Secondary battery and electronic apparatus

Abstract

Disclosed in the present application are a secondary battery and an electronic apparatus. The secondary battery comprises a housing and an electrode assembly, the housing accommodates the electrode assembly, and the electrode assembly is arranged as curved in a first direction; the electrode assembly comprises a cathode electrode piece, a separator, and an anode electrode piece in a stacked arrangement; the separator comprises a first surface and an opposing second surface along the first direction, the separator comprises a first adhesive layer arranged on the first surface and a second adhesive layer arranged on the second surface; the first adhesive layer adheres to the anode electrode piece, and the second adhesive layer adheres to the cathode electrode piece; the peel strength between the first adhesive layer and the anode electrode piece is S1, and the peel strength between the second adhesive layer and the cathode electrode piece is S2, where S1 < S2 is satisfied. The present invention facilitates reducing the risk of pore clogging for a separator while also suppressing opposing movement of an electrode assembly.

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 more and more complex, the types of electronic devices are becoming more and more diverse to meet the needs of use. Nowadays, wearable electronic devices have become popular. In order to adapt to the battery compartments of wearable electronic devices, secondary batteries need to be designed with a curved or arc-shaped structure.

[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. Summary of the Invention

[0004] 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.

[0005] In a first aspect, the present application provides a secondary battery, comprising a housing and an electrode assembly. The electrode assembly is housed in the housing and bent in a first direction. The electrode assembly comprises a cathode electrode sheet, a diaphragm, and an anode electrode sheet stacked in layers, the diaphragm comprising a first surface and a second surface disposed opposite each other along a first direction, the diaphragm comprising a first adhesive layer disposed on the first surface and a second adhesive layer disposed on the second surface, the first adhesive layer being bonded to the anode electrode sheet, the second adhesive layer being bonded to the cathode electrode sheet, the peel strength between the first adhesive layer and the anode electrode sheet being S1, the peel strength between the second adhesive layer and the cathode electrode sheet being S2, and satisfying S1<S2.

[0006] In the above embodiment, by satisfying S1<S2, the peeling strength between the diaphragm and the cathode electrode can be improved, which is beneficial to limit the deformation of the cathode electrode, suppress the rebound of the electrode, and prevent the peeling strength between the diaphragm and the anode electrode from being too high, thereby helping to reduce the risk of diaphragm clogging.

[0007] In one or more of the above embodiments, a plurality of first protrusions are provided on the surface of the anode electrode.

[0008] In the above embodiment, by providing a plurality of first protrusions on the anode electrode that is more easily deformed, it is beneficial to disperse the stress of the anode electrode, reduce the risk of diaphragm blockage, and suppress the deformation and rebound of the anode electrode, thereby maintaining the shape of the electrode assembly after bending, thereby solving the overall curvature reduction and equalization deformation problems of the secondary battery, and can improve the performance and reliability of the secondary battery.

[0009] In one or more of the above embodiments, 1.6S1≤S2≤4S1 is satisfied.

[0010] 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 diaphragm clogging, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0011] In one or more of the above embodiments, 6 N / m≤S1<9.6 N / m is satisfied.

[0012] 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 diaphragm clogging, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0013] In one or more of the above embodiments, 9.6 N / m≤S2≤15 N / m is satisfied.

[0014] In the above embodiment, when the condition of 9.6N / m≤S2≤15N / m is met, it is beneficial to suppress the deformation of the electrode assembly after bending and to reduce the risk of diaphragm clogging, thereby reducing the internal resistance and improving the electrochemical performance of the secondary battery.

[0015] 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, an orthographic projection of a first protrusion overlaps with an orthographic projection of one first recess.

[0016] In the above-described embodiment, both the first protrusion and the first recess can disperse the stress of the curved anode electrode sheet, further facilitating the suppression of deformation and rebound of the anode electrode sheet, thereby further facilitating the solution to the overall curvature reduction and equalization deformation issues of the electrode assembly and, ultimately, the entire secondary battery. Furthermore, the orthographic projections of the first protrusion and the first recess overlap, facilitating the simultaneous machining of the first protrusion and the first recess, thereby improving the machining efficiency of the first protrusion and the first recess.

[0017] In one or more of the above embodiments, a plurality of second protrusions are provided on the surface of the cathode electrode, and a plurality of second concave portions are provided on the surface of the cathode electrode facing away from the plurality of second protrusions. Along the first direction, the orthographic projections of the second protrusions and the orthographic projections of the second concave portions overlap.

[0018] In the above embodiment, the second protrusion and the second recess can both disperse the stress of the bent cathode electrode, which is further beneficial to suppressing the deformation and rebound of the cathode electrode, and is also beneficial to processing the second protrusion and the second recess at the same time, thereby improving the processing efficiency of the second protrusion and the second recess.

[0019] In one or more of the above embodiments, the shape of the first protrusion is one of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0020] In the above embodiments, the first protrusion in the form of dot protrusions, mesh protrusions or striped protrusions is conducive to dispersing the stress on the anode electrode piece and can also increase the friction between the anode electrode piece and the cathode electrode piece, thereby helping to suppress the deformation and rebound of the anode electrode piece.

[0021] In one or more of the above embodiments, the second protrusion has a shape of one of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0022] In the above embodiment, the second protrusion in the shape of a dot protrusion, a mesh protrusion or a stripe protrusion is conducive to dispersing the stress on the cathode electrode piece, and can also increase the friction between the anode electrode piece and the cathode electrode piece, thereby helping to suppress the deformation and rebound of the cathode electrode piece.

[0023] In one or more of the above embodiments, when the anode pole piece is flattened, when observed along the first direction, the sum of the areas of the plurality of first protrusions is M1, and the area of ​​the anode pole piece is M2, satisfying: 0.06M2≤M1<M2.

[0024] In the above embodiment, when the condition of 0.06M2≤M1<M2 is satisfied, it is beneficial to improve the dispersion effect of the multiple first protrusions on the overall stress of the anode electrode sheet, thereby improving the suppression of deformation of the first electrode sheet after bending.

[0025] In one or more of the above embodiments, along the first direction, the anode electrode sheet includes a first current collector and a first active material layer that are stacked, the first current collector includes a first coating area, and the first active material layer is provided on both opposite sides of the first coating area. The thickness of the anode electrode sheet corresponding to the first coating area is T1, and the height of the first protrusion is H1, satisfying H1≤0.1T1.

[0026] In the above embodiment, when the condition H1≤0.1T1 is satisfied, it is beneficial to improve the stress dispersing effect of the first protrusion on the anode pole piece, thereby further suppressing the deformation of the anode pole piece after bending, and in the embodiment where the first protrusion is pressed out by an embossing roller, satisfying this condition is also beneficial to reducing the risk of damage to the anode pole piece due to excessive pressure applied by the embossing roller, or reducing the risk of damage to the anode pole piece due to excessive local deformation.

[0027] In one or more of the above embodiments, when the anode plate is flattened, the anode plate has a first boundary line and a second boundary line arranged opposite to each other along the second direction, and a third boundary line and a fourth boundary line arranged opposite to each other along the third direction, and the first direction, the second direction and the third direction are perpendicular to each other.

[0028] In one or more of the above embodiments, the minimum distance between the plurality of first protrusions and the first boundary line is L1, the minimum distance between the plurality of first protrusions and the second boundary line is L2, 1mm≤L1≤7mm, 1mm≤L2≤7mm.

[0029] In the above embodiment, satisfying the above conditions is conducive to reducing the risk of the embossing roller pressing the cutting position of the anode electrode sheet in the second direction, thereby reducing the risk of damage to the anode electrode sheet.

[0030] In one or more of the above embodiments, the minimum distance between the first area and the third boundary line is L3, the minimum distance between the first area and the fourth boundary line is L4, 1mm≤L3≤7mm, 1mm≤L4≤7mm.

[0031] In the above embodiment, satisfying the above conditions is conducive to reducing the risk of the embossing roller pressing the cutting position of the anode electrode sheet in the third direction, thereby reducing the risk of damage to the anode electrode sheet.

[0032] In one or more of the above embodiments, the distance between any two adjacent first protrusions is F1, which satisfies 1.5 mm ≤ F1 ≤ 3 mm.

[0033] In the above embodiment, when the condition of 1.5 mm ≤ F1 ≤ 3 mm is met, it is beneficial to disperse the stress of the anode electrode piece, further suppress the deformation of the anode electrode piece after bending, and the electrode assembly is less likely to produce black spots.

[0034] In one or more of the above embodiments, when viewed along the first direction, the width of the first protrusion is R1, satisfying R1 ≥ 1 mm.

[0035] In the above embodiment, when the condition R1≥1 mm is satisfied, it is beneficial to improve the stress dispersion effect of the first protrusion on the anode electrode sheet, thereby further suppressing the deformation of the anode electrode sheet after bending, and the electrode assembly is less likely to produce black spots.

[0036] In one or more of the above embodiments, along the first direction, the anode electrode sheet, the separator and the cathode electrode sheet are sequentially stacked to form a laminate structure. In the first direction, the outermost layer of the electrode assembly is the cathode electrode sheet.

[0037] In the above embodiment, by setting the outermost layer as the cathode electrode, the outermost cathode electrode can be bonded to the second adhesive layer, which is beneficial to suppressing the rebound of the outermost cathode electrode and maintaining the shape of the electrode assembly after bending, thereby solving the overall curvature reduction, equalization and other deformation problems of the secondary battery, and can improve the performance and reliability of the secondary battery.

[0038] In one or more of the above embodiments, the shell is an aluminum-plastic film packaging bag.

[0039] In one or more of the above embodiments, the first adhesive layer includes a first adhesive, the second adhesive layer includes a second adhesive, and 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, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

[0040] In one or more of the above embodiments, the first adhesive and the second adhesive are of the same type, and the content of the second adhesive in the second adhesive layer is greater than the content of the first adhesive in the first adhesive layer.

[0041] In the above embodiment, the content of the second adhesive in the second adhesive layer is greater than the content of the first adhesive in the first adhesive layer, which is conducive to achieving a peel strength between the second adhesive layer and the cathode electrode greater than the peel strength between the first adhesive layer and the anode electrode.

[0042] In one or more of the above embodiments, the first adhesive layer includes polyvinylidene fluoride, and the content of 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%;

[0043] In the above embodiment, the specific configuration of the first adhesive layer enables the peel strength between the first adhesive layer of the diaphragm and the electrode sheet to be above 6 N / m, which is beneficial to suppressing deformation of the electrode assembly after bending.

[0044] In one or more of the above embodiments, the second adhesive layer includes acrylate, and the content of acrylate in the second adhesive layer is 0.7 mg / 5000 mm 2 -1.1mg / 5000mm 2The content of acrylate in the second adhesive layer is 85wt%-95wt%.

[0045] In the above embodiment, the specific configuration of the second adhesive layer enables the peel strength between the second adhesive layer of the diaphragm and the electrode sheet to be above 10 N / m, which is beneficial to suppressing deformation of the electrode assembly after bending.

[0046] In a second aspect, the present application further provides an electronic device, comprising the secondary battery in any one of the above embodiments.

[0047] 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.

[0048] The electrode assembly of the secondary battery in the present application is bent in a first direction. The electrode assembly includes a cathode electrode sheet, a diaphragm and an anode electrode sheet arranged in a stacked manner. The diaphragm includes a first surface and a second surface arranged relative to each other along the first direction. The diaphragm includes a first adhesive layer arranged on the first surface and a second adhesive layer arranged on the second surface. The first adhesive layer adheres to the anode electrode sheet, and the second adhesive layer adheres to the cathode electrode sheet. The peeling strength between the first adhesive layer and the anode electrode sheet is S1, and the peeling strength between the second adhesive layer and the cathode electrode sheet is S2, satisfying S1<S2. By satisfying S1<S2, the peeling strength between the diaphragm and the cathode electrode sheet can be improved, which is conducive to limiting the deformation of the cathode electrode sheet, suppressing the rebound of the electrode sheet, and preventing the peeling strength between the diaphragm and the anode electrode sheet from being too high, thereby helping to reduce the risk of diaphragm clogging. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG1 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0050] FIG2 is a cross-sectional view of a secondary battery provided in another embodiment of the present application.

[0051] FIG3 is a cross-sectional view of an anode electrode sheet, a cathode electrode sheet, and a diaphragm provided in one embodiment of the present application.

[0052] FIG4 is a cross-sectional view of a secondary battery provided in one embodiment of the present application.

[0053] FIG5 is a cross-sectional view of an anode electrode provided in one embodiment of the present application.

[0054] FIG6 is a cross-sectional view of a cathode electrode provided in an embodiment of the present application.

[0055] FIG7 is a schematic diagram of an unfolded anode electrode provided in an embodiment of the present application.

[0056] FIG8 is a schematic diagram of an unfolded anode electrode provided by another embodiment of the present application.

[0057] FIG9 is a schematic diagram of an unfolded anode electrode provided by another embodiment of the present application.

[0058] FIG10 is a schematic diagram of an unfolded cathode electrode provided in an embodiment of the present application.

[0059] FIG11 is a schematic diagram of an unfolded cathode electrode provided by another embodiment of the present application.

[0060] FIG12 is a schematic diagram of an unfolded cathode electrode provided in another embodiment of the present application.

[0061] FIG13 is a schematic diagram of an electronic device provided in an embodiment of the present application.

[0062] DESCRIPTION OF KEY EMBODIMENTS 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 Adhesive Layer 221 Base Layer 222 First Surface 2221 Second Surface 2222 Second Adhesive Layer 223 Device Body200 Electronic device 1000 First direction X Second direction Y Third direction Z DETAILED DESCRIPTION

[0063] 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.

[0064] 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.

[0065] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0066] 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.

[0067] 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°.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The present application discloses a secondary battery comprising a housing and an electrode assembly. The electrode assembly is housed in the housing and is bent in a first direction. The electrode assembly comprises a cathode electrode sheet, a diaphragm, and an anode electrode sheet arranged in a stacked manner. The diaphragm comprises a first surface and a second surface arranged opposite to each other along a first direction. The diaphragm comprises a first adhesive layer arranged on the first surface and a second adhesive layer arranged on the second surface. The first adhesive layer is bonded to the anode electrode sheet, and the second adhesive layer is bonded to the cathode electrode sheet. The peel strength between the first adhesive layer and the anode electrode sheet is S1, and the peel strength between the second adhesive layer and the cathode electrode sheet is S2, satisfying S1<S2.

[0072] By satisfying S1<S2, the peeling strength between the diaphragm and the cathode electrode can be improved, which is beneficial to limit the deformation of the cathode electrode, suppress the rebound of the electrode, and prevent the peeling strength between the diaphragm and the anode electrode from being too high, thereby reducing the risk of diaphragm clogging.

[0073] 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.

[0074] 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 .

[0075] 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.

[0076] 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.

[0077] In some embodiments, referring to FIG. 1 , the electrode assembly 20 includes a stack of multi-layer electrode sheets 21 and a multi-layer diaphragm 22 . At least one diaphragm 22 is included between any two adjacent electrode sheets 21 . The diaphragm 22 is used to isolate the two adjacent electrode sheets 21 .

[0078] 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.

[0079] 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.

[0080] In some embodiments, the first direction X is parallel to the thickness direction of the electrode assembly 20 .

[0081] 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.

[0082] In some embodiments, the secondary battery 100 is a wound battery, and the electrode assembly 20 has two curved sections (not labeled) arranged along a second direction Y and a middle section (not labeled) located between the curved sections. The second direction Y is perpendicular to the first direction X. The multi-layer cathode electrode sheet 212, the multi-layer anode electrode sheet 211, and the multi-layer separator 22 located in the middle section are arranged approximately 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 located in the curved sections are arranged approximately along the second direction Y.

[0083] In some embodiments, referring to FIG3 , 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.

[0084] In some embodiments, referring to FIG. 3 , 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. Both the third surface 212a and the fourth surface 212b of the second coating region 212c are provided with the second active material layer 2122. The second coating region 212c is a double-sided coating region.

[0085] 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.

[0086] 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.

[0087] In some embodiments, referring to Figures 3 and 4, the diaphragm 22 includes a substrate layer 222, the substrate layer 222 has a first surface 2221 and a second surface 2222 arranged opposite to each other along the first direction X, the diaphragm also includes a first adhesive layer 221 arranged on the first surface 2221 and a second adhesive layer 223 arranged on the second surface 2222, the first adhesive layer 221 is bonded to the anode electrode 211, and the second adhesive layer 223 is bonded to the cathode electrode 212.

[0088] In some embodiments, substrate layer 222 is selected from at least one of polyolefin, polyvinylidene fluoride, polyethylene terephthalate, cellulose, polyimide, polyamide, spandex, or polyphenylene phthalate. Substrate layer 222 is a microporous and porous film that allows ions to pass through and retains electrolyte.

[0089] In some embodiments, the first adhesive layer 221 is provided with a first adhesive, and the second adhesive layer 223 is provided with a second adhesive. 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, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

[0090] The peeling strength between the first adhesive layer 221 and the anode electrode 211 is S1, and the peeling strength between the second adhesive layer 223 and the cathode electrode 212 is S2, satisfying S1<S2.

[0091] By ensuring that the first adhesive layer 221 and the second adhesive layer 223 meet the condition S1 < S2, the peel strength between the separator 22 and the cathode electrode 212 can be improved, which helps limit the deformation of the cathode electrode 212 and suppress the rebound of the electrode 21. Furthermore, the peel strength between the separator and the anode electrode 211 is not excessively high, thereby reducing the risk of pore blockage in the separator 22, lowering internal resistance, and improving the chemical performance of the secondary battery 100.

[0092] In some embodiments, referring to FIG. 5 , a plurality of first protrusions 2113 are disposed on the surface of the anode plate 211 .

[0093] Research has found that the anode electrode 211 is more likely to rebound than the cathode electrode 212. By providing multiple first protrusions 2113 on the anode electrode 211 that is more easily deformed, it is beneficial to disperse the stress of the anode electrode 211, thereby reducing the blockage of the diaphragm 22 while also suppressing the deformation and rebound of the anode electrode 211, which is beneficial to maintaining the shape of the electrode assembly 20 after bending, thereby solving the overall curvature reduction and equalization deformation problems of the secondary battery 100, and can improve the performance and reliability of the secondary battery 100.

[0094] 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 reducing the risk of clogging of the diaphragm 22, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery 100.

[0095] As an illustrative example, S2 may specifically be 1.6S1, 2S1, 2.4S1, 2.8S1, 3.2S1, 3.6S1 or 4S1.

[0096] 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 reducing the risk of clogging of the diaphragm 22, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery 100.

[0097] 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.

[0098] In some embodiments, 9.6 N / m≤S2≤15 N / m is satisfied. Such a setting is beneficial to suppressing deformation of the electrode assembly 20 after bending and reducing the risk of clogging of the diaphragm 22, thereby reducing internal resistance and improving the electrochemical performance of the secondary battery 100.

[0099] 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, 12 N / m, 12.2 N / m, 12.6 N / m, 12.8 N / m, 13 N / m, 13.2 N / m, 13.6 N / m, 13.8 N / m, 14 N / m, 14.2 N / m, 14.6 N / m, 14.8 N / m or 15 N / m.

[0100] In some embodiments, the first adhesive and the second adhesive may be of the same type, and the content of the second adhesive in the second adhesive layer 223 may be greater than the content of the first adhesive in the first adhesive layer 221, so that the peeling strength S2 between the second adhesive layer 223 and the cathode electrode 212 is greater than the peeling strength S1 between the first adhesive layer 221 and the anode electrode 211.

[0101] The first adhesive 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 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.

[0102] 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:

[0103] 1) Separate the first adhesive layer 221 from the separator 22 to obtain agglomerate powder with a mass of M.

[0104] 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.

[0105] 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%.

[0106] 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.

[0107] In some embodiments, referring to FIG4 , along a first direction X, the anode electrode sheet 211, the separator 22, and the cathode electrode sheet 212 are sequentially stacked to form a laminate structure, and the outermost layer of the electrode assembly 20 is the cathode electrode sheet 212. The first adhesive layer 221 and the second adhesive layer 223 are sequentially disposed along the first direction X.

[0108] Research has found that in a curved electrode assembly 20, the electrode piece 21 near the protruding side of the electrode assembly 20 is subjected to greater stress and is more prone to deformation and rebound. When the outermost side of the two opposite sides of the electrode assembly 20 along the first direction X is the cathode electrode piece 212, the outermost cathode electrode piece 212 on the side of the electrode assembly 20 protruding outward in the first direction X is also more prone to rebound. By setting the outermost layer as the cathode electrode piece 212, the outermost cathode electrode piece 212 can be bonded to the second adhesive layer 223, which helps to suppress the rebound of the outermost cathode electrode piece 212 and maintain the shape of the bent electrode assembly 20. This helps solve the deformation problems such as the reduction of the overall curvature and equalization of the secondary battery 100, and can improve the performance and reliability of the secondary battery 100.

[0109] In some embodiments, the first adhesive layer 221 includes polyvinylidene fluoride, and the content of polyvinylidene fluoride in the first adhesive layer 221 is 3 mg / 5000 mm 2 -4mg / 5000mm 2 The content of polyvinylidene fluoride in the first adhesive layer 221 is 60 wt % to 80 wt %.

[0110] In this embodiment, the specific configuration of the first adhesive layer 221 ensures that the peel strength between the first adhesive layer 221 of the diaphragm 22 and the electrode piece 21 is above 6 N / m, which is beneficial for suppressing deformation of the electrode assembly 20 after bending.

[0111] 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 221 is 3 mg / 5000 mm 2 -4mg / 5000mm 2 Refers to the diaphragm 22 every 5000mm 2The coating weight of the area coated polyvinylidene fluoride is 3mg-4mg.

[0112] The unit "wt%" represents mass percentage (%). A polyvinylidene fluoride content of 60 wt% to 80 wt% in the first adhesive layer 221 means that the polyvinylidene fluoride in the first adhesive layer 221 of the separator 22 accounts for 60% to 80% of the mass of the entire first adhesive layer 221. The specific conversion method is: mass percentage wt% = (mass of polyvinylidene fluoride / mass of first adhesive layer 221) × 100%.

[0113] In some embodiments, the second adhesive layer 223 includes acrylate, and the content of acrylate in the second adhesive layer 223 is 0.7 mg / 5000 mm 2 -1.1mg / 5000mm 2 The content of acrylate in the second adhesive layer 223 is 85 wt % to 95 wt %.

[0114] In this embodiment, the specific configuration of the second adhesive layer 223 enables the peel strength between the second adhesive layer 223 of the diaphragm 22 and the electrode piece 21 to be above 10 N / m, which is beneficial for suppressing deformation of the electrode assembly after bending.

[0115] It should be noted that the peel strength between the diaphragm 22 and the electrode 21 is tested as follows:

[0116] 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: discharge the lithium-ion battery to 0V, then disassemble the lithium-ion battery, remove the diaphragm 22 and the electrode 21 bonded thereto as a whole, and wipe the electrolyte on the surface with dust-free paper. Then cut into 20mm×60mm strip specimens. Along the length direction of the specimen, the side of the electrode assembly 20 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 21 of the sample that is not adhered to the diaphragm 22, and place the sample in the chuck and clamp it. The angle between the pulled-up part of the sample 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 22 and the electrode 21, recorded as S, and the unit is N / m.

[0117] Among them, when the diaphragm 22 and the electrode 21 in the sample are bonded by the first adhesive layer 221, the peel strength S1 between the first adhesive layer 221 and the electrode 21 is measured; when the diaphragm 22 and the electrode 21 in the sample are bonded by the second adhesive layer 223, the peel strength S2 between the second adhesive layer 223 and the electrode 21 is measured.

[0118] 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:

[0119] 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 full charge voltage. The voltage was then constant to 0.05C. The battery was then discharged to 3.0V at a constant current rate of 0.5C. This constituted one charge-discharge cycle. After 800 charge-discharge cycles, the rate of change in the arc radius of the secondary battery 100 and the capacity retention of the secondary battery 100 were measured.

[0120] 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.

[0121] The arc radius change rate of the secondary battery 100 is obtained as follows:

[0122] 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.

[0123] 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.

[0124] The arc radius change rate of the electrode unit is obtained as (ba) / a.

[0125] 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.

[0126] 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.

[0127] The arc radius change rate and capacity retention rate of all tested secondary batteries 100 are counted. If the arc radius change rate is less than 9% and the capacity retention rate is greater than 85%, it is determined to have passed the test; otherwise, it is determined to have failed the test.

[0128] The following describes the specific implementation of the secondary battery 100 in the examples and comparative examples.

[0129] Examples and Comparative Examples

[0130] A secondary battery, the assembly process is as follows:

[0131] (1) Preparation of the anode plate 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, leaving an empty foil area at the edge of the copper foil, and dried at 110°C to obtain an anode plate 211 with a coating thickness of 150 μm and coated on one side with an anode active material layer. The above steps are repeated on the other surface of the anode plate 211 to obtain an anode plate 211 with a double-sided coating of an anode active material layer. The anode plate 211 is then placed in a rolling machine for embossing, so that a plurality of first protrusions 2113 are formed on the surface of one side of the anode plate 211, and a plurality of first concave portions 2114 are formed on the surface of the other side of the anode plate 211. Then, the excess empty foil area is removed by laser die-cutting to obtain an anode tab.

[0132] (2) Preparation of cathode electrode 212: The cathode active material lithium cobalt oxide (Li CoO2), 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.

[0133] (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.

[0134] (4) Preparation of the diaphragm 22: The diaphragm 22 has a three-layer structure, which includes a first adhesive layer 221, a base layer 222, and a second adhesive layer 223. The base layer 222 is made of polyethylene (PE). The first adhesive layer 221 includes a first adhesive, and the second adhesive layer 223 includes a second adhesive. The first adhesive layer 221 and the second adhesive layer 223 also contain inorganic ceramic particles Al2O3.

[0135] (5) Preparation of electrode assembly 20: The cathode electrode 212, the diaphragm 22 and the anode electrode 211 are stacked and the stacked structure is hot-pressed on a flat plate for 10 seconds at a temperature of 80°C and a pressure of 1.5 MPa to form the electrode assembly 20 for use.

[0136] (6) 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.

[0137] (7) Liquid injection and packaging: The electrolyte is injected into the assembled electrode assembly 20, and the secondary battery 100 is manufactured through processes such as vacuum packaging, static standing, hot pressing, and shaping.

[0138] The main parameter control and test results of each embodiment and comparative example are shown in Table 1:

[0139] Table 1:

[0140] Among them, PVDF is polyvinylidene fluoride, PDDA is acrylate, PVDF-HFP is a copolymer of vinylidene fluoride and hexafluoropropylene, and PMMA is polymethyl methacrylate.

[0141] According to Table 1 above, compared with Comparative Examples 1-4, Example 1 satisfies 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, and is also beneficial to improving the capacity retention rate of the secondary battery 100 and improving the chemical properties of the secondary battery 100.

[0142] 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.

[0143] As can be seen from 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.

[0144] In some embodiments, as shown in FIG5 , 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 will not significantly deform, thereby facilitating the resolution of deformation issues such as reduction and equalization of the secondary battery 100.

[0145] In some embodiments, referring to FIG. 5 , a plurality of first recesses 2114 are defined along the first direction X on a surface of the anode electrode 211 facing away from the plurality of first protrusions 2113 .

[0146] Both the first protrusion 2113 and the first recess 2114 can disperse the stress of the curved anode plate 211, which is further beneficial to suppressing the deformation and rebound of the anode plate 211, thereby further beneficial to solving the overall curvature reduction and equalization deformation problems of the electrode assembly 20 and even the entire secondary battery 100.

[0147] In some embodiments, referring to FIG. 5 , the orthographic projection of the first convex portion 2113 and the orthographic projection of the first concave portion 2114 overlap, which helps to further enhance the effect of suppressing deformation and rebound of the anode electrode 211 .

[0148] In some embodiments, the orthographic projection of a first convex portion 2113 may overlap with the orthographic projection of a first concave portion 2114 , or the orthographic projection of each first convex portion 2113 may overlap with the orthographic projection of a first concave portion 2114 .

[0149] When the orthographic projection of a first convex portion 2113 and the orthographic projection of a first concave portion 2114 overlap along the first direction X, it is beneficial to process the first convex portion 2113 and the first concave portion 2114 whose orthographic projections overlap together, thereby improving the processing efficiency of the first convex portion 2113 and the first concave portion 2114.

[0150] In other embodiments, the orthographic projection of one first convex portion 2113 may overlap with the orthographic projections of multiple first concave portions 2114 , or the orthographic projection of one first concave portion 2114 may overlap with the orthographic projections of multiple first convex portions 2113 .

[0151] In some embodiments, referring to FIG. 6 , a plurality of second protrusions 2123 are provided on the surface of the cathode electrode 212 . The second protrusions 2123 can disperse the stress of the bent cathode electrode 212 and suppress deformation and rebound of the cathode electrode 212 .

[0152] In some embodiments, referring to FIG. 6 , a plurality of second recesses 2124 are defined on a surface of the cathode electrode 212 facing away from the plurality of second protrusions 2123 .

[0153] The second convex portion 2123 and the second concave portion 2124 can both disperse the stress of the bent cathode electrode piece 212 , which is further beneficial to suppressing the deformation and rebound of the cathode electrode piece 212 .

[0154] In some embodiments, along the first direction X, the orthographic projection of each second protrusion 2123 and the orthographic projection of a second recess 2124 overlap, which helps to further enhance the effect of suppressing deformation and rebound of the cathode electrode 212 .

[0155] In some embodiments, the orthographic projection of a second convex portion 2123 and the orthographic projection of a second concave portion 2124 may overlap; or the orthographic projection of each second convex portion 2123 and the orthographic projection of a second concave portion 2124 may overlap.

[0156] When the orthographic projection of a second convex portion 2123 and the orthographic projection of a second concave portion 2124 overlap along the first direction X, it is beneficial to process the second convex portion 2123 and the second concave portion 2124 with overlapping orthographic projections together, thereby improving the processing efficiency of the second convex portion 2123 and the second concave portion 2124.

[0157] In other embodiments, the orthographic projection of one second convex portion 2123 may overlap with the orthographic projections of multiple second concave portions 2124 , or the orthographic projection of one second concave portion 2124 may overlap with the orthographic projections of multiple second convex portions 2123 .

[0158] It is also beneficial to process the second convex portion 2123 and the second concave portion 2124 at the same time, thereby improving the processing efficiency of the second convex portion 2123 and the second concave portion 2124.

[0159] 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.

[0160] In some embodiments, the cathode electrode 212 is formed with a second protrusion 2123 and a second concave portion 2124 by an embossing process.

[0161] In some embodiments, referring to FIG. 7 to FIG. 9 , the shape of the first protrusion 2113 is one of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0162] In some embodiments, referring to FIG. 10 to FIG. 12 , the second protrusion 2123 is in the shape of a dot-shaped protrusion, a mesh-shaped protrusion, and a striped protrusion.

[0163] In some embodiments, referring to Figures 7 to 12, the shape of the first protrusion 2113 is different from the shape of the second protrusion 2123, which is beneficial to increase 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, thereby improving the reliability of the electrode assembly 20.

[0164] In some embodiments, the shape of the first protrusion 2113 matches 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 helping to further increase 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.

[0165] The anode plate 211 and the first protrusion 2113 on the anode plate 211 are described below. The specific configuration of the cathode plate 212, the specific configuration of the second protrusion 2123 and the beneficial effects can all be referred to the specific implementation methods and beneficial effects of the anode plate 211 and the first protrusion 2113 described below, and will not be repeated here.

[0166] In some embodiments, referring to FIG. 7 , 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.

[0167] In some embodiments, referring to FIG5 , 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.

[0168] 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, the first active material layer 2112, and the second active material layer 2122 on the second surface 211b. The height H1 of the first protrusion 2113 is the height of the largest of the plurality of first protrusions 2113.

[0169] In some embodiments, referring to FIG. 7 , 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 relatively arranged along the second direction Y, and a third boundary line 21 c and a fourth boundary line 21 d relatively arranged along the third direction Z. The first direction X, the second direction Y, and the third direction Z are perpendicular to each other.

[0170] 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 .

[0171] In some embodiments, referring to FIG. 7 , 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.

[0172] 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.

[0173] In some embodiments, referring to FIG. 7 , 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.

[0174] 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.

[0175] In some embodiments, referring to FIG7 , the distance F1 between any two adjacent first protrusions 2113 satisfies 1.5 mm ≤ F1 ≤ 3 mm. This condition helps disperse the stress on the anode electrode 211, further suppresses deformation of the anode electrode 211 after bending, and reduces the risk of black spots on the electrode assembly 20.

[0176] 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.

[0177] In some embodiments, referring to FIG. 7 , 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.

[0178] 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.

[0179] It can be understood that when the first protrusion 2113 is a dot-shaped protrusion, the first protrusion 2113 is circular, and the width R 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 R 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 R of the first protrusion 2113 is the width of the first protrusion 2113 along the arrangement direction.

[0180] Referring to FIG. 13 , 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.

[0181] In some embodiments, the electronic device 1000 may be a head-mounted device such as AR glasses, VR glasses, etc., which are not listed here one by one.

[0182] In some embodiments, referring to FIG13 , 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.

[0183] 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, It comprises a shell and an electrode assembly, wherein the shell accommodates the electrode assembly, and the electrode assembly is bent toward a first direction; The electrode assembly includes a cathode electrode sheet, a diaphragm and an anode electrode sheet which are stacked, the diaphragm includes a first surface and a second surface which are arranged opposite to each other along the first direction, the diaphragm includes a first adhesive layer arranged on the first surface and a second adhesive layer arranged on the second surface, the first adhesive layer is bonded to the anode electrode sheet, the second adhesive layer is bonded to the cathode electrode sheet, the peeling strength between the first adhesive layer and the anode electrode sheet is S1, the peeling strength between the second adhesive layer and the cathode electrode sheet is S2, satisfying S1<S2.

2. The secondary battery according to claim 1, characterized in that, A plurality of first protrusions are provided on the surface of the anode electrode sheet.

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

4. The secondary battery according to claim 1, wherein Satisfies 6N / m≤S1<9.6N / m.

5. The secondary battery according to claim 1, wherein Satisfies 9.6N / m≤S2≤15N / m.

6. The secondary battery according to claim 2, characterized in that, A surface of the anode electrode sheet facing away from the plurality of first protrusions is provided with a plurality of first concave portions, and along the first direction, the orthographic projections of the first protrusions and the orthographic projections of the first concave portions overlap.

7. The secondary battery according to claim 6, characterized in that, A plurality of second protrusions are provided on the surface of the cathode electrode piece, and a plurality of second concave sections are provided on the surface of the cathode electrode piece away from the plurality of second protrusions. Along the first direction, the orthographic projections of the second protrusions and the orthographic projections of the second concave sections overlap.

8. The secondary battery according to claim 7, characterized in that, The shape of the first protrusion is one of a dot protrusion, a mesh protrusion and a stripe protrusion; and / or, The second protrusion has a shape of one of a dot protrusion, a mesh protrusion and a stripe protrusion.

9. The secondary battery according to claim 2, wherein When the anode electrode sheet is flattened, when observed along the first direction, the sum of the areas of the plurality of first protrusions is M1, and the area of ​​the anode electrode sheet is M2, satisfying: 0.06M2≤M1<M2.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, Along the first direction, the anode electrode sheet, the separator and the cathode electrode sheet are stacked in sequence to form a stacked structure. In the first direction, the outermost layer of the electrode assembly is the cathode electrode sheet.

11. The secondary battery according to claim 10, characterized in that, The shell is an aluminum-plastic film packaging bag.

12. The secondary battery according to claim 1, characterized in that, The first adhesive layer includes a first adhesive, and the second adhesive layer includes a second adhesive. 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, polyacrylic acid salt, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.

13. The secondary battery according to claim 12, characterized in that, The first adhesive and the second adhesive are of the same type, and a content of the second adhesive in the second adhesive layer is greater than a content of the first adhesive in the first adhesive layer.

14. An electronic device, characterized in that, Comprising the secondary battery according to any one of claims 1 to 13.

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