Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery comprises a housing and an electrode assembly in the housing. The electrode assembly is bent in a first direction, the electrode assembly comprises a plurality of layers of electrode sheets and a plurality of layers of separators, and each layer of separator is disposed between two adjacent layers of electrode sheets. The electrode assembly has a first part and a second part which are sequentially arranged in the first direction, the separators comprise first separators at the first part and second separators at the second part, each first separator comprises a first base material layer and a first bonding layer, and each second separator comprises a second base material layer and a second bonding layer. The peel strength between the first bonding layer and an adjacent electrode sheet is S1, the peel strength between the second bonding layer and an adjacent electrode sheet is S2, it is satisfied that 6 N / m≤S1<S2, so that the rebound of the electrode sheets can be inhibited, the peel strength between the electrode sheet close to the arc-shaped inner side of the electrode assembly and a separator is smaller, so that the risk of blocking of holes of the separator is reduced, thereby reducing the internal resistance, and improving the electrochemical performance of the secondary battery.

Description

Secondary battery and electronic device Technical Field

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

[0002] As the application scenarios of electronic devices become increasingly complex, the types of electronic devices are becoming increasingly diverse to meet usage needs. Nowadays, wearable electronic devices have become popular. In order to fit into the battery compartments of wearable electronic devices, secondary batteries need to be designed with curved or arc-shaped structures.

[0003] The electrode assembly in a secondary battery with a curved or arc-shaped structure is also curved or arc-shaped. However, after the electrode assembly is processed and bent, the active material particles on the electrode sheets in the electrode assembly are squeezed or stretched and the pressure is released, which can easily cause the electrode sheets to deform and rebound, thereby causing the secondary battery to have deformation problems such as curvature reduction and equalization.

[0004] Summary of the Invention

[0005] In view of this, the present application provides a secondary battery and an electronic device, which are conducive to solving the problems of curvature reduction, equalization and deformation of the secondary battery.

[0006] In a first aspect of the present application, a secondary battery is provided, comprising a housing and an electrode assembly. The electrode assembly is housed in the housing, the electrode assembly being bent in a first direction, the electrode assembly comprising a plurality of electrode sheets and a plurality of diaphragms, the diaphragms being arranged between two adjacent electrode sheets. The electrode assembly comprises a first portion and a second portion arranged in sequence along the first direction, the diaphragms comprising a first diaphragm located in the first portion and a second diaphragm located in the second portion, the first diaphragm comprising a first substrate layer and a first adhesive layer arranged on the surface of the first substrate layer, and the second diaphragm comprising a second substrate layer and a second adhesive layer arranged on the surface of the second substrate layer. The first adhesive layer bonds the first substrate layer and the electrode sheets of the first portion, and the peel strength between the first adhesive layer and the adjacent electrode sheets is S1. The second adhesive layer bonds the second substrate layer and the electrode sheets of the second portion, and the peel strength between the second adhesive layer and the adjacent electrode sheets is S2, satisfying 6N / m≤S1<S2.

[0007] In the above embodiment, the peel strength between the diaphragm and the electrode sheet is greater than 6 N / m, which helps suppress electrode sheet rebound and, in turn, suppress deformation after bending of the secondary battery, helping to address deformation issues such as reduced curvature and flattening of the secondary battery. By satisfying S1 < S2, the peel strength between the electrode sheet and the diaphragm in the first portion near the inner side of the electrode assembly arc is reduced, which helps reduce the risk of diaphragm clogging, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery.

[0008] In one or more of the above embodiments, along the first direction, the thickness of the electrode assembly is D, the thickness of the second portion is D1, and D / 2≤D1<D is satisfied.

[0009] In the above embodiment, when the condition D / 2≤D1<D is met, the peel strength between more than half of the electrode sheets and the diaphragm of the electrode assembly in the first direction can be above 6N / m, which is beneficial to further suppress the deformation of the electrode assembly after bending and reduce the risk of the electrode assembly reducing its curvature and becoming flat.

[0010] In one or more of the above embodiments, the thickness of the second portion is D1, satisfying 3D / 4≤D1<D.

[0011] In the above embodiment, when the condition of 3D / 4≤D1<D is met, the thickness of the electrode assembly occupied by the pole piece and the diaphragm with a peel strength of more than 6N / m can be further increased, which is beneficial to further suppress the deformation of the electrode assembly after bending and reduce the risk of the electrode assembly reducing its curvature and becoming flat.

[0012] In one or more of the above embodiments, 1.6S1≤S2≤4S1 is satisfied.

[0013] In the above embodiment, when the condition of 1.6S1≤S2≤4S1 is met, it is beneficial to suppress the deformation of the electrode assembly after bending and to reduce the risk of pore blockage in the diaphragm in the second part, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0014] In one or more of the above embodiments, 6 N / m≤S1<9.6 N / m is satisfied.

[0015] In the above embodiment, when the condition of 6N / m≤S1<9.6N / m is met, it is beneficial to suppress the deformation of the electrode assembly after bending, and to reduce the risk of pore blockage in the diaphragm in the first part, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0016] In one or more of the above embodiments, 9.6 N / m≤S2≤12 N / m is satisfied.

[0017] In the above embodiment, when the condition of 9.6N / m≤S2≤12N / m is met, it is beneficial to suppress the deformation of the electrode assembly after bending, and to reduce the risk of pore blockage in the diaphragm in the second part, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0018] In one or more of the above embodiments, the secondary battery is a laminated battery, and the multiple layers of electrode sheets and the multiple layers of separators are stacked along a first direction.

[0019] In one or more of the above embodiments, a first adhesive is provided in the first adhesive layer, and a second adhesive is provided in the second adhesive layer. The first adhesive and the second adhesive are independently selected from one or a combination of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0020] In one or more of the above embodiments, the first adhesive layer includes polyvinylidene fluoride, and the coating weight of the polyvinylidene fluoride in the first adhesive layer is 3 mg / 5000 mm 2 -4mg / 5000mm 2 The content of polyvinylidene fluoride in the first adhesive layer is 60wt%-80wt%.

[0021] In the above embodiment, the specific configuration of the first adhesive layer enables the peel strength between the first portion of the diaphragm and the electrode sheet to be above 6 N / m, which is beneficial for suppressing deformation of the electrode assembly after bending.

[0022] In one or more of the above embodiments, the second adhesive layer includes acrylate, and the coating weight of the acrylate in the second adhesive layer is 0.7 mg / 5000 mm 2 -1.1mg / 5000mm 2 The content of acrylate in the second adhesive layer is 85wt%-95wt%.

[0023] In the above embodiment, the specific configuration of the second adhesive layer enables the peeling strength between the second portion of the diaphragm and the electrode sheet to be above 10 N / m, which is beneficial for suppressing deformation of the electrode assembly after bending.

[0024] In one or more of the above embodiments, the electrode piece includes an anode electrode piece and a cathode electrode piece, the anode electrode piece separator and the cathode electrode piece are stacked along a first direction, and a plurality of first protrusions are provided on the surface of the anode electrode piece.

[0025] In the above-described embodiment, the first protrusion can disperse the stress of the bent anode electrode sheet, thereby suppressing deformation and rebound of the anode electrode sheet, thereby helping to maintain the bent shape of the anode electrode sheet and addressing deformation issues such as reduction and equalization of the overall curvature of the electrode assembly. When the overall curvature of the electrode assembly remains substantially unchanged, the secondary battery is less likely to experience significant deformation, thereby addressing deformation issues such as reduction and equalization of the secondary battery curvature.

[0026] In one or more of the above embodiments, a plurality of first recesses are provided on a surface of the anode electrode facing away from the plurality of first protrusions, and along the first direction, the orthographic projection of each first protrusion overlaps with the orthographic projection of one first recess.

[0027] In the above embodiment, both the first protrusion and the first recess can disperse the stress of the bent anode electrode, further facilitating the suppression of deformation and rebound of the anode electrode. Furthermore, the orthographic projection of each first protrusion overlaps with the orthographic projection of a first recess, facilitating simultaneous machining of the first protrusions and recesses, thereby improving machining efficiency of the first protrusions and recesses.

[0028] In one or more of the above embodiments, the anode electrode sheet is formed with the first protrusion and the first concave portion through an embossing process.

[0029] In the above embodiment, the embossing process can process the first convex portion and the first concave portion at the same time, thereby facilitating improving the processing efficiency of the first convex portion and the first concave portion.

[0030] In a second aspect of the present application, an electronic device is provided, which includes a secondary battery as described in any of the above embodiments.

[0031] In the above embodiment, the flattening problem of the secondary battery is alleviated, which is beneficial to improving the reliability of the secondary battery, thereby facilitating reduction of the reserved space of the battery compartment in the electronic device and improving the reliability of the electronic device.

[0032] The secondary battery in the present application includes a shell and an electrode assembly. The electrode assembly has a first part and a second part arranged in sequence along a first direction. The peel strength between the adjacent diaphragms and pole pieces in the first part is S1, and the peel strength between the adjacent diaphragms and pole pieces in the second part is S2, satisfying 6N / m≤S1<S2. The peel strength between the diaphragm and the pole piece is above 6N / m, which is beneficial to suppress the rebound of the pole piece, and further beneficial to suppress the deformation of the secondary battery after bending, and is beneficial to solving the deformation problems such as the reduction of the curvature and equalization of the secondary battery. By satisfying S1<S2, the peel strength between the pole piece and the diaphragm close to the inner side of the arc of the electrode assembly is smaller, which is beneficial to reduce the risk of diaphragm blockage, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0034] FIG2 is a cross-sectional view of a secondary battery provided in another embodiment of the present application.

[0035] FIG3 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0036] FIG4 is a cross-sectional view of a cathode electrode piece, an anode electrode piece, and a first diaphragm provided in one embodiment of the present application.

[0037] FIG5 is a cross-sectional view of a cathode electrode piece, an anode electrode piece, and a second diaphragm provided in one embodiment of the present application.

[0038] FIG6 is a cross-sectional view of an anode electrode provided in one embodiment of the present application.

[0039] FIG7 is a cross-sectional view of a cathode electrode provided in an embodiment of the present application.

[0040] FIG8 is a schematic diagram of an unfolded anode electrode provided by an embodiment of the present application.

[0041] FIG9 is a schematic diagram of an unfolded anode electrode provided by another embodiment of the present application.

[0042] FIG10 is a schematic diagram of an unfolded anode electrode provided in another embodiment of the present application.

[0043] FIG11 is a schematic diagram of an unfolded cathode electrode provided in an embodiment of the present application.

[0044] FIG12 is a schematic diagram of an unfolded cathode electrode provided by another embodiment of the present application.

[0045] FIG13 is a schematic diagram of a cathode electrode after unfolding provided in another embodiment of the present application.

[0046] FIG14 is a schematic diagram of an electronic device provided in an embodiment of the present application.

[0047] 1. Description of Main Component Symbols Secondary Battery 100 Housing 10 Electrode Assembly 20 Electrode Plate 21 Anode Plate 211 First Current Collector 2111 First Surface 211a Second Surface 211b First Coating Area 211c First Active Material Layer 2112 First Protrusion 2113 First Recess 2114 First Boundary Line 21a Second Boundary Line 21b Third Boundary Line 21c Fourth Boundary Line 21d Cathode Plate 212 Second Current Collector 2121 Third Surface 212a Fourth Surface 212b Second Coating Area 212c Second Active Material Layer 2122 Second Protrusion 2123 Second Recess 2124 Separator 22 First Separator 221 First Base Layer 2211 First Adhesive Layer 2212 Second Separator 222 Second Base Layer 2221 Second Adhesive Layer 2222 First Section201 Second part 202 Device body 200 Electronic device 1000 First direction X Second direction Y Third direction Z DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0049] It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be an intermediate component. When a component is considered to be "disposed on" another component, it may be directly disposed on the other component or there may be an intermediate component.

[0050] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0051] The terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the technical features indicated.

[0052] The term "perpendicular" is used to describe an ideal position between two components. In actual production or use, two components may be approximately perpendicular to each other. For example, in numerical terms, perpendicularity can refer to the angle between two lines being within 90°±10°, the dihedral angle between two planes being within 90°±10°, or the angle between a line and a plane being within 90°±10°.

[0053] It should be noted that when a parameter is greater than, equal to, or less than a certain endpoint value, it should be understood that the endpoint value is allowed to have a tolerance of ±10%. For example, if the ratio of A to B is greater than 10, it should be understood to include the case where the ratio of A to B is greater than 9, and also include the case where the ratio of A to B is greater than 11.

[0054] It should be understood that the dimensions of the layers, regions, films, plates, blocks, columns, projections, recesses, etc. shown in the drawings are provided for better understanding and more convenient description, and the present application is not limited to the dimensions shown in the drawings. Elements not relevant to the description are omitted from the details of this specification in order to make the present invention clear.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0056] The present application discloses a secondary battery, which includes a housing and an electrode assembly. The electrode assembly is housed in the housing and bent in a first direction. The electrode assembly includes a multilayer electrode sheet and a multilayer diaphragm, and the diaphragm is disposed between two adjacent electrode sheets. The electrode assembly has a first portion and a second portion arranged in sequence along the first direction. The diaphragm includes a first diaphragm located in the first portion and a second diaphragm located in the second portion. The first diaphragm includes a first substrate layer and a first adhesive layer disposed on the surface of the first substrate layer. The second diaphragm includes a second substrate layer and a second adhesive layer disposed on the surface of the second substrate layer. The first adhesive layer bonds the first substrate layer to the electrode sheet of the first portion, and the peel strength between the first adhesive layer and the adjacent electrode sheet is S1. The second adhesive layer bonds the second substrate layer and the electrode sheet of the second portion, and the peel strength between the second adhesive layer and the adjacent electrode sheet is S2, satisfying 6N / m≤S1<S2.

[0057] The peel strength between the separator and the electrode is above 6N / m, which helps suppress electrode rebound and, in turn, deformation after bending the secondary battery, helping to address deformation issues such as reduced curvature and flattening of the secondary battery. By satisfying S1 < S2, the peel strength between the electrode and the separator near the inner side of the electrode assembly's arc is reduced, which helps reduce the risk of separator clogging, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery.

[0058] The following will describe some embodiments of the present application in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0059] Referring to FIG. 1 , an embodiment of the present application provides a secondary battery 100 , which includes a housing 10 and an electrode assembly 20 . The electrode assembly 20 is accommodated within the housing 10 and is bent in a first direction X. The first direction X is the bending direction of the electrode assembly 20 , and is defined as the direction from a concave side of the electrode assembly 20 toward a convex side of the electrode assembly 20 after bending.

[0060] In some embodiments, the housing 10 is a flexible packaging bag, such as an aluminum-plastic film. In other embodiments, the housing 10 is a hard shell, such as a plastic shell, or a metal shell including at least one of steel alloy, aluminum alloy, and copper alloy.

[0061] In some embodiments, an electrolyte (not shown) may be injected into the housing 10 , and the electrolyte components include a solvent, a lithium salt, and an additive.

[0062] In some embodiments, referring to FIG. 1 , the electrode assembly 20 includes a multi-layer electrode sheet 21 and a multi-layer separator 22 . At least one separator 22 is included between any two adjacent electrode sheets 21 . The separator 22 is used to isolate the two adjacent electrode sheets 21 .

[0063] In some embodiments, referring to FIG. 1 , the secondary battery 100 is a laminated battery, wherein the multilayer electrode sheets 21 and the multilayer separators 22 are stacked along the first direction X, and the multilayer electrode sheets 21 and the multilayer separators 22 are bent along the first direction X.

[0064] In some other embodiments, please refer to Figure 2, the secondary battery 100 is a wound battery, and the multi-layer electrode sheet 21 and the multi-layer separator 22 are stacked and wound to form a wound structure, and a multi-layer structure is formed along the first direction X, and the wound electrode sheet 21 and the separator 22 are bent along the first direction X.

[0065] In some embodiments, referring to Figures 1 and 2, the electrode 21 includes an anode electrode 211 and a cathode electrode 212, and the anode electrode 211 and the cathode electrode 212 are stacked along a first direction X. One of any two adjacent layers of electrode 21 is an anode electrode 211, and the other is a cathode electrode 212, and a diaphragm 22 is provided between adjacent anode electrodes 211 and cathode electrodes 212, and the diaphragm 22 is used to isolate the anode electrode 211 and the cathode electrode 212.

[0066] In some embodiments, referring to FIG. 3 , the electrode assembly 20 includes a first portion 201 and a second portion 202 sequentially arranged along a first direction X. Along the first direction X, the second portion 202 is closer to the convex side of the electrode assembly 20 after bending than the first portion 201. The first portion 201 includes at least one cathode electrode sheet 212, an anode electrode sheet 211, and a separator 22, and the second portion 202 includes at least one cathode electrode sheet 212, an anode electrode sheet 211, and a separator 22.

[0067] In some embodiments, the secondary battery 100 is a wound battery, and the electrode assembly 20 has two curved sections along a second direction Y and a middle section located between the curved sections. The second direction Y is perpendicular to the first direction X. The first section 201 includes a multi-layer cathode electrode sheet 212, a multi-layer anode electrode sheet 211, and a multi-layer separator 22. The multi-layer cathode electrode sheet 212, the multi-layer anode electrode sheet 211, and the multi-layer separator 22 of the first section 201 located in the middle section are generally arranged along the first direction X, and the multi-layer cathode electrode sheet 212, the multi-layer anode electrode sheet 211, and the multi-layer separator 22 of the first section 201 located in the curved section are generally arranged along the second direction Y. The second part 202 includes a multi-layer cathode electrode piece 212, a multi-layer anode electrode piece 211 and a multi-layer diaphragm 22. The multi-layer cathode electrode piece 212, the multi-layer anode electrode piece 211 and the multi-layer diaphragm 22 of the second part 202 located in the middle section are roughly arranged along the first direction X, and the multi-layer cathode electrode piece 212, the multi-layer anode electrode piece 211 and the multi-layer diaphragm 22 of the second part 202 located in the curved section are roughly arranged along the second direction Y.

[0068] In some embodiments, referring to Figures 4 and 5 , the anode electrode sheet 211 includes a first current collector 2111 and a first active material layer 2112, which are stacked. When the anode electrode sheet 211 is flattened, the first current collector 2111 has a first surface 211a and a second surface 211b that are opposite each other along the thickness direction of the anode electrode sheet 211. The first current collector 2111 includes a first coating region 211c, where both the first surface 211a and the second surface 211b of the first coating region 211c are provided with the first active material layer 2112. The first coating region 211c is a double-sided coating region.

[0069] In some embodiments, referring to Figures 4 and 5 , the cathode electrode sheet 212 includes a second current collector 2121 and a second active material layer 2122 stacked together. When the cathode electrode sheet 212 is flattened, the second current collector 2121 has a third surface 212a and a fourth surface 212b that are opposite each other along the thickness direction of the cathode electrode sheet 212. The second current collector 2121 includes a second coating region 212c. The second active material layer 2122 is provided on both the third surface 212a and the fourth surface 212b of the second coating region 212c. The second coating region 212c is a double-sided coating region.

[0070] In some embodiments, the first current collector 2111 and the second current collector 2121 may be metal layers. The first current collector 2111 may be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 2121 may be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0071] In some embodiments, the first active material layer 2112 has an anodic polarity and includes an anode active material. The anode active material may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials. The second active material layer 2122 has a cathodic polarity and includes a cathode active material. The cathode active material may include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium manganese oxide.

[0072] In some embodiments, referring to Figures 1, 4, and 5, the diaphragm 22 includes a first diaphragm 221 located in the first portion 201 and a second diaphragm 222 located in the second portion 202. The first diaphragm 221 includes a first substrate layer 2211 and a first adhesive layer 2212 disposed on the first substrate layer 2211, and the second diaphragm 222 includes a second substrate layer 2221 and a second adhesive layer 2222 disposed on the second substrate layer 2221.

[0073] In some embodiments, the first adhesive layer 2212 bonds the first substrate layer 2211 and the electrode piece 21 of the first portion 201 , and the second adhesive layer 2222 bonds the second substrate layer 2221 and the electrode piece 22 of the second portion 202 .

[0074] In some embodiments, the materials of the first substrate layer 2211 and the second substrate layer 2221 are independently selected from at least one of polyolefin, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, or polyphenylene phthalamide. The first substrate layer 2211 and the second substrate layer 2221 are microporous and porous films that allow ions to pass through and retain electrolyte. In some embodiments, the polyolefin includes polypropylene and / or polyethylene.

[0075] In some embodiments, a first adhesive is provided in the first adhesive layer 2212, and a second adhesive is provided in the second adhesive layer 2222. The first adhesive and the second adhesive are each independently selected from one or a combination of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0076] In some embodiments, referring to FIG3 , the electrode assembly 20 has a first portion 201 and a second portion 202 sequentially arranged along a first direction X, the peeling strength between the first adhesive layer 2212 and the adjacent electrode piece 21 is S1, and the peeling strength between the second adhesive layer 2222 and the adjacent electrode piece 21 is S2, satisfying 6N / m≤S1<S2.

[0077] Setting the peel strength between the separator 22 and the electrode piece 21 to be greater than 6 N / m helps suppress deformation and rebound of the electrode piece 21, helps maintain the shape of the electrode piece 21 after bending, and reduces the risk of black spots on the electrode assembly 20 caused by an excessive gap between the cathode electrode piece 212 and the anode electrode piece 211. By suppressing the deformation and rebound of the electrode piece 21, the deformation of the secondary battery 100 after bending is suppressed, which helps to solve the deformation problems such as curvature reduction and equalization of the secondary battery 100. It can also reduce the reserved space in the battery compartment for accommodating the secondary battery 100, thereby facilitating the installation of the secondary battery 100 and improving the reliability and applicability of the secondary battery 100.

[0078] Furthermore, research has found that in a curved electrode assembly 20, the electrode piece 21 close to the protruding side of the electrode assembly 20 is subjected to greater stress and is more prone to deformation and rebound. During the research process, it was also found that while changing the peel strength between the electrode piece 21 and the diaphragm 22, it is necessary to adjust the first adhesive layer 2212 and the second adhesive layer 2222 accordingly. Generally, appropriately reducing the peel strength between the diaphragm 22 and the electrode piece 21 is beneficial to reducing internal resistance and improving the chemical properties of the secondary battery 100. By satisfying S1<S2, the present application reduces the peel strength between the electrode piece 21 and the diaphragm 22 in the first portion 201 close to the inner side of the arc of the electrode assembly 20, which helps reduce the risk of pores in the diaphragm 22 in the second portion 202, thereby reducing internal resistance and improving the electrochemical properties of the secondary battery 100.

[0079] In some embodiments, referring to FIG. 3 , along the first direction X, the thickness of the electrode assembly 20 is D, and the thickness of the second portion 202 is D1, satisfying D / 2 ≤ D1 < D. This configuration ensures that the peel strength between the electrode piece 21 and the separator 22 of more than half of the electrode assembly 20 in the first direction X is greater than 6 N / m, which helps further suppress deformation of the electrode assembly 20 after bending and reduces the risk of the electrode assembly 20 reducing its curvature or becoming flat.

[0080] In some embodiments, referring to FIG. 3 , the thickness of the second portion 202 is D1, satisfying 3D / 4 ≤ D1 < D. This configuration can further increase the thickness of the electrode assembly 20 occupied by the electrode piece 21 and the separator 22, which have a peel strength of at least 6 N / m. This helps further suppress deformation of the electrode assembly 20 after bending, reducing the risk of the electrode assembly 20 becoming flat or decreasing in curvature.

[0081] In some embodiments, 1.6S1≤S2≤4S1 is satisfied. Such a setting is beneficial to suppressing deformation of the electrode assembly 20 after bending, and is beneficial to reducing the risk of clogging of the diaphragm 22 in the second part 202, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery 100.

[0082] As an illustrative example, S2 may specifically be 1.6S1, 2S1, 2.4S1, 2.8S1, 3.2S1, 3.6S1 or 4S1.

[0083] In some embodiments, 6N / m≤S1<9.6N / m is satisfied. Such a setting is beneficial to suppressing deformation of the electrode assembly 20 after bending, and is beneficial to reducing the risk of clogging of the diaphragm 22 in the first part 201, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery 100.

[0084] As an illustrative example, S1 can specifically be 6 N / m, 6.2 N / m, 6.6 N / m, 6.8 N / m, 7 N / m, 7.2 N / m, 7.6 N / m, 7.8 N / m, 8 N / m, 8.2 N / m, 8.6 N / m, 8.8 N / m, 9 N / m or 9.5 N / m.

[0085] In some embodiments, 9.6 N / m≤S2≤12 N / m is satisfied. Such a setting is beneficial to suppressing deformation of the electrode assembly 20 after bending, and is beneficial to reducing the risk of clogging of the diaphragm 22 in the second part 202, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery 100.

[0086] As an illustrative example, S2 can specifically be 9.6 N / m, 10 N / m, 10.2 N / m, 10.6 N / m, 10.8 N / m, 11 N / m, 11.2 N / m, 11.6 N / m, 11.8 N / m or 12 N / m.

[0087] In some embodiments, the first adhesive and the second adhesive can be of the same type, and the content of the second adhesive in the second adhesive layer 2222 is greater than the content of the first adhesive in the first adhesive layer 2212, so that the peeling strength S2 between the second isolation film 222 and the pole piece 21 in the second part 202 is greater than the peeling strength S1 between the first isolation film 221 and the pole piece 21 in the first part 201.

[0088] The first adhesive of the first isolation film 221 may be selected from one or a combination of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The second adhesive of the second isolation film 222 may be selected from one or a combination of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0089] Taking polyvinylidene fluoride (PVDF) as the first adhesive as an example, since the PVDF crystal region belongs to the semi-definite region and has a clear melting peak at 140°C-150°C, the present application can estimate the PVDF content based on the PVDF melting peak. Specifically, the PVDF content can be determined using the following steps:

[0090] 1) Separate the first adhesive layer 2212 from the first isolation film to obtain agglomerate powder with a mass of M.

[0091] 2) Using a Mettler differential scanning calorimeter (DSC), the melting peak of the agglomerate powder with a mass of M was measured, and the heat E absorbed by the melting of the PVDF was obtained by integrating the melting peak at 140° C.-150° C.

[0092] 3) Calculate the mass M1 of PVDF, M1 = E / (Hm×η), where Hm is the melting enthalpy of PVDF when it is completely crystallized, 104.7 J / g, and η is the crystallinity of PVDF, 49.5%.

[0093] When the second adhesive is PVDF, the same method can be used to determine the content. It is understood that when each adhesive layer uses adhesives made of other materials, the above content determination method can also be set according to the properties of the adhesive.

[0094] In some embodiments, the first adhesive layer 2212 includes polyvinylidene fluoride, and the coating weight of the polyvinylidene fluoride in the first adhesive layer 2212 is 3 mg / 5000 mm 2 -4mg / 5000mm 2 The content of polyvinylidene fluoride in the first adhesive layer 2212 is 60 wt % to 80 wt %. This configuration ensures that the peel strength between the separator 22 and the electrode piece 21 of the first portion 201 is above 6 N / m, which helps to suppress deformation of the electrode assembly 20 after bending.

[0095] It should be noted that the unit "mg / mm 2 " is the dimension of coating weight. The coating weight of polyvinylidene fluoride in the first adhesive layer 222 is 3 mg / 5000 mm 2 -4mg / 5000mm 2 Refers to the first substrate layer 2211 of the first diaphragm 221, every 5000mm 2 The coating weight of the area coated polyvinylidene fluoride is 3mg-4mg.

[0096] The unit "wt%" represents mass percentage (%). A polyvinylidene fluoride content of 60 wt% to 80 wt% in the first adhesive layer 222 means that the polyvinylidene fluoride in the first adhesive layer 2212 of the first separator 221 accounts for 60% to 80% of the mass of the entire first adhesive layer 2212. The specific conversion method is: mass percentage wt% = (mass of polyvinylidene fluoride / mass of first adhesive layer 222) × 100%.

[0097] In some embodiments, the second adhesive layer 2222 includes acrylate, and the coating weight of the acrylate in the second adhesive layer 2222 is 0.7 mg / 5000 mm 2 -1.1mg / 5000mm 2 The content of acrylate in the second adhesive layer 2222 is 85 wt % to 95 wt %. This configuration ensures that the peel strength between the separator 22 and the electrode 21 in the second portion 202 is above 10 N / m, which helps to suppress deformation of the electrode assembly 20 after bending.

[0098] It should be noted that the peel strength between the diaphragm 22 and the electrode 21 is tested as follows:

[0099] According to GB / T 2792-2014 "Test method for peel strength of adhesive tape", a high-speed rail tensile tester is used to test the peel strength between the diaphragm and the electrode (the peel strength between the diaphragm 22 and the electrode 21 is tested as an example in the embodiment of this application). The test process is as follows: the lithium-ion battery is completely discharged, and then the lithium-ion battery is disassembled, the diaphragm 22 and the electrode 21 bonded thereto are removed as a whole, and the electrolyte on the surface is wiped with dust-free paper. Then cut into 20mm×60mm strip specimens. Along the length direction of the specimen, the side of the electrode assembly in the specimen is adhered to the steel plate with double-sided tape (Nitto 5000NS), and the adhesion length is not less than 40mm. Fix the steel plate at the corresponding position of the high-speed rail tensile testing machine, pull up the other end of the electrode that is not adhered to the diaphragm, and clamp the sample in the chuck. The angle between the pulled-up sample part and the steel plate in space is 180°. The chuck pulls the sample at a speed of 5±0.2mm / s. The average tensile force in the stable area is finally measured and recorded as the peel strength between the diaphragm and the electrode, recorded as F, in N / m.

[0100] In order to verify the effect of the peel strength between the electrode 21 and the separator 22 on the arc reduction and equalization deformation of the secondary battery 100, the following tests were conducted:

[0101] A comparative charge-discharge test was conducted on the secondary battery 100. The secondary battery 100 was placed in a constant temperature environment at 25°C and charged at a constant current rate of 0.5C (1C represents a current that fully charges the battery in 1 hour) to the system's full charge voltage. The voltage was then constant to 0.05C. The battery was then fully discharged at a constant current of 0.5C to 3.0V, representing one charge-discharge cycle. After 800 cycles of charge and discharge, the rate of change in the arc radius of the secondary battery 100 and the capacity retention of the secondary battery 100 were measured.

[0102] The capacity retention rate is calculated as follows: capacity retention rate = discharge capacity in the Nth cycle in mAh / discharge capacity in the initial first cycle in mAh.

[0103] The arc radius change rate of the secondary battery 100 is obtained as follows:

[0104] To obtain an initial arc radius, when the secondary battery 100 is not subjected to a cycle test, a 3D profilometer is used to scan the 3D structure of the surface of the secondary battery 100 . The scanned surface is then averaged to obtain an arc line. Three points on the arc line are fitted to obtain a standard circular arc line, and then the arc radius a is read.

[0105] To obtain the post-cycle arc radius, after the secondary battery 100 completes the cycle charge and discharge test, a 3D profilometer is used to scan the 3D structure of the surface of the secondary battery 100. The scanned surface is then averaged to obtain an arc line. Three points are taken on the arc line for fitting to obtain a standard circular arc line, and then the arc radius b is read.

[0106] The arc radius change rate of the electrode unit is obtained as (ba) / a.

[0107] The principle of point selection is as follows: the arc obtained by point fitting should coincide with the arc obtained by surface averaging as much as possible and points near the endpoints should be excluded.

[0108] It should be noted that when the risk of pore blocking of the separator 22 is reduced, the capacity retention rate of the secondary battery 100 is high, and the electrochemical performance of the secondary battery 100 is better.

[0109] The following describes the specific implementation of the secondary battery 100 in the embodiment and the comparative example.

[0110] Examples and Comparative Examples

[0111] A secondary battery, the assembly process is as follows:

[0112] (1) Preparation of the anode electrode 211: The anode active material artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, deionized water is added as a solvent, and a slurry with a weight percentage of 70 wt% is prepared and stirred evenly. The slurry is evenly coated on one surface of an anode current collector copper foil with a thickness of 10 μm, and an empty foil area is reserved at the edge of the copper foil. The anode electrode 211 with a coating thickness of 150 μm and coated on one side with an anode active material layer is obtained. The above steps are repeated on the other surface of the anode electrode 211 to obtain an anode electrode 211 with a double-sided coating of an anode active material layer. Then, the excess empty foil area is removed by laser die-cutting to obtain an anode tab.

[0113] (2) Preparation of cathode electrode 212: The cathode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and stirred evenly. The slurry is evenly coated on one surface of a cathode current collector aluminum foil with a thickness of 12μm, leaving an empty foil area at the edge of the aluminum foil, and then dried at 90°C to obtain a cathode electrode 212 with a cathode active material layer thickness of 100μm. The single-sided coated cathode electrode 212 is subsequently used as the first outer electrode. When preparing another double-sided coated first electrode (i.e., the first inner electrode), repeat the above coating steps on the other surface of the aluminum foil. Then, the excess empty foil area is removed by laser die-cutting to obtain a cathode tab.

[0114] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0115] (4) Preparation of the First Isolation Film: A three-layered isolation film is provided, comprising a first adhesive layer, a first substrate layer, and a first bonding layer stacked together. The first substrate layer is made of polyethylene (PE), the first bonding layer comprises a first adhesive, and the first bonding layer further comprises inorganic ceramic particles Al2O3.

[0116] (5) Preparation of the Second Isolation Film: A three-layered isolation film is used, comprising a second adhesive layer, a second substrate layer, and a second adhesive layer stacked in layers. The second substrate layer is made of polyethylene (PE), the second adhesive layer contains a second adhesive, and the second adhesive layer also contains inorganic ceramic particles Al2O3.

[0117] (6) Preparation of electrode assembly 20: The cathode electrode sheet 212, the separator 22, and the anode electrode sheet 211 are stacked and arranged. The stacked structure is subjected to a flat-plate hot press for 10 seconds at a temperature of 80°C and a pressure of 1.5 MPa to form an electrode assembly 20 for use. The electrode assembly 20 includes a first portion 201 and a second portion 202 arranged in sequence along a first direction X. Along the first direction X, the thickness of the electrode assembly 20 is D, and the thickness of the second portion 202 is D1.

[0118] (7) Assembly of the electrode assembly 20: Place the aluminum-plastic film with the cavities formed in it into an assembly fixture, with the cavities facing upward. Place the electrode assembly 20 in the cavities and apply external force to tighten. Then, place another aluminum-plastic film with the cavities formed in it, with the cavities facing downward, over the electrode assembly 20. Heat-seal the two aluminum-plastic films around their edges using a hot press to obtain the assembled electrode assembly 20.

[0119] (8) Liquid injection and packaging: The electrolyte is injected into the assembled electrode assembly 20, and the secondary battery 100 is manufactured through vacuum packaging, static standing, hot pressing, shaping and other processes.

[0120] The main parameter control and test results of each embodiment are shown in Table 1:

[0121] Table 1

[0122] Among them, PVDF is polyvinylidene fluoride, PDDA is acrylate, PVDF-HFP is a copolymer of vinylidene fluoride and hexafluoropropylene, and PMMA is polymethyl methacrylate.

[0123] According to Table 1 above, compared with Comparative Examples 1-5, Example 1 satisfies 6N / m≤S1<S2, which is beneficial to suppressing the deformation of the secondary battery 100 after bending, and is beneficial to solving the deformation problems such as curvature reduction and equalization of the secondary battery 100. It is also beneficial to improving the capacity retention rate of the secondary battery 100 and improving the chemical properties of the secondary battery 100.

[0124] It can be seen from Table 1 above that, compared with Comparative Example 1 and Example 6, when the condition of 6N / m≤S1<9.6N / m is satisfied in Examples 1-5, it is beneficial to suppress the deformation of the electrode assembly after bending, and is beneficial to reduce the risk of pore blockage in the diaphragm in the first part, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0125] According to Table 1 above, compared with Example 7 and Example 13, when the condition of 9.6 N / m ≤ S2 ≤ 15 N / m is satisfied in Example 2 and Examples 8-12, it is beneficial to suppress the deformation of the secondary battery 100 after bending, and to solve the deformation problems such as the reduction of the curvature and equalization of the secondary battery 100. It is also beneficial to improve the capacity retention rate of the secondary battery 100 and improve the chemical properties of the secondary battery 100.

[0126] According to Table 1 above, compared with Example 14 and Example 19, in Example 2 and Examples 15-18, when the condition D / 2≤D1<D is satisfied, it is beneficial to suppress the deformation of the secondary battery 100 after bending, and is beneficial to solving the deformation problems such as the reduction of the curvature and equalization of the secondary battery 100. It is also beneficial to improve the capacity retention rate of the secondary battery 100 and improve the chemical properties of the secondary battery 100, and preferably satisfies 3D / 4≤D1<D.

[0127] In some embodiments, referring to FIG6 , the surface of the anode electrode sheet 211 is provided with a plurality of first protrusions 2113. The first protrusions 2113 can disperse the stress of the bent anode electrode sheet 211, suppressing deformation and rebound of the anode electrode sheet 211. This helps maintain the shape of the bent anode electrode sheet 211 and helps address deformation issues such as reduction and equalization of the overall curvature of the electrode assembly 20. When the overall curvature of the electrode assembly 20 remains substantially unchanged, the secondary battery 100 is less likely to undergo significant deformation, which helps address deformation issues such as reduction and equalization of the secondary battery 100.

[0128] In some embodiments, referring to FIG. 6 , a surface of the anode plate 211 facing away from the first protrusions 2113 is provided with a plurality of first recesses 2114 . Along the first direction X, the orthographic projection of each first protrusion 2113 overlaps with the orthographic projection of a first recess 2114 .

[0129] Both the first protrusion 2113 and the first recess 2114 can disperse the stress of the curved anode electrode sheet 211, further helping to suppress deformation and rebound of the anode electrode sheet 211, thereby further helping to address the overall curvature reduction and equalization deformation issues of the electrode assembly 20 and even the entire secondary battery 100. In addition, the orthographic projection of each first protrusion 2113 overlaps with the orthographic projection of a first recess 2114, facilitating the simultaneous machining of the first protrusions 2113 and the first recesses 2114, thereby improving the machining efficiency of the first protrusions 2113 and the first recesses 2114.

[0130] In some embodiments, referring to FIG. 7 , a plurality of second protrusions 2123 are provided on the surface of the cathode electrode piece 212 . The second protrusions 2123 can disperse the stress of the bent cathode electrode piece 212 and suppress deformation and rebound of the cathode electrode piece 212 .

[0131] In some embodiments, referring to FIG. 7 , a plurality of second recesses 2124 are provided on a surface of the cathode electrode 212 facing away from the plurality of second protrusions 2123 . Along the first direction X, the orthographic projection of each second protrusion 2123 overlaps with the orthographic projection of a second recess 2124 . Both the second protrusions 2123 and the second recesses 2124 can disperse the stress of the curved cathode electrode 212 , further facilitating suppression of deformation and rebound of the cathode electrode 212 . This also facilitates simultaneous machining of the second protrusions 2123 and the second recesses 2124 , thereby improving machining efficiency of the second protrusions 2123 and the second recesses 2124 .

[0132] In some embodiments, the anode electrode sheet 211 is formed with a first protrusion 2113 and a first concave portion 2114 by an embossing process.

[0133] In some embodiments, the cathode electrode 212 is formed with a second protrusion 2123 and a second concave portion 2124 by an embossing process.

[0134] In some embodiments, referring to FIG. 8 to FIG. 10 , the shape of the first protrusion 2113 is one of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0135] In some embodiments, referring to FIG. 11 to FIG. 13 , the second protrusion 2123 is in the shape of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0136] In some embodiments, referring to Figures 8 to 13, the shape of the first protrusion 2113 is different from the shape of the second protrusion 2123, which is conducive to allowing the first protrusion 2113 to be at least partially embedded in the second recess 2124, or to allowing the second protrusion 2123 to be at least partially embedded in the first recess 2114, thereby facilitating the improvement of the friction between the cathode electrode 212, the anode electrode 211 and the diaphragm 22, thereby suppressing the risk of slippage between the cathode electrode 212, the anode electrode 211 and the diaphragm 22, and thereby improving the reliability of the electrode assembly 20.

[0137] In some embodiments, referring to FIG8 , when the anode electrode sheet 211 is flattened and viewed along the first direction X, the sum of the areas of the plurality of first protrusions 2113 is M1, and the area of ​​the anode electrode sheet 211 is M2, satisfying the condition: 0.06M2≤M1<M2. Meeting this condition helps improve the overall stress dispersion effect of the plurality of first protrusions 2113 on the anode electrode sheet 211, thereby further suppressing deformation of the first electrode sheet 211 after bending.

[0138] In some embodiments, referring to FIG6 , the thickness of the anode electrode sheet 211 corresponding to the first coating area 211c is T1, and the height of the first protrusion 2113 is H1, satisfying H1≤0.1T1. When this condition is met, it is beneficial to improve the stress dispersion effect of the first protrusion 2113 on the anode electrode sheet 211, thereby further suppressing the deformation of the anode electrode sheet 211 after bending. In the embodiment where the first protrusion 2113 is pressed out by an embossing roller, meeting this condition is also beneficial to reducing the risk of damage to the anode electrode sheet 211 caused by excessive pressure applied by the embossing roller, or reducing the risk of damage to the anode electrode sheet 211 caused by excessive local deformation.

[0139] The thickness T1 of the anode electrode 211 corresponding to the first coating region 211c is the sum of the thicknesses of the first current collector 2111 in the first coating region 211c, the first active material layer 2112 on the first side 211a, and the second active material layer 2112 on the second side 211b. The height H1 of the first protrusion 2113 is the height of the largest of the plurality of first protrusions 2113.

[0140] In some embodiments, referring to FIG8 , when the anode plate 211 is flattened, the anode plate 211 has a first boundary line 21 a and a second boundary line 21 b that are oppositely arranged along a second direction Y, and a third boundary line 21 c and a fourth boundary line 21 d that are oppositely arranged along a third direction Z. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other. The first direction X is parallel to the thickness direction of the anode plate 211, one of the second direction Y and the third direction Z is parallel to the width direction of the anode plate 211, and the other is parallel to the length direction of the anode plate 211.

[0141] In some embodiments, referring to FIG8 , the minimum distance between the plurality of first protrusions 2113 and the first boundary line 21a is L1, and the minimum distance between the plurality of first protrusions 2113 and the second boundary line 21b is L2, 1mm≤L1≤7mm, 1mm≤L2≤7mm, which is beneficial to reducing the risk of the embossing roller pressing the anode electrode 211 at the cutting position in the second direction Y, thereby reducing the risk of damage to the anode electrode 211.

[0142] As an example, L1 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm, and L2 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm.

[0143] In some embodiments, referring to FIG8 , the minimum distance between the plurality of first protrusions 2113 and the third boundary line 21c is L3, and the minimum distance between the plurality of first protrusions 2113 and the fourth boundary line 21d is L4, 1mm≤L3≤7mm, 1mm≤L4≤7mm, which is beneficial to reducing the risk of the embossing roller pressing the cutting position of the anode plate 211 in the third direction Z, thereby reducing the risk of damage to the anode plate 211.

[0144] As an example, L3 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm. L4 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, or 7 mm.

[0145] In some embodiments, referring to FIG8 , the distance F1 between any two adjacent first protrusions 2113 satisfies 1.5 mm ≤ F1 ≤ 3 mm. Meeting this condition helps disperse the stress on the anode electrode 211 , further suppressing deformation of the anode electrode 211 after bending, and making it less likely for black spots to form on the electrode assembly 20 .

[0146] As an illustrative example, F1 may specifically be 1.5 mm, 1.7 mm, 1.9 mm, 2 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm or 3 mm.

[0147] In some embodiments, referring to FIG8 , the width of the first protrusion 2113 is R1 when viewed along the first direction X, satisfying R1 ≥ 1 mm. When R1 ≥ 1 mm is satisfied, the first protrusion 2113 can effectively disperse the stress on the anode plate 211, thereby further suppressing deformation of the anode plate 211 after bending, and preventing black spots from forming on the electrode assembly 20.

[0148] As an illustrative example, R1 may specifically be 1 mm, 1.2 mm, 1.5 mm, 2 mm, 2.3 mm, 2.5 mm, 2.7 mm, 2.9 mm or 3 mm.

[0149] It can be understood that when the first protrusion 2113 is a dot-shaped protrusion, the first protrusion 2113 is circular, and the width R1 of the first protrusion 2113 is the diameter of the first protrusion 2113. When the first protrusion 2113 is a stripe-shaped protrusion, the length direction of the first protrusion 2113 is the extension direction of the stripe-shaped protrusion, the width direction of the first protrusion 2113 is the direction in which the multiple first protrusions 2113 are arranged, and the width R1 of the first protrusion 2113 is the width of the first protrusion 2113 along the arrangement direction. When the first protrusion 2113 is a reticulated protrusion, a single first protrusion 2113 is actually an inclined stripe-shaped protrusion, the length direction of the first protrusion 2113 is the extension direction of the stripe-shaped protrusion, the width direction of the first protrusion 2113 is the direction in which the multiple first protrusions 2113 are arranged, and the width R1 of the first protrusion 2113 is the width of the first protrusion 2113 along the arrangement direction.

[0150] In some embodiments, the specific configuration of the cathode electrode 212 and the specific configuration and beneficial effects of the second protrusion 2123 and the second recess 2124 can refer to the specific implementation of the above-mentioned anode electrode 211, the first protrusion 2113 and the second recess 2124, and will not be repeated here.

[0151] Referring to FIG. 14 , an embodiment of the present application further provides an electronic device 1000 . The electronic device 1000 includes the secondary battery 100 in any of the above embodiments.

[0152] In some embodiments, the electronic device 1000 may be AR glasses or VR glasses, etc., which are not listed here one by one.

[0153] In some embodiments, referring to FIG14 , the electronic device 1000 further includes a device body 200, and the secondary battery 100 is mounted in the device body 200. Since the electronic device 1000 employs the technical solution of the secondary battery 100 in any of the above embodiments, it at least has the beneficial effects brought about by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described in detail here.

[0154] In addition, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the substantive scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, characterized in that, Comprising: A housing; An electrode assembly received in the housing, the electrode assembly being bent in a first direction, the electrode assembly including multiple layers of electrode sheets and multiple layers of separators, the separators being disposed between two adjacent layers of electrode sheets; The electrode assembly has a first portion and a second portion arranged in sequence along the first direction, the separator includes a first separator located in the first portion and a second separator located in the second portion, the first separator includes a first base material layer and a first adhesive layer provided on the surface of the first base material layer, the second separator includes a second base material layer and a second adhesive layer provided on the surface of the second base material layer; The first adhesive layer bonds the first base material layer and the electrode sheet of the first portion, the peel strength between the first adhesive layer and the adjacent electrode sheet is S1, the second adhesive layer bonds the second base material layer and the electrode sheet of the second portion, the peel strength between the second adhesive layer and the adjacent electrode sheet is S2, and 6N / m ≤ S1 < S2 is satisfied.

2. The secondary battery according to claim 1, characterized in that, Along the first direction, the thickness of the electrode assembly is D, and the thickness of the second portion is D1, and D / 2 ≤ D1 < D is satisfied.

3. The secondary battery according to claim 2, characterized in that, The thickness of the second portion is D1, and 3D / 4 ≤ D1 < D is satisfied.

4. The secondary battery according to claim 1, characterized in that, 1.6S1 ≤ S2 ≤ 4S1 is satisfied.

5. The secondary battery according to claim 1, characterized in that, 6N / m ≤ S1 < 9.6N / m is satisfied.

6. The secondary battery according to claim 1, wherein 9.6N / m ≤ S2 ≤ 12N / m is satisfied.

7. The secondary battery according to claim 1, characterized in that, The secondary battery is a stacked battery, and the multiple layers of electrode sheets and the multiple layers of separators are stacked along the first direction.

8. The secondary battery according to claim 1, wherein The first adhesive layer is provided with a first adhesive, the second adhesive layer is provided with a second adhesive, and the first adhesive and the second adhesive are independently selected from one or a combination of several of polyvinylidene fluoride, copolymer of vinylidene fluoride - hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

9. The secondary battery according to claim 1, characterized in that, The electrode sheet includes an anode electrode sheet and a cathode electrode sheet, and the anode electrode sheet, the separator, and the cathode electrode sheet are stacked along the first direction; The surface of the anode electrode sheet is provided with a plurality of first protrusions.

10. The secondary battery according to claim 9, wherein The surface of the anode electrode sheet facing away from the plurality of first protrusions is provided with a plurality of first recesses, and along the first direction, the orthographic projection of each first protrusion and the orthographic projection of a first recess overlap.

11. An electronic device, characterized in that, Including the secondary battery according to any one of claims 1 to 10.

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