. The hard aluminum busbar has a positioning hole 311' near one end and a connecting hole 321' near the other end. The hard aluminum busbar is positioned with the terminal post 11' of the individual battery cell 1' through the positioning hole 311', and is fixed to the test wiring harness 2' through the connecting hole 321' by a threaded fastener connection 4'.

[0054] Under normal circumstances, the connecting piece 3′ and the individual battery cell 1′ are welded together and are not disassembled unless there are abnormalities. However, the connecting piece 3′ and the test harness 2′ are only fixedly connected by threaded fasteners 4′ during testing.

[0055] During long-term performance testing of a single battery cell 1′, the connection piece 3′ and the test harness 2′ will experience multiple connection-disconnection cycles. For example, to assess the performance degradation of a single battery cell 1′ after long-term repeated use, a cycle life test will be performed on the single battery cell 1′. The test method involves subjecting the single battery cell 1′ to thousands of charge-discharge cycles under specific ambient temperature, charge-discharge rate, and cutoff voltage. During the cycle life test, the contact resistance at the test connection will continuously increase. To control this resistance, the threaded fastener 4′ at the test structure will be disassembled periodically, the electrical connection ring 21′ of the test harness 2′ will be replaced, or the connection piece 3′ and the electrical connection ring 21′ will be wiped with lint-free paper dampened with alcohol or a special cleaning agent to remove dirt and other non-conductive substances from their surfaces, thereby reducing the contact resistance at this point and ensuring the stability of the test.

[0056] Even after reducing the resistance at the connection point by wiping the connecting piece 3' and replacing the electrical connecting ring 21', in practical applications, during cycle life testing of individual cell 1', a significant increase in contact resistance at the connection between the hard aluminum busbar and the test harness 2' still occurred after a period of testing, generating a large amount of heat. When this heat is transferred into the individual cell 1', it affects the accuracy of the test data and the lifespan of the individual cell 1', hindering the assessment of its performance.

[0057] After analyzing the causes of heat generation during cycle life testing, the inventors discovered that one of the factors was that during cycle life testing of the individual cell 1′, the test harness 2′ and the connecting piece 3′ were connected and disconnected multiple times. This process caused the hard aluminum busbar to undergo multiple stress changes. Since the hard aluminum busbar generally has poor stress fatigue resistance, when it is used again after multiple operations, the contact resistance between the hard aluminum busbar and the test harness 2′ increases, thereby generating a large amount of heat.

[0058] Based on this, this application provides a composite metal connector. Please refer to... Figures 4 to 6 , Figure 4 This is a schematic diagram of the structure of the connecting piece for testing a single battery cell 1 provided in an embodiment of this application. Figure 5 for Figure 4 Top view, Figure 6 For use Figure 4 The diagram shows a test structure of a single cell 1 with a connecting piece.

[0059] Please combine Figures 4 to 6 The composite metal connector 3 provided in this application includes a first conductive bus 31 and a second conductive bus 32 connected to each other. The first conductive bus 31 is a hard aluminum bus, and a positioning hole 311 is provided on the hard aluminum bus. The positioning hole 311 is positioned with the terminal post 11 of the single cell 1. The conductivity of the second conductive bus 32 is ≥45% IACS, and its fatigue strength is greater than that of the first conductive bus 31. The second conductive bus 32 is provided with a connection hole 321, which is used to connect the test wire harness 2 through a threaded fastener 4.

[0060] Please continue to refer to this. Figures 4 to 6 Based on the same inventive concept, this application also provides a single-cell battery test structure, which includes a single-cell battery 1, a test harness 2, a connecting piece, and a threaded fastener 4. The single-cell battery 1 includes a terminal post 11. The test harness 2 includes an electrical connection ring 21 disposed at one end of the test harness 2. The connecting piece is the aforementioned composite metal connecting piece 3, with a positioning hole 311 positioned with the terminal post 11 and a connection hole 321 aligned with the electrical connection ring 21. The threaded fastener 4 includes a bolt 41 and a nut 42. The bolt 41 passes through the electrical connection ring 21 and the connection hole 321, and the nut 42 is threadedly connected to the bolt 41 to securely connect the second conductive bus 32 to the test harness 2.

[0061] For details, please refer to [link / reference]. Figures 4 to 6 The composite metal connector 3 provided in this application includes a first conductive busbar 31 and a second conductive busbar 32, wherein the first conductive busbar 31 is a hard aluminum busbar, and the electrode post 11 is generally also made of aluminum. During the testing of a single battery cell 1, the first conductive busbar 31 can be positioned with the positioning point (recess) on the electrode post 11 of the single battery cell 1 through the positioning hole 311. After positioning, the first conductive busbar 31 is welded to the single battery cell 1.

[0062] Common grades of hard aluminum bars are 1060 and 1090. They are processed and partially annealed to achieve a semi-hard state, which has the characteristics of good thermal and electrical conductivity, low cost, lightweight and easy processing.

[0063] The second conductive busbar 32 has a conductivity ≥45% IACS, thus possessing good conductivity, which facilitates control of contact resistance during testing. Furthermore, the fatigue strength of the second conductive busbar 32 is greater than that of the first conductive busbar 31, and a connecting hole 321 is located on the second conductive busbar 32. During the testing of a single cell 1, the composite metal connecting piece 3 can be connected to the test harness 2 via the connecting hole 321 using a threaded fastener 4.

[0064] During long-term performance testing of the individual battery cell 1, such as cycle life testing, the fatigue resistance of the second conductive busbar 32 is superior to that of the first conductive busbar 31. Furthermore, when the composite metal connector 3 is repeatedly disassembled and reassembled with the test harness 2, its fatigue resistance is higher than that of the first conductive busbar 31. Figure 1 The simple hard aluminum busbar shown is better. The composite metal connector 3 is less prone to damage due to fatigue, thus avoiding the problem of connection failure with the test harness 2. This also helps prevent a sudden increase in contact resistance between the composite metal connector 3 and the test harness 2, which would generate a large amount of heat.

[0065] As described above, the composite metal connector 3 of this application adds a second conductive bar 32 with excellent conductivity and better fatigue resistance to the traditional connector (hard aluminum busbar), thereby improving the fatigue resistance of the connector. Therefore, in the long-term performance testing of a single battery cell 1, this improvement helps to enhance the connection reliability between the connector and the test harness 2, and can reduce or avoid the problem of excessive heat generation due to excessive contact resistance increase during the test, thereby ensuring the accuracy and security of long-term performance test data.

[0066] Please continue to refer to this. Figure 4 and Figure 5 In one embodiment of this application, the second conductive bus 32 is a copper bus, and the surface of the copper bus is further provided with a silver layer or a nickel layer. The first conductive bus 31 and the second conductive bus 32 are welded together by ultrasonic welding or diffusion welding.

[0067] Specifically, copper busbars have good conductivity and fatigue resistance, and the second conductive busbar 32 being a copper busbar can meet the testing requirements. However, copper and aluminum are prone to react at high temperatures, forming brittle copper-aluminum compounds (such as CuAl2) with poor conductivity, which affects the conductivity of the composite metal connector 3.

[0068] In one embodiment of this application, to avoid the reaction between copper and aluminum, a silver layer is formed on the surface of the copper busbar by chemical plating or electroplating. Silver is the most conductive metal in nature, and the silver plating layer hardly increases the contact resistance. Moreover, silver has good compatibility with aluminum, and in processes such as ultrasonic welding, it can more easily form a strong bond with aluminum atoms, while effectively blocking the direct diffusion of copper and aluminum atoms, greatly suppressing the formation of brittle copper-aluminum compounds (such as CuAl2).

[0069] In another embodiment of this application, in order to avoid the reaction between copper and aluminum, a nickel layer is formed on the surface of the copper busbar by electroplating. Nickel has stable chemical properties and can very effectively block the mutual diffusion of copper and aluminum atoms during the welding heating process, thereby preventing the formation of a brittle compound layer.

[0070] Furthermore, in this application, the welding method between the first conductive busbar 31 and the second conductive busbar 32 is ultrasonic welding or diffusion welding.

[0071] Ultrasonic welding utilizes high-frequency vibration waves (ultrasound) transmitted to the surfaces of the first conductive busbar 31 and the second conductive busbar 32. Under pressure, the metal atoms of the first conductive busbar 31 and the second conductive busbar 32 diffuse and fuse together in a solid state. The entire process involves no melting, and the temperature is far below the melting point of metals. This low temperature fundamentally avoids all the problems associated with fusion welding, reducing the generation of brittle compounds, thermal stress, and porosity. Furthermore, the welding time is typically completed within a fraction of a second.

[0072] Diffusion welding involves bringing the contact surfaces of the materials to be joined together tightly under specific temperature and pressure conditions, and maintaining this state for a period of time. Metallurgical bonding is achieved through the interdiffusion (mutual solubility) of atoms in the microscopic regions of the contact surfaces. The entire process is carried out below the melting point of the materials, thus avoiding solidification defects and porosity caused by melting, and maximizing the control over the formation of brittle compounds.

[0073] In summary, based on the composite metal connector 3 provided in this embodiment, selecting a copper busbar as the second conductive busbar 32 can improve the fatigue resistance of the connector. Simultaneously, by depositing a silver or nickel layer on the surface of the copper busbar, the formation of brittle compounds with poor conductivity between the first conductive busbar 31 and the second conductive busbar 32 under high temperatures can be reduced. Furthermore, the first conductive busbar 31 and the second conductive busbar 32 are ultrasonically welded or diffusion welded. Since ultrasonic welding and diffusion welding operate at lower temperatures, the formation of brittle compounds between the first conductive busbar 31 and the second conductive busbar 32 is further avoided, ensuring the conductivity and connection reliability of the first conductive busbar 31 and the second conductive busbar 32.

[0074] Please continue to refer to this. Figure 4 and Figure 5 In one embodiment of this application, the thickness of the silver or nickel layer is 6-15 μm.

[0075] Specifically, the silver or nickel layer is added to form a barrier layer on the surface of the copper busbar, preventing chemical reactions between the aluminum and copper busbars. For the silver layer, silver has good conductivity and will not increase the resistance of the copper busbar. However, because silver is relatively expensive, the silver layer should not be too thick. Nickel has a higher resistivity than both copper and silver; therefore, the nickel layer itself introduces some additional resistance.

[0076] In this embodiment, the thickness of the silver and nickel layers is between 6 and 15 μm, which reduces costs. Furthermore, when the nickel layer is 6-15 μm thick, the resulting increase in electrical resistance is far less than that of a thick copper-aluminum brittle compound layer.

[0077] Please continue to refer to this. Figure 4 In some embodiments of this application, the copper busbar is made of annealed oxygen-free copper, annealed TAG0.1 silver copper, or Cu T2-Y2.

[0078] Specifically, annealed oxygen-free copper is first and foremost an oxygen-free copper with extremely high purity, exceeding 99.95%. Furthermore, its oxygen content is extremely low (typically ≤0.003%). This avoids hydrogen embrittlement and ensures extremely high electrical and thermal conductivity.

[0079] Secondly, annealed oxygen-free copper has undergone "annealing" heat treatment, which eliminates internal stress, making it very soft and with excellent ductility.

[0080] Annealed TAg0.1 silver copper is an alloy in which approximately 0.1% (by weight) of silver (Ag) is precisely added to high-purity copper and then annealed (heated and then slowly cooled) to obtain a soft state.

[0081] Cu T2-Y2 is a type of pure copper with moderate strength and some elasticity. Cu T2 refers to its composition; it is a common pure copper with very high purity (copper content ≥ 99.9%) and good electrical and thermal conductivity. Y2 refers to its state, representing a "semi-hard state," meaning it has undergone a certain degree of cold working (such as cold rolling or cold drawing) to increase its strength.

[0082] Using the composite metal connector 3 provided in this embodiment, during the cycle performance test of a single cell 1, the contact resistance increment after 1000 cycles is ≤20%, and the bolt preload decay is ≤10%, which effectively reduces the increase in contact resistance and improves the connection reliability between the connector and the test harness 2.

[0083] The specific experimental details are as follows:

[0084] At room temperature, lithium-ion cells with different connecting pieces were fully charged and discharged at a current of 300A. The temperature, contact resistance, and bolt preload at the connecting pieces were measured before and after 1000 charge-discharge cycles. The measurement data are shown in the table below.

[0085]

[0086] Please continue to refer to this. Figure 4 and Figure 5In one embodiment of this application, the first conductive bus 31 includes a first sub-segment 312 and a second sub-segment 313 with an integral structure, and a positioning hole 311 is disposed in the first sub-segment 312. The second conductive bus 32 includes a third sub-segment 322 and a fourth sub-segment 323 with an integral structure, the third sub-segment 322 and the second sub-segment 313 are overlapped and connected, and a connection hole 321 is disposed in the fourth sub-segment 323.

[0087] Based on the composite metal connector 3 provided in this embodiment, the third segment 322 and the second segment 313 are overlapped and connected, which helps to improve the connection reliability between the first conductive busbar 31 and the second conductive busbar 32.

[0088] Figure 7 For a schematic diagram of another composite metal connector 3 provided in the embodiments of this application, please refer to... Figure 7 In one embodiment of this application, the end of the first conductive bus 31 is connected to the end of the second conductive bus 32. This helps to reduce material usage and save costs.

[0089] Figure 8 For a schematic diagram of another single-cell test structure provided in this application embodiment, please refer to... Figure 4 , Figure 5 , Figure 7 and Figure 8 In some embodiments of this application, a bent portion 33 is formed on the composite metal connecting piece 3.

[0090] Specifically, the bending portion 33 is generally located near the second conductive busbar 32 on the first conductive busbar 31. This allows the individual battery cell 1 with the welded composite metal connecting piece 3 to bend towards the first conductive busbar 31 during transportation or storage via the bending portion 33. This reduces the length of the composite metal connecting piece 3 and decreases the likelihood of contact with other conductive objects. Furthermore, it facilitates the use of insulating tape to wrap the composite metal connecting piece 3, improving the electrical insulation of the individual battery cell 1 from the external environment.

[0091] Please continue to refer to this. Figure 8 In some embodiments of this application, the bent portion 33 is arched.

[0092] Specifically, when the bend 33 is arched, it provides support. When the second conductive bus 32 bends towards the first conductive bus 31, the bend 33 ensures a stable distance between them. This distance provides space for the threaded fastener 4. Thus, the test harness 2 can be connected without changing the bending state, improving testing efficiency. Furthermore, it saves testing space.

[0093] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0094] The above-described embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A composite metal tab, characterized by, It includes a first conductive bus and a second conductive bus connected to each other. The first conductive bus is a hard aluminum bus and a positioning hole is provided on the hard aluminum bus. The positioning hole is used to position the electrode of the single cell. The conductivity of the second conductive busbar is ≥45% IACS, and its fatigue strength is greater than that of the first conductive busbar; the second conductive busbar is provided with a connection hole, which is used to connect the test wire harness through a threaded fastener.

2. The composite metal tab of claim 1, wherein The second conductive bus is a copper bus, and the surface of the copper bus is provided with a silver layer or a nickel layer; The first conductive busbar and the second conductive busbar are welded together by ultrasonic welding or diffusion welding.

3. The composite metal tab of claim 2, wherein, The thickness of the silver or nickel layer is 6-15 μm.

4. The composite metal tab of claim 2, wherein, The copper busbar is made of annealed oxygen-free copper, annealed TAG0.1 silver copper, or Cu T2-Y2.

5. The composite metal tab of any one of claims 1 to 4, wherein, The first conductive bus includes a first sub-segment and a second sub-segment of integral structure, and the positioning hole is disposed in the first sub-segment; The second conductive bus includes a third sub-segment and a fourth sub-segment of integral structure, the third sub-segment and the second sub-segment are connected by overlapping, and the connection hole is provided in the fourth sub-segment.

6. The composite metal tab of any one of claims 1 to 4, wherein, The end of the first conductive busbar is connected to the end of the second conductive busbar.

7. The composite metal tab of any one of claims 1 to 4, wherein The composite metal connecting piece has a bent portion formed on it.

8. The composite metal tab of claim 7, wherein, The bent portion is arched in shape.

9. A single cell testing structure, characterized by, This includes individual battery cells, test harnesses, connecting pieces, and threaded fasteners; The individual battery cell includes terminals; The test harness includes an electrical connection ring disposed at one end of the test harness; The connecting piece is a composite metal connecting piece as described in any one of claims 1 to 8, the positioning hole is positioned with the pole post, and the connecting hole is aligned with the electrical connection ring; The threaded fastener includes a bolt and a nut. The bolt passes through the electrical connection ring and the connection hole, and the nut is threadedly connected to the bolt, thereby fastening the second conductive busbar to the test harness.

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