Secondary battery and electronic apparatus

Abstract

A secondary battery and an electronic apparatus. The secondary battery comprises a packaging pouch, an electrode assembly and a first bonding member. A first electrode sheet and a second electrode sheet of the electrode assembly are stacked and wound. The first electrode sheet comprises a first current collector and a first active material layer. The first current collector comprises a first surface and a second surface, the first surface facing a winding center axis. The first active material layer comprises a first sub-layer arranged on the first surface and a second sub-layer arranged on the second surface. The first current collector comprises a first tail region in the winding direction. The first tail region is exposed to the first sub-layer and the second sub-layer and is located at the last fold in the winding direction. The first tail region comprises a third edge, the third edge being a tail edge of the electrode assembly. The first bonding member bonds the surface of the packaging pouch facing the electrode assembly, the surface of the first tail region facing the packaging pouch, and the third edge. When viewed in a second direction, the edge of the first electrode sheet arranged in the width direction overlaps the first bonding member.

Description

Secondary battery and electronic device

[0001] The present application claims priority to the Chinese patent application No. 202411545351.0, filed on October 31, 2024, and entitled "Secondary battery and electronic device", the whole content of the aforementioned priority being incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of energy storage, in particular to a secondary battery and an electronic device having the same. BACKGROUND

[0003] With the popularity of consumer electronics products such as notebook computers, mobile phones, handheld game consoles, tablet computers, mobile power supplies and drones, people's requirements for the safety performance and service life of secondary batteries are becoming more and more stringent.

[0004] A soft-pack secondary battery generally includes a packaging bag and an electrode assembly arranged in the packaging bag. In the related art, the electrode assembly is in a winding structure and adopts a current collector as a tail. In order to reduce the risk of short circuit between the positive and negative electrode sheets caused by the wrinkling or shrinkage of the separator due to the action of free electrolyte when the secondary battery is mechanically abused (such as falling, collision, etc.), a winding tape is usually arranged at the head and tail of the electrode assembly to fix the edges of the separator. However, in some cases, there may not be enough space to arrange the winding tape at the head or tail of the electrode assembly. If the winding tape is omitted, when the separator (especially the outer several layers of the separator) is wrinkled or shrunk due to mechanical abuse, the current collector at the tail will sway and contact the inner electrode sheet due to the loss of restraint, thereby reducing the safety performance and service life of the secondary battery. SUMMARY

[0005] Therefore, it is necessary to provide a secondary battery with improved safety performance and service life.

[0006] In addition, it is also necessary to provide an electronic device having the secondary battery.

[0007] The first aspect of the present application provides a secondary battery, comprising a packaging bag, an electrode assembly, and a first adhesive. The electrode assembly is arranged in the packaging bag. The electrode assembly comprises a first electrode tab and a second electrode tab, and the first electrode tab and the second electrode tab are arranged in a stacked and wound manner. The first electrode tab comprises a first current collector and a first active material layer. The first current collector comprises a first surface and a second surface opposite to each other in the thickness direction of the first current collector, and the first surface faces the winding central axis, and the second surface is away from the winding central axis. The first active material layer comprises a first sub-layer arranged on the first surface and a second sub-layer arranged on the second surface. The first current collector comprises a first end area in the winding direction. The first end area is exposed to the first sub-layer and the second sub-layer and is located at the last fold of the first current collector in the winding direction. The first end area comprises a third edge, and the third edge is an end edge of the electrode assembly. The first adhesive is arranged to adhere at least part of the first end area to the surface of the packaging bag and the third edge, and the first adhesive extends across the third edge in the winding direction and adheres part of the second surface. The width direction of the first electrode tab 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 a third direction is a direction perpendicular to the first direction and the second direction. The first electrode tab comprises a first edge and a second edge arranged opposite to each other in the first direction, and the first edge overlaps the first adhesive as viewed in the second direction.

[0008] In the present application, the first adhesive can function as an end adhesive to fix the first end area, thereby reducing the possibility of the electrode assembly being loose and the electrode tab being misaligned, and making the electrode assembly more regular as a whole. Moreover, by extending the first adhesive in the first direction, the first edge of the first electrode tab overlaps the first adhesive, so that the first adhesive can sufficiently fix the first end area arranged adjacent to the first edge in the first direction. Even if the separator is wrinkled or shrinks due to mechanical abuse, the first adhesive can reduce the risk of short circuit between the part of the first end area and the second electrode tab (especially the overhang region of the second electrode tab) located inside the first end area. Therefore, the present application can improve the safety performance and service life of the secondary battery.

[0009] In the one or more possible implementation manners of the first aspect, the first adhesive member further adheres a surface of the partial packaging bag facing the electrode assembly; the secondary battery further comprises a plurality of conductive plates, a number of the plurality of conductive plates is N, a number of the conductive plates extending from the first edge side is N1, N≥N1, and N1≥3. Therefore, the first adhesive member not only fixes the first end area, but also fixes the electrode assembly and the packaging bag, reduces the risk of the electrode assembly moving in the packaging bag under mechanical abuse, and improves the mechanical abuse resistance of the secondary battery. Meanwhile, by arranging the plurality of conductive plates, the demand for large current charging and discharging can be met, and the internal resistance of the first or second electrode plate can be reduced. Moreover, even if the electrode assembly does not have enough space to arrange the winding adhesive at the end corresponding to the first edge, the risk of contact short circuit caused by the first end area contacting the second electrode plate after the isolation film is wrinkled or shrinks can be reduced, and the safety performance and service life of the secondary battery can be improved.

[0010] In the one or more possible implementation manners of the first aspect, N=4 and N1=4. The plurality of conductive plates comprises two first conductive plates and two second conductive plates. The second electrode plate comprises a second current collector. The two first conductive plates are electrically connected to the first current collector respectively, and the two second conductive plates are electrically connected to the second current collector respectively. The two first conductive plates and the two second conductive plates are arranged in sequence in the third direction. Therefore, the demand for large current charging and discharging can be met, and the internal resistance of the first or second electrode plate can be further reduced. Moreover, even if the electrode assembly does not have enough space to arrange the winding adhesive at the end corresponding to the first edge, the risk of short circuit caused by the first end area contacting the second electrode plate after the isolation film is wrinkled or shrinks can be reduced, and the safety performance and service life of the secondary battery can be improved.

[0011] In the one or more possible implementation manners of the first aspect, the first adhesive member comprises a fourth edge, and the fourth edge is located at the same end of the electrode assembly along the first direction as the first edge. In the second direction, the distance between the fourth edge and the first edge along the first direction is L1, and 0≤L1≤2.0mm. When L1 is greater than zero, the risk that the first adhesive member fails to sufficiently fix the first edge due to process errors can be reduced, and the risk of short circuit caused by the first end area contacting the second electrode plate after the isolation film is wrinkled or shrinks can be further reduced. Moreover, by limiting the upper limit value of L1, the risk that the first adhesive member abuts against the edge of the packaging bag in the first direction can be reduced, or the risk that the first adhesive member enters the to-be-sealed area of the packaging bag before the packaging bag is sealed can be reduced, and thus the risk of liquid leakage of the packaging bag can be reduced.

[0012] In the one or more possible implementation manners of the first aspect, 0.2mm≤L1≤2.0mm. Therefore, the risk of short circuit caused by the first end area contacting the second electrode plate after the separation film is wrinkled or shrinks can be further reduced.

[0013] In the one or more possible implementation manners of the first aspect, 0.2mm≤L1≤1.4mm. Thus, the first adhesive member can not exceed the isolation film in the first direction, the influence of the first adhesive member on the length of the secondary battery can be reduced, and the risk that the first adhesive member abuts against the sealing edge of the packaging bag or enters the to-be-sealed area of the packaging bag before the packaging bag is sealed in the first direction can be further reduced, thereby reducing the risk of liquid leakage of the packaging bag.

[0014] In the one or more possible implementation manners of the first aspect, as viewed in the second direction, the extension line of the third edge in the first direction is located between the two conductive plates adjacent in the third direction. Thus, the risk that the third edge is spread compared with the electrode assembly can be reduced, the compactness of the electrode assembly is improved, and the first adhesive member adhering to the third edge can be appropriately positioned in the third direction, so that the stress between the packaging bag and the electrode assembly under mechanical abuse is reduced, thereby reducing the risk of tearing of the first end area and further improving the mechanical abuse resistance of the secondary battery.

[0015] In the one or more possible implementation manners of the first aspect, the projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge oppositely arranged in the third direction. The first adhesive member includes a seventh edge and an eighth edge oppositely arranged in the third direction. The fifth edge, the seventh edge, the eighth edge, and the sixth edge are sequentially arranged in the third direction. The distance between the fifth edge and the seventh edge in the third direction is L2, the distance between the sixth edge and the eighth edge in the third direction is L3, and 0≤|L2-L3|≤4mm. Thus, the first adhesive member can be arranged substantially centrally in the third direction, the stress between the packaging bag and the electrode assembly under mechanical abuse is further reduced, thereby reducing the risk of tearing of the first end area and further improving the mechanical abuse resistance of the secondary battery.

[0016] In the one or more possible implementation manners of the first aspect, the projection area of the electrode assembly in the second direction is S1, the area of the first adhesive member is S2, and 0.4≤S2 / S1≤1. By limiting the lower limit value of S2 / S1, the adhesion between the electrode assembly and the packaging bag can be improved to further improve the mechanical abuse resistance of the secondary battery, and the risk of local lithium precipitation due to under-voltage at the position of the electrode assembly not covered by the first adhesive member during formation can be reduced. By limiting the upper limit value of S2 / S1, the risk that the first adhesive member is easily adhered to other positions after exceeding the electrode assembly can be reduced, thereby improving the mechanical abuse resistance of the secondary battery, and the risk of air bubbles occurring during the pasting of the first adhesive member can be reduced, thereby improving the adhesion effect of the first adhesive member and the appearance of the secondary battery.

[0017] In the one or more possible implementation manners of the first aspect, 0.5≤S2 / S1≤0.7. Thus, the adhesion between the electrode assembly and the packaging bag can be further improved, and the risk of local lithium precipitation due to under-voltage in the formation process at the position of the electrode assembly not covered by the first adhesive can be reduced. Moreover, the risk of the first adhesive being easily adhered to other positions beyond the electrode assembly can be further reduced, and the risk of air bubbles occurring when the first adhesive is pasted can be reduced.

[0018] In the one or more possible implementation manners of the first aspect, the projection of the first tail region does not overlap with the projection of the plurality of conductive plates in the first direction. Thus, the influence of the first tail region on the thickness and energy density of the secondary battery can be reduced.

[0019] In the one or more possible implementation manners of the first aspect, the secondary battery further includes a second adhesive. The second adhesive adheres the surface of the packaging bag facing the electrode assembly and the part of the second surface on the same side as the third edge in the second direction. The first adhesive and the second adhesive are sequentially arranged and separated in the third direction. Thus, the first adhesive and the second adhesive can jointly fix the electrode assembly and the packaging bag, thereby reducing the risk of the electrode assembly moving in the packaging bag under mechanical abuse. Moreover, the provision of the second adhesive can improve the thickness flatness of the secondary battery and can also improve the stress problem between the packaging bag and the electrode assembly when only the first adhesive is provided.

[0020] In the one or more possible implementation manners of the first aspect, the projection of the electrode assembly in the second direction includes a fifth edge and a sixth edge oppositely arranged in the third direction. The first adhesive includes a seventh edge and an eighth edge oppositely arranged in the third direction. The second adhesive includes a ninth edge and a tenth edge oppositely arranged in the third direction. In the third direction, the fifth edge, the ninth edge, the tenth edge, the seventh edge, the eighth edge, and the sixth edge are sequentially arranged. The linear distance between the sixth edge and the eighth edge in the third direction is L3, and the linear distance between the fifth edge and the ninth edge in the third direction is L4; 0≤|L3-L4|≤4mm. Thus, the first adhesive and the second adhesive are substantially centrally arranged in the third direction, further reducing the stress between the packaging bag and the electrode assembly under mechanical abuse, thereby reducing the risk of the first tail region being torn and further improving the mechanical abuse resistance of the secondary battery.

[0021] In the one or more possible implementation manners of the first aspect, the projection 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 value of (S2+S3) / S1, the adhesion between the electrode assembly and the packaging bag can be improved to further improve the mechanical abuse resistance of the secondary battery, and the risk of local lithium precipitation caused by under-voltage during the formation process at the position of the electrode assembly not covered by the first adhesive and the second adhesive can be reduced. By limiting the upper limit value of (S2+S3) / S1, the risk of the first adhesive or the second adhesive being easily adhered to other positions after exceeding the electrode assembly can be reduced, thereby improving the mechanical abuse resistance of the secondary battery, and the risk of bubbles occurring during the pasting of the first adhesive or the second adhesive can be reduced, thereby improving the adhesion effect and the appearance of the secondary battery.

[0022] In the one or more possible implementation manners of the first aspect, 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 local lithium precipitation caused by under-voltage during the formation process at the position of the electrode assembly not covered by the first adhesive and the second adhesive can be reduced. Moreover, the risk of the first adhesive or the second adhesive being easily adhered to other positions after exceeding the electrode assembly can be further reduced, and the risk of bubbles occurring during the pasting of the first adhesive or the second adhesive.

[0023] In the one or more possible implementation manners of the first aspect, the first sub-layer includes a second end region in the winding direction, and the second sub-layer includes a third end region in the winding direction. The second end region is located at the outermost winding circle of the first electrode tab, and the third end region is located at the outer winding circle of the first electrode tab. The secondary battery further includes a third adhesive, which is arranged at the second end region, extends along the winding direction, and adheres to the first surface. The first adhesive and the third adhesive are separated in the third direction as viewed from the second direction. Therefore, the influence of the overlap of the first adhesive and the third adhesive on the thickness and energy density of the secondary battery can be reduced.

[0024] In the one or more possible implementation manners of the first aspect, the secondary battery further includes a fourth adhesive, which is arranged at the third end region, extends along the winding direction, and adheres to the second surface. The first adhesive and the fourth adhesive are separated in the third direction as viewed from the second direction. Therefore, the influence of overlap of the first adhesive and the fourth adhesive on the thickness and energy density of the secondary battery can be reduced.

[0025] In the one or more possible implementation manners of the first aspect, the secondary battery further includes a fifth adhesive. The electrode assembly includes a first end portion and a second end portion oppositely arranged in the first direction, the first edge is located at the first end portion, and the second edge is located at the second end portion. The fifth adhesive is attached to the second end portion. The first adhesive and the fifth adhesive are separated from each other in the first direction as viewed from the second direction. Thus, the fifth adhesive can be attached to the edge of the separator, so as to reduce the risk of the edge of the separator being wrinkled or shrunk to cause the first electrode tab and the second electrode tab to be in contact. In addition, since the first adhesive and the fifth adhesive are separated from each other in the first direction, the impact on the thickness and the energy density of the secondary battery can be reduced.

[0026] In the one or more possible implementation manners of the first aspect, the first adhesive includes, in sequence along a thickness direction of the first adhesive, a first adhesive layer, a substrate layer, and a second adhesive layer. The first adhesive layer is arranged on a surface of the substrate layer facing the packaging bag, and the second adhesive layer is arranged on a surface of the substrate layer facing the first end region. 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 derivatives thereof.

[0027] In the one or more possible implementation manners of the first aspect, the first electrode tab is a positive electrode tab, and the second electrode tab is a negative electrode tab.

[0028] In the one or more possible implementation manners of the first aspect, the first adhesive extends beyond the edge of the second electrode tab in the first direction. In this way, the first adhesive can better reduce the risk of the first electrode tab and the second electrode tab being in contact.

[0029] The second aspect of the present application provides an electronic device including the secondary battery. The electronic device is powered by the secondary battery, and the risk of short circuit caused by the separator being wrinkled or shrunk is reduced, so that the electronic device has higher safety and service life. BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a schematic structural view of a secondary battery from a second direction according to an embodiment of the present application.

[0031] FIG. 2 is a sectional view of the secondary battery along a section line II-II in some embodiments of FIG. 1.

[0032] FIG. 3 is a schematic structural view of the secondary battery after the packaging bag is removed in some embodiments of FIG. 1.

[0033] FIG. 4 is a schematic view of the structure of the secondary battery shown in FIG. 1, with the packaging bag removed, in another embodiment.

[0034] FIG. 5 is a schematic view of the structure of the secondary battery shown in FIG. 1, with the packaging bag removed, in another embodiment.

[0035] FIG. 6 is an expanded view of the first electrode sheet of the secondary battery shown in FIG. 2.

[0036] FIG. 7 is a cross-sectional view of the first adhesive member of the secondary battery shown in FIG. 2.

[0037] FIG. 8 is a schematic view of the overall structure of an electronic device according to an embodiment of the present application.

[0038] Explanation of Main Component Symbols

[0039] Electronic device 1 Packaging bag 10

[0040] Main body portion 11 Electrode assembly 20

[0041] Fifth edge 20A Sixth edge 20B

[0042] First end portion 20C Second end portion 20D

[0043] First electrode sheet 21 First edge 21A, 22A, 23A

[0044] Second edge 21B, 22B, 23B Second electrode sheet 22

[0045] Separator 23 First conductive plate 31

[0046] Second conductive plate 32 First adhesive member 41

[0047] Fourth edge 41A Seventh edge 41B

[0048] Eighth edge 41C Second adhesive member 42

[0049] Ninth edge 42A Tenth edge 42B

[0050] Third adhesive 50 Fourth adhesive 60

[0051] Fifth adhesive 70 Secondary battery 100

[0052] Battery compartment 101 First flat section 201

[0053] First bending section 202 Second flat section 203

[0054] Second bending section 204 First current collector 210

[0055] First active material 211 Second current collector 220

[0056] Second active material 221 Base material layer 410

[0057] First adhesive layer 411 Second adhesive layer 412

[0058] First tail region 2100 Third edge 2100A

[0059] First surface 2101 Second surface 2102

[0060] Second tail region 2110 Third tail region 2110'

[0061] First sub-layer 2111 Second sub-layer 2112

[0062] Winding center axis O Winding direction D

[0063] Winding center surface P First direction X

[0064] Second direction Y Third direction Z

[0065] Fourth direction Y' Fifth direction Z'

[0066] Straight line distance L1, L2, L3, L4

[0067] The following detailed description will further describe the present application with reference to the above drawings. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present application will be described clearly and in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Unless otherwise defined, all the technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0069] Hereinafter, the embodiments of the present application will be described in detail. However, the present application can 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 so that the present application will be thorough and complete, and fully convey the scope of the present application to those skilled in the art.

[0070] In addition, for the sake of brevity and clarity, in the drawings, the size or thickness of various components, layers, or regions can be exaggerated. Throughout the specification, like numbers refer to like elements throughout. As used herein, the terms "and / or" and "at least one of" include any and all combinations of one or more of the associated listed items. In addition, it should be understood that if an element A is referred to as being "connected" to or "coupled" to another element B, it can be directly connected to or coupled to the other element B or intervening elements can be present therebetween.

[0071] Further, use of "may" when describing embodiments of the present application means that one or more embodiments of the present application.

[0072] The specific terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0073] Spatially relative terms, such as "on", "above", and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is turned over, elements described as "above" other elements or features would then be oriented "below" the other elements or features. Thus, the exemplary term "above" can encompass both an orientation of above and below. For example, it will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the exemplary embodiments.

[0074] Referring to FIGS. 1 and 2, an embodiment of the present application provides a secondary battery 100 including a packaging pouch 10, an electrode assembly 20, and an electrolyte (not shown). The electrode assembly 20 and the electrolyte are positioned in the packaging pouch 10.

[0075] As shown in FIG. 2, the electrode assembly 20 includes a first tab 21, a second tab 22, and a separator 23 disposed between the first tab 21 and the second tab 22. The first tab 21, the separator 23, and the second tab 22 are stacked and wound. The first tab 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 opposite to a second surface 2102 in a thickness direction of the first current collector 210, the first surface 2101 faces the winding central axis O, and the second surface 2102 faces away from the winding central 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 tab 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 a first direction X, a second direction Y, and a third direction Z perpendicular to each other, a width direction of the first tab 21 or the second tab 22 is the first direction X, in some embodiments, the first direction X is also the extension direction of the winding central axis O, and a thickness direction of the electrode assembly 20 is the second direction Y. The electrode assembly 20 can be divided into a first flat section 201, a first bending section 202, a second flat section 203, and a second bending section 204 connected in sequence in a winding direction D. The first flat section 201 and the second flat section 203 are oppositely disposed in the second direction Y, and the first bending section 202 and the second bending section 204 are oppositely disposed in the third direction Z.

[0076] The first tab 21 can be a positive electrode tab, and the second tab 22 can be a negative electrode tab. Correspondingly, the first current collector 210 and the first active material layer 211 are a positive electrode current collector and a positive electrode active material layer, respectively, and the second current collector 220 and the second active material layer 221 are a negative electrode current collector and a negative electrode active material layer, respectively. Referring to FIG. 3, the first tab 21 includes a first edge 21A and a second edge 21B oppositely arranged in the first direction X. The second tab 22 includes a first edge 22A and a second edge 22B oppositely arranged in the first direction X. The separator film 23 includes a first edge 23A and a second edge 23B oppositely arranged in the first direction X. The electrode assembly 20 includes a first end 20C and a second end 20D oppositely arranged 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 precipitation of the second tab 22, the first edge 22A of the second tab 22 can be arranged to extend beyond the first edge 21A of the first tab 21 in the first direction X, and the second edge 22B of the second tab 22 can be arranged to extend beyond the second edge 21B of the first tab 21 in the first direction X. The portion of the second tab 22 extending beyond the first tab 21 is an overhang. To reduce the risk of contact between the first tab 21 and the second tab 22, the first edge 23A of the separator film 23 can be further arranged to extend beyond the first edge 22A of the second tab 22 in the first direction X, and the second edge 23B of the separator film 23 can be arranged to extend beyond the second edge 23B of the second tab 22 in the first direction X. In other embodiments, the first tab 21 can be a negative electrode tab, and the second tab 22 can be a positive electrode tab.

[0077] As shown in Figures 1 to 3, 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.

[0078] 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.

[0079] As shown in Figure 2, the outermost winding of the electrode assembly 20 is the first electrode 21, and the first electrode 21 winding the outermost ring 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 winding the outermost ring only has a first sub-layer 21111 on part of the first surface 2101, and no second sub-layer 2112 is provided on the second surface 2102 of the first current collector 210 winding the outermost ring. 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 easy to fall off after contact with the packaging bag 10. Moreover, the first current collector 210 winding the outermost ring can increase the hardness of the electrode assembly 20, which can protect the electrode assembly 20 and improve the resistance of the electrode assembly 20 to mechanical impact.

[0080] 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.

[0081] 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).

[0082] 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.

[0083] 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.

[0084] As shown in Figure 2, the first current collector 210 further 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, which 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, which 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'.

[0085] 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.

[0086] 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.

[0087] As shown in Figures 2, 3, and 6, Figure 6 is a schematic diagram of the unfolded structure of the first electrode 21 shown in Figure 2. A three-dimensional coordinate system is established in Figure 6 with the first direction X, the fourth direction Y', and the 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 first tailing region 2100 facing the surface of the packaging bag 10, and the third edge 2100A. As shown in Figure 3, 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 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. Furthermore, by setting the first adhesive 41 to adhere to the third edge 2100A, the first adhesive 41 can also act as a finishing adhesive to fix the first finishing area 2100, reduce the risk of the first finishing area 2100 moving, and thus improve the compactness of the electrode assembly 20.

[0088] 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.

[0089] 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.

[0090] As shown in Figure 7, 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.

[0091] 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.

[0092] As shown in FIG. 3, in some embodiments, the first bonding member 41 includes a fourth edge 41A, and the fourth edge 41A and the first edge 21A are located at the same end of the electrode assembly 20. Among them, it can be set that when observing along the second direction Y, the fourth edge 41A and the first edge 21A are substantially flush. That is, when observing along the second direction Y, the linear distance between the fourth edge 41A and the first edge 21A along the first direction X is zero. As shown in FIG. 4, in some other embodiments, it can also be set that the fourth edge 41A extends beyond the first edge 21A along the first direction X. When observing 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, and 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 electrode sheet 22 after the separator film 23 is wrinkled or shrunk, causing 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-sealed region of the packaging bag 10 before the packaging bag 10 is sealed can be reduced (wherein, if the first bonding member 41 enters the to-be-sealed region of the packaging bag 10, when the to-be-sealed region is sealed to form the sealing edge 12, the first bonding member 41 entering the sealing region may cause the packaging bag 10 to be damaged), thereby reducing the risk of liquid leakage of the packaging bag 10.

[0093] Further, it can be set that 0.2 mm ≤ L1 ≤ 2.0 mm. 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 electrode sheet 22 after the separator film 23 is wrinkled or shrunk, causing contact short circuit, can be further reduced. Furthermore, it can be set that 0.2 mm ≤ L1 ≤ 1.4 mm. By defining the upper limit value of L1, the first bonding member 41 does not extend beyond the first edge 21A of the separator 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, and further reducing the risk that the first bonding member 41 presses against the sealing edge 12 of the packaging bag 10 or enters the to-be-sealed region of the packaging bag 10 before packaging, thereby reducing the risk of liquid leakage of the packaging bag 10.

[0094] As shown in Figures 3 and 4, in some embodiments, when viewed along the second direction Y, the extension of the third edge 2100A along the first direction X is located between two adjacent conductive plates in the third direction Z. Specifically, when viewed from the second direction Y, the third edge 2100A may be located in the first straight section 201. This helps reduce the risk of the third edge 2100A opening relative to the electrode assembly 20, improving the compactness of the electrode assembly 20. Furthermore, due to the position of the third edge 2100A, the first adhesive 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 of tearing in the first closing region 2100 and further improving the resistance of the secondary battery 100 to mechanical abuse.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] As shown in Figure 5, 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] As shown in Figures 2 to 5, 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.

[0104] The third adhesive 50 is disposed in the second termination region 2110. Along the winding direction D (or along the fifth direction Z' shown in FIG. 6), 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 2100 (i.e., the first surface 2101 of the first termination region 2100). The third adhesive 50 reduces the risk of micro-short circuits caused by the shedding of active material from the second termination region 2110. Simultaneously, the third adhesive 50 also provides insulation protection for the first surface 2101 of the first termination region 2100, absorbing some impact force during mechanical abuse, reducing the risk of tearing of the first termination region 2100, and enhancing the strength of the first termination region 2100. Therefore, it can further improve the resistance of the electrode assembly 20 to mechanical shock.

[0105] 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.

[0106] 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.

[0107] As shown in Figures 3 to 5, 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 caused by wrinkling or shrinkage of the second edge 21B during mechanical abuse, which could result in contact between the first electrode 21 and the second electrode 22. 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.

[0108] The secondary battery 100 of this application can be a lithium secondary battery, including a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery, or a lithium-ion polymer secondary battery.

[0109] Please refer to Figure 8. One embodiment of this application also provides an electronic device 1, which includes a battery compartment 101 and the aforementioned 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 aforementioned 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-based 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.

[0110] 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.

[0111] Examples 1 to 16

[0112] (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 the mixture was stirred evenly. Foaming adhesive was first applied to a portion of the surface of the positive current collector, i.e., aluminum foil, with a thickness of 9 μm. The slurry was then uniformly coated on one surface of the aluminum foil. The foil was heated to remove the foaming adhesive and expose 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 positive active material layer with a coating thickness of 77 μm. The positive electrode was then cut to obtain the final positive electrode. Two first conductive plates, made of aluminum, were then welded onto the exposed aluminum foil. Then, referring to Figure 2, attach the third and fourth adhesive pieces to the third finishing area of ​​the aluminum foil.

[0113] (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.

[0114] (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.

[0115] (4) Preparation of the isolation membrane: A polyethylene (PE) membrane with a thickness of 9 μm was selected.

[0116] (5) Preparation of the secondary battery: The first electrode, the separator, and the second electrode are sequentially stacked and wound to obtain the electrode assembly shown in Figure 2. The arrangement of the two second conductive plates and the two first conductive plates is shown in Figure 1, that is, the two second conductive plates and the two first conductive plates are arranged sequentially along the third direction, and the extension line of the third edge along the first direction is located between the two first conductive plates (as shown in Figure 3). A fifth adhesive is set at the tail of the electrode assembly. Then, the aluminum-plastic film (thickness of 150μm) formed by punching is placed in the assembly fixture with the pit surface facing upward. The electrode assembly is placed in the pit through the first adhesive, wherein the substrate layer of the first adhesive is made of polyimide, and the first adhesive layer and the second adhesive layer are made of polypropylene. Then, electrolyte is injected into the pit of the aluminum-plastic film, and the first conductive plate and the second conductive plate are led out of the aluminum-plastic film and then encapsulated to obtain the secondary battery. The length of the electrode assembly in Examples 1 to 15 is 70.5mm, the width is 40.5mm, and the area of ​​the electrode assembly is 2855.25mm². 2 It 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.

[0117] Example 17

[0118] 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 area does not overlap with the projection of the multiple conductive plates (as shown in Figure 5).

[0119] Example 18

[0120] 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.

[0121] Comparative Example

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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%

[0128] The test results are recorded in Table 1.

[0129] 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.

[0130] Table 1

[0131] 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.

[0132] (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.

[0133] (3) In Table 1, the drop test pass rate is n / 20, indicating that out of the 20 tested secondary batteries, n batteries passed the test. The meanings of other ratio values ​​are deduced similarly.

[0134] 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.

[0135] 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 any one of claims 2 to 6, 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 according to any one of claims 1 to 15, 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 according to any one of claims 1 to 16, 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 according to any one of claims 1 to 17, 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 according to any one of claims 1 to 18, 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.

Images