Cell, secondary battery, and electronic device

Abstract

The invention discloses a battery cell, a secondary battery and an electronic device. The battery cell comprises an electrode assembly, a packaging bag, a first tab and a composite tab, the packaging bag comprises a main body part and a top sealing part. The electrode assembly is arranged in the main body part, the main body part comprises a top wall, and the top sealing part is connected to the top wall. One end of the first tab is connected with the electrode assembly, and the other end of the first tab extends out of the top sealing part. The composite tab comprises a second tab and a reference tab which are stacked along the thickness direction of the composite tab. One end of the second tab is connected with the electrode assembly, and the other end of the second tab extends out of the top sealing part. In the first direction, one end of the reference tab extends into the main body part, the reference tab is not connected with the electrode assembly, the other end of the reference tab extends out of the top sealing part, and the first direction is the direction from the main body part to the top sealing part. According to the battery cell, the risk of interference between the reference tab and the electronic element on the circuit board assembly arranged on the top wall can be reduced.

Description

Technical Field

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

[0002] In the development and analysis of lithium-ion batteries, three-electrode analysis using a reference electrode is an important method. By installing a reference electrode in the battery, the positive and negative electrodes can be separated for study, and the potential and impedance data of the positive and negative electrodes can be measured separately, providing an important basis for studying attenuation mechanisms, interface stability, etc. In current three-electrode batteries, three tabs are usually set to connect the positive electrode, negative electrode and reference electrode respectively. The three tabs are set at intervals, which are easy to interfere with the 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] An embodiment of the present application provides a battery cell, which includes an electrode assembly, a packaging bag, a first pole ear and a composite pole ear. The packaging bag includes a main body and a top seal, the electrode assembly is arranged in the main body, the main body includes a top wall, and the top seal is connected to the top wall. One end of the first pole ear is connected to the electrode assembly, the other end of the first pole ear extends from the top seal, and the first pole ear has a first polarity. The composite pole ear includes a second pole ear and a reference pole ear stacked along the thickness direction of the composite pole ear. One end of the second pole ear is connected to the electrode assembly, and the other end of the second pole ear extends from the top seal. The second pole ear has a second polarity, which is different from the first polarity. Along the first direction, one end of the reference pole ear extends into the main body and the reference pole ear is not connected to the electrode assembly, and the other end of the reference pole ear extends from the top seal, wherein the first direction is the direction from the main body to the top seal.

[0005] In the above-mentioned battery cell, the second pole ear and the first pole ear are configured to be electrically connected to an external circuit, and the reference pole ear is configured to obtain the potential of the battery cell during the cycle of the battery cell. The second pole ear and the reference pole ear are stacked in the thickness direction of the composite pole ear to form an integral composite structure, so that the second pole ear and the reference pole ear share the space in the width direction of the composite pole ear, which is conducive to reducing the risk of interference between the reference pole ear and the electronic components on the circuit board assembly arranged on the top wall.

[0006] In some embodiments of the present application, the composite pole ear also includes a first insulating glue. Along the thickness direction of the composite pole ear, the first insulating glue is arranged between the second pole ear and the reference pole ear to isolate the reference pole ear and the second pole ear, thereby reducing the risk of interference between the reference pole ear and the second pole ear and affecting the detection accuracy of the reference pole ear.

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

[0008] In some embodiments of the present application, along the thickness direction of the composite pole ear, the thickness of the second pole ear is D1, 0.05mm≤D1≤0.2mm, so as to improve the structural strength and flow capacity of the second pole ear, and to improve the packaging stability of the top seal. Along the thickness direction of the composite pole ear, the thickness of the reference pole ear is D2, 4μm≤D2≤10μm, so as to improve the structural strength and flow capacity of the reference pole ear, and to improve the packaging stability of the top seal. The top seal includes an inner unsealed area, a middle sealed area and an outer unsealed area connected in sequence along the first direction, the middle sealed area is an area that has been hot-pressed and sealed, and along the thickness direction of the composite pole ear, the thickness of the portion of the first insulating glue located in the middle sealed area is D3, 4μm≤D3≤16μm, so as to improve the insulation stability of the first insulating glue, and to improve the packaging stability of the top seal.

[0009] In some embodiments of the present application, 6.4 μm≤D3≤8 μm, so as to further improve the insulation stability of the first insulating glue and further help to improve the packaging stability of the top seal.

[0010] In some embodiments of the present application, the composite electrode tab further includes a lithium plating layer, and the lithium plating layer is arranged at the portion where the reference electrode tab extends into the main body to improve the monitoring accuracy.

[0011] In some embodiments of the present application, the lithium plating layer is arranged on the surface of the reference pole ear away from the first insulating glue, and the thickness of the lithium plating layer along the thickness direction of the composite pole ear is D4, 10μm≤D4≤40μm, so as to provide sufficient lithium source and improve the space utilization of the lithium plating layer in the main body, which is beneficial to improve the energy density of the battery cell.

[0012] In some embodiments of the present application, the first insulating glue includes a first insulating portion, and the first insulating portion is arranged in the top seal portion. Along the width direction of the composite pole lug, the two ends of the first insulating portion protrude from the second pole lug and the reference pole lug. The battery cell includes a first pole lug glue. The first pole lug glue includes a first sub-glue and a second sub-glue. The first sub-glue is connected to the surface of the second pole lug away from the reference pole lug, and the first sub-glue and the first insulating portion jointly wrap the portion of the second pole lug located in the top seal portion. The second sub-glue is connected to the surface of the reference pole lug away from the second pole lug, and the second sub-glue and the first insulating portion jointly wrap the portion of the reference pole lug located in the top seal portion. The first sub-glue and the second sub-glue are used to improve the packaging stability of the composite pole lug in the top seal portion.

[0013] In some embodiments of the present application, the top seal portion includes an inner unsealed area, a middle sealed area, and an outer unsealed area connected in sequence along a first direction, the middle sealed area is an area that has been hot-pressed and sealed, and along the thickness direction of the composite tab, the thickness of the portion of the first sub-glue located in the middle sealed area is D5, 8μm≤D5≤40μm, so as to improve the packaging stability of the top seal portion. Along the arrangement direction of the second sub-glue and the reference tab, the thickness of the portion of the second sub-glue located in the middle sealed area is D6, 8μm≤D6≤40μm, so as to improve the packaging stability of the top seal portion.

[0014] In some embodiments of the present 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 seal 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 waste generated by the second insulating portion outside the top seal portion. The size of the third insulating portion is smaller than the size of the first insulating portion to reduce the space waste generated by the third insulating portion outside the top seal portion.

[0015] In some embodiments of the present application, the electrode assembly includes a first pole piece, a diaphragm, a second pole piece and a sub-pole ear. The first pole piece, the diaphragm and the second pole piece are arranged at intervals. The second pole piece includes a first current collector, and the sub-pole ear is arranged integrally with the first current collector. A plurality of sub-pole ears are assembled into a sub-pole ear bundle, and the sub-pole ear bundle is located between the first current collector and the top wall. Along the extension direction of the composite pole ear, one end of the second pole ear is connected to the sub-pole ear bundle, and the other end of the second pole ear extends from the top seal portion, and the portion where the reference pole ear extends into the main body is located between the first current collector and the top wall, so as to reduce the influence of the reference pole ear on the cycle performance of the electrode assembly. In addition, the composite pole ear and the sub-pole ear bundle share the space between the first current collector and the top wall, which can improve the space utilization rate of the composite pole ear in the main body, thereby facilitating the improvement of the energy density of the battery cell.

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

[0017] In some embodiments of the present application, the electrode assembly includes a first pole piece, a diaphragm, and a second pole piece arranged at intervals. The first pole ear is connected to the first pole piece. The second pole piece includes a first current collector, and the second pole ear is connected to the first current collector. A portion of the reference pole ear is located between the first pole piece and the second pole piece, and along the arrangement direction of the first current collector and the top wall, the length of the portion of the reference pole ear located between the first pole piece and the second pole piece is L1, and the length of the second pole piece is L2, 5mm≤L1≤L2, so as to improve the accuracy of monitoring.

[0018] In some embodiments of the present 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 that are arranged opposite to each other, and the first edge is closer to the top wall than the second edge. The middle line between the first edge and the second edge of the first current collector is the first center line. Observed along the thickness direction of the first current collector, the edge of the portion of the reference tab located between the first pole piece and the second pole piece exceeds the first edge and does not exceed the first center line, so as to reduce the influence of the reference tab on the cycle performance of the electrode assembly.

[0019] In some embodiments of the present application, the second pole piece also 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 pole ear is located in the first groove and connected to the first current collector to improve the stability of the connection between the second pole ear and the first current collector.

[0020] In some embodiments of the present application, the electrode assembly is a winding structure. The first current collector includes a first region and a second region connected along the winding direction of the first current collector, and the first region is located at one end of the winding direction. The second pole piece also includes a first active material layer, and along the thickness direction of the first current collector, the two surfaces of the first region are not provided with the first active material layer, and at least one surface of the second region is provided with the first active material layer. One end of the second pole ear is connected to the first region to improve the stability of the connection between the second pole ear and the first current collector.

[0021] An embodiment of the present application further provides a secondary battery, wherein the material of the reference tab includes at least one of platinum, gold, copper, and aluminum.

[0022] An embodiment of the present application further provides a secondary battery, wherein the material of the first insulating glue includes at least one of polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene.

[0023] An embodiment of the present application further provides a secondary battery, which includes any one of the battery cells in the above embodiments.

[0024] An embodiment of the present application further provides an electronic device, which includes any one of the secondary batteries in the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0027] Figure 3 It is a schematic diagram of the structure of the connection between the tab glue and the composite tab of the battery cell in one embodiment of the present application.

[0028] Figure 4 It is a schematic diagram of the structure of the first insulating glue of the battery cell in one embodiment of the present application.

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

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

[0031] Figure 7 It is a schematic diagram of the structure of the second pole piece of a battery cell in one embodiment of the present application.

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

[0033] Fig. 9 It is a schematic diagram of the structure of the second pole piece in one embodiment of the present application.

[0034] Fig.10 It is a schematic diagram of the structure of a secondary battery in one embodiment of the present application.

[0035] Fig.11 It is a schematic diagram of the structure of an electronic device in one embodiment of the present application.

[0036] Main component symbols Battery cells 100A, 100B, 100C, 100D

[0037] Secondary battery 200

[0038] Electronic device 300

[0039] Electrode assembly 10

[0040] The first pole piece 11

[0041] Diaphragm 12

[0042] The second pole piece 13

[0043] First current collector 131

[0044] First edge 131A

[0045] Second edge 131B

[0046] First area 131C

[0047] Second area 131D

[0048] First active material layer 132

[0049] First groove 132A

[0050] The first pole 14

[0051] First sub-electrode bundle 14A

[0052] 141

[0053] 142 of the second paragraph

[0054] Bending section 143

[0055] Second sub-ear 15

[0056] Packaging bag 20

[0057] Main body 21

[0058] Top wall 211

[0059] Top seal 22

[0060] Inner unsealed area 22A

[0061] Middle Seal Area 22B

[0062] Outer unsealed area 22C

[0063] First tab 30

[0064] Composite tab 40

[0065] Second pole ear 41

[0066] Reference tab 42

[0067] First Insulation Glue 43

[0068] The first insulating portion 431

[0069] The second insulating portion 432

[0070] The third insulating portion 433

[0071] Lithium plating layer 44

[0072] First ear glue 51

[0073] First sub-rubber 511

[0074] Second sub-glue 512

[0075] Second pole ear glue 52

[0076] First insulating member 61

[0077] Second insulating member 62

[0078] Circuit board assembly 70

[0079] First direction X

[0080] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0081] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0082] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed" on another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

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

[0084] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items. The term "overlap" used herein refers to the overlap of the projections of two parts or the overlap of the projections of two parts.

[0085] An embodiment of the present application provides a battery cell, which includes an electrode assembly, a packaging bag, a first pole ear and a composite pole ear. The packaging bag includes a main body and a top seal, the electrode assembly is arranged in the main body, the main body includes a top wall, and the top seal is connected to the top wall. One end of the first pole ear is connected to the electrode assembly, the other end of the first pole ear extends from the top seal, and the first pole ear has a first polarity. The composite pole ear includes a second pole ear and a reference pole ear stacked along the thickness direction of the composite pole ear. One end of the second pole ear is connected to the electrode assembly, and the other end of the second pole ear extends from the top seal. The second pole ear has a second polarity, which is different from the first polarity. Along the first direction, one end of the reference pole ear extends into the main body and the reference pole ear is not connected to the electrode assembly, and the other end of the reference pole ear extends from the top seal, wherein the first direction is the direction from the main body to the top seal.

[0086] In the above-mentioned battery cell, the second pole ear and the first pole ear are configured to be electrically connected to an external circuit, and the reference pole ear is configured to obtain the potential of the battery cell during the cycle of the battery cell. The second pole ear and the reference pole ear are stacked in the thickness direction of the composite pole ear to form an integral composite structure, so that the second pole ear and the reference pole ear share the space in the width direction of the composite pole ear, which is conducive to reducing the risk of interference between the reference pole ear and the electronic components on the circuit board assembly arranged on the top wall.

[0087] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0088] See also Figure 1 An embodiment of the present 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 also read Figure 1 and Figure 2 The packaging bag 20 includes a main body 21 and a top seal 22, and the first direction X is the direction from the main body 21 to the top seal 22. The main body 21 includes a top wall 211, and the top seal 22 is connected to the top wall 211. Specifically, the packaging bag 20 is made of a packaging film, the main body 21 refers to the part where the packaging film is provided with a punching hole, and the top seal 22 refers to the part where the packaging film overlaps and joins. The electrode assembly 10 is arranged in 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 portion 22 . The first electrode tab 30 has a first polarity.

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

[0092] Along the first direction X, one end of the reference pole tab 42 extends into the main body 21 and the reference pole tab 42 is not connected to the electrode assembly 10, and the other end of the reference pole tab 42 extends from the top seal 22. The portion of the reference pole tab 42 located in the main body 21 can obtain the potential of the battery cell 100A during the cycle of the battery cell 100A. The portion of the reference pole tab 42 located outside the top seal 22 is configured to be electrically connected to the protection circuit, so that the protection circuit monitors the potential of the battery cell 100A, and then facilitates the adjustment of the charge and discharge mode to improve the safety of the battery cell 100A and extend the service life of the battery cell 100A.

[0093] In the above-mentioned battery cell 100A, the second pole tab 41 and the first pole tab 30 are configured to be electrically connected to an external circuit, and the reference pole tab 42 is configured to obtain the potential of the battery cell 100A during the cycle of the battery cell 100A. The second pole tab 41 and the reference pole tab 42 are stacked along the thickness direction of the composite pole tab 40 to form an integral composite structure, so that the second pole tab 41 and the reference pole tab 42 share the space in the width direction of the composite pole tab 40, which is conducive to reducing the risk of interference between the reference pole tab 42 and the electronic components on the circuit board assembly arranged on the top wall 211.

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

[0095] Please continue reading Figure 2 In some embodiments, the composite pole lug 40 further includes a first insulating glue 43. The first insulating glue 43 is disposed between the second pole lug 41 and the reference pole lug 42 along the thickness direction of the composite pole lug 40 to isolate the reference pole lug 42 from the second pole lug 41, thereby reducing the risk of interference between the reference pole lug 42 and the second pole lug 41 and affecting the detection accuracy of the reference pole lug 42.

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

[0097] Optionally, the material of the first insulating adhesive 43 includes at least one of polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene. The bonding 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 pole lug 41 is a sheet-like metal structure. Along the thickness direction of the composite pole lug 40, the thickness of the second pole lug 41 is D1, 0.05mm≤D1≤0.2mm. When D1 is too small (less than 0.05mm), the structural strength and current flow capacity of the second pole lug 41 are likely to be weak. When D1 is too large (greater than 0.2mm), the gap between the two layers of packaging films of the top seal 22 on both sides of the composite pole lug 40 is likely to be large, affecting the packaging stability of the top seal 22. By limiting 0.05mm≤D1≤0.2mm, the structural strength and current flow capacity of the second pole lug 41 are improved, and it is beneficial to improve the packaging stability of the top seal 22.

[0099] Optionally, D1 is one of 0.05 mm, 0.1 mm, 0.15 mm, 0.2 mm and any other value in the range of 0.05 mm ≤ D1 ≤ 0.2 mm.

[0100] Please continue reading Figure 2 In some embodiments, the reference pole tab 42 is a sheet-like metal structure. Along the thickness direction of the composite pole tab 40, the thickness of the reference pole tab 42 is D2, 4μm≤D2≤10μm. When D2 is too small (less than 4μm), the structural strength and flow capacity of the reference pole tab 42 are likely to be weak. When D2 is too large (greater than 10μm), the gap between the two layers of packaging films of the top seal 22 on both sides of the composite pole tab 40 is likely to be large, affecting the packaging stability of the top seal 22. By limiting 4μm≤D2≤10μm, the structural strength and flow capacity of the reference pole tab 42 are improved, and it is beneficial to improve the packaging stability of the top seal 22.

[0101] Optionally, D2 is one of 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm and any other value in the range of 4 μm≤D2≤10 μm.

[0102] Optionally, the material of the reference tab 42 includes 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, along the thickness direction of the composite tab 40, the thickness of the first insulating glue 43 is D3, 4μm≤D3≤16μm. When D3 is too small (less than 4μm), the insulation effect is likely to be poor. When D3 is too large (greater than 16μm), the gap between the two layers of packaging films of the top seal 22 on both sides of the composite tab 40 is likely to be large, affecting the packaging stability of the top seal 22. By limiting 4μm≤D3≤16μm, the insulation stability of the first insulating glue 43 is improved, and it is beneficial to improve the packaging stability of the top seal 22.

[0105] Optionally, D3 is 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 in the range of 4μm≤D3≤16μm.

[0106] Furthermore, 6.4 μm≤D3≤8 μm, so as to further improve the insulation stability of the first insulating glue 43 and help to further improve the packaging stability of the top sealing portion 22 .

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

[0108] In some embodiments, the lithium plating layer 44 is disposed on the surface of the reference pole tab 42 away from the first insulating glue 43, and along the thickness direction of the composite pole tab 40, the thickness of the lithium plating layer 44 is D4, 10μm≤D4≤40μm. When D4 is too small (less than 10μm), sufficient lithium source may not be provided. When D4 is too large (greater than 40μm), it is easy for the lithium plating layer 44 to occupy a large space in the main body 21 and cause space waste. By limiting 10μm≤D4≤40μm, it is easy to provide sufficient lithium source and improve the space utilization of the lithium plating layer 44 in the main body 21, which is beneficial to improve the energy density of the battery cell 100A.

[0109] Optionally, D4 is one of 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm and any other value in the range of 10 μm≤D4≤40 μm.

[0110] Please refer again Figure 1 The battery cell 100A further includes a first pole ear glue 51 and a second pole ear glue 52. One end of the first pole ear glue 51 is disposed in the top seal portion 22, and the other end of the first pole ear glue 51 extends from the top seal portion 22, and the first pole ear glue 51 at least wraps the surface of the portion of the composite pole ear 40 located in the top seal portion 22. One end of the second pole ear glue 52 is disposed in the top seal portion 22, and the other end of the second pole ear glue 52 extends from the top seal portion 22, and the second pole ear glue 52 at least wraps the surface of the portion of the first pole ear 30 located in the top seal portion 22.

[0111] Please also read Figure 2 and Figure 3 In some embodiments, the first insulating glue 43 includes a first insulating portion 431, which is disposed in the top seal portion 22. Along the width direction of the composite pole tab 40, both ends of the first insulating portion 431 protrude from the second pole tab 41 and the reference pole tab 42. The first pole tab glue 51 includes a first sub-glue 511 and a second sub-glue 512. The first sub-glue 511 is connected to the surface of the second pole tab 41 away from the reference pole tab 42. The first sub-glue 511 and the first insulating portion 431 jointly wrap the portion of the second pole tab 41 located in the top seal portion 22. The second sub-glue 512 is connected to the surface of the reference pole tab 42 away from the second pole tab 41. The second sub-glue 512 and the first insulating portion 431 jointly wrap the portion of the reference pole tab 42 located in the top seal portion 22. The first sub-glue 511 and the second sub-glue 512 are used to improve the packaging stability of the composite pole tab 40 in the top seal portion 22.

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

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

[0114] Furthermore, 16 μm≤D5≤28 μm, so as to further improve the packaging stability of the top sealing portion 22 .

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

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

[0117] Furthermore, 16 μm≤D6≤28 μm, so as to further improve the packaging stability of the top sealing portion 22 .

[0118] Please also read Figure 1 and Figure 3 It should be noted that, along the extension direction of the top seal portion 22, the top seal portion 22 includes an inner unsealed area 22A, a middle seal area 22B and an outer unsealed area 22C arranged in sequence, wherein the middle seal area 22B refers to the area of ​​the top seal portion 22 that has been hot-pressed, the inner unsealed area 22A is located on the side of the middle seal area 22B close to the electrode assembly 10 and has not been hot-pressed, and the outer unsealed area 22C is located on the side of the middle seal area 22B away from the electrode assembly 10 and has not been hot-pressed. Under the action of hot pressing, the thickness of the first insulating glue 43 and the first pole ear glue 51 located in the middle seal area 22B is relatively small, and the thickness of the first insulating glue 43 and the first pole ear glue 51 located in the inner unsealed area 22A or the outer unsealed area 22C is relatively thick. D3 refers to the thickness of the first insulating glue 43 located in the middle sealing area 22B, D5 refers to the thickness of the first sub-glue 511 located in the middle sealing area 22B, and D6 refers to the thickness of the second sub-glue 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-glue 511 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-glue 512 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 electrode tab 41 and the thickness D2 of the reference electrode tab 42 are measured by a vernier caliper. The thickness D3 of the first insulating adhesive 43, the thickness D4 of the lithium plating layer 44, the thickness D5 of the first sub-adhesive 511, the thickness D6 of the second sub-adhesive 512 and the thickness of other adhesive layers are measured by SEM. Specifically, a measuring part is selected as a sample, and the cross section of the sample is prepared by mechanical cutting, grinding, polishing and liquid nitrogen brittle breaking to ensure that the cross section is flat and has no obvious damage; ultrasonic cleaning or organic solvent cleaning is used to remove surface contaminants and residues; the sample is loaded on a conductive substrate, such as a conductive tape or a conductive carbon film; the processed sample is fixed on the sample stage of the SEM; the sample stage is placed in the sample chamber of the SEM and evacuated to ensure a high vacuum environment; a suitable acceleration voltage is selected according to the properties of different metal adhesive tapes, usually between 1-30kV; parameters such as scanning speed and scanning range are adjusted to obtain a clear image; the distance between the upper and lower edges of the part to be measured is measured and recorded as the thickness of the part to be measured, and five points are selected to calculate the average value.

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

[0124] See also 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 pole tab 41 and the reference pole tab 42 located outside the top seal portion 22. The third insulating portion 433 is located inside the main body 21 to isolate the second pole tab 41 and the reference pole tab 42 located inside the main body 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 waste caused by the second insulating portion 432 outside the top seal portion 22 .

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

[0127] Please refer again Figure 2 In some embodiments, the electrode assembly 10 includes a first pole piece 11, a diaphragm 12, a second pole piece 13, a first sub-pole ear 14, and a second sub-pole ear 15, and the polarities of the first sub-pole ear 14 and the second sub-pole ear 15 are different. The first pole piece 11, the diaphragm 12, and the second pole piece 13 are arranged at intervals, and the electrode assembly 10 is a laminated structure. The first pole piece 11 has a first polarity, and the second pole piece 13 has a second polarity. The first pole ear 30 is electrically connected to the first pole piece 11. The second pole piece 13 includes a first current collector 131, and the first sub-pole ear 14 is integrally arranged with the first current collector 131. A plurality of first sub-pole ears 14 are assembled into a first sub-pole ear bundle 14A, and the first sub-pole ear bundle 14A is located between the first current collector 131 and the top wall 211.

[0128] Along the extension direction of the composite electrode tab 40, one end of the second electrode tab 41 is connected to the sub-first electrode tab bundle 14A, and the other end of the second electrode tab 41 extends from the top seal portion 22. The portion where the reference electrode tab 42 extends into the main body 21 is located between the first current collector 131 and the top wall 211 to reduce the influence of the reference electrode tab 42 on the cycle performance of the electrode assembly 10. In addition, the composite electrode tab 40 and the first sub-electrode tab bundle 14A share the space between the first current collector 131 and the top wall 211, which can improve the space utilization of the composite electrode tab 40 in the main body 21, thereby facilitating the improvement of the energy density of the battery cell 100A.

[0129] In some embodiments, the first sub-electrode tab bundle 14A includes a first section 141, a second section 142, and a bending section 143, the first section 141 is located between the first current collector 131 and the second section 142, the first section 141 and the second section 142 are spaced apart, and the bending section 143 is connected between the first section 141 and the second section 142 to form a "U"-shaped structure. One end of the composite electrode tab 40 is located between the first section 141 and the second section 142, and the second electrode tab 41 is connected to the second section 142. Along the extension direction of the composite electrode tab 40, the reference electrode tab 42 and the first insulating glue 43 extend to the bending section 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 tab bundle 14A, and at least covers the inner surface of the first section 141, the inner surface of the bent section 143, and the side of the reference tab 42 away from the first insulating glue 43. A portion of the second insulating member 62 overlaps with the sub-electrode tab bundle 14A, and at least covers the outer surface of the bent section 143 and the outer surface of the second section 142.

[0131] See also Figure 5 One embodiment of the present application further provides a battery cell 100B. The battery cell 100B is different from the battery cell 100A in that the electrode assembly 10 is a winding structure.

[0132] Except for the above differences, the parameters of the battery cell 100B and the battery cell 100A are substantially the same, and reference may be made to the description of the battery cell 100A.

[0133] Please also read Figure 6 and Figure 7 One embodiment of the present application further provides a battery cell 100C. The battery cell 100C differs from the battery cell 100A in that the electrode assembly 10 does not include a plurality of sub-electrode tabs 14, and the second electrode tab 41 is directly connected to the first current collector 131.

[0134] The electrode assembly 10 includes a first electrode sheet 11, a separator 12, and a second electrode sheet 13 which are arranged at intervals. The electrode assembly 10 is a winding structure. The first electrode sheet 11 has a first polarity, and the second electrode sheet 13 has a second polarity. The first electrode tab 30 is electrically connected to the first electrode sheet 11. The second electrode sheet 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 tab 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 that are arranged opposite to each other. The first edge 131A is closer to the top wall 211 than the second edge 131B, and the middle line of the first current collector 131 between the first edge 131A and the second edge 131B is the first center line O.

[0136] Part of the reference pole tab 42 is located between the first pole piece 11 and the second pole piece 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 pole tab 42 located between the first pole piece 11 and the second pole piece 13 is L1, and the length of the second pole piece 13 is L2, 5mm≤L1≤L2, so as to improve the monitoring accuracy.

[0137] In some embodiments, when observed along the thickness direction of the first current collector 31 , the edge of the reference tab 42 located between the first pole piece 11 and the second pole piece 13 exceeds the first edge 131A and does not exceed the first center line O, so as to reduce the influence 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 tab 41 is located in the first groove 132A and connected to the first current collector 131, so as to improve the stability of the connection between the second electrode tab 41 and the first current collector 131. Specifically, the first groove 132A is provided on one side of the first active material layer 132 close to the first edge 131A.

[0139] Except for the above differences, the parameters of the battery cell 100C and the battery cell 100A are substantially the same, and reference may be made to the description of the battery cell 100A.

[0140] Please also read Figure 8 and Fig. 9 One embodiment of the present application further provides a battery cell 100D. The battery cell 100D differs from the battery cell 100C in that the second electrode 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, and the first region 131C is located at one end of the winding direction. Along the thickness direction of the first current collector 131, the first active material layer 132 is not provided on both surfaces of the first region 131C, and the first active material layer 132 is provided on at least one surface of the second region 131D. One end of the second electrode tab 41 is connected to the first region 131C to improve the stability of the connection between the second electrode tab 41 and the first current collector 131.

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

[0143] Except for the above differences, the parameters of the battery cell 100D and the battery cell 100C are substantially the same, and reference may be made to the description of the battery cell 100C.

[0144] See also Fig.10 One embodiment of the present application further provides a secondary battery 200, which includes the battery cell (100A, 100B, 100C, 100D) in any of the above embodiments. A secondary battery is a battery that can be used by activating the active material by charging after the battery is discharged.

[0145] In some embodiments, the secondary battery 200 includes a circuit board assembly 70, which is disposed on the top wall 211 and has a protection circuit. The circuit board assembly 70 is electrically connected to the first pole ear 30 and the composite pole ear 40. Among them, the second pole ear 41 and the first pole ear 30 are configured to form a complete current loop. The protection circuit monitors the potential of the battery cell (100A, 100B, 100C, 100D) through the reference pole ear 42, and then facilitates the adjustment of the charging and discharging mode to improve the safety of the battery cell (100A, 100B, 100C, 100D) and extend the service life of the battery cell (100A, 100B, 100C, 100D).

[0146] In the above-mentioned battery cells (100A, 100B, 100C, 100D) and the secondary battery 200, an overall composite structure is formed by the second pole tab 41, the reference pole tab 42 and the first insulating glue 43, so that the second pole tab 41 and the first insulating glue 43 share the space in the thickness direction of the second pole tab 41, which is beneficial to reduce the risk of interference between the reference pole tab 42 and the electronic components on the circuit board assembly 70 arranged on the top wall 211.

[0147] See also Fig.11 One embodiment of the present application further provides an electronic device 300, comprising the secondary battery 200 in any of the above embodiments.

[0148] Optionally, the electronic device 300 can be a mobile phone, a tablet computer, a laptop computer, a smart wearable product (e.g., a smart watch, a smart bracelet), a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, or other device with a rechargeable battery.

[0149] In the above-mentioned battery cells (100A, 100B, 100C, 100D) and electronic device 300, an overall composite structure is formed by the second pole tab 41, the reference pole tab 42 and the first insulating glue 43, so that the second pole tab 41 and the first insulating glue 43 share the space in the thickness direction of the second pole tab 41, which is beneficial to reduce the risk of interference between the reference pole tab 42 and the electronic components on the circuit board assembly arranged on the top wall 211.

[0150] The specific implementation of the battery cells in the embodiments and comparative examples are described below.

[0151] 1. High Voltage Insulation Test (Hipot Test): Hipot test (High Potential test) refers to an insulation resistance test that tests the resistance between the reference pole ear and the second pole ear to determine whether there is a short circuit between the reference pole ear and the second pole ear.

[0152] The test method is to detect the leakage current generated by the composite pole ear of the battery cell under the test voltage output by the high-voltage machine, and then calculate the resistance value between the reference pole ear and the second pole ear = test voltage / leakage current, and compare the calculated resistance value with the set judgment resistance. If the detected resistance value is greater than or equal to the preset value, the product under test is judged 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 under test is judged to have failed the test (NG). The preset value of the judgment current in this test is 5mΩ. When the resistance value is lower than 5mΩ, it means that it can be turned on but the resistance value is too small, there is a short circuit point, and it is judged to be NG; when the resistance value is greater than or equal to 5mΩ, it is judged to be OK. Take 100 battery cells for each group of embodiments and comparative examples for testing, the number of battery cells that pass the test is X1, and the test pass rate is X1 / 100.

[0153] 2. Monitor the stability test, measure the first difference and the second difference, the first difference is the difference between the potential of the second pole ear monitored after 800 cycles and the potential of the second pole ear in the first cycle, the second difference is the difference between the platform voltage after 800 cycles and the platform voltage in the first cycle. Compare the first difference and the second difference, the smaller the deviation, the better the monitoring stability, where platform voltage = discharge energy / discharge capacity. In this test, ±0.5mV is used as the preset deviation. When the deviation between the first difference and the second difference is less than the preset deviation, it is judged to be OK; when the deviation between the first difference and the second difference is greater than or equal to the preset deviation, it is judged to be NG. Take 100 battery cells for each group of embodiments and comparative examples for testing, the number of battery cells that pass the test is X2, and the test pass rate is X2 / 100.

[0154] 3. Package strength test, soak the battery cell in red ink for 12 hours, take out the battery cell from the red ink, corrode the nylon layer in the packaging film at the top seal position with aqua regia, corrode the metal layer in the packaging film at the top seal position with hydrochloric acid solution to expose the polymer layer in the packaging film, rinse with clean water, and use an optical microscope to observe whether the polymer layer in the packaging film at the top seal position is penetrated by the red ink. If it is penetrated by red ink, it means that the polymer layer in the packaging film at the top seal position has a leakage channel, and it is judged to be NG; if it is not penetrated by red ink, it is judged to be OK. Take 100 battery cells for each group of embodiments and comparative examples for testing, the number of battery cells that pass the test is X3, and the test pass rate is X3 / 100.

[0155] 4. Secondary battery volume energy density test: Use PPG (Parallel Plate Gauge) to test the initial length, width and thickness of the secondary battery 200 and record them; at a test temperature of 25°C, let the secondary battery 200 stand for 30 minutes, and charge it according to the following charging steps: 0.2C constant current charging to 4.5V, constant voltage charging to 0.05C; after standing for 10 minutes, discharge it according to the following steps: 0.2C DC discharge to 3V. Record the discharge capacity of the secondary battery 200, and calculate the volume energy density of the secondary battery = (platform voltage × discharge capacity) / (secondary battery length × secondary battery width × secondary battery thickness).

[0156] 5. Lithium plating rate of the negative electrode sheet opposite to the composite pole ear: At a test temperature of 25°C, the secondary battery 200 was left to stand for 30 minutes, and step-charged according to the following charging 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, discharge according to the following steps: 1C DC discharge to 3V. The above charging and discharging process is one cycle, which was repeated 1000 times. After that, the secondary battery 200 was disassembled to observe the lithium plating of the negative electrode sheet opposite to the lithium plating layer. The surface of the negative electrode sheet without lithium plating was golden yellow on the whole surface, and the surface of the negative electrode sheet with lithium plating was golden yellow in some areas and grayish white in some areas. 100 cells were tested in each group of embodiments and comparative examples, and the number of negative electrode sheets opposite to the lithium-plated layer on which lithium deposition occurred was recorded as X4. The lithium deposition rate of the negative electrode sheets opposite to the lithium-plated layer was X4 / 100.

[0157] Embodiment 1:

[0158] A battery cell with an initial thickness of 4.8mm, a length of 87mm, and a width of 64mm at 50% SOC has the following assembly process:

[0159] (1) Preparation of negative electrode sheet: Mix the negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, prepare a slurry with a weight percentage of 50wt%, and stir evenly. The slurry is evenly coated on one surface of the copper foil, and then dried at 90°C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side. When preparing a double-sided coated negative electrode sheet, repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a negative electrode active material layer coated on both sides. The coated electrode sheet is then cold-pressed to a thickness of 105μm, a groove is set on the negative electrode active material, and the first electrode ear is welded to the copper foil exposed in the groove.

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

[0161] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a basic organic solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was 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 used, which includes a stacked adhesive layer, a substrate layer and an adhesive layer. The first substrate layer is made of polyethylene (PE), the adhesive in the adhesive layer is PVDF, and the adhesive layer also contains inorganic particles of boehmite.

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

[0164] (6) Cell assembly: Place the aluminum-plastic film with holes punched and formed in an assembly fixture, with the holes facing upward, place the electrode assembly in the holes, and apply external force to press it. Then, place another aluminum-plastic film with holes punched and formed on the electrode assembly with the holes facing downward, and heat-seal the two aluminum-plastic films around the edges by hot pressing to obtain an assembled electrode assembly.

[0165] (7) Liquid injection packaging: The assembled electrode assembly is injected with electrolyte, and the battery cell is obtained through processes such as vacuum packaging, static standing, hot pressing, and shaping.

[0166] Comparative Example 1: Three tabs are provided to connect the positive electrode sheet, the negative electrode sheet and the reference electrode respectively, and the three tabs are provided at intervals in the width direction of the battery cell. It should be noted that, except for the structure of the tabs, other parameters of Comparative Example 1 are the same as those of Example 1.

[0167] Table 1

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

[0169]

[0170]

[0171] Note: “\” in Table 1 means that the parameter is not included.

[0172] It can be seen from Comparative Example 1 and Examples 1 to 41 that the second pole tab and the reference pole tab are stacked along the thickness direction of the composite pole tab to form an overall composite structure, which has higher monitoring stability than the three-pole tab battery cell in the prior art.

[0173] It can be seen from Examples 1 to 8 that changing D3 has no effect on the monitoring stability and volume energy density. The high-voltage insulation test pass rate increases with the increase of D3, and the packaging strength shows a downward trend when D3 is too thick (exceeding 12um). This is because when D3 is too thick, the electrode glue cannot adequately cover the composite electrode, resulting in a decrease in packaging strength. When D3 is greater than 6.4um, the distance between the positive and negative electrodes at the composite electrode position will be too large, and the electrolyte bridge may break, resulting in an increase in the lithium plating rate.

[0174] It can be seen from Examples 9 to 14 that changing the thickness D4 of the lithium plating layer, being too thick or too thin is not conducive to monitoring stability. When the lithium plating layer is too thin, the lithium plating layer cannot provide a stable potential reference. When the lithium plating layer is too thick, the contact impedance between lithium metal and lithium metal and the contact impedance between lithium metal and the reference electrode become larger, which will also lead to a decrease in monitoring stability. A lithium plating layer that is too thick will also lead to a decrease in volume 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 a portion of lithium ions, resulting in an increase in the lithium plating rate.

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

[0176] From Examples 33 to 41, it can be seen that the change in the length of L1 has no effect on the high-voltage insulation test, packaging strength and lithium precipitation rate. Too short or too long will lead to a decrease in monitoring stability. This is because when L1 is too short, the monitored potential is biased; when L1 is too long, the reference tab will be affected by the liquid junction potential, resulting in a decrease in monitoring stability. In addition, too long L1 will also lead to a decrease in volume energy density.

[0177] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the disclosure scope of the present application.

Claims

1. A battery cell, characterized in that: The battery cell comprises: Electrode assembly; A packaging bag, the packaging bag comprising a main body and a top seal, the electrode assembly is arranged in the main body, the main body comprises a top wall, and the top seal is connected to the top wall; A first electrode tab, one end of which is connected to the electrode assembly, the other end of which extends from the top seal portion, and the first electrode tab has a first polarity; and A composite electrode tab, wherein the composite electrode tab comprises a second electrode tab and a reference electrode tab stacked in a thickness direction of the composite electrode tab, wherein 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, and the second electrode tab has a second polarity, which is different from the first polarity, and along a first direction, one end of the reference electrode tab extends into the main body and the reference electrode tab is not connected to the electrode assembly, and the other end of the reference electrode tab extends from the top seal portion, wherein the first direction is the direction from the main body to the top seal portion.

2. The battery cell according to claim 1, characterized in that: The composite electrode tab further includes a first insulating glue, and along the thickness direction of the composite electrode tab, the first insulating glue is arranged between the second electrode tab and the reference electrode tab.

3. The battery cell according to claim 2, characterized in that: Along the first direction, the length of the first insulating glue is greater than or equal to the length of the reference electrode tab, and along the width direction of the composite electrode tab, the width of the first insulating glue is greater than or equal to the width of the reference electrode tab.

4. The battery cell according to claim 2, characterized in that: Along the thickness direction of the composite pole tab, the thickness of the second pole tab is D1, 0.05mm≤D1≤0.2mm; the thickness of the reference pole tab is D2, 4μm≤D2≤10μm; The top sealing portion includes an inner unsealed area, a middle sealed area and an outer unsealed area which are sequentially connected along the first direction. The middle sealed area is an area that has been hot-pressed and sealed. Along the thickness direction of the composite pole ear, the thickness of the first insulating glue located in the middle sealed area is D3, 4μm≤D3≤16μm.

5. The battery cell according to claim 4, characterized in that: 6.4μm≤D3≤8μm.

6. The battery cell according to claim 2, characterized in that: The composite electrode tab further includes a lithium plating layer, and the lithium plating layer is arranged at a portion where the reference electrode tab extends into the main body.

7. The battery cell according to claim 6, characterized in that: The lithium plating layer is arranged on the surface of the reference pole tab away from the first insulating glue, and along the thickness direction of the composite pole tab, the thickness of the lithium plating layer is D4, 10μm≤D4≤40μm.

8. The battery cell according to claim 2, characterized in that: The first insulating glue comprises a first insulating portion, the first insulating portion is arranged in the top sealing portion, and along the width direction of the composite electrode tab, two ends of the first insulating portion protrude out of the second electrode tab and the reference electrode tab; The battery cell also includes a first pole lug glue, which includes a first sub-glue and a second sub-glue, the first sub-glue is connected to the surface of the second pole lug away from the reference pole lug, the first sub-glue and the first insulating part jointly wrap the portion of the second pole lug located in the top seal portion, the second sub-glue is connected to the surface of the reference pole lug away from the second pole lug, and the second sub-glue and the first insulating part jointly wrap the portion of the reference pole lug located in the top seal portion.

9. The battery cell according to claim 8, characterized in that: The top seal portion includes an inner unsealed area, a middle sealed area and an outer unsealed area sequentially connected along the first direction, and along the thickness direction of the composite tab, the thickness of the portion of the first sub-glue located in the middle sealed area is D5, 8μm≤D5≤40μm; The thickness of the portion of the second sub-glue located in the middle sealing area is D6, 8μm≤D6≤40μm.

10. The battery cell according to claim 9, characterized in that: 16μm≤D5≤28μm; 16μm≤D6≤28μm.

11. The battery cell according to claim 8, characterized in that: The first insulating glue comprises a second insulating part and a third insulating part connected to both sides of the first insulating part, the second insulating part is located outside the top sealing part, and the third insulating part is located inside the main body; 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, and / or the size of the third insulating portion is smaller than the size of the first insulating portion.

12. The battery cell according to claim 1, characterized in that: The electrode assembly comprises a first pole piece, a diaphragm, a second pole piece and a sub-pole ear, wherein the first pole piece, the diaphragm and the second pole piece are arranged at intervals, the second pole piece comprises a first current collector, the sub-pole ear is arranged integrally with the first current collector, a plurality of the sub-pole ears are assembled into a sub-pole ear bundle, and the sub-pole ear 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, the other end of the second electrode tab extends from the top seal portion, and the portion where the reference electrode tab extends into the main body is located between the first current collector and the top wall.

13. The battery cell according to claim 12, characterized in that: The electrode assembly is a winding structure or a stacked structure.

14. The battery cell according to claim 1, characterized in that: The electrode assembly comprises a first pole piece, a diaphragm and a second pole piece which are spaced apart from each other, the first pole tab is connected to the first pole piece, the second pole piece comprises a first current collector, and the second pole tab is connected to the first current collector; Part of the reference pole tab is located between the first pole piece and the second pole piece. Along the arrangement direction of the first current collector and the top wall, the length of the part of the reference pole tab located between the first pole piece and the second pole piece is L1, and the length of the second pole piece is L2, 5mm≤L1≤L2.

15. The battery cell according to claim 14, 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 that are oppositely arranged, the first edge is closer to the top wall than the second edge, and a middle line of the first current collector between the first edge and the second edge is a first center line; Observed along the thickness direction of the first current collector, the edge of the portion of the reference electrode tab located between the first pole piece and the second pole piece exceeds the first edge and does not exceed the first center line.

16. The battery cell according to claim 15, characterized in that: The second pole piece also includes a first active material layer, the first active material layer is provided on at least one surface of the first current collector, the first active material layer is provided with a first groove exposing the first current collector, and one end of the second pole ear is located in the first groove and connected to the first current collector.

17. The battery cell according to claim 15, characterized in that: The electrode assembly is a winding structure, the first current collector includes a first region and a second region connected along the winding direction of the first current collector, and the first region is located at one end of the winding direction; the second pole piece also includes a first active material layer, along the thickness direction of the first current collector, the two surfaces of the first region are not provided with the first active material layer, and at least one surface of the second region is provided with the first active material layer, and one end of the second pole ear is connected to the first region.

18. The battery cell according to claim 1, characterized in that: The material of the reference tab includes at least one of platinum, gold, copper and aluminum.

19. The battery cell according to claim 2, characterized in that: The material of the first insulating adhesive includes at least one of polyimide, polyester, polyurethane, epoxy resin, silicone, and polytetrafluoroethylene.

20. A secondary battery, characterized in that: The secondary battery comprises the battery cell according to any one of claims 1 to 19.

21. An electronic device, characterized in that: The electronic device includes the secondary battery as claimed in claim 20.

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