Secondary battery and electronic device

Abstract

The present application discloses a secondary battery and an electronic device. The secondary battery comprises a packaging pouch and an electrode assembly accommodated in the packaging pouch. The secondary battery is provided with a recess, the packaging pouch is provided with an edge sealing structure, and the edge sealing structure is provided with a first notch at the recess. The secondary battery further comprises a first adhesive layer; the first adhesive layer is arranged at the edge sealing structure; and when observed in the thickness direction of the secondary battery, the first adhesive layer covers at least part of the first notch. The first adhesive layer is provided with a second notch, and when observed in the thickness direction of the secondary battery, the opening of the second notch faces the opening of the first notch, and the second notch is at least partially located in the first notch. The opening angle of the first notch is a first included angle α, and the opening angle of the second notch is a second included angle β, wherein 0°<α<β<180°. The tearing of the packaging pouch can be reduced, thereby reducing the liquid leakage risk of the secondary battery.

Description

Secondary batteries and electronic devices Technical Field

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

[0002] Lithium-ion batteries, as the power source for mobile devices, are key to ensuring their normal use. As mobile devices such as mobile phones and laptops become increasingly popular, their operating conditions are becoming increasingly complex, placing increasing demands on battery safety.

[0003] During the battery's recycling process, the electrode assembly will expand and continuously squeeze the packaging bag. Since the inner polygonal soft-pack battery, such as the "L"-shaped battery, has a notch structure, and the notch is concave toward the packaging bag, the expansion of the electrode assembly will continuously pull on the notch position of the packaging bag, eventually causing the notch position to tear, resulting in battery leakage and failure.

[0004] Summary of the Invention

[0005] The embodiment of the present application aims to provide a secondary battery, i.e., an electronic device, to reduce tearing at the notch of the battery packaging bag, thereby reducing battery leakage and failure.

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

[0007] In a first aspect, the present application proposes a secondary battery comprising a packaging bag and an electrode assembly housed in the packaging bag, wherein the secondary battery has a notch, the packaging bag has an edge sealing structure, and the edge sealing structure has a first notch at the notch. The secondary battery also includes a first adhesive layer, which is disposed on the edge sealing structure. When viewed along the thickness direction of the secondary battery, the first adhesive layer covers at least a portion of the first notch. The first adhesive layer is provided with a second notch. When viewed along the thickness direction of the secondary battery, the opening of the second notch is disposed toward the opening of the first notch, and the second notch is at least partially located in the first notch. The opening angle of the first notch is a first angle α, and the opening angle of the second notch is a second angle β, where 0°<α<β<180°.

[0008] In the above technical solution, the first adhesive layer can disperse the stress in the first notch portion of the packaging bag, and the first adhesive layer can also prevent the distortion and deformation of this portion, thereby improving the strength and tear resistance of this portion, thereby reducing the cyclic leakage of the secondary battery. At the same time, the provision of the first adhesive layer can improve the sealing strength of the packaging bag's edge sealing structure, which can effectively prevent the portion of the packaging bag located at the notch from being broken open. In addition, by limiting 0°<α<β<180°, the angle of the second notch of the first adhesive layer is larger, and its stress distribution is more uniform. When the electrode assembly expands, the first adhesive layer can be subjected to stress first, which can replace the tearing of the packaging bag located at the notch, thereby reducing the risk of leakage of the secondary battery. Moreover, β<180° makes it easier to disperse stress to the second notch of the first adhesive layer, which can facilitate the first adhesive layer to bear stress first. In addition, the first adhesive layer does not affect the internal space of the packaging bag, and has little impact on the external space of the packaging bag, which can ensure that the secondary battery has a high energy density.

[0009] In some preferred embodiments, 30°≤α<β≤90°, which ensures that the first adhesive layer is subjected to stress first, making it easier for the first adhesive layer to prevent tearing and damage at the first notch; at the same time, further reducing the impact of the first adhesive layer on the external dimensions of the packaging bag.

[0010] In some preferred embodiments, the first adhesive layer includes a laminated substrate layer and an adhesive layer, with the adhesive layer bonded between the edge sealing structure and the substrate layer. The substrate layer has high tear resistance, which can reduce tear damage to the first adhesive layer and, in turn, reduce damage to the packaging bag at the first notch.

[0011] In some preferred embodiments, the peel strength of the adhesive layer is a N, the maximum cohesive force of the packaging bag is b N, and a>b, which can make the adhesive layer more firmly bonded to the packaging bag and improve the bonding strength between the first adhesive layer and the packaging bag.

[0012] In some preferred embodiments, the tear resistance of the substrate layer is c N, and the tear resistance of the edge sealing structure at the first notch is d, where c>d. This can improve the tear resistance of the first wall and / or second wall, reducing the risk of tearing and damage in the portion of the packaging bag located at the first notch. Preferably, the thickness of the secondary battery is x mm, the expansion rate of the electrode assembly is y, and c>1.2×d×(x / 5)×(y / 0.08). The tear resistance of the substrate layer is adjusted based on the thickness of the secondary battery and the collision rate of the electrode assembly, thereby reducing the risk of tearing and damage in the portion of the packaging bag located at the first notch.

[0013] In some preferred embodiments, the substrate layer comprises at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide, or polyethylene. Each material has excellent weather resistance, heat resistance, abrasion resistance, and corrosion resistance, thereby reducing electrolyte corrosion of the first adhesive layer and increasing the service life of the first adhesive layer. The adhesive layer comprises at least one of epoxy resin, polyoxyethylene, or polyvinyl acetate. Using these adhesive layer materials improves the bonding strength between the first adhesive layer and the packaging bag while also extending the service life of the first adhesive layer.

[0014] In some preferred embodiments, the edge sealing structure includes a first wall portion, a second wall portion, and a connecting portion connected between the first wall portion and the second wall portion. The angle between the first wall portion and the second wall portion is a first angle α, and the first wall portion, the second wall portion, and the connecting portion together enclose a first notch. Observed along the thickness direction of the secondary battery, the first adhesive layer covers and bonds the connecting portion, as well as at least a portion of the first wall portion and at least a portion of the second wall portion. The connecting portion serves as a transition between the first wall portion and the second wall portion. Part of the first adhesive layer is bonded to the connecting portion, which can increase the stress dispersion area, reduce stress concentration, and thereby reduce tearing of the packaging bag in the first notch portion.

[0015] In some preferred embodiments, the connecting portion is arc-shaped, concave toward the interior of the packaging bag. This arc-shaped structure increases the force-bearing area, thereby dispersing stress. When subjected to external forces, the arc-shaped structure can disperse the force over a larger area, reducing single-point or localized stress concentration. Furthermore, the arc-shaped structure improves structural stability, reduces deformation and displacement of the material under force, and thereby reduces tearing of the packaging bag at the first notch. The radius of the arc-shaped connecting portion is r mm. The first adhesive layer is arc-shaped and bonded to the connecting portion and at least a portion of the first and second walls. The radius of the arc-shaped first adhesive layer is R mm, with 0.6R≤r≤0.8R. A larger radius of the first adhesive layer allows for more uniform stress distribution, thereby reducing tearing at the connecting portion.

[0016] In some preferred embodiments, the distance between the center of the first adhesive layer and the connecting portion is D mm, 0≤D≤0.3, and the center of the first adhesive layer is ensured to overlap with the center of the connecting portion as much as possible, so that the stress on various parts of the connecting portion is evenly dispersed to the second notch of the first adhesive layer, so that the first adhesive layer is preferentially stressed, thereby reducing tearing and damage at the first notch of the packaging bag.

[0017] In some preferred embodiments, when viewed along the thickness direction of the secondary battery, the center line of the second notch is located within the first notch, ensuring that the second notch of at least half the angle of the first adhesive layer can provide buffering and tear resistance, thereby reducing tearing at the first notch.

[0018] In some preferred embodiments, when viewed along the thickness of the secondary battery, the top corner of the second notch is located within the first notch, and the two bottom corners of the second notch are located on the edge sealing structure. Having the top corner of the second notch located within the first notch allows the top corner, which has a stronger tear resistance, to resist tearing forces first. Simultaneously, having the bottom corner located on the edge sealing structure improves the adhesion between the first adhesive layer and the edge sealing structure, preventing the first adhesive layer from falling off during tearing, thereby increasing the bonding strength between the first adhesive layer and the edge sealing structure.

[0019] In some preferred embodiments, the top corner of the second notch is an arc-shaped transition, which is more likely to disperse stress, reduce stress concentration, and thus improve the tear resistance of the top corner.

[0020] In a second aspect, the present application further proposes an electronic device comprising a secondary battery as described in any embodiment of the first aspect above.

[0021] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0023] FIG1 is an exploded view of a secondary battery according to some embodiments of the present application;

[0024] FIG2 is a schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0025] FIG3 is a schematic structural diagram of a first notch in some embodiments of the present application;

[0026] FIG4 is a partial enlarged view of line A in FIG2 ;

[0027] FIG5 is a schematic diagram illustrating the connection between the first adhesive layer and the sealing structure in some embodiments of the present application;

[0028] FIG6 is a schematic structural diagram of a first notch in some embodiments of the present application;

[0029] FIG7 is a schematic structural diagram of a first notch in some embodiments of the present application;

[0030] FIG8 is a schematic structural diagram of a first notch in some embodiments of the present application;

[0031] FIG9 is a schematic structural diagram of a first notch in some embodiments of the present application;

[0032] FIG10 is a schematic structural diagram of the first adhesive layer in some embodiments of the present application;

[0033] FIG11 is a schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0034] FIG12 is a schematic structural diagram of the first notch in some embodiments of the present application.

[0035] Explanation of reference numerals: 100, secondary battery; 10, packaging bag; 11, first bag body; 111, first cavity; 12, second bag body; 101, first portion; 1011, first wall portion; 102, second portion; 1021, second wall portion; 103, connecting portion; 20, electrode assembly; 30, tab; 40, notch; 50, first adhesive layer; 50a, second notch; 50a1, top corner; 50a2, bottom corner; 51, adhesive layer; 52, substrate layer; 60, edge sealing structure; 61, top edge sealing; 62, first side edge sealing; 62a, first sub-side edge sealing; 62b, second sub-side edge sealing; 63, second side edge sealing; 64, first notch; Z, first direction; Y, second direction; N, fitting circle where the connecting portion is located; M, fitting circle where the first adhesive layer is located; P, opening direction of the second notch; Q, opening of the first notch; S, center line of the second notch. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0037] It should be noted that when an element is described as being “fixed to” or “disposed on” another element, it may be directly on the other element, or one or more intervening elements may be present therebetween. When an element is described as being “connected to” another element, it may be directly connected to the other element, or one or more intervening elements may be present therebetween.

[0038] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise specifically defined.

[0039] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features described below in the different embodiments of the present application may be combined with each other as long as they do not conflict with each other.

[0041] In the first aspect, the present application proposes a secondary battery 100. Referring to FIG1 , the secondary battery 100 includes a packaging bag 10, an electrode assembly 20, and a tab 30. The packaging bag 10 is a mounting base and container for the remaining components of the secondary battery 100. The electrode assembly 20 is housed in the packaging bag 10. The electrode assembly 20 is the core component for the secondary battery 100 to realize charging and discharging. One end of the tab 30 is electrically connected to the electrode assembly 20, and the other end extends out of the packaging bag 10. Next, taking the secondary battery 100 as a lithium-ion battery as an example, the specific structure of the secondary battery 100 is explained; it can be understood that in other embodiments of the present application, the secondary battery 100 can also be a secondary battery 100 in other forms such as a sodium-ion battery.

[0042] Regarding the above-mentioned packaging bag 10, please refer to Figures 1 and 2. The packaging bag 10 can be made of a flexible material, which constitutes the mounting base, container and outer protective structure of the secondary battery 100. The packaging bag 10 is defined by a accommodating cavity (not shown in the figure), which can be used to accommodate the electrolyte (not shown in the figure) and the above-mentioned electrode assembly 20. For example, the packaging bag 10 includes a first bag body 11 and a second bag body 12. The first bag body 11 is provided with a first pit cavity 111, and the second bag body 12 is provided with a second pit cavity (not shown in the figure). The above-mentioned electrode assembly 20 can be placed in the first pit cavity 111. The second bag body 12 covers the first pit cavity 111 of the first bag body 11, and the second pit cavity communicates with the first pit cavity 111 to form a accommodating cavity. The connection between the edges of the two shells can be sealed by hot pressing to make the two shells bonded to each other to seal the accommodating cavity. Among them, the first bag body 11 and the second bag body 12 can be interconnected structures or separated structures. The above-mentioned second bag body 12 may not be provided with a pit cavity. The second bag body 12 directly covers the first pit cavity 111 of the first bag body 11, and the first pit cavity 111 forms a accommodating cavity.

[0043] Optionally, the packaging bag 10 may adopt a quadrilateral structure such as a rectangle or a trapezoidal structure, or other polygonal structures. Its shape is polygonal and it is made of flexible materials, which can adapt to spaces of various shapes. The polygonal soft-pack secondary battery 100 has the advantages of small size, light weight, high energy density, etc., and also has good safety performance and environmental protection performance. Taking the "L"-shaped packaging bag 10 as an example, please refer to Figures 1 to 3. When observed along the first direction Z, the packaging bag 10 is roughly "L"-shaped. For example, the first bag body 11 and the second bag body 12 are both "L"-shaped. The first bag body 11 and the second bag body 12 can be combined and connected to form a complete "L"-shaped packaging bag 10. The packaging bag 10 includes a first part 101 and a second part 102 that are connected. For example, along the second direction Y, the first part 101 and the second part 102 are arranged in sequence. The tabs 30 extend from the first portion 101 outside the packaging bag 10. A notch 40 is provided between the first portion 101 and the second portion 102. The first portion 101 and the second portion 102 are bent along the notch 40, giving the packaging bag 10 an overall "L" shape. The "L"-shaped secondary battery 100 can fit into the specific battery installation space of electronic devices, significantly improving the energy density of the secondary battery 100 while reducing the occupied space.

[0044] It can be understood that in the embodiments of the present application, the packaging bag 10 includes but is not limited to an "L"-shaped structure. In other embodiments, the packaging bag 10 may also adopt a polygonal structure such as a "Z" shape with notches 40, and the number of notches 40 may be two, three or more.

[0045] When the edges of the two bag bodies are hot-pressed and sealed, a sealing edge structure 60 is formed on the outside of the packaging bag 10. The sealing edge structure 60 includes a top sealing edge 61, a first side sealing edge 62, and a second side sealing edge 63. The top sealing edge 61 is located between the first side sealing edge 62 and the second side sealing edge 63. The tab 30 can extend from the top sealing edge 61 outside the first bag body 11. The sealing edge structure 60 has a first notch 64 at the recess 40. The first notch 64 can be provided in the first side sealing edge 62. For example, the first side sealing edge 62 includes a first sub-side sealing edge 62a and a second sub-side sealing edge 62b. The first notch 64 is located between the first sub-side sealing edge 62a and the second sub-side sealing edge 62b.

[0046] The notch 40 weakens the portion of the packaging bag 10 located at the first notch 64. If the secondary battery 100 or an electronic device equipped with the secondary battery 100 is accidentally dropped or collided, the first portion 101 and the second portion 102 of the packaging bag 10 may move relative to each other, or may be prone to relative movement. This can easily cause the first notch 64 of the packaging bag 10 to bend and deform. The portion of the packaging bag 10 located at the first notch 64 is relatively weak, and stress concentration may occur there, leading to tearing and damage. This can cause electrolyte leakage or the entry of impurities such as moisture and dust into the packaging bag 10, potentially leading to failure of the secondary battery 100. To reduce this risk,

[0047] In an embodiment of the present application, a first adhesive layer 50 may be provided on the edge sealing structure 60 of the packaging bag 10 . Referring to FIG. 2 to FIG. 4 , the first adhesive layer 50 is provided on the edge sealing structure 60 . When viewed along the thickness direction (first direction Z) of the secondary battery, the first adhesive layer 50 covers at least a portion of the first notch 64 .

[0048] When the electrode assembly 20 expands within the packaging bag 10, the first adhesive layer 50 disperses the stress in the portion of the packaging bag 10 located at the first notch 64. The first adhesive layer 50 also prevents distortion in this portion, improving its strength and tear resistance, thereby reducing leakage during cycling of the secondary battery 100. Furthermore, the first adhesive layer 50 enhances the seal strength of the edge sealing structure 60 of the packaging bag 10, effectively preventing the first notch 64 of the packaging bag 10 from being breached.

[0049] The first adhesive layer 50 defines a second notch 50a. When viewed along the thickness direction (first direction Z) of the secondary battery 100, the opening of the second notch 50a faces the opening Q of the first notch (the dashed line portion in the figures). As shown in Figures 4 and 5 , the opening of the second notch faces the direction P, and the opening Q of the first notch is located in the direction P of the second notch. Furthermore, the second notch 50a is at least partially located within the first notch 64. Further referring to Figure 6 , the opening angle of the first notch 64 is a first angle α, and the opening angle of the second notch 50a is a second angle β, where 0°<α<β<180°. The larger angle between the two ends of the first adhesive layer 50 allows for more uniform stress distribution. When the electrode assembly 20 expands, the first adhesive layer 50 receives stress preferentially. Furthermore, the opening angle β of the second notch 50a is less than 180°, which facilitates stress distribution to the second notch 50a of the first adhesive layer 50. This allows the second notch 50a of the first adhesive layer 50 to receive stress preferentially, thus preventing tearing of the packaging bag 10 at the first notch 64 and reducing the risk of leakage from the secondary battery 100. Furthermore, the first adhesive layer 50 does not affect the internal space of the secondary battery 100 and has minimal impact on the external space of the secondary battery 100, ensuring a high energy density for the secondary battery 100. Preferably, 30° ≤ α < β ≤ 90° ensures that the first adhesive layer 50 receives stress preferentially, more effectively preventing tearing and damage at the first notch 64, and further reducing the impact of the first adhesive layer 50 on the external dimensions of the packaging bag 10.

[0050] 7 , in some embodiments, when viewed along the thickness direction of the secondary battery (first direction Z), the center line S of the second notch is located within the first notch 64 , ensuring that at least half of the angle of the second notch 50 a of the first adhesive layer 50 can provide a buffering and tear-resistant effect, thereby reducing tearing at the first notch 64 .

[0051] Referring to Figures 7 and 8 , when viewed along the thickness direction of the secondary battery (first direction Z), the top corner 50a1 of the second notch 50a is located within the first notch 64, while the two bottom corners 50a2 of the second notch 50a are located on the edge sealing structure 60. The top corner 50a1 of the second notch 50a is located within the first notch 64, allowing the top corner 50a1, which has stronger tear resistance, to preferentially resist tearing forces. Simultaneously, the bottom corners 50a2 are located on the edge sealing structure 60, which improves the adhesion between the first adhesive layer 50 and the edge sealing structure 60, preventing the first adhesive layer 50 from falling off during tearing, thereby enhancing the bonding strength between the first adhesive layer 50 and the edge sealing structure 60.

[0052] Further, referring to FIG. 9 , the top corner 50a1 of the second notch 50a is an arc-shaped transition. The arc-shaped transition is more likely to disperse stress, reduce stress concentration, and thus improve the tear resistance of the top corner 50a1.

[0053] Referring to Figures 2 and 10 , in some embodiments, the first adhesive layer 50 includes a laminated substrate layer 52 and an adhesive layer 51. The adhesive layer 51 is bonded to the edge sealing structure 60. The substrate layer 52 has a high tear resistance, which reduces tearing damage to the first adhesive layer 50 and, consequently, reduces damage to the packaging bag 10 at the first notch 64. The adhesive layer 51 bonds the substrate layer 52 to the edge sealing structure 60, enhancing the bonding strength between the first adhesive layer 50 and the packaging bag 10, thereby increasing the strength of the packaging bag 10 at the first notch 64 and reducing tearing damage there.

[0054] As for the material of the substrate layer 52, optionally, the substrate layer 52 includes at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide or polyethylene. The material of the above-mentioned substrate layer 52 has good weather resistance, heat resistance, wear resistance and corrosion resistance, which can reduce the corrosion of the first adhesive layer 50 and extend the service life of the first adhesive layer 50.

[0055] As for the material of the adhesive layer 51, optionally, the adhesive layer 51 includes at least one of epoxy resin, polyoxyl or polyvinyl acetate. Among the materials of the above-mentioned adhesive layer 51, epoxy resin is a thermosetting resin with excellent mechanical properties and chemical stability, and has good corrosion resistance and wear resistance; polyoxyl is a polymer with a high molecular weight, and has good heat resistance, corrosion resistance and electrical insulation properties; polyvinyl acetate has excellent softness and air permeability. The use of the above-mentioned materials for the adhesive layer 51 can improve the bonding strength between the first adhesive layer 50 and the packaging bag 10 while improving the service life of the first adhesive layer 50.

[0056] In some embodiments, the peel strength of the adhesive layer 51 is a N, and the maximum cohesion of the packaging bag 10 is b N. With a > b, the adhesive layer 51 can be more firmly bonded to the packaging bag 10, improving the bonding strength between the first adhesive layer 50 and the packaging bag 10. Peel strength refers to the ability of a material to resist peeling when a peeling force is applied between the surfaces of the materials. It is generally used to describe the bonding strength between an adhesive, coating, or paint and a substrate. Maximum cohesion refers to the maximum attractive force generated between molecules or atoms within a material. It is generally used to describe the cohesive properties of a material, that is, the bonding strength between molecules or atoms within the material. The greater the maximum cohesion, the better the cohesive properties of the material, and the more difficult it is to separate or destroy the material. For example, the packaging bag 10 includes a stacked metal layer (not shown), a protective layer (not shown), and a sealing layer (not shown). The protective layer is the outer surface of the packaging bag 10, and the first adhesive layer 50 is directly bonded to the protective layer of the packaging bag 10. In the embodiments of the present application, the maximum cohesion can be considered to be the bonding strength between the protective layer and the metal layer.

[0057] The peel strength between the adhesive layer 51 and the packaging bag 10 is tested as follows:

[0058] The peel strength between the adhesive layer 51 and the packaging bag 10 was tested using a high-speed rail tensile tester in accordance with GB / T 2792-2014, "Test Method for Peel Strength of Adhesive Tapes." The test procedure is as follows: Discharge the secondary battery 100 to 0V, then disassemble it. Remove the adhesive layer 51 and the packaging bag 10 attached to it as a whole. Wipe the surface of the electrolyte with dust-free paper. Then cut the strips into 5mm x 5mm specimens. Adhere the packaging bag side of the specimen to a steel plate along its length using double-sided tape (Nitto 5000NS). Fix the steel plate at the corresponding position of the high-speed rail tensile testing machine, pull up the other end of the sample that is not adhered to the adhesive layer on the packaging bag 10, and place the sample in the chuck and clamp it. The angle between the pulled-up sample part and the steel plate in space is 180°. The chuck pulls the sample at a speed of 1±0.2mm / s. The average tensile force in the stable area is finally measured and recorded as the peel strength of the adhesive layer, recorded as a, and the unit is N / m.

[0059] The cohesion of the packaging bag 10 is tested as follows:

[0060] The cohesion of the packaging bag 10 was tested using a high-speed rail tensile tester in accordance with GB / T 2792-2014, "Test Method for Peel Strength of Adhesive Tapes." The test procedure is as follows: Discharge the secondary battery 100 to 0V, then disassemble it. Remove the packaging bag 10, including the nylon and metal layers, as a whole. Wipe the surface of the electrolyte with dust-free paper. The bag is then cut into 20mm x 60mm strips. The nylon side of the sample is adhered to a steel plate along its length using double-sided tape (Nitto 5000NS), with the adhesion length being at least 40mm. Fix the steel plate at the corresponding position of the high-speed rail tensile testing machine, pull up the other end of the metal layer of the sample that is not adhered to the nylon layer (protective layer), and clamp the sample in the chuck. The angle between the pulled-up sample part and the steel plate in space is 180°. The chuck pulls the sample at a speed of 5±0.2mm / s. The average tensile force in the stable area is finally measured and recorded as the cohesive force of the packaging bag, recorded as b, in N / m.

[0061] Optionally, in some embodiments, the tear resistance of the substrate layer 52 is c N, and the tear resistance of the edge sealing structure 60 at the first notch 64 is d, c>d, which can improve the tear resistance of the edge sealing structure 60 at the first notch 64 and reduce tearing damage at the first notch 64.

[0062] The test for the above tear resistance is as follows:

[0063] According to the national standard GB / T 29847-2013, a high-speed rail tensile testing machine is used to test the tear resistance. The test process is as follows: discharge the secondary battery 100 to 0V, then disassemble the secondary battery 100, remove the part to be tested as a whole, and wipe the electrolyte on the surface with dust-free paper. Then cut it into 5mm×50mm strip specimens, where the size of the notch part must meet the requirements that the length and width are both greater than or equal to 10mm or the diameter (fitting circle) is greater than or equal to 10mm. Use the clamps of the high-speed rail tensile testing machine to clamp both sides of the specimen. After confirming that the specimen is tightened, start measuring. The machine pulling speed is set to 60mm / min. From the beginning to the tearing process, record the maximum tension read by the equipment.

[0064] In some embodiments, please refer to Figure 11, the thickness of the secondary battery 100 in the first direction Z is x mm, the expansion rate of the electrode assembly 20 is y, c>1.2×d×(x / 5)×(y / 0.08), the force applied to the first notch 64 is related to the force of expansion of the electrode assembly 20 during the cycle, and the strength or thickness of the first adhesive layer 50 required for the secondary battery 100 with different expansion (reflected in the electrolyte / active material) is different. In this embodiment, c>1.2×d×(x / 5)×(y / 0.08) can be selected, which can improve the tear resistance at the first notch 64, reduce the damage and leakage of the packaging bag 10, and ensure that the secondary battery 100 has a higher energy density.

[0065] The expansion rate of the electrode assembly 20 is tested as follows:

[0066] The initial thickness (mm) of the secondary battery 100 was obtained using a thickness gauge. The secondary battery was then charged at a constant current of 0.5C at 45°C to the full charge voltage of the system, the constant voltage was reduced to 0.05C, and the battery was fully discharged to 3.0V at a constant current of 0.5C. This constituted one cycle. A total of 700 cycles were cycled. The thickness after the cycle (mm) was measured using a thickness gauge. The expansion rate = thickness after the cycle (mm) / initial thickness (mm).

[0067] Referring to FIG. 6 , in some embodiments, the packaging bag 10 includes a first wall portion 1011, a second wall portion 1021, and a connecting portion 103 connecting the first wall portion 1011 and the second wall portion 1021. The first wall portion 1011 is located in the first portion 101, and the second wall portion 1021 is located in the second portion 102. The first wall portion 1011, the second wall portion 1021, and the connecting portion 103 collectively enclose the first notch 64. The first adhesive layer 50 adheres to the first wall portion 1011, the second wall portion 1021, and the connecting portion 103. The connecting portion 103 serves as a transition between the first wall portion 1011 and the second wall portion 1021. When viewed along the thickness direction (first direction Z) of the secondary battery 100, the first adhesive layer 50 covers and adheres to the connecting portion 103, as well as at least a portion of the first wall portion 1011 and at least a portion of the second wall portion 1021. This increases the stress distribution area, reduces stress concentration, and thereby reduces tearing of the packaging bag 10 at the first notch 64.

[0068] Regarding the shape of the connecting portion 103, when viewed along the first direction Z, the connecting portion 103 can be configured as a straight line, a wavy line, or an arc. Taking the arc-shaped connecting portion 103 as an example, referring to Figures 2 and 3 , the connecting portion 103 is an arc-shaped portion that is concave toward the interior of the packaging bag 10. The arc-shaped structure can increase the force-bearing area, thereby dispersing stress. When subjected to external forces, the arc-shaped structure can disperse the force over a larger area, reducing single-point or localized stress concentration. Furthermore, the arc-shaped structure can improve structural stability, reduce deformation and displacement of the material under load, and thus reduce tearing in the portion of the packaging bag 10 located at the first notch 64.

[0069] Optionally, referring to Figures 2, 6, and 12, when viewed along the first direction Z, the radius of the arc-shaped connecting portion 103 is r mm, and the first adhesive layer 50 is also arc-shaped and concave toward the inside of the packaging bag 10. The radius of the arc-shaped first adhesive layer 50 is R mm, 0.6R≤r≤0.8R. The larger radius of the first adhesive layer 50 can increase the bonding area between the first adhesive layer 50 and the edge sealing structure 60, and the stress is more evenly dispersed, thereby reducing the tearing of the connecting portion 103.

[0070] The radius of the connecting portion 103 may be the radius of the connecting portion 103 itself, or the radius of the fitting circle N where the connecting portion is located; the radius of the first adhesive layer 50 may also be the radius of the first adhesive layer 50 itself, or the radius of the fitting circle M where the first adhesive layer is located.

[0071] Optionally, in some embodiments, the first adhesive layer 50 is not limited to being in an arc shape that is recessed toward the inside of the packaging bag 10 , and may also be in a rectangular, polygonal, or other shape.

[0072] 12 , in some embodiments, the center distance between the first adhesive layer 50 and the connection portion 103 is D mm, where 0≤D≤0.3. The center of the first adhesive layer 50 is preferably overlapped with the center of the connection portion 103 to preferentially bear force at the center of the first adhesive layer 50 and reduce tearing of the connection portion 103 .

[0073] In the embodiment of the present application, the first adhesive layer 50 can disperse the stress in the portion of the packaging bag 10 located at the first notch 64. The first adhesive layer 50 can also prevent distortion in this portion, thereby improving the strength and tear resistance of this portion, thereby reducing cyclic leakage of the secondary battery 100. Furthermore, the provision of the first adhesive layer 50 can enhance the sealing strength of the edge seal structure of the packaging bag 10, effectively preventing the portion of the packaging bag 10 located at the notch from being broken open. In addition, by limiting 0°<α<β<180°, the angle between the two ends of the first adhesive layer 50 is larger, and its stress dispersion is more uniform. When the electrode assembly 20 expands, the first adhesive layer 50 can be subjected to stress first, which can replace the tearing of the packaging bag 10 at the notch part, thereby reducing the risk of leakage of the secondary battery 100; and β<180°, which makes it easier to disperse the stress to the second notch 50a of the first adhesive layer 50, which can facilitate the priority stress bearing of the first adhesive layer 50; in addition, the first adhesive layer 50 does not affect the internal space of the packaging bag 10, and has little impact on the external space of the packaging bag 10, which can ensure that the secondary battery 100 has a higher energy density.

[0074] In a second aspect, the present application further proposes an electronic device, comprising the secondary battery 100 described in any embodiment of the first aspect. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device includes but is not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0075] In the embodiment of the present application, a lithium-ion battery is taken as an example and a cycle test is performed on it.

[0076] Example 1

[0077] Preparation of lithium-ion batteries

[0078] (1) Preparation of positive electrode sheet: The positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and stirred evenly. The slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 12μm, and dried to obtain a positive electrode sheet coated with a positive electrode active layer on one side. The above steps are repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet coated with a positive electrode active layer on both sides. It is cold pressed and cut into L-shape for use.

[0079] (2) Preparation of negative electrode sheet: Using graphite as the negative electrode active material, the negative electrode active material graphite, the binder styrene butadiene rubber (SBR) and the thickener sodium carboxymethyl cellulose (CMC) are mixed in a weight ratio of 96:2:2, deionized water is added as a solvent, and a slurry with a solid content of 70wt% is prepared and stirred evenly. Copper foil is selected as the negative electrode current collector, and the slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 10μm, and dried to obtain a negative electrode sheet coated with a negative electrode active layer on one side. Repeat the above steps on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet coated with a negative electrode active layer on both sides. After cold pressing, the negative electrode sheet is cut into an L shape for standby use.

[0080] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0081] (4) Preparation of isolation membrane: A polyethylene porous membrane is used as a substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one surface of the substrate layer as a separator (CCS), wherein the mass percentage of alumina ceramic in the ceramic layer is 95%.

[0082] (5) Electrode assembly preparation: Aluminum sheets are used as positive electrode tabs and welded to the aluminum foil of the positive electrode sheet. Nickel sheets are used as negative electrode tabs and welded directly to the copper foil of the negative electrode sheet. The positive electrode sheets, separators, and negative electrode sheets are alternately stacked in sequence, with separators placed between adjacent positive and negative electrode sheets to form an electrode assembly for future use.

[0083] (6) Preparation of the first adhesive layer: Epoxy resin was coated on one surface of an 8 μm thick polyethylene terephthalate film (PET) substrate layer and dried at 80° C. to form an adhesive layer with a thickness of 4 μm, thereby obtaining the first adhesive layer.

[0084] (7) Assembly of the electrode assembly: Place the aluminum-plastic film punched into an L-shape with the pit facing upward in an assembly fixture, place the electrode assembly in the pit, and set a low-density polyethylene sealing part at the two tabs. Then, cover the electrode assembly with the pit facing downward on another aluminum-plastic film punched into a shape, and heat-seal the four sides of the two aluminum-plastic films by hot pressing to obtain an L-shaped aluminum-plastic film packaging bag with a notch, wherein the sealing edge structure of the packaging bag forms a first notch at the notch, and the opening angle of the first notch is a first angle α of 60°. The above-mentioned first adhesive layer is bonded to the corresponding notch of the L-shaped sealing edge structure, and the first adhesive layer is cut into a second notch, and the opening of the second notch is set toward the opening of the first notch, and the opening angle of the first notch is a second angle β of 70°.

[0085] (8) Liquid injection packaging: The assembled electrode assembly is injected with electrolyte, and after vacuum packaging, static standing, hot pressing, shaping and other processes, the lithium-ion battery is produced.

[0086] The relevant data of Examples 2 to 20 and Comparative Examples 1 to 5, wherein no first adhesive layer is provided in Comparative Example 1, are shown in Table 1 below.

[0087] Cycle test: At room temperature of 25°C, charge the secondary battery at a constant current of 0.5C to the full charge voltage of the system, then charge it to 0.05C at a constant voltage, and then discharge it to 3.0V at a constant current of 0.5C. This constitutes one cycle. A total of 700 cycles were cycled, and 100 batteries were tested to check the tearing condition of the first notch of the lithium-ion battery.

[0088] Table 1, combined with Examples 1 to 20 and Comparative Example 1, demonstrates that the use of a first adhesive layer effectively reduces tearing at the first notch of the packaging bag. The first adhesive layer distributes stress in the first notch portion of the packaging bag and prevents distortion and deformation in this portion, improving its strength and tear resistance, thereby reducing leakage during secondary battery cycling. Furthermore, the provision of the first adhesive layer enhances the sealing strength of the packaging bag's edge seal, effectively preventing the bag from being ripped open at the notch.

[0089] In Comparative Examples 2 to 6, the first angle α is greater than or equal to the second angle β, which may cause the first notch to be subjected to force first, resulting in tearing at the first notch. In Examples 1 to 20, the first angle α is less than the second angle β, and the effect of reducing tearing at the notch is significantly better than that of Comparative Examples 1 to 6. Therefore, in the embodiments of the present application, α<β can be adopted. Because the first notch needs to be recessed toward the inside of the packaging bag, it itself has a certain angle, so the first angle α and the second angle β need to be at a certain angle, that is, the first angle α and the second angle β cannot be a straight angle. At the same time, in Example 13, when β adopts a straight angle (that is, there is no second notch structure), it may be difficult to make the first adhesive layer be subjected to force first, and the place where the force is subjected to force first may always be the first notch of the packaging bag. Therefore, in the present application, 0<α<β<180° can be selected.

[0090] In Examples 2 to 4, the tear reduction effect is significantly better than that of Examples 1 and 5. In Examples 6 to 10, the tear reduction effect is significantly better than that of Example 11. In Examples 12 and 13, it is better than that of Example 16, and better than that of Examples 17 to 20. In Examples 5, 11, 16, and 17 to 20, β>90°. In Example 1, α=20°<30°. In combination with Examples 2 to 4, Examples 6 to 10, and Examples 12 and 13, 30°≤α<β≤90° is preferably selected to ensure that the first adhesive layer is preferentially stressed, making it easier for the first adhesive layer to prevent tearing and damage at the first notch. At the same time, the impact of the first adhesive layer on the external dimensions of the packaging bag is further reduced.

[0091] The relevant test parameters of Examples 21 to 27 are shown in Table 2. The test of the peel strength between the adhesive layer and the packaging bag and the test of the cohesion of the packaging bag are as described above.

[0092] Table 2

[0093] According to Table 2 above, in conjunction with Examples 21 to 27, in Examples 21 and 22, the peel strength a of the adhesive layer is less than the maximum cohesive force b of the packaging bag. This may weaken the bond strength between the first adhesive layer and the packaging bag after multiple charge-discharge cycles, resulting in a decrease in the first adhesive layer's protection of the packaging bag and reduced tear resistance. After multiple cycles, the expansion and compression of the electrode assembly may cause tearing at the first notch. In contrast, in Examples 23 to 27, the peel strength a of the adhesive layer is greater than the maximum cohesive force b of the packaging bag. After multiple charge-discharge cycles, the bond strength between the first adhesive layer and the packaging bag remains high, which directly improves the tear resistance at the notch. Therefore, in the examples of this application, a>b is selected.

[0094] Tear resistance test: Disassemble the finished secondary battery and use a cutting fixture to cut the first notch in the packaging bag. The length and width of the first notch are both 10mm. Use the clamps of a high-speed rail tensile testing machine to clamp both sides of the first notch. After confirming that the first notch is taut, begin measurement at a pulling speed of 60mm / min. Once the first notch tears, record the tensile force. For detailed methods, refer to the tear resistance test above.

[0095] The relevant test parameters of Examples 28 to 34 are shown in Table 3 below

[0096] Table 3

[0097] According to Table 3 above, in conjunction with Examples 28 to 34, Examples 28 and 29 both employed a substrate layer with a lower tear resistance than the first and second wall portions; whereas Examples 30 to 34 all employed a substrate layer with a higher tear resistance than the first and second wall portions. The effect of reducing tearing at the notch in Examples 30 to 34 was significantly greater than that in Examples 28 to 30. This is because the substrate layer has a stronger tear resistance, which improves the tear resistance at the first notch. Furthermore, the substrate layer is preferentially stressed, protecting the first notch and thereby reducing tearing damage at the first notch. Therefore, in this application, c>d can be selected.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the idea of ​​the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A secondary battery, comprising a packaging bag and an electrode assembly accommodated in the packaging bag, the secondary battery having a notch, the packaging bag having a sealing edge structure, and the sealing edge structure having a first notch at the notch, characterized in that, the secondary battery further includes a first adhesive layer disposed on the sealing edge structure, and when observed in the thickness direction of the secondary battery, the first adhesive layer covers at least a part of the first notch; the first adhesive layer is provided with a second notch, and when observed in the thickness direction of the secondary battery, the opening of the second notch faces the opening of the first notch, and at least a part of the second notch is located within the first notch; the opening angle of the first notch is a first included angle α, and the opening angle of the second notch is a second included angle β, where 0° < α < β < 180°; 2. The secondary battery according to claim 1, characterized in that, 30°≤α＜β≤90°。 3. The secondary battery according to any one of claims 1 to 2, characterized in that, the first adhesive layer includes a base material layer and an adhesive layer stacked on each other, and the adhesive layer is bonded between the sealing edge structure and the base material layer; 4. The secondary battery according to claim 3, characterized in that, the peel strength of the adhesive layer is a N, and the maximum cohesive force of the packaging bag is b N, where a > b; 5. The secondary battery according to claim 3, characterized in that, the tear resistance of the base material layer is c N; at the first notch, the tear resistance of the sealing edge structure is d, where c > d; 6. The secondary battery according to any one of claims 1 to 5, characterized in that, the thickness of the secondary battery is x mm, and the expansion rate of the electrode assembly is y, where c > 1.2 × d × (x / 5) × (y / 0.08); 7. The secondary battery according to claim 3, characterized in that, the base material layer includes at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide or polyethylene; the adhesive layer includes at least one of epoxy resin, polyurethane or polyvinyl acetate; 8. The secondary battery according to any one of claims 1 to 7, characterized in that, the sealing edge structure includes a first wall portion, a second wall portion, and a connecting portion connecting between the first wall portion and the second wall portion; the included angle between the first wall portion and the second wall portion is the first included angle α, and the first wall portion, the second wall portion, and the connecting portion together enclose to form the first notch; when observed in the thickness direction of the secondary battery, the first adhesive layer covers and bonds the connecting portion, and at least a part of the first wall portion and at least a part of the second wall portion; 9. The secondary battery according to claim 8, characterized in that, the connecting portion is in an arc shape recessed toward the inside of the packaging bag, and the radius of the arc-shaped connecting portion is r mm; when observed in the thickness direction of the secondary battery, the first adhesive layer is in an arc shape recessed toward the inside of the packaging bag, and the radius of the arc-shaped first adhesive layer is R mm, where 0.6R ≤ r ≤ 0.8R; 10. The secondary battery according to claim 9, wherein the center distance between the first adhesive layer and the connecting portion is D mm, where 0 ≤ D ≤ 0.3; 11. The secondary battery according to claim 1, wherein when observed in the thickness direction of the secondary battery, the center line of the second notch is located within the first notch; 12. The secondary battery according to claim 1, wherein when observed in the thickness direction of the secondary battery, the apex angle of the second notch is located within the first notch, and the two base angles of the second notch are located on the sealing edge structure; 13. The secondary battery according to claim 12, characterized in that, the apex angle of the second notch has an arc transition; 14. An electronic device, characterized in that, including the secondary battery according to any one of claims 1 to 13.

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