Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery includes an electrode assembly and a first adhesive. The electrode assembly includes a first end portion and a second end portion disposed opposite to each other in a first direction. The first bonding piece is located at the first end part and is arranged on the negative pole piece located at the outermost layer in the second direction in the multi-layer structure formed by the negative pole pieces, and the second direction is the thickness direction of the electrode assembly. The first bonding piece comprises a first bonding layer, a first porous base material layer and a second bonding layer which are arranged in a stacked mode. The first bonding layer and the second bonding layer both comprise inorganic ceramic particles and are respectively bonded with the negative active material layer and the isolating membrane of the negative pole piece. At least part of the first bonding piece is bonded with the area, exceeding the positive pole piece, of the negative pole piece.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, and in particular to a secondary battery and an electronic device with the secondary battery. BACKGROUND

[0002] With the popularity of consumer electronics such as notebook computers, mobile phones, handheld game consoles, tablet computers, mobile power supplies and drones, people have increasingly strict requirements for the safety performance and service life of secondary batteries.

[0003] The secondary battery generally includes an electrode assembly. In the related art, in order to reduce the risk of lithium precipitation of the negative electrode tab, the edge of the negative electrode tab can be arranged to protrude beyond the edge of the positive electrode tab. However, the adhesion between the part of the negative electrode tab protruding beyond the edge of the positive electrode tab and the separator film is low, which can cause a poor contact interface problem, thereby causing lithium precipitation during the cycle process, and thus reducing the safety performance and service life of the secondary battery. SUMMARY

[0004] Therefore, it is necessary to provide a secondary battery with improved safety performance and service life.

[0005] In addition, it is also necessary to provide an electronic device with the secondary battery.

[0006] The first aspect of the present application provides a secondary battery, including an electrode assembly. The electrode assembly includes a separator film and a tab, the tab including a positive electrode tab and a negative electrode tab, and the separator film being arranged between the positive electrode tab and the negative electrode tab. The electrode assembly includes a first end portion and a second end portion arranged opposite to each other along a first direction. The negative electrode tab includes a first edge and a second edge arranged opposite to each other along the first direction. The positive electrode tab includes a third edge and a fourth edge arranged opposite to each other along the first direction. The first edge and the third edge are located at the first end portion, and the second edge and the fourth edge are located at the second end portion. The first edge is located outside the third edge in the first direction. The negative electrode tab includes a first negative electrode tab layer, the first negative electrode tab layer being provided with a negative electrode active material layer, and the first negative electrode tab layer being the outermost layer in a second direction of a multi-layer structure formed by the negative electrode tab. The secondary battery further includes a first adhesive. At least part of the first adhesive is located at the first end portion and arranged on the first negative electrode tab layer, and the second direction is a thickness direction of the electrode assembly and perpendicular to the first direction. At least part of the first adhesive is arranged between the first edge and the third edge in the first direction as viewed in the second direction. The first adhesive includes a first adhesive layer, a first porous substrate layer and a second adhesive layer arranged in layers. The first adhesive layer adheres to the negative electrode active material layer of the first negative electrode tab layer, the second adhesive layer adheres to the separator film, and the side of the first negative electrode tab layer facing the first adhesive is provided with the positive electrode tab. The first adhesive layer and the second adhesive layer each include a binder and inorganic ceramic particles.

[0007] In the present application, considering that the negative electrode tab outside the third edge in the first direction has a decreased adhesion between the negative electrode tab and the separator due to the lack of support from the positive electrode tab, and the first negative electrode tab layer in the negative electrode tab has a relatively small constraint force, it is more likely that the adhesion between the first negative electrode tab layer outside the third edge and the separator will decrease due to the volume expansion of the negative electrode tab during the cycle process. Therefore, the first adhesive is arranged on the first negative electrode tab layer, and at least part of the first adhesive is arranged between the first edge and the third edge in the first direction as viewed from the second direction. Therefore, the first adhesive can fix the negative active material layer of the first negative electrode tab layer outside the third edge to the separator, thereby better constraining the part of the first negative electrode tab layer outside the third edge, improving the contact interface, and thereby reducing the risk of lithium precipitation due to poor contact interface during the cycle process. Moreover, the arrangement of inorganic ceramic particles helps to create more pores in the first adhesive layer and the second adhesive layer, which, combined with the arrangement of the first porous substrate layer, improves the blockage of active ions (such as lithium ions) by the first adhesive, thereby reducing the risk of lithium precipitation due to the inability of the part of the first negative electrode tab layer outside the third edge to normally insert active ions after the arrangement of the first adhesive. Therefore, the secondary battery has higher safety performance and service life.

[0008] Based on the first aspect, in some possible implementations, the electrode assembly has a wound structure. The secondary battery further includes a tab electrically connected to the electrode assembly and protruding from the electrode assembly in a first direction. The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer, and the negative electrode sheet further includes a negative electrode current collector. The negative electrode current collector includes a first surface facing the winding center axis and a second surface facing away from the first surface. The first negative electrode active material layer is disposed on the first surface, and the second negative electrode active material layer is disposed on the second surface. The positive electrode sheet includes a first positive electrode active material layer, a positive electrode current collector, and a second positive electrode active material layer. The positive electrode current collector includes a third surface facing the winding center axis and a fourth surface facing away from the third surface. The first positive electrode active material layer is disposed on the third surface, and the second positive electrode active material layer is disposed on the fourth surface. The first negative electrode sheet layer is the last negative electrode winding of the negative electrode sheet. The positive electrode sheet includes the last positive electrode winding, which is the outermost electrode sheet of the electrode assembly. The first adhesive is provided on the side of the negative electrode winding coil facing the positive electrode winding coil. The first adhesive layer is bonded to the second negative electrode active material layer. For the electrode assembly with a wound structure, considering that the negative electrode winding coil of the negative electrode pole piece (especially the side of the negative electrode winding coil facing the positive electrode winding coil) is subjected to a relatively small binding force, it is more likely that the negative electrode pole piece will expand in volume during the cycle, thereby extending along the winding direction and causing the adhesion between the negative electrode winding coil located outside the third edge and the isolation film to weaken. Therefore, the first adhesive is provided on the side of the negative electrode winding coil facing the positive electrode winding coil. Therefore, the first adhesive can bind the negative electrode winding coil, improve the contact interface, and thus reduce the risk of lithium plating caused by poor contact interface during the cycle.

[0009] Based on the first aspect, in some possible implementations, the first negative electrode pole piece layer is the second outermost pole piece of the electrode assembly, or the first negative electrode pole piece layer is the second outermost pole piece of the electrode assembly. When there are two or fewer positive pole pieces outside the first negative electrode pole piece layer, the restraining force on the first negative electrode pole piece layer is relatively small. In this case, providing the first adhesive member is beneficial for strengthening the adhesion between the negative electrode active material layer of the first negative electrode pole piece layer and the separator, improving the contact interface, and thereby reducing the risk of lithium plating caused by poor contact interface during cycling.

[0010] In some possible implementations based on the first aspect, the negative winding last circle includes, in sequence along the winding direction of the electrode assembly, a first negative winding arc, a first negative winding layer, a second negative winding arc, and a second negative winding layer. The end of the first negative active material layer and the end of the second negative active material layer are both located at the second negative winding layer. The positive winding last circle includes a first positive winding layer, which is located at a side of the second negative winding layer away from the winding center axis. The end of the first positive active material layer is located at the first positive winding layer. The first adhesive is arranged at a side of the second negative winding layer facing the first positive winding layer. Considering that, in the negative winding last circle of the negative electrode sheet, the second negative winding layer is located at the tail of the negative winding last circle along the winding direction, it is easier for the second negative winding layer outside the third edge to be greatly extended along the winding direction under the effect of volume expansion and cause the adhesion between the second negative winding layer outside the third edge and the separator to be weakened. Therefore, the first adhesive is arranged at the side of the second negative winding layer facing the first positive winding layer, so as to fix the second negative winding layer outside the third edge to the separator, better bind the part of the second negative winding layer outside the third edge, improve the contact interface, and further reduce the risk of lithium precipitation caused by poor contact interface during the cycle.

[0011] In some possible implementations based on the first aspect, the first adhesive is also arranged at the second negative winding arc. Therefore, the second negative winding arc outside the third edge can be fixed to the separator, so as to better bind the part of the second negative winding arc at the third edge, improve the contact interface, and further reduce the risk of lithium precipitation caused by poor contact interface during the cycle.

[0012] In some possible implementations based on the first aspect, the first adhesive is also arranged at the first negative winding layer. Therefore, the first negative winding layer outside the third edge can be fixed to the separator, so as to better bind the part of the first negative winding layer at the third edge, improve the contact interface, and further reduce the risk of lithium precipitation caused by poor contact interface during the cycle.

[0013] In some possible implementations based on the first aspect, along the winding direction, the starting end of the first adhesive is attached to the Nth negative winding circle of the negative electrode sheet, the end of the first adhesive is attached to the negative winding last circle, and the difference between the number of turns of the negative winding last circle and the number of turns of the Nth negative winding circle is less than or equal to 3. Considering that other regions of the negative electrode sheet adjacent to the negative winding last circle along the winding direction are also subjected to a small binding force, the position of the starting end of the first adhesive is arranged so that the first adhesive can further fix the negative electrode sheet outside the third edge to the separator, thereby further improving the contact interface and further reducing the risk of lithium precipitation caused by poor contact interface during the cycle.

[0014] In some possible implementation manners based on the first aspect, the first adhesive member is integrally arranged along the winding direction. Thus, the first adhesive member can more stably adhere the negative pole piece and the separator, thereby better binding the negative pole piece outside the third edge, improving the contact interface, and further reducing the risk of lithium precipitation due to poor contact interface during the cycle.

[0015] In some possible implementation manners based on the first aspect, the first adhesive member is separately arranged along the winding direction. In the second direction, the first adhesive member does not overlap the tab. Thus, the thickness of the electrode assembly can be reduced due to the arrangement of the first adhesive member, thereby improving the energy density of the secondary battery.

[0016] In some possible implementation manners based on the first aspect, along the winding direction, the end of the first adhesive member is beyond the end of the first positive active material layer. Thus, when the third edge adjacent to the end of the first positive active material layer is stripped of active ions during the cycle, the region in the negative pole piece beyond the third edge for embedding the part of active ions can be fixed to the separator by the first adhesive member, the contact interface is improved, and thus the risk of lithium precipitation due to poor contact interface during the cycle can be further reduced.

[0017] In some possible implementation manners based on the first aspect, the second edge is outside the fourth edge in the first direction, and at least part of the first adhesive member is located at the second end portion and arranged on the side of the second negative winding layer facing the first positive winding layer. In the second direction, at least part of the first adhesive member is arranged between the second edge and the fourth edge in the first direction. The first adhesive member at the first end portion is separated from the first adhesive member at the second end portion in the first direction. Thus, at least part of the first adhesive member also adheres the negative pole piece outside the fourth edge in the second negative winding layer, thereby fixing the part of the negative pole piece to the separator, better binding the part of the negative pole piece outside the fourth edge, improving the contact interface, and further reducing the risk of lithium precipitation due to poor contact interface during the cycle. On this basis, the thickness of the electrode assembly can be reduced due to the arrangement of the first adhesive member, and the risk of reducing the active ion transmission speed when the first adhesive member covers a large area of the negative pole piece can also be reduced.

[0018] In some possible implementation manners based on the first aspect, the negative electrode sheet further includes a negative electrode first winding circle and a negative electrode second winding circle connected in sequence along the winding direction, and the starting end of the second negative electrode active material layer is located at the negative electrode first winding circle. The negative electrode second winding circle includes a third negative electrode winding layer and a third negative electrode winding arc connected along the winding direction. The second negative electrode winding layer is located at a side of the third negative electrode winding layer away from the winding central axis, and the first negative electrode winding arc is located at a side of the third negative electrode winding arc away from the winding central axis. The starting end of the first negative electrode active material layer is located at the third negative electrode winding layer. The secondary battery further includes a second adhesive. At least part of the second adhesive is located at the first end portion and is located at the side of the third negative electrode winding layer facing the winding central axis. The second adhesive includes a third adhesive layer, a second porous substrate layer and a fourth adhesive layer arranged in layers. The third adhesive layer is adhesive to the first negative electrode active material layer, and the fourth adhesive layer is adhesive to the separator. The third adhesive layer and the fourth adhesive layer each include a binder and inorganic ceramic particles. At least part of the second adhesive is located between the first edge and the third edge in the first direction as viewed from the second direction.

[0019] Considering that the third negative electrode winding layer of the negative electrode second winding circle of the negative electrode sheet (especially the side of the third negative electrode winding layer facing the winding central axis) is also subjected to a smaller constraint force, and considering that the starting end of the first negative electrode active material layer is specifically located at the third negative electrode winding layer, that is, the junction position of the single-sided coating area and the double-sided coating area in the negative electrode sheet is located at the third negative electrode winding layer, resulting in a larger volume expansion at the third negative electrode winding layer, in this embodiment, the second adhesive is arranged at the side of the third negative electrode winding layer of the negative electrode second winding circle facing the winding central axis, and at least part of the second adhesive is located between the first edge and the third edge in the first direction as viewed from the second direction. Therefore, the second adhesive can fix the third negative electrode winding layer located outside the third edge to the separator, thereby better constraining the part of the third negative electrode winding layer located outside the third edge, improving the contact interface, and thereby further reducing the risk of lithium precipitation due to poor contact interface during the cycle process.

[0020] In some possible implementation manners based on the first aspect, the second adhesive is also located at the third negative electrode winding arc. Therefore, the third negative electrode winding arc located outside the third edge can be fixed to the separator, thereby better constraining the part of the third negative electrode winding arc located outside the third edge, improving the contact interface, and thereby further reducing the risk of lithium precipitation due to poor contact interface during the cycle process.

[0021] In some possible implementation manners based on the first aspect, the electrode assembly is a stack structure. The outermost electrode tab of the electrode assembly in the second direction is a positive electrode tab. The first negative electrode tab layer is a sub-outer electrode tab of the electrode assembly in the second direction, and the first adhesive is arranged on a side of the first negative electrode tab layer facing the outermost positive electrode tab. For the electrode assembly in the stack structure, the first negative electrode tab layer (especially the side of the first negative electrode tab layer facing the outermost positive electrode tab) adjacent to the outermost positive electrode tab in the second direction is relatively small in constraint force, and therefore the first adhesive is arranged on the side of the first negative electrode tab layer facing the outermost electrode tab, so that the first adhesive can constrain the part of the first negative electrode tab layer outside the third edge, improve the contact interface, and thus reduce the risk of lithium precipitation due to poor contact interface in the cycle process.

[0022] In some possible implementation manners based on the first aspect, the first adhesive includes a first edge and a second edge arranged opposite to each other along the first direction, and the second edge is sequentially arranged along the first direction from the first edge. In the second direction, the first edge overlaps with the negative electrode tab, and the distance between the first edge and the first edge along the first direction is less than or equal to 0.5 mm. Therefore, the bonding area of the first adhesive with the negative electrode tab and the separator can be further increased, so as to further constrain the negative electrode tab outside the third edge, improve the contact interface, and thus further reduce the risk of lithium precipitation due to poor contact interface in the cycle process.

[0023] In some possible implementation manners based on the first aspect, the distance between the second edge and the first edge along the first direction is less than or equal to 10 mm. Therefore, the first adhesive can sufficiently cover the negative electrode tab outside the third edge while reducing the influence of the first adhesive on the thickness of the electrode assembly, and the risk of reducing the active ion transmission speed when the first adhesive covers a large area of the negative electrode tab can also be reduced.

[0024] In some possible implementation manners based on the first aspect, the porosity of the first porous substrate layer is 20% to 60%, so as to further facilitate the active ions to pass through the first adhesive, improve the blockage of the active ions due to the arrangement of the first adhesive, and thus further reduce the risk of lithium precipitation in the cycle process.

[0025] In some possible implementations of the first aspect, the material of the first porous substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid. The material of the binder in the first adhesive layer and the second adhesive layer is independently selected from at least one of polyolefin, polyacrylate, and polyacrylic acid, so that the binder has better adhesion to the inorganic ceramic particles. The material of the inorganic ceramic particles in the first adhesive layer and the second adhesive layer is independently selected from at least one of boehmite, aluminum oxide, titanium dioxide, magnesium oxide, zirconium oxide, and zinc oxide, so that the inorganic ceramic particles have higher electrochemical compatibility.

[0026] 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 lithium precipitation of the negative electrode tab outside the third edge is reduced, so that the secondary battery has higher safety and service life. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A structure schematic diagram of the secondary battery provided by an embodiment of the present application is shown from a second direction.

[0028] Figure 2 A structure schematic diagram of the secondary battery shown in Figure 1 is shown in some embodiments after the shell is removed.

[0029] Figure 3 A sectional view of the secondary battery shown in Figure 1 along the section line III-III in some embodiments.

[0030] Figure 4 A sectional view of the first adhesive member of the secondary battery shown in Figure 3 .

[0031] Figure 5 A sectional view of the secondary battery shown in Figure 1 some other embodiments.

[0032] Figure 6 A sectional view of the secondary battery shown in Figure 1 some other embodiments.

[0033] Figure 7 A sectional view of the secondary battery shown in Figure 1 some other embodiments.

[0034] Figure 8 A sectional view of the secondary battery shown in Figure 1 some other embodiments.

[0035] Figure 9 A sectional view of the secondary battery shown in Figure 8Cross-sectional view of the second adhesive member of the secondary battery shown.

[0036] Figure 10 For Figure 1 Structure schematic diagram of the secondary battery shown in other embodiments after removing the case.

[0037] Figure 11 For Figure 1 Structure schematic diagram of the secondary battery shown in other embodiments after removing the case.

[0038] Figure 12 For Figure 1 Cross-sectional view of the secondary battery shown in other embodiments along the section line III-III.

[0039] Figure 13 Structure schematic diagram of the electronic device provided by an embodiment of the present application.

[0040] Main element symbol explanation Electronic device, 1; case, 10; electrode assembly, 20; first end portion, 20A; second end portion, 20B; negative electrode tab, 21; first edge, 21A; second edge, 21B; positive electrode tab, 22; third edge, 22A; fourth edge, 22B; separator, 23; fifth edge, 23A; sixth edge, 23B; negative electrode tab, 30; positive electrode tab, 40; first adhesive member, 50; first side, 50A; second side, 50B; first adhesive layer, 51; second adhesive layer, 52; first porous base material layer, 53; second adhesive member, 60; third adhesive layer, 61; fourth adhesive layer, 62; second porous base material layer, 63; secondary battery, 100, 200; battery compartment, 101; negative current collector, 210; first negative active material layer, 211; second negative active material layer, 212; negative winding end coil, 213; negative winding start coil, 214; negative winding intermediate coil, 215; positive current collector, 220; first positive active material layer, 221; second positive active material layer, 222; positive winding end coil, 223; start end, 500, 2111, 2121; end end, 501, 2110, 2120, 2210; first surface, 2101; second surface, 2102; first negative winding arc, 2131; first negative winding layer, 2132; second negative winding arc, 2133; second negative winding layer, 2134; third negative winding layer, 2151; third negative winding arc, 2152; third surface, 2201; fourth surface, 2202; first positive winding layer, 2231; interval, L1, L2; winding central axis, O; winding direction, D; first direction, X; second direction, Y; third direction, Z; dotted line, A-A, B-B; first negative electrode tab layer, P1.

[0041] The following detailed description will further describe the present application with reference to the above figures. DETAILED DESCRIPTION

[0042] 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.

[0043] 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.

[0044] 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 document, the same numerical references refer to the same elements. As used herein, the terms "and / or", "at least one of", and "one or more 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 element B, element A can be directly connected to element B or intervening elements C can be present and element A and element B can be indirectly connected to each other through the intervening elements C.

[0045] Further, use of "may" when describing embodiments of the present application means that one or more embodiments of the present application.

[0046] The professional terms used herein are for the purpose of describing the specific embodiments and are not intended to limit the present 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" when used in this specification, means that the stated features, numbers, steps, operations, elements, and / or components are present, but does not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and / or combinations thereof.

[0047] 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 or apparatus in use or operation in addition to the orientations depicted in the figures. For example, if a device or apparatus is turned over, then an element or feature that is described as being "above" or "on" another element or feature would then be oriented "below" or "on" the other element or feature. Thus, the exemplary term "above" can encompass both an orientation that is above and below. 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.

[0048] Referring to Figures 1 to 3 , one embodiment of the present application provides a secondary battery 100, which includes a case 10, an electrode assembly 20, and an electrolyte (not shown). The secondary battery 100 can further include a tab. The electrode assembly 20 and the electrolyte are located in the case 10. The tab is electrically connected to the electrode assembly 20.

[0049] As shown in Figure 3 , the electrode assembly 20 includes a tab and a separator 23, the tab includes a negative electrode tab 21 and a positive electrode tab 22, and the separator 23 is disposed between the positive electrode tab 22 and the negative electrode tab 21. In some embodiments, the positive electrode tab 22, the separator 23, and the negative electrode tab 21 are stacked and wound, i.e., the electrode assembly 20 has a wound structure. As shown in Figure 2 , the electrode assembly 20 includes a first end portion 20A and a second end portion 20B disposed opposite to each other in a first direction X, and the tab can extend out of the electrode assembly 20 from the first end portion 20A or the second end portion 20B. In some embodiments, the tab can include a negative electrode tab 30 and a positive electrode tab 40, the negative electrode tab 30 is electrically connected to the negative electrode tab 21, the positive electrode tab 40 is electrically connected to the positive electrode tab 22, and the negative electrode tab 30 and the positive electrode tab 40 extend out of the electrode assembly 20 from the first end portion 20A.

[0050] A three-dimensional coordinate system is defined by a first direction X, a second direction Y, and a third direction Z, which are perpendicular to each other. The tabs protrude from the electrode assembly 20 along the first direction X, the second direction Y is the thickness direction of the electrode assembly 20, and the third direction Z is the arrangement direction of the positive electrode tabs 30 and the negative electrode tabs 40. Although the first direction X, the second direction Y, and the third direction Z are indicated in the drawings as specific vector directions, it should be understood that the opposite directions of the indicated directions can also be used to indicate the first direction X, the second direction Y, and the third direction Z.

[0051] Among them, such as Figure 2 As shown, the negative electrode tab 21 includes a first edge 21A and a second edge 21B arranged opposite each other along a first direction X. The positive electrode tab 22 includes a third edge 22A and a fourth edge 22B arranged opposite each other along the first direction X. The separator 23 includes a fifth edge 23A and a sixth edge 23B arranged opposite each other along the first direction X. The first edge 21A, the third edge 22A, and the fifth edge 23A are located at the first end 20A, and the second edge 21B, the fourth edge 22B, and the sixth edge 23B are located at the second end 20B. To reduce the risk of lithium plating of the negative electrode tab 21, the negative electrode tab 21 is arranged to extend beyond the third edge 22A along the first direction X, such that the first edge 21A is located outside the third edge 22A in the first direction X. Furthermore, the negative electrode tab 21 can also be arranged to extend beyond the fourth edge 22B in the first direction X, such that the second edge 21B is located outside the fourth edge 22B in the first direction X. In some embodiments, to reduce the risk of a short circuit between the positive electrode tab 22 and the negative electrode tab 21 due to shrinkage of the separator 23, the separator 23 may be arranged to extend beyond the first edge 21A along the first direction X, such that the fifth edge 23A extends beyond the first edge 21A in the first direction X. The separator 23 may also be arranged to extend beyond the second edge 21B along the first direction X, such that the sixth edge 23B is located outside the second edge 21B in the first direction X. In the embodiment of the present application, the first end 20A refers to an area within 10 mm of the fifth edge 23A of the separator 23 in the first direction X, and the second end 20B refers to an area within 10 mm of the sixth edge 23B of the separator 23 in the first direction X. Of course, the above distance ranges may be appropriately adjusted according to actual needs.

[0052] like Figure 2 and Figure 3 As shown, the negative electrode sheet 21 includes a first negative electrode sheet layer P1, which is provided with a negative electrode active material layer. The first negative electrode sheet layer P1 is the outermost layer in the multi-layer structure formed by the negative electrode sheet 21 in the second direction Y. For example, when the electrode assembly has a wound structure, the negative electrode sheet 21 includes a negative electrode winding end 213, and the first negative electrode sheet layer P1 is the negative electrode winding end 213.

[0053] The secondary battery 100 further comprises a first adhesive 50. At least part of the first adhesive 50 is located at the first end portion 20A and is provided on the first negative electrode tab layer P1. For example, when the electrode assembly 20 is in a jelly-roll structure, at least part of the first adhesive 50 is located at the negative electrode winding tail coil 213. In combination with the description of Figure 4 The first adhesive 50 comprises a first adhesive layer 51, a first porous substrate layer 53, and a second adhesive layer 52 which are stacked. The first adhesive layer 51 adheres the negative active material layer of the first negative electrode tab layer P1, and the second adhesive layer 52 adheres the separator 23. Moreover, the first negative electrode tab layer P1 is provided with the positive electrode tab 22 on the side facing the first adhesive 50 in the second direction Y. At least part of the first adhesive 50 is provided between the first edge 21A and the third edge 22A in the first direction X as viewed in the second direction Y. That is, at least part of the first adhesive 50 adheres the first negative electrode tab layer P1 located outside the third edge 22A (i.e., beyond the third edge 22A), thereby fixing this part of the first negative electrode tab layer P1 to the separator 23 and improving the interfacial adhesion.

[0054] The first adhesive layer 51 and the second adhesive layer 52 each comprise a binder and inorganic ceramic particles. The binder adheres and fixes the inorganic ceramic particles. Moreover, the inorganic ceramic particles facilitate the creation of more pores in the first adhesive layer 51 and the second adhesive layer 52, thereby facilitating the passage of active ions through the first adhesive layer 51 or the second adhesive layer 52, in combination with the provision of the first porous substrate layer 53, and improving the blockage of active ions due to the provision of the first adhesive 50.

[0055] In some embodiments, the binder in the first adhesive layer 51 and the second adhesive layer 52 is independently selected from at least one of polyolefin, polyacrylate, and polyacrylic acid, such that the binder has better adhesion to adhere the inorganic ceramic particles. The inorganic ceramic particles in the first adhesive layer 51 and the second adhesive layer 52 are independently selected from at least one of boehmite, aluminum trioxide, titanium dioxide, magnesium oxide, zirconium oxide, and zinc oxide, such that the inorganic ceramic particles have higher electrochemical compatibility. The first porous substrate layer 53 is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex, and aramid, and the first porous substrate layer 53 can be formed into a porous structure using a forming process similar to that of the separator 23, such as a melt spinning process.

[0056] In some embodiments, the porosity of the first porous substrate layer 53 is 20% to 60%, thereby further facilitating the passage of active ions through the first adhesive 50 and improving the blocking of active ions due to the provision of the first adhesive 50. The testing procedure for the porosity of the first porous substrate layer 53 can include: removing the first adhesive 50, immersing the first adhesive 50 in a toluene solvent at an environment of 45°C for 10 hours, repeating twice, and obtaining the first porous substrate layer 51. (2) Calculating the porosity φ of the first porous substrate layer 53 = [1 - m / (s*h*ρ)]*100%, where m is the mass of the first porous substrate layer 53, s is the area of the first porous substrate layer 53, h is the thickness of the first porous substrate layer 51, and p is the true density of the first porous substrate layer 53.

[0057] In some embodiments, the mass percentage of the inorganic ceramic particles in the first adhesive layer 51 or the second adhesive layer 52 is 40% to 60%. Thus, on the one hand, it is beneficial to create more pores in the first adhesive layer 51 or the second adhesive layer 52, thereby facilitating the passage of active ions through the first adhesive layer 51 or the second adhesive layer 52. On the other hand, it can also reduce the risk of reducing the adhesion of the first adhesive 50 when the mass percentage of the inorganic ceramic particles is high. In the embodiments of the present application, the testing procedure for the mass percentage of the inorganic ceramic particles can include: removing the first adhesive 50 from the secondary battery 100, cleaning with a suitable solvent (such as N-methyl pyrrolidone, NMP) to remove the electrolyte, immersing the first adhesive 50 in a toluene and ethyl acetate mixed solvent, stirring at 50°C for 20 minutes to dissolve the substrate layer; transferring to water for secondary cleaning to remove residual solvents; drying at 100°C for 2 hours to obtain an adhesive layer sample, and the dried weight is W1; placing the sample in a thermal gravimetric analyzer, heating to 600°C at 10°C / min (ensuring complete decomposition of the polymer), and then weighing the residue as W2. The mass percentage of the inorganic ceramic particles is calculated as follows: R% = [W2 / W1] * 100%.

[0058] Taking into account that the negative electrode sheet 21 extending beyond the third edge 22A has reduced adhesion to the isolation film 23 due to the lack of support from the positive electrode sheet 22, and the first negative electrode sheet layer P1 in the negative electrode sheet 21 is subjected to relatively small restraining force, it is more likely that the adhesion between the first negative electrode sheet layer P1 extending beyond the third edge 22A and the isolation film 23 will be weakened due to the volume expansion of the negative electrode sheet 21 during the cycle. Therefore, in the present application, the first adhesive 50 is arranged on the first negative electrode sheet layer P1, and when viewed from the second direction Y, at least part of the first adhesive 50 is arranged between the first edge 21A and the third edge 22A in the first direction X. Therefore, the first adhesive 50 can fix the negative electrode active material layer of the first negative electrode layer P1 exceeding the third edge 22A to the isolation film 23, thereby better restraining the portion of the first negative electrode layer P1 exceeding the third edge 22A, improving the adhesion between the portion of the first negative electrode layer P1 exceeding the third edge 22A and the isolation film 23, improving the contact interface, and thus reducing the risk of lithium plating caused by poor contact interface during the cycle.

[0059] Furthermore, because both the first adhesive layer 51 and the second adhesive layer 52 of the first adhesive member 50 are provided with inorganic ceramic particles, the inorganic ceramic particles facilitate the creation of a large number of pores in the first adhesive layer 51 and the second adhesive layer 52. Combined with the provision of the first porous substrate layer 53, this improves the barrier effect of the first adhesive member 50 on active ions (such as lithium ions). This reduces the risk of lithium plating caused by the inability to properly embed active ions after the first adhesive member 50 is provided in the first negative electrode layer P1 beyond the third edge 22A. Consequently, the secondary battery 100 has high safety performance and a long service life.

[0060] The following description will be made by taking the winding structure of the electrode assembly 20 as an example. Figure 3 As shown, when the electrode assembly 20 has a wound structure, the negative electrode sheet 21 includes a first negative electrode active material layer 211, a negative electrode current collector 210, and a second negative electrode active material layer 212, which are stacked together. The first negative electrode active material layer 211 and the second negative electrode active material layer 212 constitute the negative electrode active material layer. The negative electrode current collector 210 includes a first surface 2101 facing the winding center axis O and a second surface 2102 facing away from the first surface 2101. The first negative electrode active material layer 211 is disposed on the first surface 2101, and the second negative electrode active material layer 212 is disposed on the second surface 2102. The positive electrode sheet 22 includes a first positive electrode active material layer 221, a positive electrode current collector 220, and a second positive electrode active material layer 222, which are stacked together. The positive electrode current collector 220 includes a third surface 2201 facing the winding center axis O and a fourth surface 2202 facing away from the third surface 2201 . The first positive electrode active material layer 221 is disposed on the third surface 2201 , and the second positive electrode active material layer 222 is disposed on the fourth surface 2202 .

[0061] like Figure 3 As shown, the negative electrode sheet 21 includes a negative electrode winding end 213, and the first negative electrode sheet layer P1 is the negative electrode winding end 213. The positive electrode sheet 22 includes a positive electrode winding end 223, which is the outermost electrode sheet of the electrode assembly 20. The positive electrode winding end 223 and the negative electrode winding end 213 may be two adjacent electrode sheets in the electrode assembly 20. The negative electrode winding end 213 may include a first negative electrode winding arc 2131, a first negative electrode winding layer 2132, a second negative electrode winding arc 2133, and a second negative electrode winding layer 2134, which are sequentially connected along the winding direction D of the electrode assembly 20. The end end 2110 of the first negative electrode active material layer 211 and the end end 2120 of the second negative electrode active material layer 212 are both located on the second negative electrode winding layer 2134. In some embodiments, the first negative electrode winding layer 2132 and the second negative electrode winding layer 2134 may be straight segments, and the first negative electrode winding arc 2131 and the second negative electrode winding arc 2133 may be curved segments. In other embodiments, the first negative electrode winding arc 2131, the first negative electrode winding layer 2132, the second negative electrode winding arc 2133, and the second negative electrode winding layer 2134 may all be curved segments.

[0062] The straight section and the curved section can be defined in a manner known in the art. For example, the straight section can be a portion that is nearly straight in the winding direction D, and the curved section includes an arcuate curved section, and the curved section is an arcuate curved section along the winding direction D. In the embodiment of the present application, the curved section located at the innermost and left side of the electrode assembly 20 is extended in the second direction Y to form a dotted line AA, and the curved section located at the innermost and right side of the electrode assembly 20 is extended in the second direction Y to form a dotted line BB. The dotted lines AA and BB can serve as the boundaries between the straight section and the curved section. The winding direction D is Figure 3 The direction of rotation shown is counterclockwise around the winding center axis O, but the winding direction D can also be clockwise.

[0063] In the embodiment of the present application, the negative electrode winding last circle 213 of the negative electrode plate 21 refers to a circle structure located on the outermost side relative to the winding center axis O of the electrode assembly 20 in the multi-layer structure formed by winding the negative electrode plate 21 along the winding direction D. The meanings of other negative electrode winding circles are analogous. The outermost circle plate of the electrode assembly 20 refers to a circle structure located on the outermost side relative to the winding center axis O of the electrode assembly 20 in the multi-layer structure formed by winding the positive electrode plate 22, the isolation film 23 and the negative electrode plate 21 along the winding direction D. One circle refers to starting from a certain point on the negative electrode plate 21 or the positive electrode plate 22 as the starting end, and reaching another point along the winding direction D as the ending end. The ending end is on a straight line with the starting end and the center of this circle, and the starting end is between the ending end and the center of this circle.

[0064] The positive electrode current collector 220 can be made of an aluminum foil or a nickel foil, and the negative electrode current collector 210 can be made of at least one of a copper foil, a nickel foil, or a carbon-based current collector.

[0065] The first positive electrode active material layer 221 and the second positive electrode active material layer 222 include a positive electrode active material, which includes a compound that reversibly intercalates and deintercalates metal ions (e.g., lithium ions, sodium ions, etc., hereinafter lithium ions are taken as an example). In some embodiments, the positive electrode active material can include a lithium transition metal composite oxide. The 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 at least one of lithium cobaltate (LiCoO2), lithium nickel cobalt manganese ternary material (NCM), lithium nickel cobalt aluminum ternary material (NCA), lithium manganate (LiMn2O4), lithium nickel manganate (LiNi 0.5 Mn 1.5 O4), or lithium iron phosphate (LiFePO4).

[0066] The first negative electrode active material layer 211 and the second negative electrode active material layer 212 include a negative electrode active material, which is capable of reversibly deintercalating active ions known in the art, and the present application is not limited. For example, it can include but is not limited to one or more combinations of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based material, tin-based material, lithium titanate, or other metals capable of forming alloys with lithium, etc. Among them, the graphite can be selected from one or more combinations of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more combinations of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon alloys; the tin-based material can be selected from one or more combinations of elemental tin, tin oxide compounds, tin alloys, etc.

[0067] The separator 23 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.

[0068] In view of the fact that when the electrode assembly 20 is in a wound structure, the side of the negative electrode winding end 213 facing the positive electrode winding end 223 is subjected to a relatively small binding force (the side is provided with fewer layers of the positive electrode tab 22), it is easier for the negative electrode winding end 213 to extend in the winding direction D under the action of volume expansion and cause the adhesion between the negative electrode winding end 213 and the separator 23 to weaken, so the first adhesive 50 can be arranged on the side of the negative electrode winding end 213 facing the positive electrode winding end 223, and the first adhesive 50 adheres to the second negative electrode active material layer 212. In this way, the negative electrode winding end 213 beyond the third edge 22A can be fixed to the separator 23, so as to better bind the negative electrode winding end 213 beyond the third edge 22A, improve the adhesion between the negative electrode winding end 213 beyond the third edge 22A and the separator 23, improve the contact interface, and further reduce the risk of lithium precipitation due to poor contact interface during the cycle.

[0069] In some embodiments, the first negative electrode tab layer P1 is a secondary outer tab or a secondary secondary outer tab of the electrode assembly 20. For example, when the positive electrode winding end 223 and the negative electrode winding end 213 are two adjacent tab layers in the electrode assembly 20, the first negative electrode tab layer P1 is a secondary outer tab of the electrode assembly 20. When there are two or fewer positive electrode tabs 22 on the outer side of the first negative electrode tab layer P1, the first negative electrode tab layer P1 is subjected to a relatively small binding force, and at this time, arranging the first adhesive 50 is beneficial to strengthening the adhesion between the negative electrode active material layer of the first negative electrode tab layer P1 and the separator 23, improving the contact interface, and reducing the risk of lithium precipitation due to poor contact interface during the cycle.

[0070] In some embodiments, the positive electrode winding end 223 comprises a first positive electrode winding layer 2231 located on the side of the second negative electrode winding layer 2134 away from the winding center axis O, and the first positive electrode winding layer 2231 can be arranged opposite to the second negative electrode winding layer 2134 through the separator 23. The end 2210 of the first positive electrode active material layer 221 is located in the first positive electrode winding layer 2231. In some embodiments, when the second negative electrode winding layer 2134 is a flat section, the first positive electrode winding layer 2231 is also a flat section. In some embodiments, in the positive electrode winding end 223, the third surface 2201 of the positive electrode current collector 220 is provided with the first positive electrode active material layer 221, and the fourth surface 2202 of the positive electrode current collector 220 is not provided with the second positive electrode active material layer 222, i.e., the positive electrode winding end 223 is a single-sided coating area. This can improve the energy density of the secondary battery 100 and improve the situation that when the fourth surface 2202 of the positive electrode current collector 220 is provided with a positive electrode active material, the positive electrode active material is easily detached after contacting the shell 10, and the positive electrode current collector 220 can increase the hardness of the electrode assembly 20 when the positive electrode winding end 223 is the outermost pole piece, thereby protecting the electrode assembly 20 and improving the mechanical impact resistance of the electrode assembly 20.

[0071] Considering that the second negative electrode winding layer 2134 of the negative electrode winding end 213 is located at the tail of the negative electrode winding end 213 along the winding direction D, it is more likely to be extended along the winding direction D under the action of volume expansion and cause the adhesion between the second negative electrode winding layer 2134 located outside the third edge 22A and the separator 23 to weaken, therefore, the first adhesive 50 can be preferentially arranged on the side of the second negative electrode winding layer 2134 facing the first positive electrode winding layer 2231, and the first adhesive 50 adheres the second negative electrode active material layer 212 of the second negative electrode winding layer 2134 through the first adhesive layer 51. In this way, the second negative electrode winding layer 2134 beyond the third edge 22A can be fixed to the separator 23, thereby better restraining the part of the second negative electrode winding layer 2134 beyond the third edge 22A, improving the adhesion between the part of the second negative electrode winding layer 2134 beyond the third edge 22A and the separator 23, improving the contact interface, and thereby further reducing the risk of lithium precipitation due to poor contact interface during the cycle process.

[0072] As Figure 5 and Figure 6As shown, in some embodiments, the first adhesive 50 can be arranged on the second negative winding arc 2133, and can also be arranged on the first negative winding layer 2132. In this way, the second negative winding arc 2133 and the first negative winding layer 2132 beyond the third edge 22A can be fixed to the separator 23, so as to better bind the second negative winding arc 2133 and the first negative winding layer 2132 beyond the third edge 22A, improve the adhesion between the second negative winding arc 2133 and the first negative winding layer 2132 beyond the third edge 22A and the separator 23, and improve the contact interface, thereby further reducing the risk of lithium precipitation due to poor contact interface during the cycle process.

[0073] In some embodiments, the first adhesive 50 can be arranged separately along the winding direction D. For example, as shown in FIG. 6, the first adhesive 50 arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 is arranged separately along the winding direction D. Thus, the first adhesive 50 can be arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 in a staggered manner along the winding direction D. Figure 6 As shown, the first adhesive 50 arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 is arranged separately along the winding direction D, so that the first adhesive 50 does not overlap the tab when viewed from the second direction Y. Thus, the influence of the first adhesive 50 on the thickness of the electrode assembly 20 can be reduced, thereby improving the energy density of the secondary battery 100. For example, in some embodiments, the negative tab 30 is closer to the second negative winding layer 2134 than the positive tab 40 in the third direction Z when viewed from the second direction Y. The first adhesive 50 arranged between the first negative winding layer 2132 and the second negative winding arc 2133 has a gap, and the first adhesive 50 arranged between the second negative winding layer 2134 and the second negative winding arc 2133 also has a gap. The two gaps described above can overlap the negative tab 30 when viewed from the second direction Y, so that the first adhesive 50 does not overlap the negative tab 30. Further, the first adhesive 50 arranged on the first negative winding layer 2132 and the second negative winding layer 2134 does not overlap the positive tab 40 when viewed from the second direction Y.

[0074] As shown in FIG. 6, in some embodiments, the first adhesive 50 can be arranged separately along the winding direction D. For example, the first adhesive 50 arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 is arranged separately along the winding direction D. Thus, the first adhesive 50 can be arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 in a staggered manner along the winding direction D. Figure 7 As shown in FIG. 6, in some embodiments, the first adhesive 50 can be arranged separately along the winding direction D. For example, the first adhesive 50 arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 is arranged separately along the winding direction D. Thus, the first adhesive 50 can be arranged on the first negative winding layer 2132, the second negative winding arc 2133, and the second negative winding layer 2134 in a staggered manner along the winding direction D.

[0075] In some embodiments, the first adhesive member 50 is not limited to being positioned at the negative electrode final winding 213. Considering that other areas of the negative electrode sheet 21 adjacent to the negative electrode final winding 213 along the winding direction D are also subject to less restraining force, it is more likely that during cycling, the negative electrode sheet 21 will expand in volume, thereby extending along the winding direction D and weakening the adhesion between the negative electrode sheet 21 beyond the third edge 22A and the separator 23, the first adhesive member 50 may be positioned along the winding direction D, with the starting end 500 of the first adhesive member 50 adhering to the Nth negative electrode winding turn of the negative electrode sheet 21 and the trailing end 501 of the first adhesive member 50 adhering to the last negative electrode winding 213, with the difference between the number of turns of the last negative electrode winding 213 and the Nth negative electrode winding turn being less than or equal to 3. Therefore, the first adhesive member 50 can further improve the contact interface, thereby further reducing the risk of lithium plating caused by a poor contact interface during cycling. The starting end 500 and the trailing end 501 of the first adhesive member 50 are arranged opposite to each other along the winding direction D. When the first adhesive member 50 is arranged integrally along the winding direction D, the starting end 500 of the first adhesive member 50 is the end of the first adhesive member 50 closest to the winding center axis O along the winding direction D, and the first adhesive member 50 extends integrally from the starting end 500 to the trailing end 501. When the first adhesive member 50 is arranged separately along the winding direction D, the starting end 500 of the first adhesive member 50 is the starting end 500 of the first adhesive member 50 closest to the winding center axis O along the winding direction D, and the trailing end 501 of the first adhesive member 50 is the trailing end 501 of the first adhesive member 50 farthest from the winding center axis O along the winding direction D.

[0076] like Figure 7 As shown, in some embodiments, along the winding direction D, the tail end 501 of the first adhesive 50 extends beyond the tail end 2210 of the first positive active material layer 221. For example, along the third direction Z, the tail end 501 of the first adhesive 50 may be located between the tail end 2210 of the first positive active material layer 221 and the tail end 2120 of the second negative active material layer 212. The tail end 501 of the first adhesive 50 may also be substantially flush with the tail end 2120 of the second negative active material layer 212. Therefore, when active ions are released from the third edge 22A near the tail end 2210 of the first positive active material layer 221 during cycling, the region of the negative electrode sheet 21 beyond the third edge 22A, where these active ions are embedded, can be fixed to the separator 23 via the first adhesive 50, improving the contact interface and further reducing the risk of lithium plating caused by poor contact interface during cycling. It is understood that when the tail end 501 of the first adhesive member 50 exceeds the tail end 2210 of the first positive electrode active material layer 221, it is not limited to the tail end 2210 of the first positive electrode active material layer 221. Figure 7 The first adhesive member 50 is shown as being integrally arranged along the winding direction D. For example, based on the Figure 6In the case where the first adhesive member 50 is arranged separately along the winding direction D, the tail end 501 of the first adhesive member 50 can also be arranged to extend beyond the tail end 2210 of the first positive active material layer 221 .

[0077] like Figure 2 As shown, in some embodiments, the first adhesive member 50 includes a first side 50A and a second side 50B arranged opposite each other along a first direction X. The second side 50B and the first side 50A are arranged sequentially along the first direction X, with the second side 50B being closer to the second end 20B of the electrode assembly 20 than the first side 50A in the first direction X. The first side 50A does not extend beyond the first edge 21A of the negative electrode tab 21 in the first direction X. That is, when viewed from the second direction Y, the first side 50A overlaps the negative electrode tab 21. The spacing L1 between the first side 50A and the first edge 21A along the first direction X is less than or equal to 0.5 mm. Therefore, the bonding area between the first adhesive member 50, the negative electrode tab 21, and the separator 23 is further increased, thereby further restraining the negative electrode tab 21 extending beyond the third edge 22A, improving the bonding strength between the negative electrode tab 21 extending beyond the third edge 22A and the separator 23, and improving the contact interface, thereby further reducing the risk of lithium plating caused by poor contact interface during cycling.

[0078] In addition, the spacing L2 between the second side 50B and the first edge 21A along the first direction X can be set to be less than or equal to 10 mm. This facilitates the first adhesive 50 to fully cover the negative electrode tab 21 beyond the third edge 22A, while also reducing the impact of the first adhesive 50 on the thickness of the electrode assembly 20. Furthermore, the risk of the first adhesive 50 reducing the active ion transmission rate when covering a large area of ​​the negative electrode tab 21 can be reduced. In some embodiments, the third edge 22A is located between the second side 50B and the first side 50A along the first direction X.

[0079] like Figure 2 As shown, in some embodiments, at least a portion of the first adhesive 50 may also be located at the second end portion 20B and bonded to the second negative electrode winding layer 2134. When viewed from the second direction Y, at least a portion of the first adhesive 50 is located between the second edge 21B and the fourth edge 22B in the first direction X. That is, at least a portion of the first adhesive 50 bonds to the portion of the negative electrode tab 21 in the second negative electrode winding layer 2134 that extends beyond the fourth edge 22B, thereby securing the portion of the negative electrode tab 21 to the separator 23. This further constrains the portion of the negative electrode tab 21 that extends beyond the fourth edge 22B, improves the bonding strength between the portion of the negative electrode tab 21 that extends beyond the fourth edge 22B and the separator 23, and improves the contact interface, thereby further reducing the risk of lithium plating caused by poor contact interface during cycling.

[0080] The first adhesive 50 at the first end 20A is separated from the first adhesive 50 at the second end 20B in the first direction X. Therefore, the effect of the first adhesive 50 on the thickness of the electrode assembly 20 can be reduced, and the risk of reducing the active ion transmission rate when the first adhesive 50 covers a large area of ​​the negative electrode sheet 21 can also be reduced.

[0081] like Figure 8 As shown, in some embodiments, the negative electrode sheet 21 further includes a first negative electrode winding 214 and a second negative electrode winding 215, which are sequentially connected along a winding direction D. The starting end 2121 of the second negative electrode active material layer 212 is located at the first negative electrode winding 214, and the starting end 2111 of the first negative electrode active material layer 211 is located at the second negative electrode winding 215. Therefore, in the first negative electrode winding 214, the first negative electrode active material layer 211 is not provided on the first surface 2101 of the negative current collector 210. The second negative electrode winding 215 includes a third negative electrode winding layer 2151 and a third negative electrode winding loop 2152, which are connected along the winding direction D. The second negative electrode winding layer 2134 is located on a side of the third negative electrode winding layer 2151 that is away from the winding center axis O. The third negative electrode winding layer 2151 is located between the first negative electrode winding layer 2132 and the second negative electrode winding layer 2134 in the second direction Y. The first negative electrode winding arc 2131 is located on a side of the third negative electrode winding arc 2152 that faces away from the winding center axis O. The third negative electrode winding arc 2152 is located between the first negative electrode winding arc 2131 and the second negative electrode winding arc 2133 in the second direction Y. The starting end 2111 of the first negative electrode active material layer 211 is specifically located on the third negative electrode winding layer 2151. In some embodiments, when the first negative electrode winding layer 2132 and the second negative electrode winding layer 2134 are straight segments, the third negative electrode winding layer 2151 is also a straight segment.

[0082] The secondary battery 100 further includes a second adhesive 60. At least a portion of the second adhesive 60 is located at the first end 20A and is disposed on the side of the third negative electrode winding layer 2151 facing the winding center axis O. Figure 9 The second adhesive member 60 includes a stacked third adhesive layer 61, a second porous substrate layer 62, and a fourth adhesive layer 63. The third adhesive layer 61 is bonded to the first negative electrode active material layer 211, and the fourth adhesive layer 63 is bonded to the separator 23. Figure 2 As shown in FIG. 1 , when viewed from the second direction Y, the first adhesive 50 and the second adhesive 60 overlap, and the second adhesive 60 is blocked by the first adhesive 50. Figure 2As shown, at least part of the second adhesive member 60 is arranged between the first edge 21A and the third edge 22A in the first direction X as viewed from the second direction Y. That is, at least part of the second adhesive member 60 adheres the negative tab 21 of the third negative winding layer 2151 beyond the first edge 21A, thereby fixing the part of the negative tab 21 to the separator 23, and further improving the interfacial adhesion.

[0083] The third adhesive layer 61 and the fourth adhesive layer 62 each include a binder and inorganic ceramic particles. The binder adheres and fixes the inorganic ceramic particles. Moreover, the arrangement of the inorganic ceramic particles facilitates the creation of more pores in the third adhesive layer 61 and the fourth adhesive layer 62, thereby facilitating the passage of active ions through the third adhesive layer 61 or the fourth adhesive layer 62, in combination with the arrangement of the second porous substrate layer 63, to improve the blocking of active ions due to the arrangement of the second adhesive member 60. The second adhesive member 60 can have the same or similar material as the first adhesive member 50, for example, the specific material of the third adhesive layer 61 or the fourth adhesive layer 62 can be arranged in reference to the specific material of the first adhesive layer 51 or the second adhesive layer 52, and the specific material of the second porous substrate layer 63 can be arranged in reference to the specific material of the first porous substrate layer 53.

[0084] Considering that the third negative winding layer 2151 of the negative winding sub-coil 215 of the negative tab 21 (especially the side of the third negative winding layer 2151 facing the winding center axis O) is also less constrained and is more likely to expand in the volume during the cycle and then extend along the winding direction D, causing the adhesion between the negative tab 21 beyond the third edge 22A and the separator 23 to weaken, and considering that the starting end 2111 of the first negative active material layer 211 is specifically located at the third negative winding layer 2151, that is, the junction position of the single-coated area and the double-coated area of the negative tab 21 is located at the third negative winding layer 2151, causing the volume expansion at the third negative winding layer 2151 to be larger, therefore in this embodiment, the second adhesive member 60 is arranged on the side of the third negative winding layer 2151 of the negative winding sub-coil 215 facing the winding center axis O, and at least part of the second adhesive member 60 is arranged between the first edge 21A and the third edge 22A in the first direction X as viewed from the second direction Y. Therefore, the second adhesive member 60 can fix the third negative winding layer 2151 beyond the third edge 22A to the separator 23, thereby better constraining the part of the third negative winding layer 2151 beyond the third edge 22A, improving the adhesion between the part of the third negative winding layer 2151 beyond the third edge 22A and the separator 23, and improving the contact interface, thereby further reducing the risk of lithium precipitation during the cycle due to poor contact interface.

[0085] Furthermore, at least a portion of the second adhesive 60 may be located at the second end 20B and disposed on the side of the third negative electrode winding layer 2151 facing the winding center axis O. When viewed from the second direction Y, at least a portion of the second adhesive 60 is disposed between the second edge 21B and the fourth edge 22B in the first direction X. That is, at least a portion of the second adhesive 60 adheres to the portion of the negative electrode tab 21 in the third negative electrode winding layer 2151 that extends beyond the fourth edge 22B, thereby securing this portion of the negative electrode tab 21 to the separator 23. This further constrains the portion of the negative electrode tab 21 that extends beyond the fourth edge 22B, improves the adhesion between this portion of the negative electrode tab 21 that extends beyond the fourth edge 22B and the separator 23, and improves the contact interface, thereby further reducing the risk of lithium plating caused by poor contact interface during cycling.

[0086] like Figure 8 As shown, in some embodiments, the second adhesive 60 is also located on the third negative electrode winding arc 2152. This allows the portion of the third negative electrode winding arc 2152 that extends beyond the third edge 22A to be fixed to the separator 23, thereby better restraining the portion of the third negative electrode winding arc 2152 that extends beyond the third edge 22A, improving the adhesion between the portion of the third negative electrode winding arc 2152 that extends beyond the third edge 22A and the separator 23, and improving the contact interface, thereby further reducing the risk of lithium deposition caused by poor contact interface during cycling. The second adhesive 60 provided on the third negative electrode winding layer 2151 and the third negative electrode winding arc 2152 can be separated along the winding direction D or integrally provided along the winding direction D.

[0087] See also Figures 10 to 12 Another embodiment of the present application also provides a secondary battery 200, which is different from the above-mentioned secondary battery 100 in that the electrode assembly 20 is a laminated structure, the outermost electrode sheet of the electrode assembly 20 in the second direction Y is the positive electrode sheet 22, and the first negative electrode sheet layer P1 is the second outermost electrode sheet of the electrode assembly 20 in the second direction Y.

[0088] For the laminated electrode assembly 20, considering that the negative electrode sheet 21 adjacent to the outermost positive electrode sheet 22 in the second direction Y, i.e., the first negative electrode sheet layer P1 (particularly the side of the first negative electrode sheet layer P1 facing the outermost positive electrode sheet 22), is subject to relatively small restraining force, the first adhesive member 50 is disposed on the side of the first negative electrode sheet layer P1 facing the outermost positive electrode sheet 22. When viewed from the second direction Y, at least a portion of the first adhesive member 50 is disposed between the first edge 21A and the third edge 22A in the first direction X.

[0089] Therefore, the first adhesive 50 can fix the first negative electrode layer P1 that exceeds the third edge 22A to the isolation film 23, thereby better restraining the portion of the first negative electrode layer P1 that exceeds the third edge 22A, improving the adhesion between the portion of the first negative electrode layer P1 that exceeds the third edge 22A and the isolation film 23, and improving the contact interface, thereby reducing the risk of lithium plating caused by poor contact interface during the cycle.

[0090] like Figure 11 As shown, in some embodiments, the electrode assembly 20 further includes a third end 20C and a fourth end 20D disposed opposite each other along a third direction Y. The negative electrode tab 21 includes a seventh edge 21C and an eighth edge 21D disposed opposite each other along a third direction Z. The positive electrode tab 22 includes a ninth edge 22C and a tenth edge 22D disposed opposite each other along a third direction Z. The seventh edge 21C and the ninth edge 22C are located at the third end 20C, and the eighth edge 21D and the tenth edge 22D are located at the fourth end 20D. To further reduce the risk of lithium plating of the negative electrode tab 21, the negative electrode tab 21 can be arranged to extend beyond the ninth edge 22C along the first direction X, such that the seventh edge 21C is located outside the ninth edge 22C in the third direction Z. Furthermore, the negative electrode tab 21 can also be arranged to extend beyond the tenth edge 22D in the third direction Z, such that the seventh edge 21C is located outside the tenth edge 22D in the third direction Z.

[0091] At this time, the position of the first adhesive 50 can also be changed. Observed from the second direction Y, at least a portion of the first adhesive 50 can also be provided between the seventh edge 21C and the ninth edge 22C in the third direction Z. Therefore, the first adhesive 50 can fix the first negative electrode layer P1 that exceeds the ninth edge 22C to the isolation film 23, thereby better restraining the portion of the first negative electrode layer P1 that exceeds the ninth edge 22C, improving the adhesion between the portion of the first negative electrode layer P1 that exceeds the ninth edge 22C and the isolation film 23, improving the contact interface, and thus reducing the risk of lithium plating due to poor contact interface during the cycle. Furthermore, at least a portion of the first adhesive 50 can also be provided between the eighth edge 21D and the tenth edge 22D in the third direction Z.

[0092] The secondary batteries 100 and 200 of the present application may be lithium secondary batteries, including lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries or lithium ion polymer secondary batteries.

[0093] See also Figure 13The electronic device 1 of the present application can be, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copying machine, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable C machine, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, an illuminating appliance, a toy, a game machine, a timepiece, an electric tool, a flash, a camera, a household large storage battery, a lithium ion capacitor, and the like.

[0094] The present application is described in detail below by way of specific examples and comparative examples. The present application is described by way of example of a lithium ion soft package secondary battery and in combination with a specific preparation process and test method. It should be understood by those skilled in the art that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

[0095] Example 1 (1) Preparation of the positive electrode tab: 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, and N-methyl pyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the slurry was stirred uniformly. A portion of the surface of the positive electrode current collector, i.e., an aluminum foil, was previously pasted with foam tape, the slurry was uniformly coated on one surface of the aluminum foil, and the aluminum foil was heated to allow the foam tape to fall off to expose a portion of the surface of the aluminum foil, and then the aluminum foil was dried at 90°C, and the above coating step was repeated on the other surface of the aluminum foil to obtain a double-sided coated positive electrode tab. The initial positive electrode tab was cold-pressed to obtain a single positive electrode active material layer with a thickness of 77 μm, and then the positive electrode tab was cut and processed to obtain a positive electrode tab. Then, the positive electrode tab was welded on the exposed aluminum foil, and the positive electrode tab was made of aluminum.

[0096] (2) Preparation of the negative electrode sheet: the negative electrode active material artificial graphite, silicon-carbon material, conductive carbon black (Super P), polyacrylic acid binder (PAA), lithium difluorophosphate (LDFP) were mixed according to the weight ratio of 69:5:6:19:1, deionized water was added as a solvent, and a slurry with a weight percentage of 55 wt% was prepared and stirred uniformly. The foam tape was previously attached to part of the surface of the negative current collector, i.e. copper foil, with a thickness of 5 μm, the slurry was uniformly coated on one surface of the copper foil, heated to make the foam tape fall off to expose part of the surface of the copper foil, and then dried at 90°C, and the above coating step was repeated on the other surface of the copper foil to obtain a double-sided coated negative electrode sheet. The initial negative electrode sheet was rolled to obtain a negative electrode active material layer with a coating thickness of 70 μm. Then, the negative electrode tab was welded on the exposed copper foil, and the material of the negative electrode tab was nickel. Then, referring to Figure 2 and Figure 3 , a first adhesive member was arranged at the position of the negative electrode sheet corresponding to the third negative electrode winding layer, wherein the material of the first porous substrate layer was polypropylene, the material of the binder in the first adhesive layer and the second adhesive layer was polyacrylate, and the material of the inorganic ceramic particles was aluminum oxide.

[0097] (3) Preparation of the electrolyte: in a dry argon atmosphere, first, the organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a mass ratio of EC: EMC: DEC = 30:50:20, then lithium salt lithium hexafluorophosphate (LiPF6) was added to the organic solvent to dissolve and mix uniformly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0098] (4) Preparation of the separator film: a polyethylene (PE) film with a thickness of 9 μm was selected.

[0099] (5) Preparation of the secondary battery: the positive electrode sheet, the separator film and the negative electrode sheet were sequentially stacked and wound to obtain an electrode assembly, the punched aluminum plastic film (thickness of 150 μm) was placed in the assembly fixture with the pit surface facing up, the electrolyte was injected into the pit of the aluminum plastic film, and the positive electrode tab and the negative electrode tab were led out of the aluminum plastic film for packaging to obtain a secondary battery. The parameters of the secondary battery are recorded in Table 1.

[0100] Examples 2 to 3 The difference from Example 1 is that the value of L1 is different.

[0101] Examples 4 to 8 The difference from Example 1 is that the porosity of the first porous substrate layer is different, wherein the first porous substrate layer is a commercially available product, and the change in porosity is realized by adjusting the process production parameters such as the stretching ratio, the heat setting temperature, etc.

[0102] Example 9 The difference from Example 1 is that the secondary battery is of a stacked structure, and the setting position of the first adhesive is different from the preparation steps of the electrode assembly. The positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked to obtain an electrode assembly, and the first negative electrode sheet layer is the next outermost layer of the electrode sheet. The first adhesive is arranged on the negative active material layer of the first negative electrode sheet layer facing the outermost positive electrode sheet. The punched aluminum plastic film (thickness of 150 μm) is placed in the assembly jig with the pit facing up. The electrolyte is injected into the pit of the aluminum plastic film, and the positive and negative electrode tabs are led out of the aluminum plastic film for packaging, thereby obtaining a secondary battery.

[0103] Comparative Example 1 The difference from Example 1 is that the first adhesive is not arranged.

[0104] Comparative Example 2 The difference from Example 1 is that the first adhesive is replaced by a double-sided tape, and the material of the substrate layer is polyethylene terephthalate (PET), and the material of the adhesive layer is polyacrylate.

[0105] Comparative Example 3 The difference from Example 9 is that the first adhesive is not arranged.

[0106] Then, the lithium precipitation test is performed on the secondary batteries of each example and comparative example, and the test results are recorded in Table 1.

[0107] The steps of the lithium precipitation test can include: 1) at a test temperature of 25°C, the initial SOC of the secondary battery is adjusted to 50%, according to GB / T 31485, the secondary battery is charged at 1C constant current to 4.50V, then constant voltage charged to the current less than or equal to 0.05C, and then discharged at 1C constant current to 3.0V, which is one charge-discharge cycle; 2) repeat the above charge-discharge cycle 200 times, then disassemble the secondary battery and take out the negative electrode sheet, observe the lithium precipitation of the negative electrode sheet beyond the third edge in the third negative winding layer of the negative winding end coil, and judge the degree of lithium precipitation by comparing the lithium precipitation area. The degree of lithium precipitation is divided into slight lithium precipitation, medium lithium precipitation and severe lithium precipitation. Slight lithium precipitation is less than 0.5% of the total area of the negative electrode sheet, medium lithium precipitation is 0.5% to 5.0% of the total area of the negative electrode sheet, and severe lithium precipitation is more than 5.0% of the total area of the negative electrode sheet.

[0108] Table 1 From the data in Table 1, compared with Comparative Example 1, Example 1 can fix the part of the negative pole tab beyond the third edge to the separator by setting the first adhesive, thereby better binding the part of the negative pole tab beyond the third edge, improving the contact interface, and thus the risk of lithium precipitation of the part of the negative pole tab beyond the third edge after cycling is lower. Compared with Comparative Example 2, the first adhesive of Example 1 is provided with inorganic ceramic particles, which is conducive to creating more pores in the first adhesive layer and the second adhesive layer, combined with the setting of the first porous substrate layer, so that the part of the negative pole tab beyond the third edge can still normally embed lithium ions, and thus the risk of lithium precipitation of the part of the negative pole tab beyond the third edge after cycling is also lower.

[0109] In Examples 1-2, the distance L1 between the first edge of the first adhesive and the first edge in the first direction is less than or equal to 0.5 mm. Compared with Example 3, Examples 1-2 can further increase the bonding area of the first adhesive with the negative pole tab and the separator, thereby further binding the negative pole tab beyond the third edge, improving the contact interface, and thus the risk of lithium precipitation of the part of the negative pole tab beyond the third edge after cycling is also lower.

[0110] The porosity of the first porous substrate layer in Examples 4-6 is 20% to 60%. Compared with Example 7, the porosity of the first porous substrate layer in Examples 4-6 is larger, which is conducive to the passage of active ions through the first adhesive, and thus the risk of lithium precipitation of the part of the negative pole tab beyond the third edge after cycling is lower. Compared with Example 8, Examples 4-6 improve the risk of poor adhesion when the porosity of the first porous substrate layer is large (which may be due to the large amount of inorganic ceramic particles added and the corresponding decrease in the amount of binder), and thus the risk of the first adhesive falling off during the cycling process is reduced, i.e., the first adhesive can stably bond the negative pole tab and the separator to improve the contact interface, and thus the risk of lithium precipitation of the part of the negative pole tab beyond the third edge after cycling is lower.

[0111] In Example 9, the secondary battery is a stacked structure. The first adhesive can also be applicable to the stacked structure, and compared with Comparative Example 3, the first adhesive of Example 3 can improve the adhesion of the negative active material layer of the first negative pole tab layer to the separator, and thus the risk of lithium precipitation of the part of the negative pole tab is reduced.

[0112] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly comprising a separator and pole pieces, the pole pieces comprising a positive pole piece and a negative pole piece, the separator being disposed between the positive pole piece and the negative pole piece, wherein: The electrode assembly includes a first end and a second end disposed opposite to each other along a first direction; the negative electrode sheet includes a first edge and a second edge disposed opposite to each other along the first direction; the positive electrode sheet includes a third edge and a fourth edge disposed opposite to each other along the first direction, the first edge and the third edge are located at the first end, the second edge and the fourth edge are located at the second end, and the first edge is located outside the third edge in the first direction; The negative electrode sheet includes a first negative electrode sheet layer, the first negative electrode sheet layer is provided with a negative electrode active material layer, and the first negative electrode sheet layer is the outermost layer in a second direction of a multi-layer structure formed by the negative electrode sheet. The secondary battery also includes a first adhesive, at least a portion of the first adhesive is located at the first end and is provided on the first negative electrode sheet layer. The second direction is the thickness direction of the electrode assembly and is perpendicular to the first direction. When viewed from the second direction, at least part of the first adhesive member is disposed between the first edge and the third edge in the first direction; The first adhesive member includes a first adhesive layer, a first porous substrate layer and a second adhesive layer that are stacked together. The first adhesive layer is bonded to the negative electrode active material layer of the first negative electrode sheet, and the second adhesive layer is bonded to the isolation film. The positive electrode sheet is provided on the side of the first negative electrode sheet facing the first adhesive member. The first adhesive layer and the second adhesive layer both include a binder and inorganic ceramic particles.

2. The secondary battery according to claim 1, wherein The electrode assembly is a wound structure, and the secondary battery further includes a tab, which is electrically connected to the electrode assembly and protrudes from the electrode assembly along the first direction; The negative electrode active material layer includes a first negative electrode active material layer and a second negative electrode active material layer. The negative electrode sheet also includes a negative electrode current collector. The negative electrode current collector includes a first surface facing the winding center axis and a second surface facing away from the first surface. The first negative electrode active material layer is provided on the first surface, and the second negative electrode active material layer is provided on the second surface. The positive electrode sheet includes a first positive electrode active material layer, a positive electrode current collector, and a second positive electrode active material layer. The positive electrode current collector includes a third surface facing the winding center axis and a fourth surface facing away from the third surface. The first positive electrode active material layer is provided on the third surface, and the second positive electrode active material layer is provided on the fourth surface. The first negative electrode sheet layer is the negative electrode winding last turn of the negative electrode sheet, the positive electrode sheet includes the positive electrode winding last turn, the positive electrode winding last turn is the outermost electrode sheet of the electrode assembly, the first adhesive is arranged on the side of the negative electrode winding last turn facing the positive electrode winding last turn, and the first adhesive layer is bonded to the second negative electrode active material layer.

3. The secondary battery according to claim 2, wherein The first negative electrode layer is a secondary outer electrode of the electrode assembly, or; The first negative electrode plate layer is the secondary outer ring plate of the electrode assembly.

4. The secondary battery according to claim 2, wherein The negative electrode winding end includes a first negative electrode winding arc, a first negative electrode winding layer, a second negative electrode winding arc, and a second negative electrode winding layer connected in sequence along the winding direction of the electrode assembly, and the tail end of the first negative electrode active material layer and the tail end of the second negative electrode active material layer are both located in the second negative electrode winding layer; The positive electrode winding end includes a first positive electrode winding layer, the first positive electrode winding layer is located on a side of the second negative electrode winding layer away from the winding center axis; the tail end of the first positive electrode active material layer is located on the first positive electrode winding layer; The first adhesive is provided on a side of the second negative electrode winding layer facing the first positive electrode winding layer.

5. The secondary battery according to claim 4, wherein The first adhesive is further provided on the second negative electrode winding arc.

6. The secondary battery according to claim 5, wherein The first adhesive is also provided on the first negative electrode winding layer.

7. The secondary battery according to claim 4, wherein Along the winding direction, the starting end of the first adhesive is bonded to the Nth negative electrode winding circle of the negative electrode sheet, and the ending end of the first adhesive is bonded to the last negative electrode winding circle, and the difference between the number of turns of the last negative electrode winding circle and the Nth negative electrode winding circle is less than or equal to 3.

8. The secondary battery according to any one of claims 3 to 7, wherein The first adhesive member is integrally provided along the winding direction.

9. The secondary battery according to any one of claims 3 to 7, wherein The first adhesive members are spaced apart along the winding direction, and in the second direction, the first adhesive members do not overlap with the tabs.

10. The secondary battery according to claim 4, wherein Along the winding direction, the tail end of the first adhesive member exceeds the tail end of the first positive electrode active material layer.

11. The secondary battery according to claim 4, wherein The second edge is located outside the fourth edge in the first direction, at least a portion of the first adhesive is located at the second end and is provided on a side of the second negative electrode winding layer facing the first positive electrode winding layer, and when viewed from the second direction, at least a portion of the first adhesive is provided between the second edge and the fourth edge in the first direction; The first adhesive component located at the first end portion is separated from the first adhesive component located at the second end portion in the first direction.

12. The secondary battery according to claim 4, wherein The negative electrode sheet further includes a negative electrode first winding circle and a negative electrode second winding circle connected in sequence along the winding direction, and the starting end of the second negative electrode active material layer is located at the negative electrode first winding circle; The negative electrode secondary winding includes a third negative electrode winding layer and a third negative electrode winding arc connected along the winding direction, the second negative electrode winding layer is located on a side of the third negative electrode winding layer away from the winding center axis, the first negative electrode winding arc is located on a side of the third negative electrode winding arc away from the winding center axis, and the starting end of the first negative electrode active material layer is located on the third negative electrode winding layer; The secondary battery also includes a second adhesive, at least a portion of which is located at the first end and is arranged on the side of the third negative electrode winding layer facing the winding center axis, the second adhesive includes a third adhesive layer, a second porous substrate layer and a fourth adhesive layer that are stacked, the third adhesive layer is bonded to the first negative electrode active material layer, and the fourth adhesive layer is bonded to the isolation film, and the third adhesive layer and the fourth adhesive layer both include a binder and inorganic ceramic particles; when viewed from the second direction, at least a portion of the second adhesive is arranged between the first edge and the third edge in the first direction.

13. The secondary battery according to claim 12, wherein The second adhesive is also located on the third negative electrode winding arc.

14. The secondary battery according to claim 1, wherein The electrode assembly is a laminated structure, the outermost electrode sheet of the electrode assembly in the second direction is the positive electrode sheet, the first negative electrode sheet layer is the second outermost electrode sheet of the electrode assembly in the second direction, and the first adhesive is arranged on the side of the first negative electrode sheet layer facing the outermost positive electrode sheet.

15. The secondary battery according to claim 1, wherein The first adhesive includes a first edge and a second edge arranged opposite to each other along the first direction, and the second edge and the first edge are arranged in sequence along the first direction; in the second direction, the first edge overlaps with the negative electrode sheet, and the distance between the first edge and the first edge along the first direction is less than or equal to 0.5 mm.

16. The secondary battery according to claim 15, wherein A distance between the second side and the first edge along the first direction is less than or equal to 10 mm.

17. The secondary battery according to claim 1, wherein The porosity of the first porous substrate layer is 20% to 60%.

18. The secondary battery according to claim 1, wherein The secondary battery satisfies at least one of the following conditions: (1) The material of the first porous substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyamide, spandex and aramid; (2) The material of the adhesive in the first adhesive layer and the second adhesive layer is independently selected from at least one of polyolefin, polyacrylate and polyacrylic acid; (3) The material of the inorganic ceramic particles in the first adhesive layer and the second adhesive layer is independently selected from at least one of boehmite, aluminum oxide, titanium dioxide, magnesium oxide, zirconium oxide, and zinc oxide.

19. An electronic device comprising a battery compartment, wherein: The electronic device further includes a secondary battery according to any one of claims 1 to 17, wherein the secondary battery is disposed in the battery compartment.

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