Secondary battery and electronic device

Abstract

The application discloses a secondary battery and an electronic device. The secondary battery comprises a shell, an electrode assembly, a first adhesive layer and a second adhesive layer. The electrode assembly is arranged in the shell, and the electrode assembly comprises a first electrode sheet wound in a first direction. The first electrode sheet comprises a tail section forming an outermost circle of the electrode assembly, and the tail section comprises a first surface facing away from the shell and a second surface facing the shell. The first adhesive layer comprises a first part adhered to the first surface and a second part extending beyond the tail section in the first direction. The second adhesive layer comprises a third part adhered to the second surface and a fourth part extending beyond the tail section in the first direction. In the thickness direction of the tail section, the second adhesive layer, the tail section and the first adhesive layer are sequentially stacked, and at least part of the fourth part overlaps the second part. The overlapping of at least part of the fourth part and the second part reduces the risk of adhesion of the second part to the shell, thereby improving the reliability of the secondary battery.

Description

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] With the development of society and the advancement of technology, the application of electronic devices is becoming more and more extensive, and the reliability requirements for secondary batteries used in electronic devices are becoming higher and higher.

[0003] At present, during the production process of secondary batteries, adhesive tape is pasted on the electrode. The adhesive tape completely covers the electrode and extends beyond the electrode in the width direction. The extending portion of the adhesive tape will be folded during the packaging process of the electrode assembly. When the adhesive tape is pasted to the shell, there is a risk of causing the electrode to be folded, thereby reducing the reliability of the secondary battery. Summary of the Invention

[0004] In view of this, it is necessary to provide a secondary battery that reduces the risk of electrode folding.

[0005] Some embodiments of the present application provide a secondary battery, which includes a shell, an electrode assembly, a first glue layer, and a second glue layer. The electrode assembly is arranged in the shell, and the electrode assembly includes a first electrode piece, a second electrode piece, and a separator located between the first electrode piece and the second electrode piece. The first electrode piece, the second electrode piece, and the separator are stacked and wound, and the winding center axis direction of the electrode assembly is a first direction. The first electrode piece includes a tail section, and the tail section constitutes the outermost circle of the electrode assembly. The tail section includes a first surface facing away from the shell and a second surface facing the shell. The first glue layer includes a first adhesive layer, and the first glue layer includes a first part bonded to the first surface and a second part extending beyond the tail section in the first direction, and the first part is connected to the second part. The second glue layer includes a second adhesive layer, and the second glue layer includes a third part bonded to the second surface and a fourth part extending beyond the tail section in the first direction, and the third part is connected to the fourth part. In the thickness direction of the tail section, the second glue layer, the first pole piece and the first glue layer are stacked in sequence, and the first adhesive layer and the second adhesive layer are arranged facing each other; in the thickness direction of the tail section, at least part of the fourth part overlaps with the second part.

[0006] In the above embodiment, the first adhesive layer and the second adhesive layer are arranged opposite to each other, and at least part of the fourth part overlaps with the second part, so that the fourth part covers at least part of the first adhesive layer of the second part toward the shell, which is beneficial to reducing the risk of adhesion between the second part and the shell, thereby reducing the risk of folding the first electrode when the second part is folded, and further beneficial to improving the reliability of the secondary battery.

[0007] In some embodiments, the first adhesive layer and the second adhesive layer are provided separately.

[0008] In the above embodiment, the first adhesive layer and the second adhesive layer are provided separately, which is conducive to using the adhesive laminating structure to adhere the second adhesive layer, thereby facilitating reducing the difficulty of the adhesive laminating process and improving the consistency of the adhesive laminating effect.

[0009] In some embodiments, the first adhesive layer further includes a fifth portion, which extends beyond the tail segment in the first direction, and the fifth portion, the first portion, and the second portion are sequentially connected in the first direction; the second adhesive layer further includes a sixth portion, which extends beyond the tail segment in the first direction, and the sixth portion, the third portion, and the fourth portion are sequentially connected in the first direction; in the thickness direction of the tail segment, at least a portion of the sixth portion overlaps with the fifth portion.

[0010] In the above embodiment, at least part of the sixth part overlaps with the fifth part, which helps to reduce the risk of the first adhesive layer of the fifth part adhering to the shell, and further helps to reduce the risk of the shell driving the fifth part and the fifth part driving the first pole piece to fold.

[0011] In some embodiments, the first adhesive layer also includes a fifth part, which extends beyond the tail segment in the first direction, and the fifth part, the first part, and the second part are connected in sequence in the first direction; the secondary battery also includes a third adhesive layer, the third adhesive layer includes a seventh part bonded to the second surface and an eighth part extending beyond the tail segment in the first direction, the third adhesive layer and the second adhesive layer are separately arranged, and the seventh part is connected to the eighth part; in the thickness direction of the tail segment, at least part of the eighth part overlaps with the fifth part.

[0012] In the above embodiment, at least a portion of the eighth portion overlaps with the fifth portion, which helps reduce the risk of the first adhesive layer of the fifth portion adhering to the housing, thereby reducing the risk of the housing causing the fifth portion to fold over, and the fifth portion causing the first pole piece to fold over. Furthermore, the separate second and third adhesive layers help reduce the length of the adhesive layer applied to the second surface along the first direction, thereby saving adhesive.

[0013] In some embodiments, the tail section includes a first straight section, a first bent section, a second straight section, and a second bent section connected in sequence along the winding direction, the electrode assembly includes a first end face perpendicular to the first direction, and the second adhesive layer extends from the first straight section across the first end face to the second straight section.

[0014] In the above embodiment, the second adhesive layer extends from the first straight section across the first end surface to the second straight section, which helps the second adhesive layer to restrain the entire electrode assembly, thereby improving the drop performance of the secondary battery.

[0015] In some embodiments, the second portion and the fourth portion are an integrally formed adhesive layer.

[0016] In the above embodiment, the second part and the fourth part are an integrally arranged adhesive layer, which is conducive to folding the part of the integral adhesive layer that exceeds the tail section along the first direction directly toward the second surface and then sticking it to the second surface. Compared with the separate arrangements of the first adhesive layer and the second adhesive layer, the adhesive mechanism and the corresponding adhesive station specifically used for sticking the second adhesive layer are eliminated, which is conducive to reducing costs.

[0017] In some embodiments, the first adhesive layer further includes a fifth portion, which extends beyond the tail section in the first direction, and the fifth portion, the first portion, and the second portion are sequentially connected in the first direction. The secondary battery further includes a third adhesive layer, which includes a seventh portion bonded to the second surface and an eighth portion extending beyond the tail section in the first direction. The third adhesive layer is separate from the second adhesive layer, and the seventh portion is connected to the eighth portion. The third adhesive layer and the second adhesive layer are sequentially disposed along the first direction. The eighth portion is integrally formed with the fifth portion, and in the thickness direction of the tail section, at least a portion of the fourth portion overlaps with the second portion, and at least a portion of the eighth portion overlaps with the fifth portion.

[0018] In the above embodiment, at least part of the eighth part overlaps with the fifth part, which helps to reduce the risk of the first adhesive layer of the fifth part adhering to the shell, and further helps to reduce the risk of the shell driving the fifth part and the fifth part driving the first pole piece to fold.

[0019] In some embodiments, the third portion at least partially overlaps with the seventh portion in a thickness direction of the tail section.

[0020] In the above embodiment, in the thickness direction of the tail section, the third part and the seventh part at least partially overlap, which is beneficial to increasing the area of ​​the second surface covered by the second adhesive layer along the first direction, thereby helping to enhance the effect of the second adhesive layer in limiting the exposure of debris generated by the first pole piece during the puncture test or the impact test, thereby reducing the risk of the first pole piece debris being exposed and short-circuiting with the second pole piece during the test.

[0021] In some embodiments, the secondary battery further comprises a third adhesive layer and a fourth adhesive layer. The third adhesive layer comprises a seventh portion bonded to the second surface and an eighth portion extending beyond the tail section in the first direction. The third adhesive layer is separate from the second adhesive layer, and the seventh portion is connected to the eighth portion. The fourth adhesive layer comprises a ninth portion bonded to the first surface and a tenth portion extending beyond the tail section in the first direction. The fourth adhesive layer is separate from the first adhesive layer, and the ninth portion is connected to the tenth portion. The eighth portion and the tenth portion are integrally formed as an adhesive layer. In the thickness direction of the tail section, at least a portion of the fourth portion overlaps with the second portion, and at least a portion of the eighth portion overlaps with the tenth portion.

[0022] In the above embodiment, the provision of the third adhesive layer and the fourth adhesive layer is beneficial to further increasing the area of ​​the adhesive layer covering the first surface. In the embodiment provided with the first section and the second section, the first adhesive layer is attached to the junction of the first section and the second section, which is beneficial to reducing the risk of the active material at the tail of the first section piercing the isolation membrane and lithium plating, and is also beneficial to reducing the risk of the burrs at the tail of the second pole piece piercing the isolation membrane and short-circuiting with the first pole piece.

[0023] In some embodiments, the housing is an aluminum-plastic film packaging bag.

[0024] In some embodiments, the first portion and the first surface have a first peel strength, the third portion and the second surface have a second peel strength, and the first peel strength is less than the second peel strength.

[0025] In the above embodiment, the second bonding strength is greater than the first bonding strength, which is beneficial to reducing the risk of bonding failure between the first adhesive layer and the second adhesive layer, thereby reducing the risk of bonding between the second portion of the first adhesive layer and the housing.

[0026] In some embodiments, the electrode assembly also includes an electrode terminal. In a first direction, the shell includes a first end and a second end arranged opposite to each other, the electrode terminal is located at the first end, and the second part and the fourth part are located at the second end; the shell also includes a first packaging part and a second packaging part, and the first packaging part and the second packaging part are arranged as a whole at the second end.

[0027] In some embodiments, the tail section includes a first straight section, a first bent section, a second straight section, and a second bent section connected in sequence along the winding direction, and at least part of the first section is bonded to the first surface of the first straight section or the first surface of the second straight section.

[0028] In the above embodiment, at least part of the first portion is bonded to the first surface of the first straight segment or the first surface of the second straight segment, so that when the wound electrode assembly ends at the first straight segment or the second straight segment, the thickness difference of the secondary battery is reduced.

[0029] In some embodiments, along the first direction, the length of the second portion is L1, and the length of the fourth portion is L2, satisfying L1<L2.

[0030] In the above embodiment, L1<L2, which helps the fourth part cover the first adhesive layer of the second part, thereby helping to reduce the risk of adhesion between the second part and the housing.

[0031] In addition, the present application also provides an electronic device that is beneficial for improving reliability.

[0032] Some embodiments of the present application provide an electronic device, which includes a secondary battery as described in any of the above embodiments.

[0033] In the above embodiment, the probability of the first electrode in the secondary battery being folded is reduced, which is beneficial to improving the reliability of the secondary battery and further beneficial to improving the reliability of the electronic device.

[0034] The secondary battery disclosed herein comprises a housing, an electrode assembly, a first adhesive layer, and a second adhesive layer. The electrode assembly is disposed within the housing and includes a wound first electrode sheet, with the winding axis of the electrode assembly oriented in a first direction. The first electrode sheet includes a tail section forming the outermost coil of the electrode assembly, the tail section including a first surface facing away from the housing and a second surface facing the housing. The first adhesive layer includes a first portion bonded to the first surface and a second portion extending beyond the tail section in the first direction. The second adhesive layer includes a third portion bonded to the second surface and a fourth portion extending beyond the tail section in the first direction. The second adhesive layer, the first electrode sheet, and the first adhesive layer are stacked sequentially along the thickness of the tail section, with at least a portion of the fourth portion overlapping the second portion. The first adhesive layer and the second adhesive layer are disposed opposite each other, with at least a portion of the fourth portion overlapping the second portion, such that the fourth portion covers the first adhesive layer of the second portion facing the housing. This reduces the risk of the second portion adhering to the housing, thereby reducing the risk of the first electrode sheet being folded when the second portion folds, thereby improving the reliability of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic structural diagram of a secondary battery provided in one embodiment of the present application.

[0036] Figure 2 for Figure 1 A schematic cross-sectional view of a secondary battery according to an embodiment of the present invention is shown along the cutting line CC.

[0037] Figure 3 for Figure 1 Schematic diagram of the assembly of the secondary battery.

[0038] Figure 4 for Figure 1 A schematic cross-sectional view of a secondary battery according to an embodiment of the present invention is shown along the cutting line CC.

[0039] Figure 5 A schematic diagram of the unfolded tail section, the first adhesive layer, and the second adhesive layer provided in one embodiment of the present application.

[0040] Figure 6 A schematic diagram of an unfolded tail section, a first adhesive layer, and a second adhesive layer provided in another embodiment of the present application.

[0041] Figure 7 for Figure 5 Schematic diagram of the tail section, the first adhesive layer, and the second adhesive layer from another perspective.

[0042] Figure 8A schematic diagram of the unfolded tail section, the first adhesive layer, and the second adhesive layer provided in yet another embodiment of the present application.

[0043] Figure 9 A schematic diagram of the unfolded tail section and the first adhesive layer, the second adhesive layer, and the third adhesive layer provided in one embodiment of the present application.

[0044] Figure 10 This is a schematic diagram of the first end surface behind the hidden shell of a secondary battery provided by one embodiment of the present application.

[0045] Figure 11 This is a schematic diagram of the electrode assembly, the first adhesive layer, and the second adhesive layer when viewed from the first bending section toward the second bending section according to another embodiment of the present application.

[0046] Figure 12 A schematic diagram of the unfolded tail section, the first adhesive layer, and the second adhesive layer provided in yet another embodiment of the present application.

[0047] Figure 13 A schematic diagram of the unfolded tail section and the first adhesive layer, the second adhesive layer, and the third adhesive layer provided in another embodiment of the present application.

[0048] Figure 14 A schematic diagram of the unfolded tail section, the first adhesive layer, and the second adhesive layer provided in yet another embodiment of the present application.

[0049] Figure 15 A schematic diagram of an unfolded tail section and a first adhesive layer, a second adhesive layer, a third adhesive layer, and a fourth adhesive layer provided in an embodiment of the present application.

[0050] Figure 16 A schematic diagram of an unfolded tail section and a first adhesive layer, a second adhesive layer, a third adhesive layer, and a fourth adhesive layer provided in another embodiment of the present application.

[0051] Figure 17 A schematic diagram of an electronic device provided in one embodiment of the present application.

[0052] Description of main component symbols

[0053] Secondary battery 100

[0054] Housing 10

[0055] Main body 11

[0056] Edge banding 12

[0057] First packaging unit 13

[0058] Second packaging unit 14

[0059] First end 15

[0060] Second end 16

[0061] Electrode assembly 20

[0062] First pole piece 21

[0063] Tail section 211

[0064] First surface 211a

[0065] The first paragraph

[0066] Second paragraph 2112a

[0067] Second surface 211b

[0068] The first straight section 2111

[0069] First side portion 2111b

[0070] Second side portion 2111c

[0071] First bending section 2112

[0072] The second straight section

[0073] Second bending section 2114

[0074] Second pole piece 22

[0075] Isolation film 23

[0076] First end surface 24

[0077] Second end surface 25

[0078] First electrode terminal 101

[0079] Second electrode terminal 102

[0080] First adhesive layer 30

[0081] First base layer 31

[0082] First adhesive layer 32

[0083] Part 1 33

[0084] Part 2 34

[0085] Part 5 35

[0086] Second adhesive layer 40

[0087] Second base layer 41

[0088] Second adhesive layer 42

[0089] Part 343

[0090] Part 44

[0091] Part 6 45

[0092] The third adhesive layer 50

[0093] Part 7 51

[0094] Part 8 52

[0095] Fourth adhesive layer 60

[0096] Part 9 61

[0097] Part 10 62

[0098] First direction X

[0099] Second direction Y

[0100] The third direction Z

[0101] Electronic device 1000 DETAILED DESCRIPTION

[0102] 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.

[0103] It should be noted that when a component is considered to be "connected to" another component, it can 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 can be directly disposed on the other component or there may be an intermediate component. The terms "top", "bottom", "upper", "lower", "left", "right", "front", "back", and similar expressions used herein are for illustrative purposes only.

[0104] The term "perpendicular" is used to describe the ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular between the two components. For example, combined with numerical descriptions, perpendicular can refer to the angle between two straight lines being in the range of 90°±10°, perpendicular can also refer to the dihedral angle between two planes being in the range of 90°±10°, and perpendicular can also refer to the angle between a straight line and a plane being in the range of 90°±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if the overall extension direction is a straight line or a plane.

[0105] 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 allows a tolerance of ±5%.

[0106] 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.

[0107] The present application discloses a secondary battery, which includes a shell, an electrode assembly, a first adhesive layer, and a second adhesive layer. The electrode assembly is arranged in the shell, and the electrode assembly includes a first electrode piece, a second electrode piece, and an isolation film 23 located between the first electrode piece and the second electrode piece. The first electrode piece, the second electrode piece, and the isolation film 23 are stacked and wound, and the winding center axis direction of the electrode assembly is the first direction. The first electrode piece includes a tail section, which constitutes the outermost circle of the electrode assembly. The tail section includes a first surface 211a facing away from the shell and a second surface 211b facing the shell. The first adhesive layer includes a first adhesive layer, the first adhesive layer includes a first portion bonded to the first surface 211a and a second portion extending beyond the tail section in the first direction, and the first portion is connected to the second portion. The second adhesive layer includes a second adhesive layer, the second adhesive layer includes a third portion bonded to the second surface 211b and a fourth portion extending beyond the tail section in the first direction, and the third portion is connected to the fourth portion. In the thickness direction of the tail section, the second glue layer, the first pole piece and the first glue layer are stacked in sequence, and the first adhesive layer and the second adhesive layer are arranged facing each other; in the thickness direction of the tail section, at least part of the fourth part overlaps with the second part.

[0108] The above-mentioned first adhesive layer and the second adhesive layer are arranged opposite to each other, and at least part of the fourth part overlaps with the second part, so that the fourth part covers at least part of the first adhesive layer of the second part toward the shell, which is beneficial to reducing the risk of adhesion between the second part and the shell, thereby reducing the risk of folding the first electrode when the second part is folded, and further beneficial to improving the reliability of the secondary battery.

[0109] 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.

[0110] See also Figure 1 and Figure 2The embodiment of the present application provides a secondary battery 100, which includes a housing 10, an electrode assembly 20, a first adhesive layer 30, and a second adhesive layer 40. The electrode assembly 20 is disposed in the housing 10. The electrode assembly 20 includes a first electrode piece 21, a second electrode piece 22, and a separator 23 located between the first electrode piece 21 and the second electrode piece 22. The first electrode piece 21, the second electrode piece 22, and the separator 23 are stacked and wound. The first electrode piece 21 includes a tail section 211, which constitutes the outermost circle of the electrode assembly 20. The tail section 211 includes a first surface 211a facing away from the housing 10 and a second surface 211b facing the housing 10. The first adhesive layer 30 is bonded to the first surface 211a, the second adhesive layer 40 is bonded to the second surface 211b, and the second adhesive layer 40 is also bonded to the first adhesive layer 30.

[0111] The tail segment 211 constitutes the outermost circle of the electrode assembly 20, which can be understood as follows: the outermost circle layer structure of the wound electrode assembly 20 is the first pole piece 21, and the part of the first pole piece 21 located in the outermost circle is the tail segment 211 of the first pole piece 21.

[0112] In some embodiments, along the thickness direction of the electrode assembly 20 , the starting portion of the winding of the first electrode sheet 21 overlaps with the ending portion of the winding of the tail section 211 of the first electrode sheet 21 .

[0113] In some embodiments, see Figure 1 and Figure 3 The housing 10 has a main body 11 and a sealing edge 12. The main body 11 is used to accommodate the electrode assembly 20. The sealing edge 12 extends outward from the circumference of the main body 11. The housing 10 includes a first packaging portion 13 and a second packaging portion 14. One side of the first packaging portion 13 is connected to one side of the second packaging portion 14. The first packaging portion 13 and the second packaging portion 14 are folded toward each other along the connection position until the periphery of the first packaging portion 13 contacts the periphery of the second packaging portion 14. The separated portion of the first packaging portion 13 and the second packaging portion 14 forms the main body 11. The contacting periphery of the first packaging portion 13 and the periphery of the second packaging portion 14 are sealed to form the sealing edge 12.

[0114] In some embodiments, after the periphery of the first packaging part 13 contacts the periphery of the second packaging part 14 , air can be evacuated between the first packaging part 13 and the second packaging part 14 , which is beneficial to improve the tightness of the contact between the first packaging part 13 and the second packaging part 14 and the electrode assembly 20 .

[0115] In some embodiments, see Figure 1 and Figure 3The shell 10 has a first end 15 and a second end 16 that are arranged opposite to each other. The second end 16 of the shell 10 is a part where one side of the first packaging part 13 is connected and folded with one side of the second packaging part 14. The first packaging part 13 and the second packaging part 14 are connected in an integrally formed manner, that is, the second end 16 of the shell 10 is an integrally formed arrangement.

[0116] In some embodiments, the periphery of the first packaging portion 13 and the periphery of the second packaging portion 14 are in contact and sealed to form a packaging bag.

[0117] In some embodiments, the first packaging part 13 and the second packaging part 14 can be made of non-metallic materials such as plastic, rubber or carbon fiber composite materials, or can be made of metal materials such as copper, iron or aluminum alloy.

[0118] The first packaging portion 13 and the second packaging portion 14 can also be made of a composite of multiple materials, such as aluminum-plastic film.

[0119] The materials of the first packaging part 13 and the second packaging part 14 may be the same or different.

[0120] In some embodiments, the first electrode 21 and the second electrode 22 have opposite polarities, with one of the first electrode 21 and the second electrode 22 being a positive electrode and the other being a negative electrode. The electrode is formed by combining an active material layer on a metal layer, with electrode pieces of different polarity using different metal materials and active materials of different polarities.

[0121] The positive electrode active material may be one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, lithium iron manganese phosphate, cobalt-free materials, and sodium ion materials. The negative electrode active material may be one or more of artificial graphite, natural graphite, and silicon materials.

[0122] As an illustrative example, the first electrode 21 is a positive electrode, and the first electrode 21 is bonded to the aluminum metal layer using positive electrode active material. The second electrode 22 is a negative electrode, and the second electrode 22 is bonded to the copper metal layer using negative electrode active material.

[0123] In some embodiments, the isolation film 23 is made of insulating film materials such as polyethylene film, polypropylene film, polyester film, or polyimide film, so as to isolate the first pole piece 21 from the second pole piece 22 .

[0124] In some embodiments, see Figures 1 to 3The secondary battery 100 further includes a first electrode terminal 101 and a second electrode terminal 102. The first electrode terminal 101 is connected to the first electrode piece 21, and the second electrode terminal 102 is connected to the second electrode piece 22. The first electrode terminal 101 connected to the first electrode piece 21 has the same polarity as the first electrode piece 21, and the second electrode terminal 102 connected to the second electrode piece 22 has the same polarity as the second electrode piece 22. At least portions of the first electrode terminal 101 and the second electrode terminal 102 extend outside the housing 10 to guide the polarity of the first electrode piece 21 and the second electrode piece 22.

[0125] In some embodiments, see Figure 1 and Figure 3 , the first electrode terminal 101 and the second electrode terminal 102 both extend out of the housing 10 from the first end 15 .

[0126] In some embodiments, the material of the first electrode terminal 101 is the same as that of the first electrode piece 21 , and the material of the second electrode terminal 102 is the same as that of the second electrode piece 22 .

[0127] See also Figures 3 to 5 , define the direction along the central axis of the winding structure as the first direction X, and the first direction X is the width direction of the first pole piece 21 and the second pole piece 22, define the first pole piece 21 to be wound along the length direction of the first pole piece 21, and the second pole piece 22 to be wound along the length direction of the second pole piece 22, when the first pole piece 21 and the second pole piece 22 are in the unfolded state without being wound, the length direction of the first pole piece 21 and the second pole piece 22 is the second direction Y, the thickness direction of the first pole piece 21 and the second pole piece 22 is the third direction Z, and the first direction X is perpendicular to the second direction Y and the third direction Z.

[0128] It is understandable that in the wound state, the thickness directions of the first pole piece 21 at different positions are different, the thickness directions of the tail section 211 at different positions are also different, and the thickness direction of the tail section 211 is perpendicular to the winding direction of the tail section 211 .

[0129] See also Figures 3 to 5 After the first electrode piece 21, the second electrode piece 22 and the isolation film 23 are stacked and wound to form an electrode assembly 20 with a wound structure, the electrode assembly 20 has a first end face 24 and a second end face 25 arranged opposite to each other along the first direction X, and the outermost circle of the electrode assembly 20 is the tail section 211 of the first electrode piece 21, and the tail section 211 includes a first surface 211a facing away from the shell 10 and a second surface 211b facing the shell 10.

[0130] In some embodiments, the first end surface 24 and the second end surface 25 are both arranged perpendicular to the first direction X.

[0131] In some embodiments, the first electrode terminal 101 connected to the first electrode piece 21 and the second electrode terminal 102 connected to the second electrode piece 22 both extend outward from the first end surface 24 .

[0132] In other embodiments, the first electrode terminal 101 connected to the first electrode piece 21 and the second electrode terminal 102 connected to the second electrode piece 22 may both extend outward from the second end surface 25, or one of the first electrode terminal 101 connected to the first electrode piece 21 and the second electrode terminal 102 connected to the second electrode piece 22 may extend outward from the first end surface 24 and the other may extend outward from the second end surface 25. No specific limitation is made here.

[0133] In some embodiments, see Figure 1 and Figure 4 The first surface 211a has a first section 2111a with active material combined therewith and a second section 2112a without active material layer combined therewith, and the second surface 211b is not coated with active material.

[0134] In some embodiments, see Figure 4 The tail section 211 includes a first straight section 2111, a first bent section 2112, a second straight section 2113 and a second bent section 2114 which are sequentially connected along the winding direction.

[0135] In some embodiments, see Figure 4 The tail section 211 is fixed with tail glue at the end and is located at the first straight section 2111 or the second straight section 2113 . For example, if the tail portion is in the first straight section 2111, the first straight section 2111 includes a first side portion 2111b and a second side portion 2111c with the tail portion as the boundary, and along the direction from the first straight section 2111 to the second straight section 2113, the thickness of the electrode assembly 20 corresponding to the first side portion 2111b is less than the thickness of the electrode assembly 20 corresponding to the second side portion 2111c; for another example, if the tail portion is in the second straight section 2113, the second straight section 2113 includes a first side portion 2111b and a second side portion 2111c with the tail portion as the boundary, and along the direction from the first straight section 2111 to the second straight section 2113, the thickness of the electrode assembly 20 corresponding to the first side portion 2111b is less than the thickness of the electrode assembly 20 corresponding to the second side portion 2111c.

[0136] See also Figure 5The first adhesive layer 30 includes a first base layer 31 and a first adhesive layer 32 bonded to the first base layer 31. The first adhesive layer 32 is adhesive. The first adhesive layer 30 includes a first portion 33 bonded to the first surface 211a and a second portion 34 extending beyond the tail section 211 in the first direction X. The first portion 33 and the second portion 34 are connected, which facilitates the adhesion of the first adhesive layer 30 to the first surface 211a.

[0137] In the related art, after the first adhesive layer 30 is attached to the first surface 211a, the second portion 34 extends beyond the tail section 211, with the first adhesive layer 32 of the second portion 34 facing the casing 10. This poses a risk of the second portion 34 adhering to the casing 10 when the wound electrode assembly 20 is packaged. If the second portion 34 adheres to the casing 10, there is a risk that the casing 10 will pull on the second portion 34, causing the first adhesive layer 30 to fold over the first electrode sheet 21 during packaging, disassembly, transportation, or use of the secondary battery 100, thereby reducing the reliability of the secondary battery 100. For example, when the first and second packaging portions 13, 14 are folded toward or away from each other along their connection, the first or second packaging portion 13, 14 may cause the second portion 34 to fold over. Alternatively, when the secondary battery 100 is subjected to an impact, local deformation of the first and second packaging portions 13, 14 may cause the second portion 34 to fold over.

[0138] See also Figure 5 and Figure 6 In the embodiment of the present application, the second adhesive layer 40 includes a second base layer 41 and a second adhesive layer 42 bonded to the second base layer 41. The second adhesive layer 42 is adhesive. The second adhesive layer 40 includes a third portion 43 bonded to the second surface 211b and a fourth portion 44 extending beyond the tail section 211 in the first direction X. The third portion 43 and the fourth portion 44 are connected. Along the third direction Z, the second adhesive layer 40, the first pole piece 21, and the first adhesive layer 30 are stacked in sequence. The first adhesive layer 32 and the second adhesive layer 42 are disposed opposite each other. Along the third direction Z, at least a portion of the fourth portion 44 overlaps with the second portion 34. In this embodiment, the first adhesive layer 32 and the second adhesive layer 42 are arranged facing each other, and at least a portion of the fourth portion 44 overlaps with the second portion 34, so that the fourth portion 44 covers at least a portion of the first adhesive layer 32 of the second portion 34 facing the shell 10, which is beneficial to reducing the risk of the second portion 34 adhering to the shell 10, thereby reducing the risk of the first electrode 21 being folded when the second portion 34 is folded, and further beneficial to improving the reliability of the secondary battery 100.

[0139] In some embodiments, see Figure 5 and Figure 6 The first adhesive layer 32 is connected to the second adhesive layer 42 , which helps to reduce the risk of adhesion between the second part 34 and the housing 10 .

[0140] In some embodiments, the material used for the first base layer 31 and the second base layer 41 includes at least one of polyethylene terephthalate, polyimide, or polypropylene. The material used for the first base layer 31 and the material used for the second base layer can be the same or different.

[0141] In some embodiments, the first adhesive layer 32 and the second adhesive layer 42 include an adhesive; the adhesive includes at least one of polymethyl methacrylate, polypropylene, polyethylene, polyamide, styrene-butadiene rubber, nitrile rubber, butadiene rubber, isoprene rubber, ethylene-propylene rubber, and chloroprene rubber. The material of the adhesive in the first adhesive layer 32 and the material of the adhesive in the second adhesive layer 42 can be the same or different.

[0142] In some embodiments, see Figure 5 and Figure 6 The first adhesive layer 30 and the second adhesive layer 40 are separately provided. The first adhesive layer 30 and the second adhesive layer 40 are separately provided, which is conducive to using a gluing mechanism to stick the second adhesive layer 40, thereby reducing the difficulty of the gluing process and improving the consistency of the gluing effect.

[0143] In some embodiments, see Figure 5 and Figure 6 Along the first direction X, the length of the second part 34 is L1, and the length of the fourth part 44 is L2, satisfying L1<L2, which is beneficial for the fourth part 44 to cover the first adhesive layer 32 of the second part 34, thereby reducing the risk of adhesion between the second part 34 and the shell 10.

[0144] In some embodiments, L1 is greater than 0 mm and less than 4 mm, and a certain amount is reserved for the first adhesive layer 30 to extend beyond the first pole piece 21 along the first direction X, which is beneficial for the adhesive bonding operation of the adhesive bonding mechanism and helps to reduce the risk of the first adhesive layer 30 being too long and thus reducing the battery energy density and packaging strength.

[0145] In some embodiments, see Figure 7 Along the winding direction of the first pole piece 21, the width of the second part 34 is W1, and the width of the fourth part 44 is W2, satisfying W1≤W2, which is beneficial for the fourth part 44 to cover the first adhesive layer 32 of the second part 34, thereby helping to reduce the risk of adhesion between the second part 34 and the shell 10.

[0146] In some embodiments, see Figure 8The first adhesive layer 30 further includes a fifth portion 35. In the first direction X, the fifth portion 35 exceeds the tail section 211, and the fifth portion 35, the first portion 33, and the second portion 34 are sequentially connected in the first direction X. The fifth portion 35 exceeding the tail section 211 is conducive to increasing the area of ​​the first adhesive layer 30 covering the first surface 211a along the first direction X. Figure 4 In an embodiment in which a first section 2111a and a second section 2112a are provided, the first adhesive layer 30 is attached to the junction of the first section 2111a and the second section 2112a. This is beneficial to reducing the risk of active material at the tail of the first section 2111a piercing the isolation membrane 23 and lithium plating, and is also beneficial to reducing the risk of burrs at the tail of the second electrode 22 piercing the isolation membrane 23 and contacting the first electrode 21 for short circuit.

[0147] In some embodiments, see Figure 8 The second adhesive layer 40 further includes a sixth portion 45. In the first direction X, the sixth portion 45 extends beyond the tail section 211. The sixth portion 45, the third portion 43, and the fourth portion 44 are sequentially connected in the first direction X. Along the third direction Z, at least a portion of the sixth portion 45 overlaps with the fifth portion 35. This overlap of at least a portion of the sixth portion 45 with the fifth portion 35 helps reduce the risk of adhesion between the first adhesive layer 32 of the fifth portion 35 and the housing 10, thereby reducing the risk of the housing 10 driving the fifth portion 35, which in turn drives the first pole piece 21 to fold.

[0148] In some other embodiments, see Figure 9 The secondary battery 100 further includes a third adhesive layer 50, which is disposed separately from the second adhesive layer 40. Along the third direction Z, the first adhesive layer 30, the first electrode 21, and the third adhesive layer 50 are stacked in sequence. The third adhesive layer 50 includes a third base layer and a third adhesive layer, which is disposed opposite the first adhesive layer 32. The third adhesive layer 50 includes a seventh portion 51 bonded to the second surface 211b and an eighth portion 52 extending beyond the tail section 211 in the first direction X. The seventh portion 51 is connected to the eighth portion 52. Along the third direction Z, at least a portion of the eighth portion 52 overlaps with the fifth portion 35. This overlap of the eighth portion 52 with the fifth portion 35 reduces the risk of the first adhesive layer 32 of the fifth portion 35 adhering to the housing 10, thereby reducing the risk of the housing 10 causing the fifth portion 35 to fold, which in turn causes the first electrode 21 to fold. In addition, the second adhesive layer 40 and the third adhesive layer 50 are provided separately, which is beneficial to reducing the length of the adhesive layer attached to the second surface 211 b along the first direction X, thereby saving adhesive.

[0149] In some embodiments, see Figure 10The second adhesive layer 40 extends from the first straight section 2111 across the first end surface 24 of the electrode assembly 20 to the second straight section 2113, which helps the second adhesive layer 40 to restrain the entire electrode assembly 20, thereby improving the drop performance of the secondary battery 100.

[0150] In some embodiments, see Figure 11 The first electrode terminal 101 connected to the first electrode piece 21 and the second electrode terminal 102 connected to the second electrode piece 22 both extend outward from the second end surface 25, and the second adhesive layer 40 extends from the first straight section 2111 across the first end surface 24 of the electrode assembly 20 to the second straight section 2113, which helps the second adhesive layer 40 to restrain the entire electrode assembly 20, thereby helping to improve the drop performance of the secondary battery 100.

[0151] In some embodiments, see Figure 12 The second portion 34 and the fourth portion 44 are an integrally formed adhesive layer.

[0152] It should be noted that "integrally provided" can be understood as a continuous whole, and the second portion 34 and the fourth portion 44 being an integrally provided adhesive layer can be understood as the second portion 34 and the fourth portion 44 being a continuous, integral adhesive layer. For example, the second portion 34 and the fourth portion 44 can be integrally formed to form an integrally provided adhesive layer. In the case where the first adhesive layer 30 and the second adhesive layer 40 are integrally provided, it is advantageous to fold the portion of the continuous adhesive layer extending beyond the tail section 211 in the first direction X directly toward the second surface 211b and then adhere it to the second surface 211b. Compared to the case where the first adhesive layer 30 and the second adhesive layer 40 are provided separately, this eliminates the need for a dedicated adhesive application mechanism and corresponding adhesive application station for affixing the second adhesive layer 40, thereby reducing costs.

[0153] In some embodiments, see Figure 13 and Figure 14The first adhesive layer 30 further includes a fifth portion 35. In the first direction X, the fifth portion 35 extends beyond the tail section 211. The fifth portion 35, the first portion 33, and the second portion 34 are sequentially connected in the first direction X. The secondary battery 100 further includes a third adhesive layer 50. The third adhesive layer 50 includes a seventh portion 51 adhered to the second surface 211b and an eighth portion 52 extending beyond the tail section 211 in the first direction X. The third adhesive layer 50 and the second adhesive layer 40 are separately provided, and the seventh portion 51 is connected to the eighth portion 52. Along the first direction X, the third adhesive layer 50 and the second adhesive layer 40 are sequentially provided. The eighth portion 52 and the fifth portion 35 are an adhesive layer integrally provided. Along the third direction Z, at least a portion of the fourth portion 44 overlaps with the second portion 34, and at least a portion of the eighth portion 52 overlaps with the fifth portion 35. At least part of the eighth portion 52 overlaps with the fifth portion 35 , which helps reduce the risk of the first adhesive layer 32 of the fifth portion 35 adhering to the shell 10 , thereby helping reduce the risk of the shell 10 driving the fifth portion 35 and the fifth portion 35 driving the first pole piece 21 to fold.

[0154] In some embodiments, see Figure 14 Along the third direction Z, the third portion 43 at least partially overlaps the seventh portion 51, which helps increase the area of ​​the second adhesive layer 40 covering the second surface 211b along the first direction X. This helps improve the effectiveness of the second adhesive layer 40 in limiting the exposure of debris generated by the first electrode sheet 21 during a penetration test or an impact test, thereby reducing the risk of debris from the first electrode sheet 21 being exposed and short-circuiting with the second electrode sheet 22 during the test. The third portion 43 at least partially overlaps the seventh portion 51, which also helps reduce the risk of the second adhesive layer 40 becoming loose when packaging the electrode assembly 20 and evacuating the gas.

[0155] In some embodiments, see Figure 14 The sum of the length of the first adhesive layer 30 and the lengths of the second adhesive layer 40 and the third adhesive layer 50 is greater than twice the width of the first electrode sheet 21 along the first direction X, which is conducive to achieving at least partial overlap between the third portion 43 and the seventh portion 51 in the third direction Z, and the sum of the length of the first adhesive layer 30 and the lengths of the second adhesive layer 40 and the third adhesive layer 50 is less than or equal to four times the width of the first electrode sheet 21 along the first direction X, which is conducive to reducing the risk of increasing the thickness of the electrode assembly 20 after winding due to excessively long adhesive layers.

[0156] In some embodiments, see Figure 15The secondary battery 100 further includes a third adhesive layer 50 and a fourth adhesive layer 60. The third adhesive layer 50 is provided separately from the second adhesive layer 40. The third adhesive layer 50 includes a seventh portion 51 bonded to the second surface 211b and an eighth portion 52 extending beyond the tail section 211 in the first direction X. The seventh portion 51 is connected to the eighth portion 52. The fourth adhesive layer 60 is provided separately from the first adhesive layer 30. The fourth adhesive layer 60 includes a ninth portion 61 bonded to the first surface 211a and a tenth portion 62 extending beyond the tail section 211 in the first direction X. The ninth portion 61 is connected to the tenth portion 62. The eighth portion 52 and the tenth portion 62 are integrally provided. Along the third direction Z, at least a portion of the fourth portion 44 overlaps with the second portion 34, and at least a portion of the eighth portion 52 overlaps with the tenth portion 62. The provision of the third adhesive layer 50 and the fourth adhesive layer 60 is beneficial to further increasing the area of ​​the adhesive layer covering the first surface 211a. In an embodiment in which a first section 2111a and a second section 2112a are provided, the first adhesive layer 30 is attached to the junction of the first section 2111a and the second section 2112a, which is beneficial to reducing the risk of active material at the tail of the first section 2111a piercing the isolation membrane 23 and lithium plating, and is also beneficial to reducing the risk of burrs at the tail of the second electrode 22 piercing the isolation membrane 23 and contacting the first electrode 21 for short circuit.

[0157] In some embodiments, see Figure 15 Along the third direction Z, the first portion 33 and the ninth portion 61 at least partially overlap, which is beneficial to further increase the area of ​​the adhesive layer covering the first surface 211a, and the first adhesive layer 30 and the second adhesive layer 40 are arranged separately, which is beneficial to the risk of the adhesive layer on the first surface 211a being wrinkled due to excessive continuous length, and is beneficial to reducing bubbles between the first portion 33, the fourth portion 44 and the first pole piece 21.

[0158] In some embodiments, see Figure 16 Along the third direction Z, the third portion 43 and the seventh portion 51 at least partially overlap, which is beneficial to increasing the area of ​​the second surface 211b covered by the adhesive layer in the first direction X, and is also beneficial to reducing the risk of wrinkling due to excessive continuous length of the adhesive layer on the second surface 211b, and is beneficial to reducing bubbles between the third portion 43, the fourth portion 44 and the first pole piece 21.

[0159] In some embodiments, there is a first peel strength between the first portion 33 and the first surface 211a, and there is a second peel strength between the third portion 43 and the second surface 211b. The first peel strength is less than the second peel strength, which helps to reduce the risk of debonding between the first adhesive layer 30 and the second adhesive layer 40.

[0160] The first peel strength between the first portion 33 and the first surface 211a is tested as follows:

[0161] Disassemble the secondary battery 100 to obtain the first electrode 21. Soak the first electrode 21 in dimethyl carbonate (DMC) for 4 hours to remove the electrolyte. Then bake it at 85°C for 30 minutes and cut it into a 10CM×10CM sample. Adhere the first adhesive layer 32 of the first part 33 to the first surface 211a of the sample. Use double-sided tape (Nitto 5000NS) to stick the second surface 211b of the sample to the steel plate. Use adhesive tape to stick the first part 33, and fix one end of the adhesive tape on a tensile testing machine. Use the tensile testing machine to pull the adhesive tape at a speed of 50mm / min in the 180° direction. Record the tensile force (F·N) when it stabilizes, which is the first peel strength between the first part 33 and the first surface 211a.

[0162] The test of the second peel strength between the third portion 43 and the second surface 211 b may refer to the test of the first peel strength between the first portion 33 and the first surface 211 a , which will not be described in detail here.

[0163] In the embodiment where the housing 10 includes a first end 15 and a second end 16 oppositely disposed, along the first direction X, the first electrode terminal 101 and the second electrode terminal 102 extend out of the housing 10 at the first end 15 , and the second portion 34 extends beyond the first electrode piece 21 from the second end 16 .

[0164] In some embodiments, when viewed along the first direction X, at least a portion of the second portion 34 overlaps with the first straight segment 2111 or the second straight segment 2113 .

[0165] In some embodiments, at least a portion of the first portion 33 is bonded to the first surface 211a of the first straight segment 2111 or the first surface 211a of the second straight segment 2113, so that when the wound electrode assembly 20 ends at the first straight segment 2111 or the second straight segment 2113, the thickness difference of the secondary battery 100 is reduced.

[0166] In some embodiments, the first adhesive layer 30 and the second adhesive layer 40 are disposed on the first side portion 2111b. The thickness of the electrode assembly 20 corresponding to the first side portion 2111b is less than the thickness of the electrode assembly 20 corresponding to the second side portion 2111c. This facilitates ensuring that the first adhesive layer 30 and the second adhesive layer 40 do not increase the overall thickness of the electrode assembly 20 along the direction from the first straight portion to the second straight portion, thereby facilitating a reduction in the overall size of the secondary battery 100 and, in turn, improving the energy density of the secondary battery 100. Furthermore, the first adhesive layer 30 and the second adhesive layer 40 being located on the first side portion 2111b facilitates improving the uniformity of the thickness of the electrode assembly 20 along the direction from the first straight portion to the second straight portion, thereby reducing the risks of deformation and cycle failure of the secondary battery 100.

[0167] In some embodiments, the second electrode piece 22 ends at the curved side of the electrode assembly 20, that is, corresponding to the positions of the first bent section 2112 and the second bent section 2114, and the tail section 211 of the first electrode piece 21 ends at the first straight section 2111 or the second straight section 2113, so that the inward side of the first straight section 2111 or the second straight section 2113 is not adjacent to the second electrode piece 22, which is conducive to freeing up space for the arrangement of the first adhesive layer 30, thereby helping to reduce the risk of the first adhesive layer 30 causing an increase in the electrode assembly 20.

[0168] See also Figure 17 The embodiments of the present application further provide an electronic device 1000, which includes the secondary battery 100 of any of the above embodiments. The probability of the first electrode 21 in the secondary battery 100 being folded is reduced, which is beneficial to improving the reliability of the secondary battery 100 and, in turn, the reliability of the electronic device 1000.

[0169] Since the electronic device 1000 adopts the technical solution of any of the above embodiments of the secondary battery 100 , it at least has the beneficial effects brought by the technical solution of any of the above embodiments, which will not be described in detail here.

[0170] 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 spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, characterized in that: The secondary battery includes: case; an electrode assembly disposed within the housing, the electrode assembly comprising a first electrode sheet, a second electrode sheet, and a separator located between the first electrode sheet and the second electrode sheet, the first electrode sheet, the second electrode sheet, and the separator being stacked and wound, with the winding center axis of the electrode assembly being in a first direction; the first electrode sheet comprising a tail section, the tail section constituting an outermost ring of the electrode assembly, the tail section comprising a first surface facing away from the housing and a second surface facing the housing; a first adhesive layer, comprising a first bonding layer, the first adhesive layer comprising a first portion bonded to the first surface and a second portion extending beyond the tail section in the first direction, the first portion being connected to the second portion; The second adhesive layer includes a second adhesive layer, the second adhesive layer includes a third portion adhered to the second surface and a fourth portion extending beyond the tail segment in the first direction, the third portion being connected to the fourth portion; in the thickness direction of the tail segment, the second adhesive layer, the tail segment, and the first adhesive layer are stacked in sequence, the first adhesive layer and the second adhesive layer are arranged facing each other; in the thickness direction of the tail segment, at least part of the fourth portion overlaps with the second portion.

2. The secondary battery according to claim 1, wherein The first adhesive layer and the second adhesive layer are provided separately.

3. The secondary battery according to claim 2, wherein The first adhesive layer also includes a fifth part, which extends beyond the tail section in the first direction, and the fifth part, the first part, and the second part are connected in sequence in the first direction; the second adhesive layer also includes a sixth part, which extends beyond the tail section in the first direction, and the sixth part, the third part, and the fourth part are connected in sequence in the first direction; in the thickness direction of the tail section, at least part of the sixth part overlaps with the fifth part.

4. The secondary battery according to claim 2, wherein: The first adhesive layer also includes a fifth part, which extends beyond the tail segment in the first direction, and the fifth part, the first part and the second part are connected in sequence in the first direction; the secondary battery also includes a third adhesive layer, which includes a seventh part adhered to the second surface and an eighth part extending beyond the tail segment in the first direction, the third adhesive layer and the second adhesive layer are separately arranged, and the seventh part is connected to the eighth part; in the thickness direction of the tail segment, at least part of the eighth part overlaps with the fifth part.

5. The secondary battery according to claim 2, wherein The tail section includes a first straight section, a first bent section, a second straight section and a second bent section connected in sequence along the winding direction, the electrode assembly includes a first end face perpendicular to the first direction, and the second glue layer extends from the first straight section across the first end face to the second straight section.

6. The secondary battery according to claim 1, wherein The second part and the fourth part are an integrally arranged adhesive layer.

7. The secondary battery according to claim 6, characterized in that The first adhesive layer further includes a fifth portion, which extends beyond the tail section in the first direction, and the fifth portion, the first portion, and the second portion are sequentially connected in the first direction. The secondary battery further includes a third adhesive layer, which includes a seventh portion bonded to the second surface and an eighth portion extending beyond the tail section in the first direction. The third adhesive layer and the second adhesive layer are provided separately, and the seventh portion is connected to the eighth portion. Along the first direction, the third adhesive layer and the second adhesive layer are arranged in sequence; The eighth portion and the fifth portion are an integrally provided adhesive layer. In the thickness direction of the tail section, at least a portion of the fourth portion overlaps with the second portion, and at least a portion of the eighth portion overlaps with the fifth portion.

8. The secondary battery according to claim 7, wherein: In a thickness direction of the tail section, the third portion at least partially overlaps with the seventh portion.

9. The secondary battery according to claim 6, wherein The secondary battery further includes a third adhesive layer and a fourth adhesive layer, the third adhesive layer including a seventh portion bonded to the second surface and an eighth portion extending beyond the tail section in the first direction, the third adhesive layer and the second adhesive layer being provided separately, and the seventh portion being connected to the eighth portion; The fourth adhesive layer includes a ninth portion bonded to the first surface and a tenth portion extending beyond the tail section in the first direction. The fourth adhesive layer and the first adhesive layer are provided separately, and the ninth portion is connected to the tenth portion. The eighth portion and the tenth portion are an integrally provided adhesive layer. In the thickness direction of the tail section, at least a portion of the fourth portion overlaps with the second portion, and at least a portion of the eighth portion overlaps with the tenth portion.

10. The secondary battery according to claim 1, wherein The shell is a packaging bag.

11. The secondary battery according to claim 10, wherein The first portion and the first surface have a first peeling strength, the third portion and the second surface have a second peeling strength, and the first peeling strength is smaller than the second peeling strength.

12. The secondary battery according to claim 10, characterized in that The electrode assembly also includes an electrode terminal. In the first direction, the shell includes a first end and a second end arranged opposite to each other, the electrode terminal is located at the first end, and the second part and the fourth part are located at the second end; the shell also includes a first packaging part and a second packaging part, and the first packaging part and the second packaging part are integrally arranged at the second end.

13. The secondary battery according to claim 1, wherein The tail section includes a first straight section, a first bent section, a second straight section, and a second bent section sequentially connected along the winding direction, and at least part of the first section is bonded to the first surface of the first straight section or the first surface of the second straight section.

14. The secondary battery according to claim 1, wherein Along the first direction, the length of the second portion is L1, and the length of the fourth portion is L2, satisfying L1<L2.

15. An electronic device, characterized in that: The secondary battery according to any one of claims 1 to 14 is included.

Images