Secondary battery and electronic device

Abstract

The application discloses a secondary battery and an electronic device, comprising a shell, an electrode assembly, a first adhesive and a second adhesive. The electrode assembly is arranged in the shell, and the electrode assembly comprises a first pole piece, a separator and a second pole piece which are arranged in a stacked and wound manner. The first pole piece comprises a first section which constitutes a part of an outermost circle of the electrode assembly. The first section has a first surface facing a winding central axis and a second surface away from the winding central axis. Along the winding direction of the first section, the first section comprises a tail section. The first surface and the second surface of the tail section are empty foil areas. The first adhesive is at least partially adhered to the first surface of the tail section. The second adhesive is arranged on the second surface of the tail section and adheres the second surface of the tail section to the shell. In a direction perpendicular to the first surface, the projection of the second adhesive partially overlaps the projection of the first adhesive. The secondary battery disclosed by the application has a reduced risk of failure due to falling or collision.

Description

[Technical Field]

[0001] This application relates to the field of electrochemical technology, and more particularly to a secondary battery and electronic device. [Background Technology]

[0002] With the development of technology, consumer electronics products such as mobile phones and laptops are very popular. As a core component of electronic products, rechargeable batteries (lithium-ion batteries) have become an important component that determines the development of electronic products due to their advantages such as high operating voltage and long service life.

[0003] Lithium-ion batteries typically consist of a casing and electrode components. To reduce the risk of drop failure in lithium-ion batteries, the commonly used method is to bond the electrode components to the casing with adhesive to reduce the relative movement between the electrode components and the casing, thereby reducing the risk of collision failure between the electrode components and the casing.

[0004] However, for the outermost electrode of the electrode assembly, there is still a risk of electrode tearing at the junction where the adhesive is applied and where it is not. Furthermore, when the adhesive is applied at the end, the end of the electrode is still in a semi-bound state, which can easily lead to electrode tearing when the lithium-ion battery is dropped, resulting in lithium-ion battery failure. [Summary of the Invention]

[0005] The embodiments of this application aim to provide a secondary battery and electronic device to improve the problem of easy tearing of the outermost electrode, thereby reducing the failure risk of lithium-ion batteries.

[0006] In order to solve its technical problems, the embodiments of this application adopt the following technical solutions:

[0007] This application discloses a secondary battery, including a housing, an electrode assembly, a first adhesive member, and a second adhesive member. The electrode assembly is disposed within the housing and includes a first electrode, a second electrode, and a separator film located between the first and second electrodes. The first electrode, the second electrode, and the separator film are stacked and wound together, with the winding center axis of the electrode assembly pointing in a first direction. The first electrode includes a first segment, forming the outermost portion of the electrode assembly. The first segment has a first surface facing the winding center axis and a second surface facing away from the winding center axis. Along the winding direction of the first segment, the first segment includes a terminal segment, where both the first and second surfaces are empty foil areas. The first adhesive member is at least partially bonded to the first surface of the terminal segment. The second adhesive member is disposed on the second surface of the terminal segment and bonds the second surface of the terminal segment to the housing. Along a direction perpendicular to the first surface, the second adhesive member partially overlaps with the first adhesive member.

[0008] In the above technical solution, the first adhesive is at least partially bonded to the first surface of the terminal section, which can improve the tensile strength of the terminal section and thus reduce the risk of tearing. The second adhesive is disposed on the second surface of the terminal section and bonds the terminal section to the housing, which can reduce the relative movement between the electrode assembly and the housing and further improve the tensile strength of the terminal section, thereby further reducing the risk of tearing. At the same time, along the direction perpendicular to the first surface, the projection of the second adhesive partially overlaps with the projection of the first adhesive. When the secondary battery is dropped or colliding, part of the shear force on the second adhesive can be transmitted to the first adhesive, thereby reducing the concentration of shear force and further reducing the risk of tearing of the terminal section.

[0009] In some preferred embodiments, the portion of the second adhesive that overlaps with the first adhesive is designated as the first portion. Along a direction perpendicular to the first surface, the projection of the first portion falls within the projection range of the first adhesive. This shear force transmission between the first and second adhesives effectively reduces the risk of tearing at the finishing section.

[0010] In some preferred embodiments, the area of ​​the first part is S1, the area of ​​the second adhesive part is S2, and 15% ≤ S1 / S2 ≤ 50%. Sufficient adhesive area of ​​the second adhesive part can, on the one hand, improve the tensile strength of the finishing section, and on the other hand, ensure sufficient overlap between the second adhesive part and the first adhesive part for shear force transmission, thereby reducing the risk of tearing at the finishing section.

[0011] In some preferred embodiments, along the winding direction of the first segment, the distance between the first adhesive and the end of the final segment is a first distance, which is greater than or equal to 2 mm. Allowing for this first distance ensures that the first adhesive is fully bonded to the final segment, thereby effectively reducing curling of the first adhesive.

[0012] In some preferred embodiments, the first segment further includes a coating segment connected to the closing segment.

[0013] In some preferred embodiments, one end of the first adhesive is adhered to the coating section, and the other end is adhered to the finishing section, and the first adhesive covers the connection between the coating section and the finishing section. Along a first direction, the length of the first adhesive is L1 mm, the length of the first section is L2 mm, and 0 ≤ L1 - L2 ≤ 3. The first direction is parallel to the winding center axis of the electrode assembly. This reduces the risk of burrs and other protrusions piercing the separator, thereby reducing the risk of short circuits, and also reduces the shedding of active material layers at the interface.

[0014] In some preferred embodiments, the first adhesive member includes a first sub-adhesive member and a second sub-adhesive member. The first sub-adhesive member is disposed on the first surface. The second sub-adhesive member is disposed on the first surface, and the second sub-adhesive member is bonded to the first sub-adhesive member at its terminal section. Along a direction perpendicular to the first surface, the projection of the second sub-adhesive member on the second surface partially overlaps with the second adhesive member.

[0015] In some preferred embodiments, one end of the first sub-adhesive is adhered to the coating section, and the other end is adhered to the termination section, and the first sub-adhesive covers the junction of the coating section and the termination section. Along the first direction, the length of the first sub-adhesive is L3 mm, the length of the first section is L2 mm, and 0 ≤ L3 - L2 ≤ 3. The first sub-adhesive completely covers the junction in the first direction X to further reduce the puncture of the release liner by burrs or other protrusions, thereby reducing the risk of short circuits and reducing the shedding of active material layers at the junction.

[0016] In some preferred embodiments, the first adhesive member includes a plurality of second sub-adhesive members. The plurality of second sub-adhesive members are arranged sequentially on the first surface along the winding direction of the first segment, with adjacent second sub-adhesive members bonded to each other. Along the winding direction of the first segment, the second sub-adhesive members at the beginning of the arrangement bond the first sub-adhesive member to the end segment, and along a direction perpendicular to the first surface, the projections of the second sub-adhesive members at the end of the arrangement partially overlap with the projections of the second adhesive members. This arrangement of multiple sub-adhesive members further reduces the formation of air bubbles during bonding and further reduces shear force concentration, thereby lowering the risk of tearing at the end segment.

[0017] In some preferred embodiments, the first adhesive and the second adhesive are adhesive tapes to facilitate the application of adhesive to the first adhesive and the second adhesive, thereby improving production efficiency.

[0018] In some preferred embodiments, the first segment includes a first straight segment, a first curved segment, a second straight segment, and a second curved segment connected together. The first straight segment and the second straight segment are arranged opposite each other in a second direction, and the first curved segment and the second curved segment are both connected between the first straight segment and the second straight segment, and the first curved segment and the second curved segment are arranged opposite each other in a third direction. The second adhesive part is disposed on the first straight segment or the second straight segment, and the first direction, the second direction, and the third direction are mutually perpendicular to each other. The straight segment facilitates the adhesion and receptivity of the second adhesive part, which can facilitate adhesion and improve the adhesion effect, thereby improving the tensile strength of the first segment and reducing the risk of tearing of the first segment.

[0019] In some preferred embodiments, the peel strength between the separator and the first or second electrode is 8 N / m to 12 N / m, thereby effectively increasing the overall bonding strength of the electrode assembly.

[0020] In some preferred embodiments, the first adhesive is a single-sided adhesive that is only sticky on one side, the single-sided adhesive comprising a first substrate layer and a first adhesive layer coated on one side of the first substrate layer.

[0021] In some preferred embodiments, the second adhesive is a double-sided adhesive that is sticky on both sides, the double-sided adhesive including a second substrate layer and a second adhesive layer and / or a hot melt adhesive layer coated on both sides of the second substrate layer.

[0022] In some preferred embodiments, the casing is a packaging bag.

[0023] In some preferred embodiments, the first electrode is a cathode electrode, and the second electrode is an anode electrode; the first section has an active material layer only on its first surface, and the active material layer is disposed on the first surface of the coating section. Since there is no corresponding anode electrode on the outer side of the single-sided cathode electrode, one less active material layer can be removed, thereby improving the energy density of the secondary battery.

[0024] In some preferred embodiments, the second adhesive is used to fix the finishing section. By directly fixing the finishing section with the second adhesive, one finishing glue and adhesive application process can be eliminated, which can reduce tearing of the finishing section and achieve the purpose of cost reduction and efficiency improvement.

[0025] Secondly, this application also proposes an electronic device comprising the secondary battery described in any of the above embodiments.

[0026] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. [Attached Image Description]

[0027] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0028] Figure 1 This is an exploded view of a secondary battery according to some embodiments of this application;

[0029] Figure 2 This is a schematic diagram of the winding structure of the electrode assembly in some embodiments of this application;

[0030] Figure 3a This is a schematic diagram of the stacked structure of the first electrode, the separator, and the second electrode in some embodiments of this application;

[0031] Figure 3bThis is a schematic diagram of the structure of the separator membrane in some embodiments of this application;

[0032] Figure 4 This is a schematic diagram (viewed along the X direction) of the bonding structure between the first segment and the first adhesive and the second adhesive in some embodiments of this application.

[0033] Figure 5a This is a schematic diagram of the bonding structure between the first segment and the first adhesive and the second adhesive in some embodiments of this application (viewed along the M direction);

[0034] Figure 5b This is a schematic diagram of the structure of a first adhesive member and a second adhesive member according to some embodiments of this application;

[0035] Figure 6 This is a schematic diagram (viewed along the X direction) of the bonding structure between the first segment and the first adhesive and the second adhesive in some embodiments of this application.

[0036] Figure 7 This is a schematic diagram of the bonding structure between the first segment and the first adhesive and the second adhesive in some embodiments of this application (viewed along the M direction);

[0037] Figure 8 This is a schematic diagram of the bonding structure of a first sub-adhesive and a plurality of second sub-adhesives in some embodiments of this application.

[0038] Explanation of reference numerals in the attached figures:

[0039] 100. Secondary batteries;

[0040] 10. Shell; 11. First shell; 12. Second shell;

[0041] 20. Electrode assembly; 20a. Winding center; 21. First electrode; 211. First current collector; 212. First active material layer; 213. First section; 213a. First surface; 213b. Second surface; 2131. Finishing section; 2132. Coating section; 22. Second electrode; 221. Second current collector; 222. Second active material layer; 23. Separating membrane; 231. Base layer; 232. Ceramic adhesive layer; 24. First straight section; 25. First curved section; 26. Second straight section; 27. Second curved section;

[0042] 30. First adhesive component; 30a. First substrate layer; 30b. First adhesive layer; 31. First sub-adhesive component; 32. Second sub-adhesive component;

[0043] 40. Second adhesive component; 40a. First part; 41. Second substrate layer; 42. Second adhesive layer;

[0044] N, winding direction; X, first direction; Y, second direction; Z, third direction; M, direction perpendicular to the first face.

Detailed Implementation Methods

[0045] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0046] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0047] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0049] Firstly, this application proposes a secondary battery 100, please refer to... Figure 1 and Figure 2 The secondary battery 100 includes a housing 10, an electrode assembly 20, a first adhesive member 30, and a second adhesive member 40. The electrode assembly 20 is housed within the housing 10. The second adhesive member 40 is used to finish the electrode assembly 20, connecting it into a structurally stable whole. The second adhesive member 40 also serves to bond the electrode assembly 20 to the housing 10, reducing relative movement between the two components.

[0050] For the aforementioned housing 10, please refer to Figure 1The housing 10 encloses a receiving cavity (not shown in the figure), which can accommodate the electrode assembly 20 and the electrolyte (not shown in the figure). In the embodiments of this application, the housing 10 can be a packaging bag, for example, the housing 10 can be a multi-layer composite film packaging bag containing a metal layer. The packaging bag can be an aluminum-plastic film packaging bag including a PP (polypropylene) layer and an aluminum layer. PP layers can be provided on both surfaces in the thickness direction of the aluminum layer to facilitate the insulating sealing of the packaging bag.

[0051] Optionally, the housing 10 includes a first housing 11 and a second housing 12. The first housing 11 and / or the second housing 12 are punched with a cavity (not shown in the figure). The electrode assembly 20 can be disposed in the cavity. The first housing 11 and the second housing 12 are then heat-pressed to form a complete housing 10, wherein the cavity forms a receiving cavity.

[0052] For the electrode assembly 20 mentioned above, please refer to... Figures 1 to 3a The electrode assembly 20 is disposed in the receiving cavity of the housing 10. The electrode assembly 20 includes a first electrode 21, a second electrode 22, and a separating membrane 23. The first electrode 21, the second electrode 22, and the separating membrane 23 are stacked and wound to form a wound electrode assembly 20. The separating membrane 23 is disposed between the first electrode 21 and the second electrode 22 to separate them. Figure 2 (A wound structure of the electrode assembly 20 is shown). The first electrode 21 and the second electrode 22 have opposite polarities; for example, the first electrode 21 is a cathode electrode and the second electrode 22 is an anode electrode. The first electrode 21 includes a first current collector 211 and a first active material layer 212, the first active material layer 212 being coated on at least one surface of the first current collector 211. The second electrode 22 includes a second current collector 221 and a second active material layer 222, the second active material layer 222 being coated on at least one surface of the first current collector 211. Alternatively, in some other embodiments, the first electrode 21 is an anode electrode and the second electrode 22 is a cathode electrode.

[0053] For the separator 23 of the electrode assembly 20, the separator 23 can be bonded between the first electrode 21 and the second electrode 22 in order to improve the overall bonding strength of the electrode assembly 20 and improve the flatness of the interface between the first electrode 21 and the second electrode 22, thereby reducing the risk of end-tear and enhancing the cycle performance of the secondary battery.

[0054] Please refer to Figure 3a and Figure 3b The separator 23 includes a base layer and an adhesive layer 232 disposed on at least one surface of the base layer 231. For example, the adhesive layer 232 is disposed on both surfaces of the base layer 231 in the thickness direction. When the separator 23 is disposed between the first electrode 21 and the second electrode 22, the first electrode 21 and the second electrode 22 can be bonded at the same time.

[0055] The base layer 231 is made of one or more of the following: high molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, poly(p-phenylene), polynaphthalene, polyimide, polyamide, aramid, and poly(p-phenylenebenzodithiazole). The adhesive layer 232 may be made of at least one of the following: polyvinylidene fluoride or vinyl-polysilsesquioxane.

[0056] In some embodiments, the peel strength between the separator 23 and the first electrode 21 or the second electrode 22 is 8 N / m to 12 N / m, thereby effectively improving the overall bonding strength of the electrode assembly 20. The peel strength can be controlled by the amount of adhesive in the adhesive layer 232. When the peel strength is too high, too much adhesive will clog the pores on the surfaces of the first electrode 21 and the second electrode 22, causing problems such as lithium plating black spots. On the other hand, too little adhesive will result in low bonding strength of the electrode assembly 20 and low interface flatness between the first electrode 21 and the second electrode 22. When dropped, the electrode assembly 20 is more likely to move between the housing 10, increasing the risk of tearing at the end.

[0057] In the embodiments of this application, the first electrode 21 is used as the cathode electrode, the second electrode 22 as the anode electrode, and the electrode assembly 20 is of the wound type. The first electrode 21 includes a first segment 213, which constitutes the outermost ring of the electrode assembly 20. Please refer to... Figure 2 and Figure 4 The first segment 213 has a first surface 213a facing the winding center 20a of the electrode assembly 20 and a second surface 213b facing away from the winding center 20a. The first segment 213 is wound along the winding direction N (along the length direction of the first electrode 21). The first segment 213 has a terminal segment 2131, which is also the winding end of the first segment 213. Both the first surface 213a and the second surface 213b of the terminal segment 2131 are empty foil areas; in this embodiment, the empty foil areas are areas not coated with the active material layer.

[0058] It should be noted that when the first current collector 211 of the first electrode 21 is coated with the first active material layer 212, the first surface 213a is the surface of the first active material layer 212 facing the winding center 20a. When the first current collector 211 is not coated with the first active material layer 212, the surface of the first current collector 211 facing the winding center 20a is the first surface 213a. The second surface 213b is the same, and the second electrode 22 is similar.

[0059] Optionally, the first segment 213 further includes a coating segment 2132 connected to the aforementioned ending segment 2131. This coating segment 2132 is the section of the first segment 213 coated with an active material layer. Preferably, the first segment 213 has a first active material layer 212 only on its first surface 213a. This first active material layer 212 is disposed on the first surface 213a of the coating segment 2132, which is a single-sided cathode electrode used in the first segment 213. In this embodiment, the outermost layer uses a single-sided cathode electrode, and there is no corresponding anode electrode on the outside of the single-sided cathode electrode, which can reduce one layer of active material layer, thereby improving the energy density of the secondary battery 100.

[0060] For the first adhesive component 30 mentioned above, please refer to... Figure 4 The first adhesive 30 is at least partially bonded to the first surface 213a of the finishing section 2131, which is an empty foil area. The shear force on the empty foil area can be transmitted to the first adhesive 30, thereby increasing the tensile strength of the finishing section 2131 and reducing the risk of tearing of the finishing section 2131.

[0061] Optionally, one end of the first adhesive member 30 is bonded to the coating section 2132, that is, the first adhesive member 30 is bonded to the first active material layer 212 of the coating section 2132, and the other end is bonded to the termination section 2131, and the first adhesive member 30 covers the connection between the coating section 2132 and the termination section 2131. When the first active material layer 212 is coated on the first surface 213a, at the junction of the coating section 2132 and the termination section 2131, the first active material layer 212 is prone to developing protruding structures such as burrs and streaks. These protruding structures can easily interfere with the separator 23 and can easily cause powder shedding and detachment of this part of the first active material layer 212. In this embodiment, by covering it with the first adhesive member 30, the probability of burrs and other protruding structures piercing the separator 23 can be reduced, thereby reducing the risk of short circuit and reducing powder shedding and detachment of the active material layer at the junction.

[0062] When the first adhesive 30 covers the junction of the coated section 2132 and the termination section 2131, the first adhesive 30 can completely cover the junction in the first direction X. For example, please refer to further details. Figure 5a Along the first direction X, the length of the first adhesive 30 is L1 mm, the length of the first segment 213 is L2 mm, and 0≤L1-L2≤3; wherein the first direction X is parallel to the winding center axis of the electrode assembly 20, and the first adhesive 30 completely covers the junction in the first direction X, so as to further reduce the short circuit caused by burrs and other protruding structures at the junction piercing the separator 23 and reduce the shedding of active material at the junction.

[0063] Please continue to refer to Figure 4 and Figure 5aAlong the winding direction N of the first segment 213, the distance between the first adhesive 30 and the end of the closing segment 2131 is a first distance W, which is greater than or equal to 2mm, to reserve cutting space at the end of the first segment 213. It should be noted that when the first adhesive 30 covers the end of the closing segment 2131, there are no other components after the end for the first adhesive 30 to adhere to, meaning the first adhesive 30 is prone to insufficient adhesion, which may cause curling at the end. Furthermore, there is a significant risk of cutting the first adhesive 30 when cutting the first segment 213, which will also cause curling at the end. This curling will affect the energy density of the secondary battery 100 and may interfere with the separator 23. In this embodiment, reserving a first distance allows the first adhesive 30 to be fully adhered to the closing segment 2131, thereby effectively reducing curling of the first adhesive 30.

[0064] Optionally, the first adhesive component 30 can be adhesive tape. In use, the adhesive tape can be directly adhered to the first surface 213a of the finishing section 2131 and to the first active material layer 212 of the coating section 2132. For example, the first adhesive component 30 is a single-sided adhesive with adhesiveness on only one side. The single-sided adhesive includes a first substrate layer 30a and a first adhesive layer 30b coated on one side of the first substrate layer 30a (see reference). Figure 5b The first adhesive layer 30b can directly bond the first active material layer 212 and the termination section 2131. The shear force on the empty foil area of ​​the termination section 2131 can be transferred to the single-sided adhesive, thereby reducing the tearing of the termination section 2131. Furthermore, the single-sided adhesive directly covers the junction between the coating section 2132 and the termination section 2131, thereby reducing the puncture of the release membrane 23 by burrs and other protrusions.

[0065] The first substrate layer 30a is made of at least one of polyethylene terephthalate (PET), polyimide, or polypropylene. PET has excellent physical and mechanical properties, a long-term operating temperature up to 120°C, excellent electrical insulation properties, and good electrical performance even at high temperatures and high frequencies. It also exhibits good creep resistance, fatigue resistance, abrasion resistance, and dimensional stability. Using PET as the first adhesive component 30 can significantly improve the tensile strength of the termination section 2131, thereby reducing the risk of tearing of the termination section 2131. The first adhesive layer 30b is made of at least one of polyacrylic acid (PAA), polymethyl methacrylate, polypropylene, polyethylene, polyamide, styrene-butadiene rubber, nitrile rubber, butadiene rubber, isoprene rubber, ethylene propylene rubber, or chloroprene rubber.

[0066] The second adhesive component 40 is bonded between the electrode assembly 20 and the housing 10. For example, please refer to [reference needed]. Figure 1 as well as Figure 4 and Figure 5a The second adhesive 40 is disposed on the second surface 213b of the end section 2131 to further improve the tensile strength of the end section 2131; and the second adhesive 40 is bonded between the second surface 213b of the end section 2131 and the housing 10, which can reduce the relative movement between the electrode assembly 20 and the housing 10. When the secondary battery 100 is dropped or colliding, the bonding effect of the second adhesive 40 can effectively reduce the collision between the electrode assembly 20 and the housing 10, thereby reducing the risk of failure of the secondary battery 100.

[0067] The second adhesive component 40 can also be made of adhesive tape, such as double-sided adhesive tape, which includes a second substrate layer 41 and a second adhesive layer 42 and / or a hot melt adhesive layer coated on both sides of the second substrate layer 41. One side of the second adhesive component 40 is bonded to the electrode assembly 20, and the other side is bonded to the housing 10, reducing the relative movement between the electrode assembly 20 and the housing 10. The material of the second substrate layer 41 includes one or more of polyester resin, cellulose derivatives, polyvinyl chloride, polyolefin, polystyrene, polyester, polyimide, polyamide, polycarbonate or polyphenylene sulfide, and polyethylene terephthalate. When the second adhesive layer 42 is an adhesive layer, the material includes one or more of rubber-based resin, acrylic resin, or silicone resin. When the second adhesive layer 42 is a hot melt adhesive layer, the material includes one or more of styrene-isoprene-styrene block copolymer, ethylene-vinyl acetate copolymer, polyurethane elastomer, polyurethane acrylate, polyisobutylene, or polybutadiene. After the electrode assembly 20 is wound, it can be fixed by the second adhesive 40, which can reduce the finishing process of applying adhesive and finishing glue, and can improve the energy density of the secondary battery 100 while reducing tearing of the finishing section.

[0068] Along the direction M perpendicular to the first surface 213a, the second adhesive member 40 partially overlaps with the first adhesive member 30; that is, along the direction M perpendicular to the first surface 213a, the projection of the second adhesive member 40 partially overlaps with the projection of the first adhesive member 30. When the secondary battery 100 is dropped or colliding, the second adhesive member 40 adheres to the electrode assembly 20 and the housing 10, which can reduce the relative movement between the electrode assembly 20 and the housing 10. However, the second adhesive member 40 will be subjected to a large shear force, which can easily lead to tearing of the end section 2131 of the second adhesive member 40. In this embodiment, since the projection of the first adhesive member 30 overlaps with the projection of the second adhesive member 40, part of the shear force on the second adhesive member 40 can be transmitted to the first adhesive member 30, thereby reducing the concentration of shear force and further reducing the risk of tearing of the end section 2131.

[0069] In some embodiments, the portion of the second adhesive 40 that overlaps with the projection of the first adhesive 30 is a first portion 40a. Along the direction M perpendicular to the first surface 213a, the projection of the first portion 40a falls within the projection range of the first adhesive 30. The shear force transmission between the first adhesive 30 and the second adhesive 40 can effectively reduce the risk of tearing of the finishing section 2131.

[0070] Preferably, the area of ​​the first part 40a is S1, and the area of ​​the second adhesive part 40 is S2, with 15% ≤ S1 / S2 ≤ 50%. The sufficient adhesive area of ​​the second adhesive part 40 can improve the tensile strength of the finishing section 2131 on the one hand, and ensure that there is sufficient overlap between the second adhesive part 40 and the first adhesive part 30 for shear force transmission on the other hand, thereby reducing the risk of tearing at the finishing section.

[0071] Furthermore, the actual adhesive area between the second adhesive component 40 and the first segment 213 is S3, and the effective adhesive area between the second adhesive component 40 and the first segment 213 is S4, where S3 > S4. Sufficient actual adhesive area reduces the risk of tearing of the first segment 213.

[0072] In some embodiments, please refer to Figure 6 and Figure 7 The first adhesive component 30 includes a first sub-adhesive component 31 and a second sub-adhesive component 32. The first sub-adhesive component 31 is disposed on the first surface 213a, and the second sub-adhesive component 32 is also disposed on the first surface 213a. The second sub-adhesive component 32 is bonded to the first sub-adhesive component 31 at the end section 2131. If the length of the first adhesive component 30 is too long (30mm) along the winding direction N of the first section 213, air bubbles may appear when bonding the first section 213. These air bubbles not only affect the energy density of the secondary battery 100, but also lead to poor bonding effect of the first adhesive component 30, resulting in an insignificant shear force transmission effect between the second adhesive component 40 and the first adhesive component 30. In this embodiment of the application, the first adhesive member 30 is configured as a structure with two sub-adhesive members, namely, the first adhesive member 30 includes a first sub-adhesive member 31 and a second sub-adhesive member 32 bonded together. Both the first adhesive member 30 and the second adhesive member 40 are relatively short, which can effectively reduce the formation of air bubbles during the bonding process. The projection of the second sub-adhesive member 32 on the second surface 213b partially overlaps with the second adhesive member 40, allowing all the shear force of the second adhesive member 40 to be transferred to the second sub-adhesive member 32, and then to the first sub-adhesive member 31, thereby reducing shear force concentration.

[0073] Optionally, one end of the first sub-adhesive 31 is adhered to the coating section 2132, and the other end is adhered to the termination section 2131, with the first sub-adhesive 31 covering the connection between the coating section 2132 and the termination section 2131. Because a shorter first sub-adhesive 31 is used, the adhesion of the first sub-adhesive 31 reduces the occurrence of air bubbles during bonding and covers any protruding structures such as burrs at the connection point, reducing the risk of burrs piercing the release membrane 23, thereby lowering the risk of short circuits and reducing the shedding of active material layers at the interface.

[0074] Furthermore, along the first direction X, the length of the first sub-adhesive 31 is L3 mm, and the length of the first segment 213 is L2 mm, where 0 ≤ L3 - L2 ≤ 3. The first sub-adhesive 31 completely covers the junction in the first direction X to further reduce the puncture of the separator 23 by burrs or other protrusions, thereby reducing the risk of short circuits.

[0075] The first adhesive component 30 described above can also employ multiple sub-adhesive components, for example, please refer to further details. Figure 8 The first adhesive element 30 includes a plurality of second sub-adhesive elements 32.

[0076] Multiple second sub-adhesives 32 are arranged sequentially on the first surface 213a along the winding direction N of the first segment 213, with adjacent second sub-adhesives 32 bonded to each other. Along the winding direction N of the first segment 213, the second sub-adhesives 32 at the beginning of the arrangement bond the first sub-adhesive 31 to the end segment 2131. Along the direction M perpendicular to the first surface 213a, the projection of the second sub-adhesive 32 at the end of the arrangement partially overlaps with the projection of the second adhesive 40. This arrangement of multiple sub-adhesives further reduces air bubbles during bonding and further reduces shear force concentration, thereby reducing the risk of tearing of the end segment 2131.

[0077] In some embodiments, please refer to Figure 7 Along the winding direction N of the first segment 213, the length of the first sub-adhesive 31 is L4 mm, where L4 ≤ 30. When the length of the first sub-adhesive 31 exceeds 30 mm, air bubbles are prone to appear during bonding. Therefore, in the embodiments of this application, the length of the first sub-adhesive 31 is preferably less than 30 mm. The second sub-adhesive 32 can also be configured similarly, that is, along the winding direction N of the first segment 213, the length of the second sub-adhesive 32 is L5 mm, where L5 ≤ 30, thereby reducing the appearance of air bubbles during bonding.

[0078] Please refer to Figure 2 and Figure 4 , Figure 2The diagram illustrates the winding structure of the electrode assembly 20. The first segment 213 includes a first straight segment 24, a first curved segment 25, a second straight segment 26, and a second curved segment 27 connected to each other. The first straight segment 24 and the second straight segment 26 are positioned opposite each other in the second direction Y. The first curved segment 25 and the second curved segment 27 are both connected between the first straight segment 24 and the second straight segment 26, and are positioned opposite each other in the third direction Z. For example, the first segment 213 is first wound to form the first curved segment 25, then straightened to form the second straight segment 26, the second straight segment 26 extends and is wound to form the second curved segment 27, and finally straightened to form the first straight segment 24.

[0079] The second adhesive member 40 is partially disposed on the first straight section 24 or partially disposed on the second straight section 26. For example, when the winding end of the first section 213 is close to the first straight section 24, the second adhesive member 40 can be partially bonded to the first straight section 24; or as... Figure 2 When the winding end of the first segment 213 approaches the second straight segment, the second adhesive 40 can be partially bonded to the second straight segment 26. Placing the second adhesive 40 partially on the flat first straight segment 24 or the second straight segment 26 facilitates bonding and improves the bonding effect, thereby increasing the tensile strength of the first segment 213 and reducing the risk of tearing of the first segment 213.

[0080] Regarding the thickness of electrode assembly 20, when the thickness of electrode assembly 20 is greater than or equal to 6.95 mm (along... Figure 2 When the thickness of the electrode assembly 20 is in the second direction Y, the length of the first adhesive 30 should be greater than or equal to 30mm (at this time, multiple first sub-adhesives 31 can be used). The relationship between the thickness of the electrode assembly 20 and the length L of the corner (first bending segment 25 or second bending segment 27) of the outermost first segment 213 is L=(π*T) / 2. In this application, in order to achieve the anti-collision tearing effect and at the same time prevent the generation of air bubbles in the adhesive, the thickness of the electrode assembly 20 satisfies: L+H+W≤25~30mm. H is the length of the second active material layer 222 exceeding the first active material layer 212 along the winding direction N of the first segment 213, that is Figure 2 The intermediate dimension H; W is the distance between the first adhesive part 30 and the end of the tail section 2131 (that is, the first distance W mentioned above).

[0081] In the embodiments of this application, the first adhesive member 30 is at least partially bonded to the first surface 213a of the terminal section 2131, which can improve the tensile strength of the terminal section 2131 and thus reduce the risk of tearing of the terminal section 2131. The second adhesive member 40 is disposed on the second surface 213b of the terminal section 2131 and bonds the terminal section 2131 to the housing 10, which can reduce the relative movement between the electrode assembly 20 and the housing 10 and further improve the tensile strength of the terminal section 2131, thereby further reducing the risk of tearing of the terminal section 2131. At the same time, along the direction perpendicular to the first surface 213a, the projection of the second adhesive member 40 partially overlaps with the projection of the first adhesive member 30. When the secondary battery 100 is dropped or colliding, part of the shear force on the second adhesive member 40 can be transmitted to the first adhesive member 30, thereby reducing the concentration of shear force and further reducing the risk of tearing of the terminal section 2131.

[0082] Example

[0083] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0084] Example 1

[0085] Preparation of positive electrode (cathode)

[0086] Lithium cobalt oxide (LiCoO2), conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, which was then stirred until homogeneous. The slurry was uniformly coated onto one surface of a 9 μm thick aluminum foil used as a positive electrode current collector and dried at 90°C to obtain a positive electrode sheet with a positive active material layer thickness of 110 μm. This single-sided coating of the positive electrode sheet was then completed. The above steps were repeated on the other surface of the positive electrode sheet to obtain a double-sided coated positive electrode sheet. After coating, the sheet was cold-pressed, cut, and slit, then dried under vacuum at 85°C for 4 hours to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm.

[0087] Preparation of negative electrode (anode)

[0088] Graphite powder (negative electrode active material), conductive carbon black (Super P) (conductive agent), and styrene-butadiene rubber (SBR) (binder) were mixed in a weight ratio of 96:1.5:2.5. Deionized water was then added as a solvent to prepare a slurry with a solid content of 70 wt%, and the mixture was stirred evenly. The slurry was uniformly coated onto one surface of a 5 μm thick copper foil used as a negative electrode current collector, and dried at 110°C to obtain a single-sided negative electrode sheet with a negative electrode active material layer thickness of 130 μm. This single-sided coating of the negative electrode sheet was then completed. The above steps were repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, the sheet was cold-pressed, cut, and slit, then dried under vacuum at 120°C for 12 hours to obtain a negative electrode sheet with dimensions of 76.6 mm × 875 mm.

[0089] Preparation of the separating membrane

[0090] Polyvinylidene fluoride (adhesive) and alumina ceramic were mixed at a mass ratio of 9:1, and deionized water was added as a solvent to prepare a slurry with a solid content of 25wt%. The slurry was stirred evenly and then uniformly coated on one surface of a 5μm thick polyethylene porous polymer film. After drying, the slurry was uniformly coated on the other surface of the polyethylene porous polymer film to obtain a double-sided alumina ceramic layer coated with a 2μm layer on both sides.

[0091] Preparation of electrolyte

[0092] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution. Then, lithium hexafluorophosphate (LiPF6) was added to the organic solvent, dissolved, and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0093] Preparation of the first adhesive component

[0094] Polyacrylic acid (PAA) is coated on one surface of an 8μm first substrate layer polyethylene terephthalate film (PET), and dried at 80°C to form a first adhesive layer with a thickness of 4μm, thus obtaining the first adhesive part.

[0095] Preparation of the second adhesive component

[0096] A styrene-isoprene-styrene block copolymer is heated to 150°C for hot melting and then coated onto one surface of a polyethylene terephthalate (PET) film with a thickness of 8 μm as a second substrate layer. The film is then dried at 120°C to form a second adhesive layer with a thickness of 8 μm.

[0097] Polyacrylic acid (PAA) is coated on the other surface of the second substrate layer and dried at 80°C to form a second adhesive layer with a thickness of 4μm, thereby obtaining a second adhesive component containing a second adhesive layer, a second substrate layer and a second adhesive layer stacked sequentially.

[0098] Preparation of lithium-ion batteries

[0099] The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrode to act as a separator. The electrode assembly is then wound to obtain a wound structure. The outermost layer is a positive electrode with a single-sided active material coating. A modified polypropylene first adhesive is used to bond the coated section and the empty foil section of the outermost positive electrode.

[0100] The second adhesive component prepared above is bonded to the outer surface of the electrode assembly using the second adhesive layer. The electrode assembly is then placed in an aluminum-plastic film packaging bag, while the first adhesive layer is bonded to the inner surface of the casing. Following processes such as top-side sealing, vacuum drying, liquid injection, formation (temperature 85℃, pressure 1.05MPa, 3.5V), capacity testing, and degassing, a lithium-ion battery is obtained.

[0101] The lithium-ion battery weighs 61.5g and has a liquid retention coefficient of 1.75g / Ah. The first adhesive layer has dimensions of 20mm × 30mm, and the orthographic projection dimension of the electrode assembly along the stacking direction of the electrode assembly, adhesive, and housing is 30mm × 40mm, i.e., S5 = 600mm. 2 S6 = 1200mm 2 The actual area covered by adhesive is S = S5 = 600 mm². 2 Along the thickness direction of the positive electrode sheet, the area of ​​the overlapping region between the projection of the second adhesive component and the first adhesive component is 100 mm². 2 (S1=100mm 2 The distance between the first adhesive and the end of the positive electrode sheet is 3.2 mm (W = 3.2 mm), the length difference (length along the central axis of the electrode assembly) between the first adhesive and the outer single-sided positive electrode sheet (including the empty foil area) is 0.8 mm (L1-L2 = 0.8 mm), and the peel strength of the separator is 10 N / m.

[0102] Example 2

[0103] The difference from Example 1 is that S1 = 60mm 2 .

[0104] Example 3

[0105] The difference from Example 1 is that S1 = 90mm 2 .

[0106] Example 4

[0107] The difference from Example 1 is that S1 = 150mm 2 .

[0108] Example 5

[0109] The difference from Example 1 is that S1 = 240 mm 2 .

[0110] Example 6

[0111] The difference from Example 1 is that S1 = 300mm 2 .

[0112] Example 7

[0113] The difference from Example 1 is that S1 = 360mm 2 .

[0114] Example 8

[0115] Unlike Example 1, W = 2 mm.

[0116] Example 9

[0117] Unlike Example 1, L1-L2 = 3mm.

[0118] The difference between Example 10 and Example 1 is that L1-L2 = 0mm.

[0119] Example 11

[0120] The difference from Example 1 is that S1 = 150mm 2 The mass ratio of polyvinylidene fluoride to alumina ceramic is 6:4, and the peel strength between the separator and the positive electrode is 7 N / m.

[0121] Example 12

[0122] The difference from Example 1 is that S1 = 150mm 2 The mass ratio of polyvinylidene fluoride to alumina ceramic is 8:2, and the peel strength between the separator and the positive electrode is 8 N / m.

[0123] Example 13

[0124] The difference from Example 1 is that S1 = 150mm 2 The mass ratio of polyvinylidene fluoride to alumina ceramic is 9.5:0.5, and the peel strength between the separator and the positive electrode is 12 N / m.

[0125] Example 14

[0126] The difference from Example 1 is that S1 = 150mm 2The mass ratio of polyvinylidene fluoride to alumina ceramic is 9.8:0.2, and the peel strength between the separator and the positive electrode is 13 N / m.

[0127] Comparative Example 1

[0128] Unlike Example 1, the first adhesive does not cover the empty foil segment, and the projections of the first adhesive and the second adhesive in the thickness direction of the positive electrode sheet do not overlap, so S1 = 0.

[0129] Test methods and equipment:

[0130] Drop foil tear rate test:

[0131] The lithium-ion batteries were pretreated at 25°C and left to stand at room temperature for 60 minutes before the drop test. The batteries were then placed in a fixture and dropped freely from a height of 1.5m using a drop tester in the following sequence: head-tail-head right corner-tail right corner-head left corner-tail left corner (angle: 45±15°), repeated 6 times. After the drop test, the battery cells were disassembled, and the aluminum foil was inspected for tears.

[0132] Drop failure rate test:

[0133] The lithium-ion batteries were pretreated at 25°C and left to stand at room temperature for 60 minutes before the drop test. The batteries were then placed in a clamp and dropped freely from a height of 1.5m using a drop tester in the following sequence: head-tail-right head corner-right tail corner-left head corner-left tail corner (angle: 45±15°), repeated 6 times. The battery voltage was measured and recorded after each drop test. The appearance of the batteries was inspected and photographed before and after the test. The drop test passed the following criteria: no smoke, no leakage, and voltage drop <30mV.

[0134] Peel strength test:

[0135] According to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes", a high-speed rail tensile testing machine was used to test the peel strength between the separator and the positive or negative electrode sheet (in this embodiment, the peel strength between the separator and the positive electrode sheet is taken as an example). The test procedure is as follows: The lithium-ion battery is discharged to 0V, then the lithium-ion battery is disassembled, and the separator and the electrode sheet it is bonded to are removed as a whole. The electrolyte on the surface is wiped off with lint-free paper. Then, it is cut into strips of 20mm × 60mm. Along the length of the sample, the side of the sample with the electrode assembly is adhered to a steel plate with double-sided adhesive (Nitto 5000NS), with an adhesion length of not less than 40mm. The steel plate is fixed in the corresponding position of the high-speed rail tensile testing machine. The other end of the electrode sheet that is not adhered to the diaphragm is pulled up, and the sample is placed in the clamp and clamped. The angle between the pulled-up part of the sample and the steel plate in space is 180°. The clamp pulls the sample at a speed of 5±0.2mm / s. The average tensile force in the stable area is finally measured and recorded as the peel strength between the diaphragm and the electrode sheet, denoted as F, with the unit N / m.

[0136] The relevant preparation parameters and performance tests for each embodiment and comparative example are shown in Tables 1 and 2:

[0137] Table 1

[0138]

[0139]

[0140] According to Table 1 above, and in conjunction with Comparative Example 1 and Examples 1 to 14, it can be seen that when the first adhesive member covers the empty foil section, and the projections of the first adhesive member and the second adhesive member overlap in the thickness direction of the positive electrode sheet, the drop foil tear rate and drop failure rate are significantly reduced. This is because some of the shear force on the second adhesive member can be transmitted to the first adhesive member, thereby reducing shear force concentration and thus reducing foil tearing. Furthermore, since the first adhesive member is bonded from the coated section to the empty foil section, it can cover the edge burrs of the active material layer, reducing the risk of burrs piercing the separator and thus lowering the drop failure rate.

[0141] In Example 2 above, S1 / S2 = 10%, and the area occupied by the first part is relatively small. At this time, the risk of aluminum foil tearing and drop failure is relatively large. In Example 7, S1 / S2 = 60%, and the excessively large area of ​​the first part makes it easy to cut the first adhesive component during cutting, causing the edge of the first adhesive component to curl. Therefore, Example 7 also has a lower aluminum foil tear rate and drop failure risk. In Example 3, S1 / S2 = 15%, and in Example 6, S1 / S2 = 50%, the aluminum foil tear rate and drop failure risk are both low. In this application, preferably, 15% ≤ S1 / S2 ≤ 50%.

[0142] The length of the first adhesive component in the electrode width direction should not be too large or too small. If it is too large, it will easily cause curling in the electrode width direction, entering the top sealing area and affecting the energy density of the lithium-ion battery. If it is too small, it will be difficult to cover the burrs at the edge of the active material layer, and it will easily puncture the separator, leading to a short circuit. In this application, it is preferred that 0≤L1-L2≤3.

[0143] Furthermore, a first distance W ≥ 2mm can better reduce curling in the length direction of the electrode sheet during the cutting of the first adhesive component. Referring to Example 11, when the peel strength between the separator and the positive electrode sheet is 7 N / m, the bonding strength of the electrode assembly is not high, resulting in a continued risk of aluminum foil tearing. Referring to Example 14, when the peel strength between the separator and the positive electrode sheet is 13 N / m, the peel strength is too high, and excessive adhesive will clog the pores on the surfaces of the positive and negative electrode sheets, causing problems such as lithium plating black spots, thus resulting in a continued risk of drop failure for the lithium-ion battery. Referring to Examples 11 to 14, in this application, it is preferable that the peel strength of the separator is 8 N / m to 12 N / m, which has a lower drop aluminum foil tear rate and lower drop failure risk.

[0144] Secondly, this application also proposes an electronic device comprising the secondary battery described in any of the embodiments of the first aspect. The electronic device can be a portable consumer electronic device, a power tool, a drone, a wearable electronic device, an electric vehicle, etc.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A secondary battery, characterized in that, include: case; An electrode assembly is disposed within the housing. The electrode assembly includes a first electrode, a second electrode, and a separator film located between the first electrode and the second electrode. The first electrode, the second electrode, and the separator film are stacked and wound together. The winding center axis of the electrode assembly is a first direction. The first electrode includes a first segment, which constitutes the outermost portion of the electrode assembly. The first segment has a first surface facing the winding center axis and a second surface facing away from the winding center axis. Along the winding direction of the first segment, the first segment includes a tail segment, and the first surface and the second surface of the tail segment are both empty foil areas. The first adhesive component is at least partially bonded to the first surface of the finishing section; The first adhesive component includes a first sub-adhesive component and a second sub-adhesive component disposed on the first surface, wherein the second sub-adhesive component is bonded to the first sub-adhesive component at the tail section; The second adhesive component is disposed on the second surface of the tail section and adhesively bonds the second surface of the tail section to the housing. Along a direction perpendicular to the first surface, the second adhesive part partially overlaps with the first adhesive part, wherein the projection of the second sub-adhesive part on the second surface partially overlaps with the second adhesive part.

2. The secondary battery according to claim 1, characterized in that, The portion of the second adhesive that overlaps with the first adhesive is the first portion, the area of ​​the first portion is S1, the area of ​​the second adhesive is S2, and 15%≤S1 / S2≤50%.

3. The secondary battery according to claim 1, characterized in that, Along the winding direction of the first segment, the distance between the first adhesive and the end of the tail segment is the first distance, which is greater than or equal to 2mm.

4. The secondary battery according to claim 1, characterized in that, The first segment also includes a coating segment connected to the closing segment.

5. The secondary battery according to claim 4, characterized in that, One end of the first adhesive is bonded to the coating section, and the other end is bonded to the finishing section, and the first adhesive covers the connection between the coating section and the finishing section; Along the first direction, the length of the first adhesive is L1 mm, the length of the first segment is L2 mm, and 0 ≤ L1 - L2 ≤ 3.

6. The secondary battery according to claim 4, characterized in that, One end of the first sub-adhesive is adhered to the coating section, and the other end is adhered to the finishing section, and the first sub-adhesive covers the connection between the coating section and the finishing section; Along the first direction, the length of the first sub-adhesive is L3 mm, the length of the first segment is L2 mm, and 0 ≤ L3 - L2 ≤ 3.

7. The secondary battery according to claim 1, characterized in that, The first adhesive component includes a plurality of second sub-adhesive components; The plurality of second sub-adhesives are arranged sequentially on the first surface along the winding direction of the first segment, and adjacent second sub-adhesives are bonded to each other. Along the winding direction of the first segment, the second sub-adhesive at the starting end is bonded to the first sub-adhesive on the ending segment. Along the direction perpendicular to the first surface, the projection of the second sub-adhesive at the ending end overlaps with the projection of the second adhesive.

8. The secondary battery according to claim 1, characterized in that, The first adhesive and the second adhesive are adhesive tape.

9. The secondary battery according to claim 1, characterized in that, The first segment includes a first straight segment, a first curved segment, a second straight segment, and a second curved segment that are connected to each other; The first straight segment and the second straight segment are arranged opposite to each other in a second direction, the first curved segment and the second curved segment are both connected between the first straight segment and the second straight segment, and the first curved segment and the second curved segment are arranged opposite to each other in a third direction; The second adhesive is disposed on the first straight section or the second straight section, and the first direction, the second direction and the third direction are perpendicular to each other.

10. The secondary battery according to claim 1, characterized in that, The peel strength between the separator and the first or second electrode is 8 N / m to 12 N / m.

11. The secondary battery according to claim 8, characterized in that, The first adhesive is a single-sided adhesive that is only sticky on one side, and the single-sided adhesive includes a first substrate layer and a first adhesive layer coated on one side of the first substrate layer.

12. The secondary battery according to claim 8, characterized in that, The second adhesive is a double-sided adhesive with adhesive on both sides. The double-sided adhesive includes a second substrate layer and a second adhesive layer coated on both sides of the second substrate layer. The second adhesive layer is an adhesive layer and / or a hot melt adhesive layer.

13. The secondary battery according to claim 1, characterized in that, The casing is a packaging bag.

14. The secondary battery according to claim 4, characterized in that, The first electrode is a cathode electrode, and the second electrode is an anode electrode; the first segment has an active material layer only on the first surface, and the active material layer is disposed on the first surface of the coated segment.

15. The secondary battery according to claim 1, characterized in that, The second adhesive is used to fix the finishing section.

16. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 15.

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