Secondary batteries and electronic devices

Abstract

A secondary battery and an electronic device are disclosed. The secondary battery includes a packaging bag, an electrode assembly, and a first adhesive. A first electrode and a second electrode of the electrode assembly are stacked and wound together. The first electrode includes a first current collector and a first active material layer. The first current collector includes a first surface and a second surface, the first surface facing a winding center axis. The first active material layer includes a first sub-layer disposed on the first surface and a second sub-layer disposed on the second surface. The first current collector includes a first tailing region in the winding direction. The first tailing region is exposed beyond the first and second sub-layers and is located at the last fold in the winding direction. The first tailing region includes a third edge, which is the tailing edge of the electrode assembly. The first adhesive adheres to the surface of the packaging bag facing the electrode assembly, the surface of the first tailing region facing the packaging bag, and the third edge. Viewed in a second direction, the edge of the first electrode disposed in the width direction overlaps with the first adhesive.

Description

Technical Field

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

[0002] With the increasing popularity of consumer electronics products such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, people are becoming more and more demanding in terms of the safety performance and lifespan of rechargeable batteries.

[0003] Pouch batteries typically consist of a packaging bag and an electrode assembly housed within the bag. In related technologies, the electrode assembly has a wound structure and uses a current collector as the termination. To reduce the risk of short circuits between the positive and negative electrodes due to wrinkling or shrinkage of the separator caused by free electrolyte during mechanical abuse (such as drops or impacts), adhesive wrapping is usually applied to the head and tail of the electrode assembly to secure the edges of the separator. However, in some cases, there may not be sufficient space at the head or tail of the electrode assembly to provide the adhesive wrapping. If this wrapping is omitted, after the separator (especially the outer layers) wrinkles or shrinks during mechanical abuse, the terminated current collector will become unrestrained and move, potentially short-circuiting with the inner electrodes, thus reducing the safety performance and lifespan of the secondary battery. Summary of the Invention

[0004] In view of this, it is necessary to propose a secondary battery with improved safety performance and service life.

[0005] Additionally, it is necessary to provide an electronic device having the secondary battery.

[0006] This application provides a rechargeable battery, including a packaging bag, an electrode assembly, and a first adhesive. The electrode assembly is disposed within the packaging bag. The electrode assembly includes a first electrode and a second electrode, which are stacked and wound together. The first electrode includes a first current collector and a first active material layer. The first current collector includes a first surface and a second surface opposite to each other along its thickness direction, the first surface facing a winding center axis and the second surface facing away from the winding center axis. The first active material layer includes a first sub-layer disposed on the first surface and a second sub-layer disposed on the second surface. The first current collector includes a first terminal region in the winding direction. The first terminal region is exposed beyond the first and second sub-layers and is located at the last fold of the first current collector in the winding direction. The first terminal region includes a third edge, which is the terminal edge of the electrode assembly. The first adhesive adheres to at least a portion of the first terminal region facing the packaging bag and the third edge, and the first adhesive extends across the third edge in the winding direction and adheres to a portion of the second surface. The width direction of the first electrode is a first direction, and the thickness direction of the electrode assembly is a second direction. The first and second directions are perpendicular to each other, and a third direction is a direction perpendicular to the first and second directions. The first electrode includes a first edge and a second edge disposed opposite to each other along the first direction. When viewed along the second direction, the first edge overlaps with the first adhesive member.

[0007] In this application, the first adhesive component acts as a finishing adhesive to fix the first finishing area, thereby reducing the possibility of loose electrode assembly and misalignment of electrode sheets, making the electrode assembly more regular overall. Furthermore, by extending the first adhesive component along the first direction, the first edge of the first electrode sheet overlaps with the first adhesive component. Therefore, the first adhesive component can fully fix the first finishing area located near the first edge in the first direction. Even if the separator wrinkles or shrinks during mechanical abuse, the first adhesive component can reduce the risk of short circuit between this portion of the first finishing area and the second electrode sheet located inside the first finishing area (especially the protruding area of ​​the second electrode sheet). Therefore, this application can improve the safety performance and service life of the secondary battery.

[0008] Based on the first aspect, in one or more of the above possible implementations, the first adhesive also adheres to a portion of the packaging bag facing the electrode assembly surface; the secondary battery also includes multiple conductive plates, the number of which is N, and the number of conductive plates extending from one side of the first edge is N1, where N≥N1, N1≥3. Therefore, the first adhesive serves both as a finishing adhesive to fix the first finishing area and as a fixation between the electrode assembly and the packaging bag, reducing the risk of the electrode assembly shifting within the packaging bag under mechanical abuse and improving the secondary battery's resistance to mechanical abuse. Simultaneously, by providing multiple conductive plates, the requirements for high-current charging and discharging can be met, and the internal resistance of the first or second electrode can be reduced. Moreover, even if there is insufficient space at the end of the electrode assembly corresponding to the first edge to provide adhesive, the risk of a short circuit caused by the first finishing area contacting the second electrode due to wrinkling or shrinkage of the separator can be reduced, improving the safety performance and service life of the secondary battery.

[0009] Based on the first aspect, in one or more of the above possible implementations, N=4, N1=4. The multiple conductive plates include two first conductive plates and two second conductive plates. The second electrode includes a second current collector. The two first conductive plates are electrically connected to the first current collector, and the two second conductive plates are electrically connected to the second current collector. The two first conductive plates and the two second conductive plates are arranged sequentially in a third-direction upward direction. Therefore, the requirements for high-current charging and discharging can be met, and the internal resistance of the first or second electrode can be further reduced. Moreover, even if there is insufficient space at the end of the electrode assembly corresponding to the first edge to accommodate the adhesive wrapping, the risk of a short circuit caused by the first tailing area contacting the second electrode after the separator wrinkles or shrinks can be reduced, improving the safety performance and service life of the secondary battery.

[0010] Based on the first aspect, in one or more of the above possible implementations, the first adhesive element includes a fourth edge, which is located at the same end of the electrode assembly along the first direction as the first edge. Viewed along the second direction, the distance between the fourth edge and the first edge along the first direction is L1, where 0 ≤ L1 ≤ 2.0 mm. When L1 is greater than zero, the risk of the first adhesive element failing to adequately fix the first edge due to process errors can be reduced, further reducing the risk of a short circuit caused by the first finishing area contacting the second electrode sheet after the separator film wrinkles or shrinks. Moreover, by limiting the upper limit of L1, the risk of the first adhesive element pressing against the sealing edge of the packaging bag in the first direction can be reduced, or the risk of the first adhesive element entering the unsealed area of ​​the packaging bag before sealing can be reduced, thereby reducing the risk of leakage from the packaging bag.

[0011] Based on the first aspect, in one or more of the above possible implementations, 0.2mm ≤ L1 ≤ 2.0mm. Therefore, the risk of a short circuit caused by the first closing area contacting the second electrode after the separator membrane wrinkles or shrinks can be further reduced.

[0012] Based on the first aspect, in one or more of the above possible implementations, 0.2mm ≤ L1 ≤ 1.4mm. Therefore, the first adhesive does not extend beyond the separator along the first direction, reducing the impact of the first adhesive on the length of the secondary battery. It also further reduces the risk that the first adhesive will press against the sealing edge of the packaging bag or enter the packaging bag's unsealed area before sealing in the first direction, thereby reducing the risk of leakage from the packaging bag.

[0013] Based on the first aspect, in one or more of the above possible implementations, when viewed along the second direction, the extension line of the third edge along the first direction is located between two adjacent conductive plates in the third direction. This helps reduce the risk of the third edge opening relative to the electrode assembly, improves the compactness of the electrode assembly, and allows the first adhesive member bonding the third edge to have a suitable position along the third direction, reducing stress between the packaging bag and the electrode assembly under mechanical abuse, thereby reducing the risk of tearing in the first closing area and further improving the secondary battery's resistance to mechanical abuse.

[0014] Based on the first aspect, in one or more of the above possible implementations, the projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge disposed opposite to each other along a third direction. The first adhesive includes a seventh edge and an eighth edge disposed opposite to each other along a third direction. Along the third direction, the fifth edge, seventh edge, eighth edge, and sixth edge are arranged sequentially. The distance between the fifth edge and the seventh edge along the third direction is L2, and the distance between the sixth edge and the eighth edge along the third direction is L3; 0 ≤ |L2 - L3| ≤ 4 mm. Therefore, the first adhesive can be positioned approximately centrally along the third direction, further reducing the stress between the packaging bag and the electrode assembly under mechanical abuse, thereby reducing the risk of tearing in the first finishing area and further improving the resistance to mechanical abuse of the secondary battery.

[0015] Based on the first aspect, in one or more of the above possible implementations, the projected area of ​​the electrode assembly along the second direction is S1, and the area of ​​the first adhesive is S2, where 0.4 ≤ S2 / S1 ≤ 1. By limiting the lower limit of S2 / S1, the adhesive force between the electrode assembly and the packaging bag can be increased to further improve the mechanical abuse resistance of the secondary battery. It also reduces the risk of localized lithium plating due to undervoltage at locations of the electrode assembly not covered by the first adhesive during formation. By limiting the upper limit of S2 / S1, the risk of the first adhesive easily bonding to other locations after extending beyond the electrode assembly can be reduced, thereby improving the mechanical abuse resistance of the secondary battery. Furthermore, the risk of air bubbles forming during the bonding process of the first adhesive can be reduced, thus improving the bonding effect of the first adhesive and the appearance of the secondary battery.

[0016] Based on the first aspect, in one or more of the above possible implementations, 0.5 ≤ S2 / S1 ≤ 0.7. Therefore, the adhesion between the electrode assembly and the packaging bag can be further improved, and the risk of localized lithium plating due to undervoltage during formation at locations of the electrode assembly not covered by the first adhesive can be reduced. Furthermore, the risk of the first adhesive easily adhering to other locations after extending beyond the electrode assembly can be further reduced, as can the risk of air bubbles appearing during the application of the first adhesive.

[0017] Based on the first aspect, in one or more of the above possible implementations, when viewed along the first direction, the projection of the first termination region does not overlap with the projections of the multiple conductive plates. Therefore, the impact of the first termination region on the thickness and energy density of the secondary battery can be reduced.

[0018] Based on the first aspect, in one or more of the above possible implementations, the secondary battery further includes a second adhesive member. The second adhesive member adheres to the surface of the packaging bag facing the electrode assembly and a portion of the second surface located on the same side as the third edge in a second direction. The first adhesive member and the second adhesive member are arranged sequentially and separated in a third direction. Therefore, the first and second adhesive members can jointly secure the electrode assembly to the packaging bag, thereby reducing the risk of the electrode assembly shifting within the packaging bag under mechanical abuse. Furthermore, the additional second adhesive member improves the thickness flatness of the secondary battery and also alleviates the stress problem between the packaging bag and the electrode assembly when only the first adhesive member is used.

[0019] Based on the first aspect, in one or more of the above possible implementations, the projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge disposed opposite to each other along the third direction. The first adhesive includes a seventh edge and an eighth edge disposed opposite to each other along the third direction. The second adhesive includes a ninth edge and a tenth edge disposed opposite to each other along the third direction. Along the third direction, the fifth edge, the ninth edge, the tenth edge, the seventh edge, the eighth edge, and the sixth edge are arranged sequentially. The straight-line distance between the sixth edge and the eighth edge along the third direction is L3, and the straight-line distance between the fifth edge and the ninth edge along the third direction is L4; 0≤|L3-L4|≤4mm. Therefore, the first adhesive and the second adhesive are generally centered along the third direction, further reducing the stress between the packaging bag and the electrode assembly under mechanical abuse, thereby reducing the risk of tearing in the first closing area and further improving the mechanical abuse resistance of the secondary battery.

[0020] Based on the first aspect, in one or more of the above possible implementations, the projected area of ​​the electrode assembly along the second direction is S1, the area of ​​the first adhesive is S2, the area of ​​the second adhesive is S3, and 0.4 ≤ (S2 + S3) / S1 ≤ 1. By limiting the lower limit of (S2 + S3) / S1, the adhesive force between the electrode assembly and the packaging bag can be increased to further improve the mechanical abuse resistance of the secondary battery. It also reduces the risk of localized lithium plating due to undervoltage at locations of the electrode assembly not covered by the first and second adhesives during formation. By limiting the upper limit of (S2 + S3) / S1, the risk of the first or second adhesive extending beyond the electrode assembly and easily bonding to other locations can be reduced, thereby improving the mechanical abuse resistance of the secondary battery. Furthermore, the risk of air bubbles appearing during the bonding process of the first or second adhesive can be reduced, thus improving the bonding effect and the appearance of the secondary battery.

[0021] Based on the first aspect, in one or more of the above possible implementations, 0.5 ≤ (S2 + S3) / S1 ≤ 0.7. Therefore, the adhesion between the electrode assembly and the packaging bag can be further improved, and the risk of localized lithium plating due to undervoltage during formation can be reduced at locations of the electrode assembly not covered by the first and second adhesives. Furthermore, the risk of the first or second adhesive extending beyond the electrode assembly and easily adhering to other locations can be further reduced, as can the risk of air bubbles appearing during the application of the first or second adhesive.

[0022] Based on the first aspect, in one or more of the above possible implementations, the first sublayer includes a second terminal region in the winding direction, and the second sublayer includes a third terminal region in the winding direction. The second terminal region is located at the outermost winding of the first electrode, and the third terminal region is located at the second outermost winding of the first electrode. The secondary battery also includes a third adhesive member disposed in the second terminal region and extending along the winding direction to adhere to the first surface. Viewed from a second direction, the first adhesive member and the third adhesive member are separated in a third direction. Therefore, the impact on the thickness and energy density of the secondary battery when the first adhesive member and the third adhesive member overlap can be reduced.

[0023] Based on the first aspect, in one or more of the above possible implementations, the secondary battery further includes a fourth adhesive member. The fourth adhesive member is disposed in the third terminal region and extends along the winding direction to adhere to the second surface. Viewed from the second direction, the first adhesive member and the fourth adhesive member are separated in the third direction. Therefore, the impact on the thickness and energy density of the secondary battery when the first and fourth adhesive members overlap can be reduced.

[0024] Based on the first aspect, in one or more of the above possible implementations, the secondary battery further includes a fifth adhesive member. The electrode assembly includes a first end and a second end disposed opposite each other in a first direction, with a first edge located at the first end and a second edge located at the second end. The fifth adhesive member adheres to the second end. Viewed from a second direction, the first adhesive member and the fifth adhesive member are separated in the first direction. Therefore, the fifth adhesive member can adhere to the edge of the separator, reducing the risk of short circuits between the first and second electrodes caused by wrinkling or shrinkage of the separator edge during mechanical abuse. Furthermore, since the first adhesive member and the fifth adhesive member are separated in the first direction, the impact on the thickness and energy density of the secondary battery can be reduced.

[0025] Based on the first aspect, in one or more of the above possible implementations, the first adhesive layer includes a first adhesive layer, a substrate layer, and a second adhesive layer sequentially stacked along the thickness direction of the first adhesive layer. The first adhesive layer is disposed on the surface of the substrate layer facing the packaging bag, and the second adhesive layer is disposed on the surface of the substrate layer facing the first finishing region. The material of the substrate layer includes at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. The materials of the first adhesive layer and the second adhesive layer independently include at least one selected from polyethylene, polypropylene, polyurethane, epoxy resin, styrene-butadiene rubber, polyvinylidene fluoride, polyacrylate, and polyacrylic acid and their derivatives.

[0026] Based on the first aspect, in one or more of the above possible implementations, the first electrode is a positive electrode and the second electrode is a negative electrode.

[0027] Based on the first aspect, in one or more of the above possible implementations, the first adhesive extends beyond the edge of the second electrode in a first direction. This arrangement allows the first adhesive to better reduce the risk of contact between the first and second electrodes.

[0028] A second aspect of this application provides an electronic device including the aforementioned secondary battery. The electronic device is powered by the secondary battery, and the risk of short circuits caused by wrinkles or shrinkage of the separator is reduced, thus providing higher safety and a longer service life. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a secondary battery provided in one embodiment of this application when viewed from a second direction.

[0030] Figure 2 for Figure 1 The secondary battery shown is a cross-sectional view along section line II-II in some embodiments.

[0031] Figure 3 for Figure 1The diagram shown illustrates the structure of a secondary battery after removing the packaging bag in some embodiments.

[0032] Figure 4 for Figure 1 The diagram shown is a structural schematic of the secondary battery after the packaging bag has been removed in some other embodiments.

[0033] Figure 5 for Figure 1 The diagram shown is a structural schematic of the secondary battery after the packaging bag has been removed in some other embodiments.

[0034] Figure 6 for Figure 2 The diagram shows the unfolded view of the first electrode of the secondary battery.

[0035] Figure 7 for Figure 2 A cross-sectional view of the first adhesive component of the secondary battery shown.

[0036] Figure 8 This is a schematic diagram of the overall structure of an electronic device provided in one embodiment of this application.

[0037] Explanation of main component symbols

[0038] Electronic device 1; Packaging bag 10

[0039] Main body 11 Electrode assembly 20

[0040] Fifth edge 20A Sixth edge 20B

[0041] First end 20C Second end 20D

[0042] First pole piece 21; First edge 21A, 22A, 23A

[0043] Second edge 21B, 22B, 23B Second pole piece 22

[0044] 23 Isolation membrane 23 First conductive plate 31

[0045] Second conductive plate 32 First adhesive component 41

[0046] Fourth edge 41A Seventh edge 41B

[0047] Eighth edge 41C Second adhesive 42

[0048] Ninth Edge 42A Tenth Edge 42B

[0049] Third adhesive component 50; Fourth adhesive component 60

[0050] Fifth adhesive component 70, secondary battery 100

[0051] Battery compartment 101 First straight section 201

[0052] First bend section 202; Second straight section 203

[0053] Second bend segment 204 First current collector 210

[0054] First active material 211; Second current collector 220

[0055] Second active material 221 Substrate layer 410

[0056] First adhesive layer 411 Second adhesive layer 412

[0057] First finishing area 2100; Third edge 2100A

[0058] First surface 2101 Second surface 2102

[0059] Second finishing area 2110 Third finishing area 2110'

[0060] First sub-layer 2111 Second sub-layer 2112

[0061] Winding center axis O, winding direction D

[0062] The first direction of the winding center plane P is X

[0063] Second direction Y, Third direction Z

[0064] Fourth direction Y' Fifth direction Z'

[0065] Straight-line distances L1, L2, L3, L4

[0066] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0067] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. 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 in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0068] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to provide a thorough and detailed understanding of this application to those skilled in the art.

[0069] Additionally, for brevity and clarity, the dimensions or thicknesses of various components and layers may be enlarged in the accompanying drawings. Throughout the text, the same numerical values ​​refer to the same elements. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more of the associated enumerated items. Furthermore, it should be understood that when element A is referred to as "connecting" element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0070] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".

[0071] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0072] Spatial terms, such as "above," may be used herein for convenience in describing the relationship between one element or feature and another element (or feature) or feature (or feature) illustrated in the figures. It should be understood that, in addition to the directions depicted in the figures, spatial terms are intended to include different orientations of the device or apparatus during use or operation. For example, if the device in the figure is flipped, an element described as "above" or "on" other elements or features would be oriented "below" or "under" other elements or features. Therefore, the exemplary term "above" can include both above and below orientations. It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, a first element, component, region, layer, or portion discussed below may be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0073] Please see Figure 1 and Figure 2One embodiment of this application provides a secondary battery 100, including a packaging bag 10, an electrode assembly 20, and an electrolyte (not shown). The electrode assembly 20 and the electrolyte are located inside the packaging bag 10.

[0074] like Figure 2 As shown, the electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separator 23, with the separator 23 disposed between the first electrode 21 and the second electrode 22. The first electrode 21, the separator 23, and the second electrode 22 are stacked and wound together. The first electrode 21 includes a first current collector 210 and a first active material layer 211 disposed on the first current collector 210. The first current collector 210 includes a first surface 2101 and a second surface 2102 opposite to each other along the thickness direction of the first current collector 210. The first surface 2101 faces the winding center axis O, and the second surface 2102 faces away from the winding center axis O. The first active material layer 211 includes a first sub-layer 2111 disposed on the first surface 2101 and a second sub-layer 2112 disposed on the second surface 2102. The second electrode 22 includes a second current collector 220 and a second active material layer 221 disposed on the second current collector 220. A three-dimensional coordinate system is defined by three perpendicular directions: a first direction X, a second direction Y, and a third direction Z. The width direction of the first electrode 21 or the second electrode 22 is the first direction X. In some embodiments, the first direction X is also the extension direction of the winding center axis O. The thickness direction of the electrode assembly 20 is the second direction Y. The electrode assembly 20 can be divided into a first straight segment 201, a first bent segment 202, a second straight segment 203, and a second bent segment 204 connected sequentially in the winding direction D. The first straight segment 201 and the second straight segment 203 are arranged opposite each other in the second direction Y, and the first bent segment 202 and the second bent segment 204 are arranged opposite each other in the third direction Z.

[0075] The first electrode 21 can be a positive electrode, and the second electrode 22 can be a negative electrode. Correspondingly, the first current collector 210 and the first active material layer 211 are the positive current collector and the positive active material layer, respectively, and the second current collector 220 and the second active material layer 221 are the negative current collector and the negative active material layer, respectively. Please refer to... Figure 3The first electrode 21 includes a first edge 21A and a second edge 21B disposed opposite to each other in the first direction X. The second electrode 22 includes a first edge 22A and a second edge 22B disposed opposite to each other in the first direction X. The separator 23 includes a first edge 23A and a second edge 23B disposed opposite to each other in the first direction X. The electrode assembly 20 includes a first end 20C and a second end 20D disposed opposite to each other in the first direction X. The first edges 21A, 22A, and 23A are located at the first end 20C of the electrode assembly 20, and the second edges 21B, 22B, and 23B are located at the second end 20D of the electrode assembly 20. To reduce the risk of lithium plating of the second electrode 22, the first edge 22A of the second electrode 22 may be disposed beyond the first edge 21A of the first electrode 21 in the first direction X, and the second edge 22B of the second electrode 22 may be disposed beyond the second edge 21B of the first electrode 21 in the first direction X. The portion of the second electrode 22 that extends beyond the first electrode 21 is called an overhang. To reduce the risk of contact between the first electrode 21 and the second electrode 22, the first edge 23A of the separator 23 can be further provided to extend beyond the first edge 22A of the second electrode 22 along the first direction X, and the second edge 23B of the separator 23 can be provided to extend beyond the second edge 23B of the second electrode 22 along the first direction X. In other embodiments, the first electrode 21 can also be configured as a negative electrode and the second electrode 22 as a positive electrode.

[0076] like Figures 1 to 3 As shown, the secondary battery 100 may further include multiple conductive plates. All conductive plates are electrically connected to the electrode assembly 20 and extend out of the packaging bag 10, and the conductive plates can be connected to external components (not shown). The first direction X is also the direction in which the conductive plates extend out of the electrode assembly 20 (i.e., the direction from the electrode assembly 20 to the conductive plate). The multiple conductive plates include at least one first conductive plate 31 and at least one second conductive plate 32. The first conductive plate 31 is electrically connected to the first current collector 210 or to the first current collector 210 via a first tab (not shown), and the second conductive plate 32 is electrically connected to the second current collector 220 or to the second current collector 220 via a second tab (not shown). Furthermore, viewed from the second direction Y, the first conductive plate 31 may extend out of the electrode assembly 20 from either the first edge 21A or the second edge 21B, and the second conductive plate 32 may extend out of the electrode assembly 20 from either the first edge 21A or the second edge 21B. In some embodiments, to meet the requirements of high-current charging and discharging and reduce the internal resistance of the first electrode 21 or the second electrode 22, the number of the first conductive plate 31 or the second conductive plate 32 can be increased accordingly. Therefore, the number of conductive plates in the plurality of conductive plates can be N, and the number of conductive plates extending from the first edge 21A side can be N1, where N≥N1, N1≥3. Thus, the first conductive plate 31 or the second conductive plate 32 can achieve parallel current sharing, thereby facilitating the reduction of the internal resistance of the first electrode 21 or the second electrode 22 and meeting the requirements of high-current charging and discharging.

[0077] Further, in some embodiments, N=4 and N1=4 can be set. The plurality of conductive plates includes two first conductive plates 31 and two second conductive plates 32. Therefore, the first conductive plates 31 can achieve parallel current sharing, thereby reducing the internal resistance of the first electrode 21; the second conductive plates 32 can achieve parallel current sharing, thereby reducing the internal resistance of the second electrode 22. Moreover, the two first conductive plates 31 and the two second conductive plates 32 are arranged sequentially in the third direction Z, that is, the two conductive plates on either side of a first conductive plate 31 in the third direction Z have different polarities, and the two conductive plates on either side of a second conductive plate 32 in the third direction Z have different polarities. This helps to reduce the risk of short circuits caused by contact between the conductive plates and adjacent conductive plates during mechanical abuse. In some embodiments, the packaging bag 10 includes a connected main body 11 and a sealing edge 12, the main body 11 for accommodating the electrode assembly 20 and the electrolyte, and the sealing edge 12 facing the first edge 21A. Both first conductive plates 31 and two second conductive plates 32 extend out of the packaging bag 10 from the sealing edge 12.

[0078] like Figure 2 As shown, the outermost winding of the electrode assembly 20 is the first electrode 21, and the first electrode 21 of the outermost winding includes a single-sided coated area and a double-sided empty foil area connected in sequence along the winding direction D. That is, the first current collector 210 of the outermost winding only has a first sub-layer 21111 on a portion of its first surface 2101, and no second sub-layer 2112 is provided on its second surface 2102. Therefore, the outer surface of the outermost winding of the electrode assembly 20 is the second surface 2102. This can improve the energy density of the secondary battery 100 and improve the situation where the active material on the outer surface of the electrode assembly 20 is prone to falling off after contact with the packaging bag 10. Moreover, the first current collector 210 of the outermost winding can increase the hardness of the electrode assembly 20, which can protect the electrode assembly 20 and improve the electrode assembly 20's resistance to mechanical impact.

[0079] The positive electrode current collector can be made of aluminum foil or nickel foil, and the negative electrode current collector can be made of at least one of copper foil, nickel foil or carbon-based current collector.

[0080] The positive electrode active material layer comprises a positive electrode active material, which includes a compound that reversibly inserts and de-intercalates metal ions (such as lithium ions, sodium ions, etc., hereinafter taking lithium ions as an example) (i.e., a lithiation intercalation compound). In some embodiments, the first active material may include a lithium transition metal composite oxide. This lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive electrode active material is selected from lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese ternary materials (NCM), lithium nickel cobalt aluminum ternary materials (NCA), lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 At least one of lithium iron phosphate (LiFePO4) or lithium iron phosphate (LiFePO4).

[0081] The negative electrode active material layer contains a negative electrode active material, which is a known negative electrode active material capable of reversible intercalation and deintercalation of active ions, and this application is not limited to this. For example, it may include, but is not limited to, one or more combinations of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium. Among them, graphite may be selected from one or more combinations of artificial graphite, natural graphite, and modified graphite; silicon-based materials may be selected from one or more combinations of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; tin-based materials may be selected from one or more combinations of elemental tin, tin oxide compounds, and tin alloys.

[0082] The separator 23 comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene comprises at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.

[0083] like Figure 2As shown, the first current collector 210 also includes a first termination region 2100 in the winding direction D. The first termination region 2100 is exposed in the first sub-layer 21111 and the second sub-layer 2112, that is, the first termination region 2100 is a double-sided empty foil region. The first termination region 2100 is located at the last fold of the first current collector 210 along the winding direction D. The first termination region 2100 includes a third edge 2100A in the winding direction D. The third edge 2100A is the termination edge of the electrode assembly 20. The third edge 2100A may be located in the first straight section 201 of the electrode assembly 20, or at the junction of the first straight section 201 and the second bent section 204, or in the second bent section 204. In some embodiments, the first sub-layer 2111 includes a second termination region 2110 in the winding direction D. The second termination region 2110 is located at the outermost winding of the first electrode 21. The second sublayer 2112 includes a third termination region 2110' in the winding direction D, which is located on the second outermost winding of the first electrode 21. Both the second termination region 2110 and the third termination region 2110' may be located in the second straight section 203 of the electrode assembly 20. The first termination region 2100 is exposed above the second termination region 2110 and the third termination region 2110'.

[0084] In this embodiment, the outermost winding of the first electrode 21 refers to the outermost ring of the multi-layer structure formed by winding the first electrode 21 along the winding direction D, relative to the winding center axis O of the electrode assembly 20; the second outermost winding refers to the ring of the multi-layer structure formed by winding the first electrode 21 along the winding direction D, located on the side of the outermost ring facing the winding center axis O and adjacent to the outermost ring. Furthermore, a "ring" refers to starting from a point on the first electrode 21 as the starting end, moving along the winding direction D to another point as the ending end, with the ending end, the starting end, and the center of this ring all on a straight line, and the starting end located between the ending end and the center of this ring.

[0085] In this embodiment, a virtual plane passing through the winding center axis O and perpendicular to the second direction Y is defined as the winding center plane P. The winding center plane P divides the electrode assembly 20 into two parts with approximately the same thickness in the second direction Y. Each turn of the winding center plane P and the electrode assembly 20 has two intersections, one at the first bending segment 202 and the other at the second bending segment 204. Each fold of the winding refers to the starting edge of the fold, which is the intersection of the winding center plane P and one bending segment, and the ending edge of the fold, which extends along the winding direction D to the intersection of the winding center plane P and another bending segment. Therefore, the last fold refers to the first current collector 210 of the outermost first electrode 21, which starts at the intersection of the winding center plane P and the second bending segment 204 and extends along the winding direction D to the winding end of the first current collector 210.

[0086] like Figure 2 , Figure 3 and Figure 6 As shown, where Figure 6 for Figure 2 The diagram shows the structure of the first pole piece 21 after it has been unfolded. Figure 6 A three-dimensional coordinate system is established using a first direction X, a fourth direction Y', and a fifth direction Z', where the fourth direction Y' is the thickness direction of the first electrode 21 and the fifth direction Z' is the length direction of the first electrode 21. The secondary battery 100 also includes a first adhesive member 41. The first adhesive member 41 adheres to the surface of the packaging bag 10 facing the electrode assembly 20, at least a portion of the surface of the first termination region 2100 facing the packaging bag 10, and the third edge 2100A. Figure 3 As shown, viewed along the second direction Y, the first edge 21A of the first electrode 21 overlaps with the first adhesive member 41. The first adhesive member 41 secures the electrode assembly 20 to the packaging bag 10, thereby reducing the risk of the electrode assembly 20 shifting within the packaging bag 10 under mechanical abuse. Furthermore, by bonding the third edge 2100A to the first adhesive member 41, the first adhesive member 41 also acts as a finishing adhesive to secure the first finishing area 2100, reducing the risk of movement of the first finishing area 2100 and thus improving the compactness of the electrode assembly 20.

[0087] When the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode, the edge of the first adhesive member 41 in the first direction X can be flush with the first edge 21A, or it can extend beyond the first edge 21A and be located between the first electrode 21 and the second electrode 22, or extend beyond the edge of the second electrode 22 in the first direction X.

[0088] When the first electrode 21 is a negative electrode and the second electrode 22 is a positive electrode, the edge of the first adhesive member 41 in the first direction X can be flush with the first edge 21A or extend beyond the first edge 21A.

[0089] like Figure 7As shown, in some embodiments, the first adhesive layer 41 includes a first adhesive layer 411, a substrate layer 410, and a second adhesive layer 412 sequentially stacked along the thickness direction of the first adhesive layer 41. The first adhesive layer 411 is disposed on the surface of the substrate layer 410 facing the packaging bag 10. The second adhesive layer 412 is disposed on the surface of the substrate layer 410 facing the first finishing region 2100. The material of the substrate layer 410 includes at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. The materials of the first adhesive layer 411 and the second adhesive layer 412 independently include at least one selected from polyethylene, polypropylene, polyurethane, epoxy resin, styrene-butadiene rubber, polyvinylidene fluoride, polyacrylate, and polyacrylic acid and their derivatives. The material of the first adhesive layer 411 may be the same as or different from the material of the second adhesive layer 412, and the materials of the first adhesive layer 411 and the second adhesive layer 412 have high adhesive performance.

[0090] In this application, the first adhesive member 41 can fix the electrode assembly 20 to the packaging bag 10, thereby reducing the risk of the electrode assembly 20 shifting within the packaging bag 10 under mechanical abuse. It also acts as a finishing adhesive to fix the first finishing area 2100, thereby improving the mechanical abuse resistance of the secondary battery 100. Moreover, by extending the first adhesive member 41 along the first direction X, the projection of the first edge 21A of the first electrode 21 falls within the projection range of the first adhesive member 41. Therefore, the first adhesive member 41 can fully fix the first finishing area 2100 located near the first edge 21A in the first direction X. Thus, even if the first edge 21A of the separator 23 wrinkles or shrinks during mechanical abuse, the first adhesive member 41 can reduce the risk of short circuit between this part of the first finishing area 2100 and the second electrode 22 (especially the protruding area of ​​the second electrode 22) located inside the first finishing area 2100. In particular, when the number N1 of conductive plates extending from the first edge 21A side is greater than or equal to 3, resulting in insufficient space for the first end 20C of the electrode assembly 20 to provide adhesive wrapping, even omitting the head adhesive wrapping can reduce the risk of short circuits caused by wrinkling or shrinkage of the first edge 21A of the separator 23. Therefore, this application can improve the safety performance and service life of the secondary battery 100.

[0091] like Figure 3 As shown, in some embodiments, the first adhesive member 41 includes a fourth edge 41A, which is located at the same end of the electrode assembly 20 as the first edge 21A. It can be configured such that, when viewed along the second direction Y, the fourth edge 41A and the first edge 21A are approximately flush. That is, when viewed along the second direction Y, the straight-line distance between the fourth edge 41A and the first edge 21A along the first direction X is zero. Figure 4As shown, in some other embodiments, the fourth edge 41A may also be set to extend beyond the first edge 21A along the first direction X. When observed along the second direction Y, the linear distance between the fourth edge 41A and the first edge 21A along the first direction X is L1, where 0 < L1 ≤ 2.0 mm. In this way, the risk that the first bonding member 41 fails to fully fix the first edge 21A due to process errors can be reduced, and further, the risk that the first finishing region 2100 disposed adjacent to the first edge 21A contacts the protruding region of the second pole piece 22 after the isolation film 23 wrinkles or shrinks, causing a contact short circuit, can be reduced. Moreover, by defining the upper limit value of L1, the risk that the first bonding member 41 presses against the sealing edge 12 of the packaging bag 10 in the first direction X can be reduced, or the risk that the first bonding member 41 enters the to-be-packaged region of the packaging bag 10 before the packaging bag 10 is packaged can be reduced (where, if the first bonding member 41 enters the to-be-packaged region of the packaging bag 10, after the to-be-packaged region is packaged to form the sealing edge 12, the first bonding member 41 that enters the packaging region may cause the packaging bag 10 to be damaged), thereby reducing the risk of liquid leakage from the packaging bag 10.

[0092] Further, 0.2 mm ≤ L1 ≤ 2.0 mm can be set. By defining the lower limit value of L1, the risk that the first finishing region 2100 disposed adjacent to the first edge 21A contacts the protruding region of the second pole piece 22 after the isolation film 23 wrinkles or shrinks, causing a contact short circuit, can be further reduced. Even further, 0.2 mm ≤ L1 ≤ 1.4 mm can be set. By defining the upper limit value of L1, the first bonding member 41 does not extend beyond the first edge 21A of the isolation film 23 along the first direction X, reducing the influence of the setting of the first bonding member 41 on the length of the secondary battery 100. Also, the risk that the first bonding member 41 presses against the sealing edge 12 of the packaging bag 10 in the first direction X or enters the to-be-packaged region of the packaging bag 10 before packaging can be further reduced, thereby reducing the risk of liquid leakage from the packaging bag 10.

[0093] [[ID=**6**]]As shown in FIGS. 3 and Figure 4 As shown, in some embodiments, when observed along the second direction Y, the extension line of the third edge 2100A along the first direction X is located between two adjacent conductive plates in the third direction Z. Among them, when observed from the second direction Y, the third edge 2100A may be located in the first straight section 201. This helps to reduce the risk that the third edge 2100A spreads relative to the electrode assembly 20, improving the compactness of the electrode assembly 20. Moreover, due to the position of the third edge 2100A, the first bonding member 41 bonding the third edge 2100A has a suitable position along the third direction Z, which can reduce the stress between the packaging bag 10 and the electrode assembly 20 under mechanical abuse, thereby reducing the risk that the first finishing region 2100 tears, and further improving the anti-mechanical abuse performance of the secondary battery 100.

[0094] It should be noted that in the original text, "如3和" seems to be incomplete. I translated it as "As shown in FIGS. 3 and" for the sake of context integrity, but it might need further confirmation according to the actual situation.In some embodiments, the projection of the electrode assembly 20 in the second direction Y includes a fifth edge 20A and a sixth edge 20B disposed opposite to each other along the third direction Z. The first adhesive member 41 also includes a seventh edge 41B and an eighth edge 41C disposed opposite to each other along the third direction Z, with the fourth edge 41A connecting the seventh edge 41B and the eighth edge 41C respectively. Along the third direction Z, the fifth edge 20A, the seventh edge 41B, the eighth edge 41C, and the sixth edge 20B are disposed sequentially. Along the third direction Z, the seventh edge 41B is closer to the fifth edge 20A than the eighth edge 41C, and the eighth edge 41C is closer to the sixth edge 20B than the seventh edge 41B. The distance between the fifth edge 20A and the seventh edge 41B along the third direction Z is L2, and the distance between the sixth edge 20B and the eighth edge 41C along the third direction Z is L3, then 0≤|L2-L3|≤4mm. Thus, the first adhesive 41 is positioned approximately centered along the third direction Z, further reducing the stress between the packaging bag 10 and the electrode assembly 20 under mechanical abuse, thereby reducing the risk of tearing in the first closing area 2100 and further improving the mechanical abuse resistance of the secondary battery 100.

[0095] In some embodiments, the projected area of ​​the electrode assembly 20 along the second direction Y is S1, and the area of ​​the first adhesive member 41 is S2, where 0.4 ≤ S2 / S1 ≤ 1. By limiting the lower limit of S2 / S1, the adhesive force between the electrode assembly 20 and the packaging bag 10 can be improved to further enhance the mechanical abuse resistance of the secondary battery 100. Furthermore, it can reduce the risk of localized lithium plating due to undervoltage at locations of the electrode assembly 20 not covered by the first adhesive member 41 during formation. By limiting the upper limit of S2 / S1, the risk of the first adhesive layer 411 of the first adhesive member 41 easily bonding to other locations after extending beyond the electrode assembly 20 can be reduced, thereby improving the mechanical abuse resistance of the secondary battery 100. It can also reduce the risk of air bubbles forming during the bonding of the first adhesive member 41, thereby improving the bonding effect of the first adhesive member 41 and the appearance of the secondary battery 100.

[0096] Furthermore, a value of 0.5 ≤ S2 / S1 ≤ 0.7 can be set to further improve the adhesion between the electrode assembly 20 and the packaging bag 10, and reduce the risk of local lithium plating due to undervoltage at the location of the electrode assembly 20 not covered by the first adhesive 41 during the formation process. Moreover, it can further reduce the risk that the first adhesive layer 411 of the first adhesive 41, extending beyond the electrode assembly 20, will easily adhere to other locations, and reduce the risk of air bubbles appearing during the application of the first adhesive 41.

[0097] like Figure 5As shown, in some embodiments, when viewed along the second direction Y, the extension of the third edge 2100A along the first direction X can also be located on the same side of all conductive plates, and the third edge 2100A can be approximately located at the intersection of the first straight segment 201 and the second bent segment 204. Furthermore, when viewed along the first direction X, the projection of the first termination region 2100 does not overlap with the projections of all conductive plates. Therefore, the impact of the first termination region 2100 on the thickness and energy density of the secondary battery 100 can be reduced.

[0098] Furthermore, in this case, in addition to the first adhesive member 41, the secondary battery 100 may also include a second adhesive member 42. The second adhesive member 42 adheres to a portion of the surface of the packaging bag 10 facing the electrode assembly 20 and a portion of the second surface 2102. The second adhesive member 42 is separated from the first adhesive member 41 in the third direction Z. The first adhesive member 41 and the second adhesive member 42 can jointly fix the electrode assembly 20 to the packaging bag 10, thereby reducing the risk of the electrode assembly 20 shifting within the packaging bag 10 under mechanical abuse. Moreover, the additional provision of the second adhesive member 42 can improve the thickness flatness of the secondary battery 100 and also alleviate the stress problem between the packaging bag 10 and the electrode assembly 20 when only the first adhesive member 41 is provided. The second adhesive member 42 may have a layered structure similar to the first adhesive member 41, which will not be described in detail in this application.

[0099] The electrode assembly 20, projected along the second direction Y, includes a fifth edge 20A and a sixth edge 20B positioned opposite each other along the third direction Z. The first adhesive member 41 also includes a seventh edge 41B and an eighth edge 41C positioned opposite each other along the third direction Z, with the fourth edge 41A connecting the seventh edge 41B and the eighth edge 41C. The second adhesive member 42 includes a ninth edge 42A and a tenth edge 42B positioned opposite each other along the third direction Z. Along the third direction Z, the fifth edge 20A, the ninth edge 42A, the tenth edge 42B, the seventh edge 41B, the eighth edge 41C, and the sixth edge 20B are arranged sequentially. The distance between the sixth edge 20B and the eighth edge 41C along the third direction is L3, and the distance between the fifth edge 20A and the ninth edge 42A along the third direction is L4, therefore 0 ≤ |L3 - L4| ≤ 4 mm. Thus, the first adhesive 41 and the second adhesive 42 are generally centered along the third direction Z, which further reduces the stress between the packaging bag 10 and the electrode assembly 20 under mechanical abuse, thereby reducing the risk of tearing in the first closing area 2100 and further improving the mechanical abuse resistance of the secondary battery 100.

[0100] In some embodiments, the projected area of ​​the electrode assembly 20 along the second direction Y is S1, the area of ​​the first adhesive 41 is S2, and the area of ​​the second adhesive 42 is S3, where 0.4 ≤ (S2 + S3) / S1 ≤ 1. By limiting the lower limit of (S2 + S3) / S1, the adhesive force between the electrode assembly 20 and the packaging bag 10 can be increased to further improve the resistance to mechanical abuse of the secondary battery 100. It also reduces the risk of localized lithium plating due to undervoltage at locations of the electrode assembly 20 not covered by the first adhesive 41 and the second adhesive 42 during formation. By limiting the upper limit of (S2 + S3) / S1, the risk of the first adhesive 41 or the second adhesive 42 easily bonding to other locations after extending beyond the electrode assembly 20 can be reduced, thereby improving the resistance to mechanical abuse of the secondary battery 100. Furthermore, it reduces the risk of air bubbles appearing during the bonding process of the first adhesive 41 or the second adhesive 42, thereby improving the bonding effect and the appearance of the secondary battery 100.

[0101] Furthermore, a value of 0.5 ≤ (S2 + S3) / S1 ≤ 0.7 can be set to further improve the adhesion between the electrode assembly 20 and the packaging bag 10, and reduce the risk of local lithium plating due to undervoltage at the locations of the electrode assembly 20 not covered by the first adhesive 41 and the second adhesive 42 during the formation process. Moreover, it can further reduce the risk that the first adhesive 41 or the second adhesive 42, after extending beyond the electrode assembly 20, may easily adhere to other locations, and reduce the risk of air bubbles appearing during the application of the first adhesive 41 or the second adhesive 42.

[0102] like Figures 2 to 5 As shown, in some embodiments, the secondary battery 100 may further include at least one of a third adhesive member 50 and a fourth adhesive member 60. In some embodiments, the secondary battery 100 includes both the third adhesive member 50 and the fourth adhesive member 60.

[0103] The third adhesive element 50 is disposed in the second finishing area 2110. Along the winding direction D (or along...) Figure 6 As shown in the fifth direction Z', a portion of the third adhesive 50 covers the second termination region 2110, and another portion of the third adhesive 50 extends along the winding direction D and adheres to and covers the first surface 2101 of the first current collector 210 (i.e., the first surface 2101 located in the first termination region 2100). The third adhesive 50 can reduce the risk of micro-short circuits caused by the shedding of active material from the second termination region 2110. At the same time, the third adhesive 50 also provides insulation protection for the first surface 2101 of the first termination region 2100. In the event of mechanical abuse, it can absorb some of the impact force, reduce the risk of tearing of the first termination region 2100, and enhance the strength of the first termination region 2100. Therefore, it can further improve the mechanical shock resistance of the electrode assembly 20.

[0104] A fourth adhesive 60 is disposed in the third termination region 2110'. Along the winding direction D, a portion of the fourth adhesive 60 covers the third termination region 2110', and another portion of the fourth adhesive 60 extends along the winding direction D and adheres to and covers the second surface 2102 of the first current collector 210. The fourth adhesive 60 can reduce the risk of micro-short circuits caused by the shedding of active material from the third termination region 2110'. At the same time, the fourth adhesive 60 can also enhance the strength of the first current collector 210 wound around the outermost ring, thus further improving the resistance of the electrode assembly 20 to mechanical shock.

[0105] Viewed from the second direction Y, the first adhesive 41 and the third adhesive 50 are separated in the third direction Z, thereby reducing the impact on the thickness and energy density of the secondary battery 100 when the first adhesive 41 and the third adhesive 50 overlap. Viewed from the second direction Y, the first adhesive 41 and the fourth adhesive 60 are separated in the third direction Z, thereby reducing the impact on the thickness and energy density of the secondary battery 100 when the first adhesive 41 and the fourth adhesive 60 overlap. In some embodiments, the third adhesive 50 and the fourth adhesive 60 can be single-sided adhesives, and the materials of their substrate layer and adhesive layer can refer to those of the first adhesive 41.

[0106] like Figures 3 to 5 As shown, in some embodiments, the secondary battery 100 may further include at least one fifth adhesive member 70. The fifth adhesive member 70 adheres to the second end 20D of the electrode assembly 20. The fifth adhesive member 70 may adhere to the second edge 21B of the separator 23, reducing the risk of short circuits in the contact between the first electrode 21 and the second electrode 22 due to wrinkling or shrinkage of the second edge 21B during mechanical abuse. Viewed from the second direction Y, the first adhesive member 41 and the fifth adhesive member 70 are separated in the first direction X, thereby reducing the impact on the thickness and energy density of the secondary battery 100 when the first adhesive member 41 and the fifth adhesive member 70 overlap. In some embodiments, the fifth adhesive member 70 may be a single-sided adhesive, and the materials of its substrate layer and adhesive layer may refer to those of the first adhesive member 41.

[0107] The secondary battery 100 of this application can be a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0108] Please see Figure 8This application also provides an electronic device 1, which includes a battery compartment 101 and a secondary battery 100 disposed within the battery compartment 101. The secondary battery 100 of this application is applicable to electronic devices 1 in various fields. The electronic device 1 is powered by the secondary battery 100, and the secondary battery 100 has a reduced risk of short circuits due to wrinkles or shrinkage of the separator 23, thus exhibiting high safety and long service life. In one embodiment, the electronic device 1 of this application may be, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable C-type devices, mini CD-ROMs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0109] The present application will be described in detail below through specific embodiments and comparative examples. Specifically, a lithium-ion secondary battery, a first electrode as a positive electrode, and a second electrode as a negative electrode are used as examples to illustrate the present application, along with specific preparation processes and testing methods. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0110] Examples 1 to 16

[0111] (1) Preparation of the first electrode: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 96.5:1.5:2. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and stirred evenly. Foaming adhesive was pre-applied to a portion of the surface of the positive current collector (aluminum foil) with a thickness of 9 μm. The slurry was then uniformly coated onto one surface of the aluminum foil. Heating was performed to remove the foaming adhesive, exposing a portion of the aluminum foil surface. The foil was then dried at 90°C. The coating process was repeated on the other surface of the aluminum foil to obtain a double-coated positive electrode. The initial positive electrode was cold-pressed to obtain a single coating layer of positive active material with a thickness of 77 μm. After cutting and other processes, the positive electrode was obtained. Then, two first conductive plates, made of aluminum, were welded onto the exposed aluminum foil. Then, refer to... Figure 2 The third and fourth adhesive pieces are then attached to the third finishing area of ​​the aluminum foil.

[0112] (2) Preparation of the second electrode: Artificial graphite, silicon carbide, conductive carbon black (Super P), polyacrylic acid binder (PAA), and lithium difluorophosphate (LDPF) were mixed in a weight ratio of 69:5:6:19:1. Deionized water was added as a solvent to prepare a slurry with a weight percentage of 55 wt%, and the mixture was stirred evenly. Foaming adhesive was pre-applied to a portion of the copper foil (a 5 μm thick negative electrode current collector). The slurry was then evenly coated onto one surface of the copper foil. Heating was performed to remove the foaming adhesive, exposing the copper foil surface. The foil was then dried at 90°C. The coating process was repeated on the other surface of the copper foil to obtain a double-coated negative electrode. The initial negative electrode was rolled to obtain a 70 μm thick negative electrode active material layer. Then, two second conductive plates, made of nickel, were welded onto the exposed copper foil.

[0113] (3) Preparation of electrolyte: In a dry argon atmosphere, the organic solvents 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. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0114] (4) Preparation of the isolation membrane: A polyethylene (PE) membrane with a thickness of 9 μm was selected.

[0115] (5) Preparation of secondary battery: The first electrode, the separator, and the second electrode are sequentially stacked and wound to obtain the desired result. Figure 2 The electrode assembly shown, wherein the two second conductive plates and the two first conductive plates are arranged as follows: Figure 1 As shown, the two second conductive plates and the two first conductive plates are arranged sequentially along a third direction, and the extension line of the third edge along the first direction is located between the two first conductive plates (e.g., Figure 3 (As shown). A fifth adhesive element is provided at the tail of the electrode assembly. Then, the perforated aluminum-plastic film (150 μm thick) is placed in the assembly fixture with the perforated surface facing upwards. The electrode assembly is placed in the perforation using the first adhesive element, wherein the substrate layer of the first adhesive element is made of polyimide, and the first and second adhesive layers are made of polypropylene. Electrolyte is then injected into the perforation of the aluminum-plastic film, and the first and second conductive plates are led out of the aluminum-plastic film and then encapsulated to obtain a secondary battery. The electrode assembly in Examples 1 to 15 has a length of 70.5 mm, a width of 40.5 mm, and an area of ​​2855.25 mm². 2It should be noted that the length, width, and area of ​​the electrode assembly described above are the dimensions of the electrode assembly projected along the second direction, measured using a micrometer. The differences between the various embodiments lie in the relevant parameters L1, |L2-L3|, and S2, which are specifically recorded in Table 1.

[0116] Example 17

[0117] The difference from Embodiment 1 is that the termination position of the first electrode is different; when viewed along the first direction, the projection of the first termination region does not overlap with the projections of the multiple conductive plates (e.g., Figure 5 (As shown).

[0118] Example 18

[0119] The difference from Embodiment 1 is that the ending position of the first electrode is different. When viewed along the first direction, the extension line of the third edge along the first direction is located at the middle position of the first conductive plate along the third direction.

[0120] Comparative Example

[0121] Unlike Embodiment 1, the first adhesive does not extend along the first direction, that is, the projection of the first edge does not fall within the projection range of the first adhesive.

[0122] Then, drop tests, volumetric energy density tests, cycle capacity retention tests, and secondary battery expansion rate tests were conducted on the secondary batteries of each embodiment and comparative example.

[0123] The drop test steps are as follows: 1) Under an environment of 20±5℃, the secondary battery is left to stand for 5 minutes, then charged at a constant current of 0.2C to 4.53V, and then charged at a constant voltage of 0.025C, and left to stand for 5 minutes; 2) The secondary battery is placed in the clamping chamber, and the secondary battery is dropped sequentially from a position of 1m onto the cement ground along the four corners and six surfaces in a round, for a total of 5 rounds, or 50 drops; 3) After the drops are completed, if the secondary battery does not catch fire, explode, or leak, the secondary battery passes the drop test. Twenty secondary batteries from each example and each comparative example were tested, and the corresponding test results are recorded in Table 1.

[0124] The volumetric energy density test procedure is as follows: 1) Under ambient conditions of 25℃, the secondary battery was left to stand for 10 minutes, charged at a constant current of 0.2C to 4.5V, charged at a constant voltage of 0.02C, and left to stand for 5 minutes; then discharged at a constant current of 0.2C to 3V, left to stand for 5 minutes, and the discharge capacity C0 was recorded; 2) The length, width, and thickness of the secondary battery were measured using a PPG (Parallel Plate Gauge), and the volumetric energy density was calculated using the following formula: Volumetric energy density = 3.92C0 / (length × width × thickness). The test results are recorded in Table 1.

[0125] The test steps for cycle capacity retention and secondary battery expansion rate are as follows: At room temperature (25℃), the secondary battery is charged to 4.53V with a constant current and constant voltage of 3C, cut off at 0.02C, and left to stand for 5 minutes. The thickness of the secondary battery is measured using PPG and recorded as the thickness of the first full charge. Then, it is discharged to 3V with a constant current of 1C, and then discharged to 3V with a constant current of 0.7C. After standing for 5 minutes, this process is recorded as one cycle, and the discharge capacity of the first cycle is recorded. The above steps are repeated for 1000 charge and discharge cycles. The thickness of the secondary battery after the 1000th full charge and the discharge capacity of the secondary battery after 1000 cycles are recorded.

[0126] Cycle capacity retention rate = (Discharge capacity of the secondary battery after 1000 cycles / Discharge capacity of the first cycle) × 100% Secondary battery expansion rate = [(Thickness of the secondary battery after 1000 full charges - Thickness of the secondary battery after the first full charge) / Thickness of the secondary battery after the first full charge] × 100%

[0127] The test results are recorded in Table 1.

[0128] Does the first adhesive have air bubbles? Visually inspect the condition of the first adhesive on the surface of the electrode assembly to determine if air bubbles are present.

[0129] Table 1

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136] Note: (1) In Table 1, L1 means "-0.1mm", which means that the first edge of the first electrode extends beyond the fourth edge of the first adhesive in the first direction by a distance of 0.1mm.

[0137] (2) The values ​​of the error of |L2-L3| in Table 1 within the range of ±0.05mm can be regarded as the corresponding values. For example, the values ​​within the range of -0.05mm≤|L2-L3|≤0.05mm can be regarded as |L2-L3|=0mm, and so on.

[0138] (3) In Table 1, the drop test pass rate is n / 20, indicating that out of the 20 secondary batteries tested, n secondary batteries passed the test. The meanings of other ratio values ​​are deduced similarly.

[0139] A comparison of the experimental data in Table 1 with those in Example 1 shows that aligning the first edge of the first electrode with the fourth edge of the first adhesive significantly improves the drop pass rate of the secondary battery. A comparison of the experimental data from Examples 1 to 7 in Table 1 shows that when 0.2mm ≤ L1 ≤ 2.0mm, the drop test pass rate of the secondary battery is high; when L1 > 2.0mm, the drop pass rate does not continue to improve. It is conceivable that an excessively large L1 could lead to the first adhesive occupying too much space in the first direction, increasing the risk of the first adhesive contacting the sealing edge of the packaging bag in the first direction, and increasing the risk of reduced packaging reliability due to the first adhesive entering the packaging bag sealing area. To balance high drop safety performance of the secondary battery with reducing the associated risks caused by the first adhesive extending too far beyond the edge of the first electrode in the first direction, 0.2mm ≤ L1 ≤ 2.0mm is preferred; further preferred is 0.2mm ≤ L1 ≤ 1.4mm. By comparing the experimental data of Examples 1 and 8 to 10 in Table 1, it can be seen that when 0≤|L2-L3|≤4mm, the secondary battery has a high drop test pass rate. When |L2-L3|>4mm, the first adhesive is more biased towards one edge of the electrode assembly in the third direction, which increases the stress between the packaging bag and the electrode assembly during the drop, resulting in a lower drop test pass rate for the secondary battery. A comparison of the experimental data from Examples 1 and 11-16 in Table 1 shows that the value of S2 / S1 affects the cycle capacity retention rate, expansion rate, and presence of air bubbles in the first adhesive component. When S2 / S1 ≥ 0.4, the area of ​​the electrode assembly covered by the first adhesive component is not too small, which improves the drop resistance of the secondary battery and reduces the risk of local lithium plating due to undervoltage at the electrode assembly not covered by the first adhesive component during formation, thus improving the cycle capacity retention rate of the secondary battery. Furthermore, the first adhesive component has a certain area, which can reduce the expansion of the secondary battery during cycling to some extent, thus reducing the expansion rate. When S2 / S1 ≤ 1, it reduces the likelihood of the first adhesive component extending beyond the electrode assembly and easily contacting other parts. To mitigate the risk of adhesion and improve the drop resistance of the secondary battery, a value of 0 ≤ S2 / S1 ≤ 1 is chosen. This balances the secondary battery's high drop resistance, high cycle capacity retention, and low expansion rate. When S2 / S1 ≥ 1, air bubbles appear on the surface of the first adhesive component. This is because the area of ​​the first adhesive component is too large, leading to air bubbles during the bonding process. Furthermore, when S2 / S1 > 1, the first adhesive component is prone to adhesion to other locations after extending beyond the electrode assembly, which negatively impacts the drop resistance of the secondary battery. Therefore, a value of 0.5 ≤ S2 / S1 ≤ 0.7 is preferred. This improves the drop resistance, cycle capacity retention, and expansion rate of the secondary battery while also enhancing the adhesion of the first adhesive component and the appearance of the secondary battery.By comparing the experimental data of Examples 1, 17, and 18 in Table 1, it can be seen that the volumetric energy density of the secondary battery is the highest when the projection of the first closing region does not overlap with the projection of the multiple conductive plates. This is because the location of the conductive plates is where the electrode assembly has a relatively large thickness, and the fact that the first closing region does not overlap with the projection of the conductive plates avoids the accumulation of thickness at the location of the conductive plates. When the extension line of the third edge along the first direction is located between the two first conductive plates, the volumetric energy density of the secondary battery is in the middle. When the extension line of the third edge along the first direction is located at the middle position of the first conductive plate along the third direction, that is, when the extension line of the third edge overlaps with the first conductive plate, there is an accumulation of the thickness of the conductive plates and the thickness of the closing region at the location of the conductive plates, resulting in the lowest volumetric energy density of the secondary battery.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A secondary battery, wherein, include: Packaging bags; An electrode assembly is disposed within the packaging bag. The electrode assembly includes a first electrode and a second electrode, which are stacked and wound together. The first electrode includes a first current collector and a first active material layer. The first current collector includes a first surface and a second surface opposite to each other along its thickness direction. The first surface faces the winding center axis, and the second surface faces away from the winding center axis. The first active material layer includes a first sub-layer disposed on the first surface and a second sub-layer disposed on the second surface. The first current collector includes a first tailing region in the winding direction, which is exposed between the first sub-layer and the second sub-layer and is located at the last fold of the first current collector along the winding direction. The first tailing region includes a third edge, which is the tailing edge of the electrode assembly. as well as A first adhesive member is used to adhere at least a portion of the first finishing area facing the surface of the packaging bag and the third edge, and the first adhesive member crosses the third edge along the winding direction and adheres to a portion of the second surface; the width direction of the first electrode sheet is a first direction, the thickness direction of the electrode assembly is a second direction, the first direction and the second direction are perpendicular to each other, and the third direction is a direction perpendicular to the first direction and the second direction; the first electrode sheet includes a first edge and a second edge disposed opposite to each other along the first direction, and when viewed along the second direction, the first edge overlaps with the first adhesive member.

2. The secondary battery as described in claim 1, wherein, The first adhesive also adheres to a portion of the packaging bag facing the electrode assembly; the secondary battery further includes a plurality of conductive plates, the number of which is N, and the number of which extends from one side of the first edge is N1, where N≥N1 and N1≥3.

3. The secondary battery as described in claim 2, wherein, N=4, N1=4, the plurality of conductive plates include two first conductive plates and two second conductive plates, the second electrode includes a second current collector, the two first conductive plates are electrically connected to the first current collector respectively, the two second conductive plates are electrically connected to the second current collector respectively, and the two first conductive plates and the two second conductive plates are arranged sequentially in the third direction.

4. The secondary battery according to any one of claims 1 to 3, wherein, The first adhesive includes a fourth edge, which is located at the same end of the electrode assembly along the first direction as the first edge. When viewed along the second direction, the distance between the fourth edge and the first edge along the first direction is L1, where 0 ≤ L1 ≤ 2.0 mm.

5. The secondary battery as described in claim 4, wherein, 0.2mm≤L1≤2.0mm.

6. The secondary battery as described in claim 5, wherein, 0.2mm≤L1≤1.4mm.

7. The secondary battery as described in claim 2, wherein, Viewed along the second direction, the extension of the third edge along the first direction lies between the two conductive plates that are adjacent to each other in the third direction.

8. The secondary battery as described in claim 7, wherein, The projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge disposed opposite to each other along the third direction, and the first adhesive includes a seventh edge and an eighth edge disposed opposite to each other along the third direction; along the third direction, the fifth edge, the seventh edge, the eighth edge, and the sixth edge are arranged sequentially; the distance between the fifth edge and the seventh edge along the third direction is L2, and the distance between the sixth edge and the eighth edge along the third direction is L3; 0≤|L2-L3|≤4mm.

9. The secondary battery as described in claim 7 or 8, wherein, The projected area of ​​the electrode assembly along the second direction is S1, and the area of ​​the first adhesive is S2, where 0.4 ≤ S2 / S1 ≤ 1.

10. The secondary battery as claimed in claim 9, wherein, 0.5≤S2 / S1≤0.

7.

11. The secondary battery as described in claim 2, wherein, When viewed along the first direction, the projection of the first termination region does not overlap with the projection of the plurality of conductive plates.

12. The secondary battery as claimed in claim 11, wherein, The secondary battery further includes a second adhesive member that adheres to the surface of the packaging bag facing the electrode assembly and a portion of the second surface located on the same side as the third edge in the second direction. The first adhesive member and the second adhesive member are arranged sequentially and separated in the third direction.

13. The secondary battery as described in claim 12, wherein, The projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge disposed opposite to each other along the third direction; the first adhesive includes a seventh edge and an eighth edge disposed opposite to each other along the third direction; the second adhesive includes a ninth edge and a tenth edge disposed opposite to each other along the third direction; along the third direction, the fifth edge, the ninth edge, the tenth edge, the seventh edge, the eighth edge, and the sixth edge are arranged sequentially; the straight-line distance between the sixth edge and the eighth edge along the third direction is L3, and the straight-line distance between the fifth edge and the ninth edge along the third direction is L4; 0≤|L3-L4|≤4mm.

14. The secondary battery as claimed in claim 12 or 13, wherein, The projected area of ​​the electrode assembly along the second direction is S1, the area of ​​the first adhesive is S2, the area of ​​the second adhesive is S3, and 0.4≤(S2+S3) / S1≤1.

15. The secondary battery as described in claim 14, wherein, 0.5≤(S2+S3) / S1≤0.

7.

16. The secondary battery as claimed in claim 1, wherein, The first sub-layer includes a second terminal region in the winding direction, the second sub-layer includes a third terminal region in the winding direction, the second terminal region is located at the outermost winding of the first electrode, and the third terminal region is located at the second outermost winding of the first electrode. The secondary battery also includes a third adhesive member, which is disposed in the second tailing area and extends along the winding direction and is bonded to the first surface. When viewed from the second direction, the first adhesive member and the third adhesive member are separated in the third direction. And / or, the secondary battery further includes a fourth adhesive member disposed in the third finishing region and extending along the winding direction to adhere to the second surface, wherein, viewed from the second direction, the first adhesive member and the fourth adhesive member are separated in the third direction.

17. The secondary battery as claimed in claim 1, wherein, The secondary battery further includes a fifth adhesive member. The electrode assembly includes a first end and a second end disposed opposite to each other in the first direction. The first edge is located at the first end, and the second edge is located at the second end. The fifth adhesive member is bonded to the second end. When viewed from the second direction, the first adhesive member and the fifth adhesive member are separated in the first direction.

18. The secondary battery as claimed in claim 1, wherein, The first adhesive component includes a first adhesive layer, a substrate layer, and a second adhesive layer stacked sequentially along the thickness direction of the first adhesive component. The first adhesive layer is disposed on the surface of the substrate layer facing the packaging bag, and the second adhesive layer is disposed on the surface of the substrate layer facing the first finishing area. The material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. The materials of the first adhesive layer and the second adhesive layer independently include at least one of polyethylene, polypropylene, polyurethane, epoxy resin, styrene-butadiene rubber, polyvinylidene fluoride, polyacrylate and polyacrylic acid and their derivatives.

19. The secondary battery as claimed in claim 1, wherein, The first electrode is the positive electrode, and the second electrode is the negative electrode.

20. The secondary battery as claimed in claim 19, wherein, The first adhesive extends beyond the edge of the second electrode in the first direction.

21. An electronic device, wherein, The electronic device includes a secondary battery as described in any one of claims 1 to 20.

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