Battery cell, secondary battery, and electronic device

Abstract

An electrode group, a secondary battery, and an electronic device are provided. The electrode group includes an electrode assembly, a packaging bag, a first tab, and a composite tab. The packaging bag includes a main body portion and a top seal portion. The electrode assembly is disposed in the main body portion. The main body portion includes a top wall. The top seal portion is connected to the top wall. One end of the first tab is connected to the electrode assembly. The other end of the first tab extends from the top seal portion. The composite tab includes a second tab and a reference tab that are stacked in a thickness direction of the composite tab. One end of the second tab is connected to the electrode assembly. The other end of the second tab extends from the top seal portion. In a first direction in which the main body portion points to the top seal portion, one end of the reference tab extends into the main body portion and the reference tab is not connected to the electrode assembly. The other end of the reference tab extends from the top seal portion. The electrode group can reduce the risk of interference between the reference tab and an electronic element disposed on a circuit board assembly provided on the top wall.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a battery cell, a secondary battery, and an electronic device. Background Technology

[0002] In the research and analysis of lithium-ion battery cells, three-electrode analysis using a reference electrode is an important method. By incorporating a reference electrode into the cell, the positive and negative electrodes can be studied separately, allowing for individual measurement of their potential and impedance data. This provides crucial information for studying degradation mechanisms and interface stability. Currently, three-electrode cells typically use three tabs connected to the positive, negative, and reference electrodes respectively. The spacing between these tabs can easily lead to interference with electronic components on the circuit board assembly. Summary of the Invention

[0003] In view of the above situation, it is necessary to provide a battery cell that can solve the above problems.

[0004] This application provides a battery cell comprising an electrode assembly, a packaging bag, a first tab, and a composite tab. The packaging bag includes a main body and a top seal. The electrode assembly is disposed within the main body, which includes a top wall, and the top seal is connected to the top wall. One end of the first tab is connected to the electrode assembly, and the other end extends from the top seal. The first tab has a first polarity. The composite tab includes a second tab and a reference tab stacked along the thickness direction of the composite tab. One end of the second tab is connected to the electrode assembly, and the other end extends from the top seal. The second tab has a second polarity different from the first polarity. Along a first direction, one end of the reference tab extends into the main body and is not connected to the electrode assembly, while the other end extends from the top seal. The first direction is the direction from the main body to the top seal.

[0005] In the aforementioned battery cell, the second tab and the first tab are configured to be electrically connected to an external circuit, and the reference tab is configured to acquire the battery cell's potential during cell cycling. By stacking the second tab and the reference tab along the thickness direction of the composite tab to form an integral composite structure, the second tab and the reference tab share the space in the width direction of the composite tab, which helps reduce the risk of interference between the reference tab and electronic components on the circuit board assembly mounted on the top wall.

[0006] In some embodiments of this application, the composite tab further includes a first insulating adhesive. Along the thickness direction of the composite tab, the first insulating adhesive is disposed between the second tab and the reference tab to isolate the reference tab and the second tab, thereby reducing the risk of interference between the reference tab and the second tab affecting the detection accuracy of the reference tab.

[0007] In some embodiments of this application, along the first direction, the length of the first insulating adhesive is greater than or equal to the length of the reference tab, and along the width direction of the composite tab, the width of the first insulating adhesive is greater than or equal to the width of the reference tab, so as to improve the isolation stability of the first insulating adhesive between the second tab and the reference tab.

[0008] In some embodiments of this application, along the thickness direction of the composite tab, the thickness of the second tab is D1, 0.05mm≤D1≤0.2mm, to improve the structural strength and current carrying capacity of the second tab, and to improve the packaging stability of the top seal. Along the thickness direction of the composite tab, the thickness of the reference tab is D2, 4μm≤D2≤10μm, to improve the structural strength and current carrying capacity of the reference tab, and to improve the packaging stability of the top seal. The top seal includes an inner unsealed area, a middle sealing area, and an outer unsealed area connected sequentially along the first direction. The middle sealing area is the area that has undergone heat sealing. Along the thickness direction of the composite tab, the thickness of the portion of the first insulating adhesive located within the middle sealing area is D3, 4μm≤D3≤16μm, to improve the insulation stability of the first insulating adhesive, and to improve the packaging stability of the top seal.

[0009] In some embodiments of this application, 6.4μm≤D3≤8μm is used to further improve the insulation stability of the first insulating adhesive and further improve the encapsulation stability of the top seal.

[0010] In some embodiments of this application, the composite tab further includes a lithium plating layer disposed in the portion of the reference tab that extends into the main body, so as to improve the accuracy of monitoring.

[0011] In some embodiments of this application, a lithium plating layer is disposed on the surface of the reference tab away from the first insulating adhesive. Along the thickness direction of the composite tab, the thickness of the lithium plating layer is D4, 10μm≤D4≤40μm, so as to provide sufficient lithium source and improve the space utilization rate of the lithium plating layer in the main body, thereby helping to improve the energy density of the battery cell.

[0012] In some embodiments of this application, the first insulating adhesive includes a first insulating portion disposed within the top seal portion. Along the width direction of the composite tab, the two ends of the first insulating portion protrude from the second tab and the reference tab. The battery cell includes a first tab adhesive. The first tab adhesive includes a first sub-adhesive and a second sub-adhesive. The first sub-adhesive is attached to the surface of the second tab away from the reference tab, and the first sub-adhesive and the first insulating portion together encapsulate the portion of the second tab located within the top seal portion. The second sub-adhesive is attached to the surface of the reference tab away from the second tab, and the second sub-adhesive and the first insulating portion together encapsulate the portion of the reference tab located within the top seal portion. The first and second sub-adhesives are used to improve the encapsulation stability of the composite tab within the top seal portion.

[0013] In some embodiments of this application, the top seal includes an inner unsealed area, a middle sealed area, and an outer unsealed area connected sequentially along a first direction. The middle sealed area is the region that has undergone heat sealing. Along the thickness direction of the composite tab, the thickness of the portion of the first sub-adhesive located within the middle sealed area is D5, where 8μm≤D5≤40μm, to improve the encapsulation stability of the top seal. Along the arrangement direction of the second sub-adhesive and the reference tab, the thickness of the portion of the second sub-adhesive located within the middle sealed area is D6, where 8μm≤D6≤40μm, to improve the encapsulation stability of the top seal.

[0014] In some embodiments of this application, the first insulating adhesive includes a second insulating portion and a third insulating portion connected to both sides of the first insulating portion. The second insulating portion is located outside the top sealing portion, and the third insulating portion is located inside the main body portion. Along the width direction of the composite tab, the size of the second insulating portion is smaller than the size of the first insulating portion to reduce the space wastage of the second insulating portion outside the top sealing portion. The size of the third insulating portion is smaller than the size of the first insulating portion to reduce the space wastage of the third insulating portion outside the top sealing portion.

[0015] In some embodiments of this application, the electrode assembly includes a first electrode, a diaphragm, a second electrode, and a sub-electrode. The first electrode, diaphragm, and second electrode are spaced apart. The second electrode includes a first current collector, and the sub-electrode is integrally formed with the first current collector. Multiple sub-electrodes are aggregated into a sub-electrode bundle, which is located between the first current collector and the top wall. Along the extension direction of the composite electrode, one end of the second electrode is connected to the sub-electrode bundle, and the other end of the second electrode extends from the top seal. The portion of the reference electrode extending into the main body is located between the first current collector and the top wall to reduce the impact of the reference electrode on the cycle performance of the electrode assembly. Furthermore, the composite electrode and the sub-electrode bundle share the space between the first current collector and the top wall, which can improve the space utilization rate of the composite electrode within the main body, thereby contributing to increasing the energy density of the battery cell.

[0016] In some embodiments of this application, the electrode assembly is a wound structure or a stacked structure.

[0017] In some embodiments of this application, the electrode assembly includes a first electrode, a diaphragm, and a second electrode arranged at intervals. A first tab is connected to the first electrode. The second electrode includes a first current collector, and the second tab is connected to the first current collector. A portion of the reference tab is located between the first and second electrodes. Along the arrangement direction of the first current collector and the top wall, the length of the portion of the reference tab located between the first and second electrodes is L1, and the length of the second electrode is L2, where 5mm ≤ L1 ≤ L2, to improve monitoring accuracy.

[0018] In some embodiments of this application, along the arrangement direction of the first current collector and the top wall, the first current collector includes a first edge and a second edge disposed opposite to each other, with the first edge closer to the top wall than the second edge. The midline between the first edge and the second edge of the first current collector is a first centerline. Viewed along the thickness direction of the first current collector, the edge of the portion of the reference tab located between the first electrode and the second electrode extends beyond the first edge but does not exceed the first centerline, thereby reducing the impact of the reference tab on the cycle performance of the electrode assembly.

[0019] In some embodiments of this application, the second electrode further includes a first active material layer, at least one surface of the first current collector is provided with the first active material layer, the first active material layer is provided with a first groove exposing the first current collector, and one end of the second electrode tab is located in the first groove and connected to the first current collector, so as to improve the stability of the connection between the second electrode tab and the first current collector.

[0020] In some embodiments of this application, the electrode assembly is a wound structure. The first current collector includes a first region and a second region connected along the winding direction of the first current collector, with the first region located at one end of the winding direction. The second electrode further includes a first active material layer. Along the thickness direction of the first current collector, the first region has no first active material layer on two surfaces, while at least one surface of the second region has the first active material layer. One end of the second electrode tab is connected to the first region to improve the stability of the connection between the second electrode tab and the first current collector.

[0021] Embodiments of this application also provide a secondary battery, wherein the material of the reference electrode includes at least one selected from platinum, gold, copper, and aluminum.

[0022] Embodiments of this application also provide a secondary battery, wherein the material of the first insulating adhesive includes at least one selected from polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene.

[0023] The embodiments of this application also provide a secondary battery, which includes any of the cells described in the above embodiments.

[0024] Embodiments of this application also provide an electronic device, which includes any of the secondary batteries described in the above embodiments. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the battery cell structure in one embodiment of this application.

[0026] Figure 2 This is a schematic diagram of the connection between the electrode assembly and the composite tab of the battery cell in one embodiment of this application.

[0027] Figure 3 This is a schematic diagram of the connection between the electrode adhesive and the composite electrode in one embodiment of this application.

[0028] Figure 4 This is a schematic diagram of the structure of the first insulating adhesive of the battery cell in one embodiment of this application.

[0029] Figure 5 This is a schematic diagram of the winding structure of the electrode assembly of the battery cell in one embodiment of this application.

[0030] Figure 6 This is a schematic diagram of the connection between the electrode assembly and the composite tab of the battery cell in one embodiment of this application.

[0031] Figure 7 This is a schematic diagram of the structure of the second electrode of the battery cell in one embodiment of this application.

[0032] Figure 8 This is a schematic diagram of the connection between the electrode assembly and the composite tab of the battery cell in one embodiment of this application.

[0033] Figure 9 This is a schematic diagram of the structure of the second electrode in one embodiment of this application.

[0034] Figure 10 This is a schematic diagram of the structure of a secondary battery in one embodiment of this application.

[0035] Figure 11 This is a schematic diagram of the structure of an electronic device in one embodiment of this application.

[0036] Explanation of key component symbols: Cells 100A, 100B, 100C, 100D

[0037] Secondary battery 200

[0038] Electronic Devices 300

[0039] Electrode assembly 10

[0040] First Polar Film 11

[0041] Diaphragm 12

[0042] Second pole piece 13

[0043] First current collector 131

[0044] First Edge 131A

[0045] Second edge 131B

[0046] Area 131C

[0047] Second Zone 131D

[0048] First active material layer 132

[0049] First groove 132A

[0050] First son, Ji'er 14

[0051] First sub-pole ear bundle 14A

[0052] First paragraph, 141

[0053] Second paragraph, 142

[0054] Bending section 143

[0055] Second son, Ji'er 15

[0056] Packaging bag 20

[0057] Main body 21

[0058] Top Wall 211

[0059] Top sealing section 22

[0060] Unsealed area 22A

[0061] Central Sealing Zone 22B

[0062] Unsealed area 22C

[0063] First ear 30

[0064] Composite electrode 40

[0065] Second pole ear 41

[0066] Reference electrode 42

[0067] First insulating adhesive 43

[0068] First insulating part 431

[0069] Second insulating part 432

[0070] Third Insulation Section 433

[0071] Lithium plating layer 44

[0072] First-class ear gel 51

[0073] First-grade glue 511

[0074] Second glue 512

[0075] Second-stage ear glue 52

[0076] First insulating component 61

[0077] Second insulating component 62

[0078] Circuit board assembly 70

[0079] First direction X

[0080] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0081] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0082] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0083] When one value is considered "equal" to another, it means that they are equal within a set deviation range, which is within 5%. In other words, if at least one of the two values ​​fluctuates within the set deviation range, they are considered approximately equal even if their values ​​are not equal. Similarly, when one value is considered to have a "1:1" ratio with another, it means that they are equal within a set deviation range, which is within 5%. Again, if at least one of the two values ​​fluctuates within the set deviation range, they are considered equal in ratio even if their values ​​are not equal.

[0084] 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 of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The term "overlap" as used herein refers to the overlapping of the projected portions of two components or the coincidence of the projected portions of two components.

[0085] This application provides a battery cell comprising an electrode assembly, a packaging bag, a first tab, and a composite tab. The packaging bag includes a main body and a top seal. The electrode assembly is disposed within the main body, which includes a top wall, and the top seal is connected to the top wall. One end of the first tab is connected to the electrode assembly, and the other end extends from the top seal. The first tab has a first polarity. The composite tab includes a second tab and a reference tab stacked along the thickness direction of the composite tab. One end of the second tab is connected to the electrode assembly, and the other end extends from the top seal. The second tab has a second polarity different from the first polarity. Along a first direction, one end of the reference tab extends into the main body and is not connected to the electrode assembly, while the other end extends from the top seal. The first direction is the direction from the main body to the top seal.

[0086] In the aforementioned battery cell, the second tab and the first tab are configured to be electrically connected to an external circuit, and the reference tab is configured to acquire the battery cell's potential during cell cycling. By stacking the second tab and the reference tab along the thickness direction of the composite tab to form an integral composite structure, the second tab and the reference tab share the space in the width direction of the composite tab, which helps reduce the risk of interference between the reference tab and electronic components on the circuit board assembly mounted on the top wall.

[0087] The embodiments of this application will be further described below with reference to the accompanying drawings.

[0088] Please see Figure 1 One embodiment of this application provides a battery cell 100A, which includes an electrode assembly 10, a packaging bag 20, a first electrode tab 30, and a composite electrode tab 40.

[0089] Please refer to the following: Figure 1 and Figure 2 The packaging bag 20 includes a main body 21 and a top sealing portion 22, with the first direction X being the direction from the main body 21 to the top sealing portion 22. The main body 21 includes a top wall 211, and the top sealing portion 22 is connected to the top wall 211. Specifically, the packaging bag 20 is made of a sealing film, the main body 21 refers to the portion of the sealing film with perforations, and the top sealing portion 22 refers to the portion of the sealing film that overlaps and joins. An electrode assembly 10 is disposed within the main body 21, and the top wall 211 and the electrode assembly 10 are arranged along the first direction X. The electrode assembly 10 is used to convert chemical energy into electrical energy.

[0090] One end of the first electrode tab 30 is connected to the electrode assembly 10, and the other end of the first electrode tab 30 extends from the top seal 22. The first electrode tab 30 has a first polarity.

[0091] The composite tab 40 includes a second tab 41 and a reference tab 42 stacked along the thickness direction of the composite tab 40. One end of the second tab 41 is connected to the electrode assembly 10, and the other end of the second tab 41 extends from the top seal 22. The second tab 41 has a second polarity, which is different from the first polarity. The second tab 41 and the first tab 30 are configured to be electrically connected to an external circuit (e.g., the motherboard of an electronic device) to form a complete current loop. Optionally, the first tab 30 has a negative polarity and the second tab 41 has a positive polarity; or the first tab 30 has a positive polarity and the second tab 41 has a negative polarity.

[0092] Along the first direction X, one end of the reference tab 42 extends into the main body 21 and is not connected to the electrode assembly 10, while the other end of the reference tab 42 extends out from the top seal 22. The portion of the reference tab 42 located inside the main body 21 can acquire the potential of the battery cell 100A during its cycling process. The portion of the reference tab 42 located outside the top seal 22 is configured to be electrically connected to a protection circuit, so that the protection circuit can monitor the potential of the battery cell 100A, thereby facilitating the adjustment of the charging and discharging mode to improve the safety of the battery cell 100A and extend its service life.

[0093] In the aforementioned battery cell 100A, the second tab 41 and the first tab 30 are configured to be electrically connected to an external circuit, and the reference tab 42 is configured to acquire the potential of the battery cell 100A during its cycling process. By stacking the second tab 41 and the reference tab 42 along the thickness direction of the composite tab 40 to form an integral composite structure, the second tab 41 and the reference tab 42 share the space in the width direction of the composite tab 40, which helps reduce the risk of interference between the reference tab 42 and electronic components on the circuit board assembly mounted on the top wall 211.

[0094] Furthermore, during the packaging process of the 100A battery cell, the second tab 41 and the reference tab 42 are packaged in the same area of ​​the top seal 22, which can reduce the probability of false sealing and improve the packaging reliability of the top seal 22.

[0095] Please continue reading. Figure 2 In some embodiments, the composite tab 40 further includes a first insulating adhesive 43. Along the thickness direction of the composite tab 40, the first insulating adhesive 43 is disposed between the second tab 41 and the reference tab 42 to isolate the reference tab 42 and the second tab 41, thereby reducing the risk of interference between the reference tab 42 and the second tab 41, which could affect the detection accuracy of the reference tab 42.

[0096] In some embodiments, along the first direction X, the length of the first insulating adhesive 43 is greater than or equal to the length of the reference tab 42, and along the width direction of the composite tab 40, the width of the first insulating adhesive 43 is greater than or equal to the width of the reference tab 42, so as to improve the isolation stability of the first insulating adhesive 43 between the second tab 41 and the reference tab 42.

[0097] Optionally, the material of the first insulating adhesive 43 includes at least one selected from polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene. The adhesive strength of the first insulating adhesive 43 can be adjusted by selecting different material types and / or mass ratios.

[0098] Please continue reading. Figure 2 In some embodiments, the second tab 41 is a sheet-like metal structure. Along the thickness direction of the composite tab 40, the thickness of the second tab 41 is D1, where 0.05mm ≤ D1 ≤ 0.2mm. When D1 is too small (less than 0.05mm), the structural strength and current-carrying capacity of the second tab 41 are easily weakened. When D1 is too large (greater than 0.2mm), the gap between the two encapsulation films of the top seal portion 22 located on both sides of the composite tab 40 is easily increased, affecting the encapsulation stability of the top seal portion 22. By limiting D1 to 0.05mm ≤ D1 ≤ 0.2mm, the structural strength and current-carrying capacity of the second tab 41 are improved, and the encapsulation stability of the top seal portion 22 is also improved.

[0099] Optionally, D1 can be any value within the range of 0.05mm, 0.1mm, 0.15mm, 0.2mm, and any other value within the range of 0.05mm≤D1≤0.2mm.

[0100] Please continue reading. Figure 2 In some embodiments, the reference tab 42 is a sheet-like metal structure. Along the thickness direction of the composite tab 40, the thickness of the reference tab 42 is D2, where 4μm ≤ D2 ≤ 10μm. When D2 is too small (less than 4μm), the structural strength and current-carrying capacity of the reference tab 42 are easily weakened. When D2 is too large (greater than 10μm), the gap between the two encapsulation films of the top seal portion 22 located on both sides of the composite tab 40 is easily increased, affecting the encapsulation stability of the top seal portion 22. By limiting 4μm ≤ D2 ≤ 10μm, the structural strength and current-carrying capacity of the reference tab 42 are improved, and the encapsulation stability of the top seal portion 22 is also improved.

[0101] Optionally, D2 can be any value within the range of 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, and any other value within the range of 4μm≤D2≤10μm.

[0102] Optionally, the reference tab 42 may be made of at least one of platinum, gold, copper, and aluminum.

[0103] It is understood that in other embodiments, the reference tab 42 is a metal wire.

[0104] Please continue reading. Figure 2 In some embodiments, the thickness of the first insulating adhesive 43 along the thickness direction of the composite tab 40 is D3, where 4μm ≤ D3 ≤ 16μm. When D3 is too small (less than 4μm), the insulation effect is easily poor. When D3 is too large (greater than 16μm), the gap between the two encapsulation films of the top seal portion 22 located on both sides of the composite tab 40 is easily large, affecting the encapsulation stability of the top seal portion 22. By limiting 4μm ≤ D3 ≤ 16μm, the insulation stability of the first insulating adhesive 43 is improved, and the encapsulation stability of the top seal portion 22 is also improved.

[0105] Optionally, D3 can be any value within the range of 4μm, 5μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 9μm, 10μm, and any other value within the range of 4μm≤D3≤16μm.

[0106] Furthermore, 6.4μm≤D3≤8μm is used to further improve the insulation stability of the first insulating adhesive 43, and also to further improve the encapsulation stability of the top seal 22.

[0107] Please continue reading. Figure 2 In some embodiments, the composite tab 40 further includes a lithium plating layer 44 disposed at the portion of the reference tab 42 that extends into the main body 21, in order to improve the accuracy of monitoring.

[0108] In some embodiments, a lithium plating layer 44 is disposed on the surface of the reference tab 42 opposite to the first insulating adhesive 43. Along the thickness direction of the composite tab 40, the thickness of the lithium plating layer 44 is D4, where 10 μm ≤ D4 ≤ 40 μm. When D4 is too small (less than 10 μm), sufficient lithium source may not be provided. When D4 is too large (greater than 40 μm), the lithium plating layer 44 occupies a large space within the main body 21, resulting in wasted space. By limiting the thickness to 10 μm ≤ D4 ≤ 40 μm, sufficient lithium source can be provided, and the space utilization rate of the lithium plating layer 44 within the main body 21 can be improved, thereby increasing the energy density of the 100A battery cell.

[0109] Optionally, D4 can be any value within the range of 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, and any other value within the range of 10μm≤D4≤40μm.

[0110] Please refer to it again. Figure 1 The battery cell 100A also includes a first tab adhesive 51 and a second tab adhesive 52. One end of the first tab adhesive 51 is disposed inside the top sealing portion 22, and the other end of the first tab adhesive 51 extends out of the top sealing portion 22. The first tab adhesive 51 at least covers the surface of the portion of the composite tab 40 located inside the top sealing portion 22. One end of the second tab adhesive 52 is disposed inside the top sealing portion 22, and the other end of the second tab adhesive 52 extends out of the top sealing portion 22. The second tab adhesive 52 at least covers the surface of the portion of the first tab 30 located inside the top sealing portion 22.

[0111] Please refer to the following: Figure 2 and Figure 3 In some embodiments, the first insulating adhesive 43 includes a first insulating portion 431 disposed within the top sealing portion 22. Along the width direction of the composite tab 40, both ends of the first insulating portion 431 protrude from the second tab 41 and the reference tab 42. The first tab adhesive 51 includes a first sub-adhesive 511 and a second sub-adhesive 512. The first sub-adhesive 511 is attached to the surface of the second tab 41 away from the reference tab 42, and together with the first insulating portion 431, it covers the portion of the second tab 41 located within the top sealing portion 22. The second sub-adhesive 512 is attached to the surface of the reference tab 42 away from the second tab 41, and together with the first insulating portion 431, it covers the portion of the reference tab 42 located within the top sealing portion 22. The first sub-adhesive 511 and the second sub-adhesive 512 are used to improve the encapsulation stability of the composite tab 40 within the top sealing portion 22.

[0112] Please continue reading. Figure 3 In some embodiments, along the arrangement direction of the first sub-adhesive 511 and the second tab 41, the thickness of the first sub-adhesive 511 is D5, where 8μm ≤ D5 ≤ 40μm. When D5 is too small (less than 8μm), the encapsulation strength of the portion of the top seal 22 corresponding to the first sub-adhesive 511 is relatively weak. When D5 is too large (greater than 40μm), the gap between the two encapsulation films of the top seal 22 located on both sides of the composite tab 40 is relatively large, affecting the encapsulation stability of the top seal 22. By limiting 8μm ≤ D5 ≤ 40μm, the encapsulation stability of the top seal 22 is improved.

[0113] Optionally, D5 can be any value within the range of 8μm, 9μm, 10μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 30μm, 35μm, 40μm, and any other value within the range of 8μm≤D5≤40μm.

[0114] Furthermore, 16μm≤D5≤28μm is used to further improve the packaging stability of the top seal 22.

[0115] Please continue reading. Figure 3 In some embodiments, along the arrangement direction of the second sub-adhesive 512 and the reference tab 42, the thickness of the second sub-adhesive 512 is D6, where 8μm ≤ D6 ≤ 40μm. When D6 is too small (less than 8μm), the encapsulation strength of the portion of the top seal 22 corresponding to the second sub-adhesive 512 is relatively weak. When D6 is too large (greater than 40μm), the gap between the two encapsulation films of the top seal 22 located on both sides of the composite tab 40 is relatively large, affecting the encapsulation stability of the top seal 22. By limiting 8μm ≤ D6 ≤ 40μm, the encapsulation stability of the top seal 22 is improved.

[0116] Optionally, D6 can be any value within the range of 8μm, 9μm, 10μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 30μm, 35μm, 40μm, and any other value within the range of 8μm≤D6≤40μm.

[0117] Furthermore, 16μm≤D6≤28μm is used to further improve the packaging stability of the top seal 22.

[0118] Please refer to the following: Figure 1 and Figure 3 It should be noted that, along the extension direction of the top seal 22, the top seal 22 includes an inner unsealed area 22A, a middle sealed area 22B, and an outer unsealed area 22C arranged sequentially. The middle sealed area 22B refers to the area of ​​the top seal 22 that has undergone heat pressing. The inner unsealed area 22A is located on the side of the middle sealed area 22B closest to the electrode assembly 10 and has not undergone heat pressing. The outer unsealed area 22C is located on the side of the middle sealed area 22B furthest from the electrode assembly 10 and has not undergone heat pressing. Under the action of heat pressing, the thickness of the first insulating adhesive 43 and the first tab adhesive 51 at the middle sealed area 22B is smaller, while the thickness of the first insulating adhesive 43 and the first tab adhesive 51 at the inner unsealed area 22A or the outer unsealed area 22C is larger. D3 refers to the thickness of the first insulating adhesive 43 located in the middle sealing area 22B, D5 refers to the thickness of the first sub-adhesive 511 located in the middle sealing area 22B, and D6 refers to the thickness of the second sub-adhesive 512 located in the middle sealing area 22B.

[0119] In some embodiments, along the thickness direction of the composite tab 40, the thickness of the first insulating adhesive 43 located in the inner unsealed area 22A or the outer unsealed area 22C is 5 μm to 20 μm.

[0120] In some embodiments, the thickness of the first sub-adhesive 511 at the portion located in the inner unsealed area 22A or the outer unsealed area 22C is 10 μm to 50 μm.

[0121] In some embodiments, the thickness of the second sub-adhesive 512 at the portion located in the inner unsealed area 22A or the outer unsealed area 22C is 10 μm to 50 μm.

[0122] It should be noted that the thickness D1 of the second tab 41 and the thickness D2 of the reference tab 42 are measured by vernier calipers. The thicknesses D3 of the first insulating adhesive 43, D4 of the lithium plating layer 44, D5 of the first sub-adhesive 511, D6 of the second sub-adhesive 512, and the thicknesses of other adhesive layers were measured using SEM. Specifically, the measurement area was selected as the sample, and the cross-section of the sample was prepared by mechanical cutting, grinding, polishing, and liquid nitrogen brittle fracture to ensure that the cross-section was flat and without obvious damage. Ultrasonic cleaning or organic solvent cleaning was used to remove surface contaminants and residues. The sample was loaded onto a conductive substrate, such as conductive tape or conductive carbon film. The prepared sample was fixed on the SEM sample stage. The sample stage was placed in the SEM sample chamber and a vacuum was drawn to ensure a high vacuum environment. An appropriate accelerating voltage was selected according to the properties of different metal adhesive papers, usually between 1-30kV. The scanning speed, scanning range, and other parameters were adjusted to obtain a clear image. The distance between the upper and lower edges of the measured area was measured and recorded as the thickness of the measured area, and the average value was calculated from five points.

[0123] In some embodiments, the thickness of the lithium plating layer 44 is less than or equal to the thickness of the first sub-adhesive 511 at the location of the first sub-adhesive 511 in the inner unsealed region 22A or the outer unsealed region 22C, or the thickness of the lithium plating layer 44 is less than or equal to the thickness of the second sub-adhesive 512 at the location of the first sub-adhesive 511 in the inner unsealed region 22A or the outer unsealed region 22C, so that the lithium plating layer 44 and the second sub-adhesive 512 share the space in the thickness direction of the reference electrode tab 42, thereby improving the space utilization rate of the lithium plating layer 44 in the main body 21, which in turn helps to improve the energy density of the battery cell 100A.

[0124] Please see Figure 4 In some embodiments, the first insulating adhesive 43 includes a second insulating portion 432 and a third insulating portion 433 connected to both sides of the first insulating portion 431. The second insulating portion 432 is located outside the top seal portion 22 to isolate the second electrode tab 41 and the reference electrode tab 42 located outside the top seal portion 22. The third insulating portion 433 is located inside the main body portion 21 to isolate the second electrode tab 41 and the reference electrode tab 42 located inside the main body portion 21.

[0125] In some embodiments, along the width direction of the composite tab 40, the size of the second insulating portion 432 is smaller than the size of the first insulating portion 431, so as to reduce the space wastage of the second insulating portion 432 outside the top seal portion 22.

[0126] In some embodiments, the size of the third insulating portion 433 is smaller than the size of the first insulating portion 431 along the width direction of the composite tab 40, so as to reduce the space waste generated by the third insulating portion 433 in the main body portion 21.

[0127] Please refer to it again. Figure 2 In some embodiments, the electrode assembly 10 includes a first electrode 11, a diaphragm 12, a second electrode 13, a first sub-electrode 14, and a second sub-electrode 15, wherein the first sub-electrode 14 and the second sub-electrode 15 have different polarities. The first electrode 11, the diaphragm 12, and the second electrode 13 are spaced apart, and the electrode assembly 10 has a stacked structure. The first electrode 11 has a first polarity, and the second electrode 13 has a second polarity. The first electrode 30 is electrically connected to the first electrode 11. The second electrode 13 includes a first current collector 131, and the first sub-electrode 14 is integrally formed with the first current collector 131. A plurality of first sub-electrodes 14 are aggregated to form a first sub-electrode bundle 14A, which is located between the first current collector 131 and the top wall 211.

[0128] Along the extending direction of the composite tab 40, one end of the second tab 41 is connected to the first tab bundle 14A, and the other end of the second tab 41 extends from the top seal 22. The portion of the reference tab 42 extending into the main body 21 is located between the first current collector 131 and the top wall 211, so as to reduce the impact of the reference tab 42 on the cycle performance of the electrode assembly 10. Furthermore, the composite tab 40 and the first tab bundle 14A share the space between the first current collector 131 and the top wall 211, which can improve the space utilization rate of the composite tab 40 within the main body 21, thereby helping to improve the energy density of the battery cell 100A.

[0129] In some embodiments, the first sub-electrode bundle 14A includes a first segment 141, a second segment 142, and a bent segment 143. The first segment 141 is located between the first current collector 131 and the second segment 142, and the first segment 141 and the second segment 142 are spaced apart. The bent segment 143 connects the first segment 141 and the second segment 142 to form a "U"-shaped structure. One end of the composite electrode 40 is located between the first segment 141 and the second segment 142, and the second electrode 41 is connected to the second segment 142. Along the extending direction of the composite electrode 40, the reference electrode 42 and the first insulating adhesive 43 extend to the bent segment 143.

[0130] Please continue reading. Figure 2In some embodiments, the battery cell 100A includes a first insulating member 61 and a second insulating member 62. Along the thickness direction of the electrode assembly 10, the first insulating member 61 is disposed on one side of the electrode assembly 10, and the second insulating member 62 is disposed on the other side of the electrode assembly 10. A portion of the first insulating member 61 overlaps with the sub-electrode bundle 14A and at least covers the inner surface of the first segment 141, the inner surface of the bent segment 143, and the side of the reference electrode 42 away from the first insulating adhesive 43. A portion of the second insulating member 62 overlaps with the sub-electrode bundle 14A and at least covers the outer surface of the bent segment 143 and the outer surface of the second segment 142.

[0131] Please see Figure 5 An embodiment of this application also provides a battery cell 100B. The difference between battery cell 100B and battery cell 100A is that the electrode assembly 10 has a wound structure.

[0132] Apart from the differences mentioned above, the parameters of cell 100B and cell 100A are roughly the same, and you can refer to the description of cell 100A above.

[0133] Please refer to the following: Figure 6 and Figure 7 An embodiment of this application also provides a battery cell 100C. The difference between battery cell 100C and battery cell 100A is that the electrode assembly 10 does not include multiple sub-tabs 14, and the second tab 41 is directly connected to the first current collector 131.

[0134] The electrode assembly 10 includes a first electrode 11, a diaphragm 12, and a second electrode 13 spaced apart. The electrode assembly 10 has a wound structure. The first electrode 11 has a first polarity, and the second electrode 13 has a second polarity. A first tab 30 is electrically connected to the first electrode 11. The second electrode 13 includes a first current collector 131 and a first active material layer 132. Along the thickness direction of the first current collector 131, at least one surface of the first current collector 131 is provided with the first active material layer 132.

[0135] The second electrode 41 is connected to the first current collector 131. Along the arrangement direction of the first current collector 131 and the top wall 211, the first current collector 131 includes a first edge 131A and a second edge 131B disposed opposite to each other. The first edge 131A is closer to the top wall 211 than the second edge 131B, and the midline between the first edge 131A and the second edge 131B of the first current collector 131 is the first centerline O.

[0136] A portion of the reference tab 42 is located between the first electrode 11 and the second electrode 13. Specifically, along the arrangement direction of the first current collector 131 and the top wall 211, the length of the portion of the reference tab 42 located between the first electrode 11 and the second electrode 13 is L1, and the length of the second electrode 13 is L2, where 5mm ≤ L1 ≤ L2, in order to improve the monitoring accuracy.

[0137] In some embodiments, when viewed along the thickness direction of the first current collector 31, the edge of the reference tab 42 located between the first electrode 11 and the second electrode 13 extends beyond the first edge 131A and does not exceed the first centerline O, so as to reduce the impact of the reference tab 42 on the cycle performance of the electrode assembly 10.

[0138] In some embodiments, the first active material layer 132 is provided with a first groove 132A exposing the first current collector 131, and one end of the second electrode 41 is located in the first groove 132A and connected to the first current collector 131 to improve the stability of the connection between the second electrode 41 and the first current collector 131. Specifically, the first groove 132A is provided on the side of the first active material layer 132 near the first edge 131A.

[0139] Apart from the differences mentioned above, the parameters of cell 100C and cell 100A are roughly the same. Please refer to the description of cell 100A above.

[0140] Please refer to the following: Figure 8 and Figure 9 An embodiment of this application also provides a battery cell 100D. The difference between battery cell 100D and battery cell 100C is that the second tab 41 is connected to the empty foil area of ​​the first current collector 131.

[0141] The first current collector 131 includes a first region 131C and a second region 131D connected along the winding direction of the first current collector 131. The first region 131C is located at one end of the winding direction. Along the thickness direction of the first current collector 131, the two surfaces of the first region 131C are not provided with the first active material layer 132, while at least one surface of the second region 131D is provided with the first active material layer 132. One end of the second electrode 41 is connected to the first region 131C to improve the stability of the connection between the second electrode 41 and the first current collector 131.

[0142] Optionally, the first region 131C is located at the beginning of the winding direction, or the first region 131C is located at the beginning of the winding direction.

[0143] Apart from the differences mentioned above, the parameters of cell 100D and cell 100C are roughly the same. Please refer to the description of cell 100C above.

[0144] Please see Figure 10 An embodiment of this application also provides a secondary battery 200, which includes the battery cells (100A, 100B, 100C, 100D) in any of the above embodiments. A secondary battery is a battery that can be used by recharging to activate the active materials after the battery has been discharged.

[0145] In some embodiments, the secondary battery 200 includes a circuit board assembly 70 disposed on the top wall 211 and having a protection circuit. The circuit board assembly 70 is electrically connected to a first tab 30 and a composite tab 40. A second tab 41 and the first tab 30 are configured to form a complete current loop. The protection circuit monitors the potential of the cells (100A, 100B, 100C, 100D) via a reference tab 42, thereby facilitating the adjustment of the charging and discharging mode to improve the safety of the cells (100A, 100B, 100C, 100D) and extend their service life.

[0146] In the aforementioned battery cells (100A, 100B, 100C, 100D) and secondary battery 200, a composite structure is formed by the second tab 41, the reference tab 42, and the first insulating adhesive 43. This allows the second tab 41 and the first insulating adhesive 43 to share the space in the thickness direction of the second tab 41, which helps to reduce the risk of interference between the reference tab 42 and the electronic components on the circuit board assembly 70 disposed on the top wall 211.

[0147] Please see Figure 11 An embodiment of this application also provides an electronic device 300, including the secondary battery 200 in any of the above embodiments.

[0148] Optionally, the electronic device 300 may be a device with a rechargeable battery, such as a mobile phone, tablet computer, laptop computer, smart wearable product (e.g., smartwatch, smart bracelet), virtual reality (VR) terminal device, augmented reality (AR) terminal device, etc.

[0149] In the aforementioned battery cells (100A, 100B, 100C, 100D) and electronic device 300, a composite structure is formed by the second electrode 41, the reference electrode 42, and the first insulating adhesive 43. This allows the second electrode 41 and the first insulating adhesive 43 to share the space in the thickness direction of the second electrode 41, which helps to reduce the risk of interference between the reference electrode 42 and the electronic components on the circuit board assembly disposed on the top wall 211.

[0150] The following describes the specific implementation methods of the battery cells in the embodiments and comparative examples.

[0151] 1. High-voltage insulation test (Hipot test): The Hipot test is an insulation resistance test that measures the resistance between the reference tab and the second tab to determine whether there is a short circuit between the reference tab and the second tab.

[0152] The test method involves detecting the leakage current generated by the composite tab of the battery cell under the test voltage output by the high-voltage generator. The resistance between the reference tab and the second tab is then calculated as: test voltage / leakage current. This calculated resistance value is compared to a set judgment resistance. If the detected resistance value is greater than or equal to the preset value, the product is considered to have passed the test (OK). If the detected resistance value is less than the preset value, the test voltage is instantly cut off, and the product is deemed to have failed the test (NG). In this test, the preset judgment current is 5mΩ. A resistance value below 5mΩ indicates conduction, but the resistance is too low, indicating a short circuit, and is therefore deemed NG. A resistance value greater than or equal to 5mΩ is deemed OK. For each example and comparative example, 100 battery cells are tested. The number of cells that pass the test is X1, and the pass rate is X1 / 100.

[0153] 2. A stability monitoring test is conducted, measuring a first difference and a second difference. The first difference is the difference between the potential of the second electrode after 800 cycles and the potential of the second electrode during the first cycle. The second difference is the difference between the plateau voltage after 800 cycles and the plateau voltage during the first cycle. The first and second differences are compared; the smaller the deviation, the better the stability. Plateau voltage = discharge energy / discharge capacity. In this test, ±0.5mV is used as the preset deviation. If the deviation between the first and second differences is less than the preset deviation, it is considered OK; if the deviation is greater than or equal to the preset deviation, it is considered NG. 100 cells are tested in each example and comparative example. The number of cells that pass the test is X2, and the pass rate is X2 / 100.

[0154] 3. Encapsulation strength test: The battery cell was immersed in red ink for 12 hours. After removing the cell from the red ink, aqua regia was used to etch the nylon layer in the encapsulation film at the top seal, and hydrochloric acid solution was used to etch away the metal layer in the encapsulation film at the top seal, exposing the polymer layer in the encapsulation film. The cell was then rinsed with water, and an optical microscope was used to observe whether the polymer layer in the encapsulation film at the top seal had been penetrated by red ink. If it had been penetrated by red ink, it indicated a leakage channel in the polymer layer of the encapsulation film at the top seal, and was deemed NG (Not Acceptable). If it had not been penetrated by red ink, it was deemed OK. 100 cells were tested in each example and comparative example. The number of cells that passed the test was X3, and the pass rate was X3 / 100.

[0155] 4. Secondary Battery Volumetric Energy Density Test: The initial length, width, and thickness of secondary battery 200 were measured and recorded using a PPG (Parallel Plate Gauge). At a test temperature of 25°C, secondary battery 200 was left to stand for 30 minutes and then charged according to the following steps: constant current charging at 0.2C to 4.5V, constant voltage charging at 0.05C. After standing for 10 minutes, it was discharged according to the following steps: DC discharge at 0.2C to 3V. The discharge capacity of secondary battery 200 was recorded, and the volumetric energy density of the secondary battery was calculated as follows: (Platform voltage × Discharge capacity) / (Length of secondary battery × Width of secondary battery × Thickness of secondary battery).

[0156] 5. Lithium plating rate of the negative electrode opposite the composite tab: At a test temperature of 25℃, the secondary battery 200 was left to stand for 30 minutes and then charged in stages according to the following steps: (a) 2.0C constant current charging to 4.23V, constant voltage charging to 1.8C; (b) 1.8C constant current charging to 4.3V, constant voltage charging to 1.4C; (c) 1.4C constant current charging to 4.4V, constant voltage charging to 1.0C; (d) 1.0C constant current charging to 4.5V, constant voltage charging to 0.05C; After standing for 10 minutes, it was discharged according to the following steps: 1C DC discharge to 3V. The above charge and discharge process constitutes one cycle, and is repeated 1000 times. Afterwards, the secondary battery 200 was disassembled, and the lithium plating of the negative electrode opposite the lithium plating layer was observed. The surface of the negative electrode without lithium plating was entirely golden yellow, while the surface of the negative electrode with lithium plating was partially golden yellow and partially grayish white. For each set of examples and comparative examples, 100 cells were tested. The number of lithium deposits on the negative electrode opposite the lithium plating layer was recorded as X4. The lithium plating rate of the negative electrode opposite the lithium plating layer is X4 / 100.

[0157] Example 1:

[0158] A battery cell with an initial thickness of 4.8mm at 50% SOC, a length of 87mm, and a width of 64mm is assembled as follows:

[0159] (1) Preparation of the negative electrode sheet: Artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5. Deionized water was added as a solvent to prepare a slurry with a weight percentage of 50 wt%. The slurry was stirred evenly and uniformly coated onto one surface of a copper foil. The slurry was then dried at 90°C to obtain a negative electrode sheet with a single-sided coating of the negative electrode active material layer. When preparing a double-sided coated negative electrode sheet, the above steps were repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of the negative electrode active material layer. The coated electrode sheet was then cold-pressed to a thickness of 105 μm. Grooves were formed on the negative electrode active material, and the first electrode tab was welded to the copper foil exposed in the groove.

[0160] (2) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of an aluminum foil and then dried at 90°C to obtain a positive electrode sheet with a single-sided coating of the positive electrode active material. When preparing a double-sided coated positive electrode sheet, the above coating steps were repeated on the other surface of the aluminum foil. The coated electrode sheet was then cold-pressed to a thickness of 95 μm, and grooves were formed on the positive electrode active material. The second tab in the composite tab was welded to the aluminum foil exposed in the groove. The reference tab was made of copper.

[0161] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0162] (4) Preparation of the diaphragm: A three-layer diaphragm is adopted, which includes a laminated adhesive layer, a substrate layer and an adhesive layer. The first substrate layer is made of polyethylene (PE), the adhesive layer is made of PVDF, and the adhesive layer also contains inorganic boehmite particles.

[0163] (5) Electrode assembly preparation: The positive electrode, separator and negative electrode are wound and arranged.

[0164] (6) Cell assembly: Place the punched aluminum-plastic film in the assembly fixture with the punched surface facing up, place the electrode assembly in the punched surface, and apply external force to press it tight. Then cover the electrode assembly with another punched aluminum-plastic film with the punched surface facing down, and heat seal the two aluminum-plastic films around their perimeter by hot pressing to obtain the assembled electrode assembly.

[0165] (7) Electrolyte injection and encapsulation: Electrolyte is injected into the assembled electrode assembly, and the battery cell is obtained through vacuum encapsulation, standing, hot pressing, shaping and other processes.

[0166] Comparative Example 1: Three tabs are provided to connect to the positive electrode, the negative electrode, and the reference electrode, respectively. The three tabs are spaced apart along the width of the cell. It should be noted that, except for the structure of the tabs, all other parameters of Comparative Example 1 are the same as those of Example 1.

[0167] Table 1

[0168] (Except for the parameters mentioned in Table 1, all other parameters in Examples 2 to 41 are the same as those in Example 1. The thickness of the second electrode tab is D1 = 0.1 mm, the thickness of the reference electrode tab is D2 = 6 μm, and L2 = 70 mm.)

[0169]

[0170]

[0171] Note: In Table 1, "\" indicates that the parameter is not included.

[0172] As can be seen from Comparative Example 1 and Examples 1 to 41, by stacking the second tab and the reference tab along the thickness direction of the composite tab to form an integral composite structure, the monitoring stability is higher compared with the three-tab battery cells of the prior art.

[0173] As can be seen from Examples 1 to 8, changing D3 has no effect on monitoring stability and volumetric energy density. The pass rate of high voltage insulation test increases with the increase of D3. The encapsulation strength shows a decreasing trend when D3 is too thick (more than 12um). This is because when D3 is too thick, the tab adhesive does not cover the composite tab sufficiently, resulting in a decrease in encapsulation strength. When D3 is greater than 6.4um, the distance between the positive and negative electrode plates at the composite tab position will be too large, which may cause electrolyte bridging and lead to an increase in lithium plating rate.

[0174] As can be seen from Examples 9 to 14, changing the thickness D4 of the lithium plating layer, whether too thick or too thin, is detrimental to monitoring stability. When the lithium plating layer is too thin, it cannot provide a stable potential reference. When the lithium plating layer is too thick, the contact resistance between lithium metals and between lithium metal and the reference electrode increases, which also leads to a decrease in monitoring stability. An excessively thick lithium plating layer also leads to a decrease in volumetric energy density and an increase in lithium plating rate. The reason for the increase in lithium plating rate is that when the thickness of the lithium plating layer is too large, the lithium plating layer itself may deintercalate some lithium ions, leading to an increase in lithium plating rate.

[0175] As can be seen from Examples 15 to 23 and Examples 24 to 32, the thickness variation of D5 and D6 has no effect on the pass rate of high voltage insulation test, monitoring stability test, energy density and lithium plating rate. Too thick or too thin will affect the packaging strength.

[0176] As can be seen from Examples 33 to 41, changes in the length of L1 have no effect on high-voltage insulation testing, packaging strength, and lithium plating rate. Both excessively short and excessively long L1 will lead to a decrease in monitoring stability. This is because when L1 is too short, the monitored potential will deviate; when L1 is too long, the reference tab will be affected by the liquid junction potential, resulting in decreased monitoring stability. Furthermore, an excessively long L1 will also lead to a decrease in volumetric energy density.

[0177] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes: Electrode assembly; A packaging bag, the packaging bag comprising a main body and a top sealing part, the electrode assembly being disposed within the main body, the main body including a top wall, and the top sealing part being connected to the top wall; A first electrode tab, one end of which is connected to the electrode assembly, and the other end of which extends from the top seal, the first electrode tab having a first polarity; and A composite electrode tab includes a second electrode tab and a reference electrode tab stacked along the thickness direction of the composite electrode tab. One end of the second electrode tab is connected to the electrode assembly, and the other end of the second electrode tab extends from the top seal portion. The second electrode tab has a second polarity, which is different from the first polarity. Along a first direction, one end of the reference electrode tab extends into the main body portion and is not connected to the electrode assembly. The other end of the reference electrode tab extends from the top seal portion. The first direction is the direction from the main body portion to the top seal portion. The composite electrode also includes a first insulating adhesive, which is disposed between the second electrode and the reference electrode along the thickness direction of the composite electrode. The first insulating adhesive includes a first insulating portion disposed within the top sealing portion. Along the width direction of the composite electrode tab, both ends of the first insulating portion protrude from the second electrode tab and the reference electrode tab. The first insulating adhesive further includes a second insulating portion and a third insulating portion connected to both sides of the first insulating portion. The second insulating portion is located outside the top sealing portion, and the third insulating portion is located inside the main body portion. Along the width direction of the composite tab, the size of the second insulating portion is smaller than the size of the first insulating portion. The battery cell also includes a first tab adhesive, which includes a first sub-adhesive and a second sub-adhesive. The first sub-adhesive is connected to the surface of the second tab away from the reference tab. The first sub-adhesive and the first insulating portion together wrap the portion of the second tab located inside the top seal portion. The second sub-adhesive is connected to the surface of the reference tab away from the second tab. The second sub-adhesive and the first insulating portion together wrap the portion of the reference tab located inside the top seal portion.

2. The battery cell as described in claim 1, characterized in that, Along the first direction, the length of the first insulating adhesive is greater than or equal to the length of the reference tab, and along the width direction of the composite tab, the width of the first insulating adhesive is greater than or equal to the width of the reference tab.

3. The battery cell as described in claim 1, characterized in that, Along the thickness direction of the composite tab, the thickness of the second tab is D1, 0.05mm≤D1≤0.2mm; the thickness of the reference tab is D2, 4μm≤D2≤10μm; The top sealing portion includes an inner unsealed area, a middle sealing area, and an outer unsealed area connected sequentially along the first direction. The middle sealing area is the area that has been heat-sealed. Along the thickness direction of the composite tab, the thickness of the portion of the first insulating adhesive located in the middle sealing area is D3, where 4μm≤D3≤16μm.

4. The battery cell as described in claim 3, characterized in that, 6.4μm≤D3≤8μm.

5. The battery cell as described in claim 1, characterized in that, The composite tab also includes a lithium plating layer, which is disposed at the portion of the reference tab that extends into the main body.

6. The battery cell as described in claim 5, characterized in that, The lithium plating layer is disposed on the surface of the reference electrode that is away from the first insulating adhesive. Along the thickness direction of the composite electrode, the thickness of the lithium plating layer is D4, where 10μm≤D4≤40μm.

7. The battery cell as described in claim 1, characterized in that, The top sealing portion includes an inner unsealed area, a middle sealing area, and an outer unsealed area connected sequentially along the first direction. Along the thickness direction of the composite tab, the thickness of the portion of the first sub-adhesive located within the middle sealing area is D5, where 8μm≤D5≤40μm. The thickness of the portion of the second sub-adhesive located within the central sealing area is D6, where 8μm≤D6≤40μm.

8. The battery cell as described in claim 7, characterized in that, 16μm≤D5≤28μm; 16μm≤D6≤28μm.

9. The battery cell as described in claim 1, characterized in that, The electrode assembly includes a first electrode, a diaphragm, a second electrode, and a sub-electrode tab. The first electrode, the diaphragm, and the second electrode are spaced apart. The second electrode includes a first current collector. The sub-electrode tab is integrally formed with the first current collector. A plurality of sub-electrode tabs are aggregated into a sub-electrode tab bundle. The sub-electrode tab bundle is located between the first current collector and the top wall. Along the extension direction of the composite electrode tab, one end of the second electrode tab is connected to the sub-electrode tab bundle, and the other end of the second electrode tab extends out from the top seal portion. The portion of the reference electrode tab that extends into the main body portion is located between the first current collector and the top wall.

10. The battery cell as described in claim 9, characterized in that, The electrode assembly has a wound structure or a stacked structure.

11. The battery cell as described in claim 1, characterized in that, The electrode assembly includes a first electrode, a diaphragm, and a second electrode arranged at intervals. The first electrode tab is connected to the first electrode, and the second electrode includes a first current collector. The second electrode tab is connected to the first current collector. The reference tab is located between the first electrode and the second electrode, along the arrangement direction of the first current collector and the top wall. The length of the portion of the reference tab located between the first electrode and the second electrode is L1, and the length of the second electrode is L2, where 5mm ≤ L1 ≤ L2.

12. The battery cell as described in claim 11, characterized in that, Along the arrangement direction of the first current collector and the top wall, the first current collector includes a first edge and a second edge disposed opposite to each other, the first edge being closer to the top wall than the second edge, and the midline of the first current collector between the first edge and the second edge being a first centerline; Viewed along the thickness direction of the first current collector, the edge of the portion of the reference tab located between the first electrode and the second electrode extends beyond the first edge but does not exceed the first centerline.

13. The battery cell as described in claim 12, characterized in that, The second electrode further includes a first active material layer, at least one surface of the first current collector is provided with the first active material layer, the first active material layer is provided with a first groove exposing the first current collector, and one end of the second electrode tab is located in the first groove and connected to the first current collector.

14. The battery cell as described in claim 12, characterized in that, The electrode assembly is a wound structure. The first current collector includes a first region and a second region connected along the winding direction of the first current collector. The first region is located at one end of the winding direction. The second electrode also includes a first active material layer. Along the thickness direction of the first current collector, the first active material layer is not provided on two surfaces of the first region, and the first active material layer is provided on at least one surface of the second region. One end of the second electrode tab is connected to the first region.

15. The battery cell as described in claim 1, characterized in that, The reference electrode is made of at least one of platinum, gold, copper, and aluminum.

16. The battery cell as described in claim 1, characterized in that, The material of the first insulating adhesive includes at least one of polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene.

17. A secondary battery, characterized in that, The secondary battery includes the cell as described in any one of claims 1 to 16.

18. An electronic device, characterized in that, The electronic device includes the secondary battery as described in claim 17.

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