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

[0002] Lithium-ion batteries are the power source for mobile devices and are crucial for ensuring their normal operation. As mobile devices such as mobile phones and laptops become more widespread, their operating conditions become more complex, leading to increasingly stringent safety requirements for batteries.

[0003] During battery cycling, the electrode assembly expands and continuously squeezes the packaging bag. For internal polygonal soft-pack batteries, such as "L"-shaped batteries, there is a notch structure. The notch is recessed into the packaging bag. The expansion of the electrode assembly will continuously pull on the notch of the packaging bag, eventually causing the notch to tear, resulting in battery leakage and failure.

[0004] Summary of the Invention

[0005] The embodiments of this application aim to provide a secondary battery, i.e., an electronic device, to reduce tearing at the gap in the battery packaging bag, thereby reducing battery leakage failure.

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

[0007] In a first aspect, this application proposes a secondary battery, including a packaging bag and an electrode assembly housed within the packaging bag. The secondary battery has a notch, and the packaging bag has a sealing structure with a first notch at the notch. The secondary battery also includes a first adhesive layer disposed on the sealing structure. 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 has a second notch. Viewed along 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 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°.

[0008] In the above technical solution, the first adhesive layer can disperse the stress in the first notch portion of the packaging bag, and can also prevent torsional deformation in this portion, improving its strength and tear resistance, thereby reducing the leakage of the secondary battery during circulation. Simultaneously, the first adhesive layer enhances the sealing strength of the packaging bag's sealing structure, effectively reducing the risk of the packaging bag being punctured at the notch. Furthermore, with 0° < α < β < 180°, the angle of the second notch in the first adhesive layer is larger, resulting in more uniform stress distribution. When the electrode assembly expands, the first adhesive layer can preferentially bear the stress, replacing the tearing of the packaging bag at the notch, thus reducing the risk of leakage from the secondary battery. Moreover, with β < 180°, stress is more easily dispersed to the second notch of the first adhesive layer, facilitating preferential stress bearing by the first adhesive layer. Additionally, the first adhesive layer does not affect the internal space of the packaging bag and has minimal impact on the external space, ensuring a high energy density for the secondary battery.

[0009] In some preferred embodiments, 30°≤α<β≤90° ensures that the first adhesive layer is given priority in bearing the force, making it easier for the first adhesive layer to block tearing at the first notch; at the same time, it further reduces the impact of the first adhesive layer on the outer dimensions of the packaging bag.

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

[0011] In some preferred embodiments, 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. This allows the adhesive layer to bond the packaging bag more firmly, thereby improving 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 cN, and the tear resistance of the sealing structure at the first notch is d, where c > d. This improves the tear resistance of the first wall and / or the second wall, reducing tearing damage to the portion of the packaging bag located at the first notch. Preferably, 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). The tear resistance of the substrate layer is adjusted according to the thickness of the secondary battery and the collision rate of the electrode assembly, thereby reducing tearing damage to the portion of the packaging bag located at the first notch.

[0013] In some preferred embodiments, the substrate layer includes at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide, or polyethylene. Each material possesses good weather resistance, heat resistance, abrasion resistance, and corrosion resistance, which can reduce the corrosion of the first adhesive layer by the electrolyte and improve its service life. The bonding layer includes at least one of epoxy resin, polyoxyethylene, or polyvinyl acetate. Using the above-mentioned bonding layer materials can improve the bonding strength between the first adhesive layer and the packaging bag while also increasing the service life of the first adhesive layer.

[0014] In some preferred embodiments, the sealing structure includes a first wall portion, a second wall portion, and a connecting portion connecting the first wall portion and the second wall portion. The included angle between the first wall portion and the second wall portion is a first included angle α, and the first wall portion, the second wall portion, and the connecting portion together form a first notch. Viewed along the thickness direction of the secondary battery, a 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 acts as a transition for connecting the first wall portion and the second wall portion; the partial bonding of the connecting portion with the first adhesive layer can increase the stress dispersion area, reduce stress concentration, and thus reduce tearing of the packaging bag at the first notch portion.

[0015] In some preferred embodiments, the connecting portion is arc-shaped and concave towards the inside of the packaging bag. This arc-shaped structure increases the stress-bearing area, thereby dispersing stress. When subjected to external forces, the arc-shaped structure can distribute the force over a larger area, reducing stress concentration at single points or in localized areas. Furthermore, the arc-shaped structure improves structural stability, reducing material deformation and displacement under stress, and thus reducing 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 adheres to the connecting portion and at least part of the first and second walls. The radius of the arc-shaped first adhesive layer is R mm, where 0.6R ≤ r ≤ 0.8R. A larger radius of the first adhesive layer results in more uniform stress dispersion, further reducing tearing of the connecting portion.

[0016] In some preferred embodiments, the center distance between the first adhesive layer and the connecting part is D mm, 0≤D≤0.3, to ensure that the center of the first adhesive layer overlaps with the center of the connecting part as much as possible. This facilitates the uniform distribution of stress on each part of the connecting part to the second notch of the first adhesive layer, so that the first adhesive layer can bear the stress preferentially and reduce 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 centerline of the second notch is located within the first notch, ensuring that the second notch, which has at least half an angle to the first adhesive layer, can provide cushioning and tear resistance, thereby reducing tearing at the first notch.

[0018] In some preferred embodiments, when viewed along the thickness direction of the secondary battery, the apex of the second notch is located within the first notch, and the two bottom corners of the second notch are located on the sealing structure. The apex of the second notch being located within the first notch allows the more tear-resistant apex to preferentially resist tearing forces. Simultaneously, the bottom corners being located on the sealing structure improves the adhesion between the first adhesive layer and the sealing structure, making the first adhesive layer less prone to detachment during tearing and increasing the bonding strength between the first adhesive layer and the sealing structure.

[0019] In some preferred embodiments, the apex of the second notch has 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 apex.

[0020] Secondly, this application also proposes an electronic device including a secondary battery as described in any of the embodiments of the first aspect above.

[0021] 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, the following are specific embodiments of this application. Attached Figure Description

[0022] 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.

[0023] Figure 1 is an exploded view of a secondary battery according to some embodiments of this application;

[0024] Figure 2 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application;

[0025] Figure 3 is a schematic diagram of the structure of the first notch in some embodiments of this application;

[0026] Figure 4 is a magnified view of section A in Figure 2;

[0027] Figure 5 is a schematic diagram showing the connection between the first adhesive layer and the sealing structure in some embodiments of this application;

[0028] Figure 6 is a schematic diagram of the structure of the first notch in some embodiments of this application;

[0029] Figure 7 is a schematic diagram of the structure at the first notch in some embodiments of this application;

[0030] Figure 8 is a schematic diagram of the structure at the first notch in some embodiments of this application;

[0031] Figure 9 is a schematic diagram of the structure at the first notch in some embodiments of this application;

[0032] Figure 10 is a schematic diagram of the structure of the first adhesive layer in some embodiments of this application;

[0033] Figure 11 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application;

[0034] Figure 12 is a schematic diagram of the structure of the first notch in some embodiments of this application.

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

[0036] 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.

[0037] It should be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component, or there can be one or more intermediate components in between. When a component is described as "connected to" another component, it can be directly connected to the other component, or there can be one or more intermediate components in between.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Firstly, this application proposes a secondary battery 100. Referring to Figure 1, the secondary battery 100 includes a packaging bag 10, an electrode assembly 20, and tabs 30. The packaging bag 10 serves as the mounting base and container for the remaining components of the secondary battery 100. The electrode assembly 20 is housed within the packaging bag 10 and is the core component for charging and discharging the secondary battery 100. One end of the tab 30 is electrically connected to the electrode assembly 20, while the other end extends outside the packaging bag 10. Next, taking a lithium-ion battery as an example, the specific structure of the secondary battery 100 will be described. It is understood that in other embodiments of this application, the secondary battery 100 may also be a sodium-ion battery or other types of secondary battery 100.

[0042] Referring to Figures 1 and 2, the packaging bag 10 can be made of a flexible material and serves as the mounting base, container, and outer protective structure of the secondary battery 100. The packaging bag 10 defines a receiving cavity (not shown in the figures), which can be used to contain the electrolyte (not shown in the figures) and the aforementioned 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 has a first cavity 111, and the second bag body 12 has a second cavity (not shown in the figures). The electrode assembly 20 can be placed within the first cavity 111. The second bag body 12 covers the first cavity 111 of the first bag body 11, and the second cavity communicates with the first cavity 111 to form a receiving cavity. The two shells can be bonded together by heat-sealing the connection between their edges to seal the receiving cavity. The first bag 11 and the second bag 12 can be connected to each other or separated from each other. The second bag 12 may not have a cavity. The second bag 12 directly covers the first cavity 111 of the first bag 11, and the first cavity 111 forms a receiving cavity.

[0043] Optionally, the packaging bag 10 can adopt a rectangular, trapezoidal, or other quadrilateral structure, or other polygonal structures. Its shape is polygonal, and it is made of flexible material, allowing it to adapt to various spatial shapes. The polygonal soft-pack secondary battery 100 has advantages such as small size, light weight, and high energy density, while also possessing good safety and environmental performance. Taking an "L"-shaped packaging bag 10 as an example, referring to Figures 1 to 3, 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 mentioned above are both "L"-shaped, and 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 connected first part 101 and a second part 102, for example, along the second direction Y, the first part 101 and the second part 102 are arranged sequentially. The aforementioned tab 30 can extend out of the packaging bag 10 from the first part 101. A notch 40 is provided between the first part 101 and the second part 102. The first part 101 and the second part 102 are bent along the notch 40, so that the packaging bag 10 as a whole presents an "L" shape. The "L"-shaped secondary battery 100 can adapt to the specific battery installation space of electronic devices, and can significantly improve the energy density of the secondary battery 100 while reducing the space occupied.

[0044] It is understood that in the embodiments of this 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 with notches 40, such as a "Z" shape. The number of notches 40 may be two, three, or more.

[0045] When the edges of the two bags are heat-sealed, a sealing structure 60 is formed on the outside of the packaging bag 10. The sealing 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 aforementioned tab 30 can extend out of the first bag body 11 from the top sealing edge 61. The sealing structure 60 has a first notch 64 at the notch 40. The first notch 64 can be formed 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 makes the portion of the packaging bag 10 located at the first notch 64 relatively weak. When the secondary battery 100 or an electronic device equipped with the secondary battery 100 is accidentally dropped or impacted, the first part 101 and the second part 102 of the packaging bag 10 may move relative to each other or tend to move relative to each other. This can easily cause bending and deformation at the first notch 64 of the packaging bag 10. Since the portion of the packaging bag 10 located at the first notch 64 is relatively weak, stress concentration may occur in this area, leading to tearing and damage. This can result in electrolyte leakage or the entry of impurities such as moisture and dust into the packaging bag 10, ultimately causing the secondary battery 100 to fail. To mitigate this risk...

[0047] In the embodiments of this application, a first adhesive layer 50 may be provided on the sealing structure 60 of the packaging bag 10. Referring to Figures 2 to 4, the first adhesive layer 50 is provided on the sealing structure 60. When viewed along the thickness (first direction Z) of the secondary battery, the first adhesive layer 50 covers at least part of the first gap 64.

[0048] When the electrode assembly 20 expands inside 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 twisting deformation in this portion, improving its strength and tear resistance, thereby reducing leakage during the cycle of the secondary battery 100. Simultaneously, the first adhesive layer 50 enhances the sealing strength of the sealing structure 60 of the packaging bag 10, effectively reducing the risk of the first notch 64 of the packaging bag 10 being punctured.

[0049] The first adhesive layer 50 has a second notch 50a. 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 dotted line portion in the figure), as shown in Figures 4 and 5. The opening of the second notch faces the P direction, and the opening Q of the first notch is located in the P-direction of the second notch. Furthermore, the second notch 50a is at least partially located within the first notch 64. Referring further to Figure 6, the opening angle of the first notch 64 is a first included angle α, and the opening angle of the second notch 50a is a second included angle β, where 0° < α < β < 180°. The larger angle between the two ends of the first adhesive layer 50 results in more uniform stress distribution. When the electrode assembly 20 expands, the first adhesive layer 50 preferentially bears the stress. Furthermore, the opening angle β of the second notch 50a is less than 180°, making it easier for the stress to be distributed to the second notch 50a of the first adhesive layer 50. This allows the second notch 50a of the first adhesive layer 50 to preferentially bear the stress, replacing the tear in the packaging bag 10 located at the first notch 64, thereby reducing the risk of leakage of the secondary battery 100. At the same time, the first adhesive layer 50 does not affect the internal space of the secondary battery 100 and has little impact on the external space, ensuring that the secondary battery 100 has a high energy density. Preferably, 30°≤α<β≤90° ensures that the first adhesive layer 50 preferentially bears the stress, making it easier for the first adhesive layer 50 to prevent tearing at the first notch 64. Simultaneously, it further reduces the impact of the first adhesive layer 50 on the external dimensions of the packaging bag 10.

[0050] Referring to Figure 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 the second notch 50a of the first adhesive layer 50 at least half an angle can provide cushioning and tear resistance, thereby reducing tearing at the first notch 64.

[0051] Referring to Figures 7 and 8, observing along the thickness direction of the secondary battery (first direction Z), the apex 50a1 of the second notch 50a is located within the first notch 64, and the two bottom corners 50a2 of the second notch 50a are located on the sealing structure 60. The apex 50a1 of the second notch 50a being located within the first notch 64 allows the more tear-resistant apex 50a1 to preferentially resist tearing forces. Simultaneously, the bottom corners 50a2 being located on the sealing structure 60 improve the adhesion between the first adhesive layer 50 and the sealing structure 60, making the first adhesive layer 50 less prone to detachment during tearing and increasing the bonding strength between the first adhesive layer 50 and the sealing structure 60.

[0052] Furthermore, referring to Figure 9, the apex 50a1 of the second notch 50a has 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 apex 50a1.

[0053] Referring to Figures 2 and 10, in some embodiments, the first adhesive layer 50 includes a substrate layer 52 and an adhesive layer 51 stacked together. The adhesive layer 51 bonds the aforementioned sealing structure 60. The substrate layer 52 has high tear resistance, which can reduce tearing damage to the first adhesive layer 50, thereby reducing damage to the packaging bag 10 at the first notch 64. The adhesive layer 51 bonds the substrate layer 52 to the sealing structure 60, which can improve the bonding strength between the first adhesive layer 50 and the packaging bag 10, thereby improving the strength of the packaging bag 10 at the first notch 64 and reducing tearing damage in that area.

[0054] Optionally, the substrate layer 52 may include at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide, or polyethylene. The material of the 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] Optionally, the adhesive layer 51 may include at least one of epoxy resin, polyoxygenated ester, or polyvinyl acetate. Among the materials of the adhesive layer 51, epoxy resin is a thermosetting resin with excellent mechanical properties and chemical stability, and has good corrosion resistance and wear resistance; polyoxygenated ester is a polymer with high molecular weight, and has good heat resistance, corrosion resistance, and electrical insulation properties; polyvinyl acetate has excellent flexibility and breathability. By using the above-mentioned materials of the adhesive layer 51, the bonding strength between the first adhesive layer 50 and the packaging bag 10 can be improved, while the service life of the first adhesive layer 50 can also be improved.

[0056] In some embodiments, the peel strength of the adhesive layer 51 is a N, and the maximum cohesive force of the packaging bag 10 is b N, where a > b. This allows the adhesive layer 51 to adhere more firmly 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 peel force is applied between material surfaces; it is typically used to describe the bonding strength between an adhesive, coating, or paint and a substrate. Maximum cohesive force refers to the maximum value of the attractive force between molecules or atoms within a material; it is typically used to describe the cohesive properties of a material, i.e., the bonding strength between molecules or atoms within the material. The greater the maximum cohesive force, the better the cohesive properties of the material, and the more difficult it is to separate or destroy. 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 covers 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 this embodiment, the maximum cohesive force can be considered as the adhesive force between the protective layer and the metal layer.

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

[0058] According to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes", the peel strength between the adhesive layer 51 and the packaging bag 10 was tested using a high-speed rail tensile testing machine. The test procedure is as follows: The secondary battery 100 was discharged to 0V, and then the secondary battery 100 was disassembled. The adhesive layer 51 and the packaging bag 10 bonded to it were removed as a whole, and the electrolyte on the surface was wiped off with lint-free paper. Then, it was cut into strips of 5mm × 5mm. Along the length of the sample, the side with the packaging bag was adhered to the steel plate with double-sided tape (Nitto 5000NS). The steel plate is fixed in the corresponding position of the high-speed rail tensile testing machine. The other end of the sample that is not adhered to the adhesive layer on the packaging bag 10 is pulled up. The sample is placed in the clamp and clamped. The angle between the pulled sample part and the steel plate in space is 180°. The clamp pulls the sample at a speed of 1±0.2mm / s. Finally, the average tensile force in the stable area is measured and recorded as the peel strength of the adhesive layer, denoted as a, with the unit being N / m.

[0059] The cohesive strength of packaging bag 10 was tested as follows:

[0060] The cohesive strength of the packaging bag 10 was tested using a high-speed rail tensile testing machine according to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes". The test procedure is as follows: The secondary battery 100 was discharged to 0V, and then the secondary battery 100 was disassembled. The packaging bag 10, including the nylon layer and the metal layer, was removed as a whole, and the electrolyte on the surface was wiped off with lint-free paper. Then, it was cut into strips of 20mm × 60mm. Along the length of the sample, the nylon layer side of the sample was adhered to the 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 sample that is not adhered to the metal layer (protective layer) is pulled up. The sample is placed in the clamp and clamped. The angle between the pulled sample part 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 cohesive force of the packaging bag, denoted as b, with the unit N / m.

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

[0062] The tear resistance test results are as follows:

[0063] According to the national standard GB / T 29847-2013, the tear resistance was tested using a high-speed rail tensile testing machine. The test procedure is as follows: The secondary battery 100 was discharged to 0V, then disassembled, and the part to be tested was removed as a whole. The electrolyte on the surface was wiped off with lint-free paper. Then, it was cut into strips of 5mm × 50mm, where the dimensions of the notched portion must meet the requirement that both the length and width are greater than or equal to 10mm, or the diameter (fitted circle) is greater than or equal to 10mm. The clamps of the high-speed rail tensile testing machine were used to clamp both sides of the sample. After confirming that the sample was taut, the measurement began. The machine's pulling speed was set to 60mm / min. From the start until the tear occurred, the maximum tensile force read by the equipment was recorded.

[0064] In some embodiments, referring 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, and c>1.2×d×(x / 5)×(y / 0.08). The force at the first notch 64 is related to the force of the expansion of the electrode assembly 20 during the cycle. The strength or thickness of the first adhesive layer 50 required for secondary batteries 100 with different expansion (reflected in 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 high energy density.

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

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

[0067] Referring to Figure 6, in some embodiments, the packaging bag 10 has 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 together form the first notch 64. The first adhesive layer 50 bonds the first wall portion 1011, the second wall portion 1021, and the connecting portion 103. The connecting portion 103 serves as a transition for the connection between the first wall portion 1011 and the second wall portion 1021. Viewed along the thickness direction (first direction Z) of the secondary battery 100, the first adhesive layer 50 covers and bonds 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, which can increase the stress dispersion area, reduce stress concentration, and thus reduce tearing of the packaging bag 10 at the first notch 64.

[0068] Regarding the shape of the connecting portion 103, 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 shape that is concave towards the inside of the packaging bag 10. The arc-shaped structure can increase the stress-bearing area, thereby dispersing stress. When subjected to external force, the arc-shaped structure can distribute the force over a larger area, reducing stress concentration at single points or in local areas. Furthermore, the arc-shaped structure can improve the stability of the structure, reduce the deformation and displacement of the material under stress, and thus reduce tearing of the packaging bag 10 at the first notch 64.

[0069] Optionally, referring to Figures 2, 6, and 12, when observing along the first direction Z, the radius of the arc-shaped connecting part 103 is r mm, and the first adhesive layer 50 is also arc-shaped and concave towards the inside of the packaging bag 10. The radius of the arc-shaped first adhesive layer 50 is R mm, where 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 sealing structure 60, resulting in more uniform stress distribution and thus reducing tearing of the connecting part 103.

[0070] The radius of the connecting part 103 can be the radius of the connecting part 103 itself, or the radius of the fitting circle N on which the connecting part is located; similarly, the radius of the first adhesive layer 50 can be the radius of the first adhesive layer 50 itself, or the radius of the fitting circle M on which the first adhesive layer is located.

[0071] Optionally, in some embodiments, the first adhesive layer 50 is not limited to an arc shape that is recessed into the packaging bag 10, but can also be rectangular, polygonal, etc.

[0072] Referring to Figure 12, in some embodiments, the center distance between the first adhesive layer 50 and the connecting portion 103 is D mm, where 0 ≤ D ≤ 0.3, in order to ensure that the center of the first adhesive layer 50 overlaps with the center of the connecting portion 103 as much as possible, so that the center of the first adhesive layer 50 is given priority in bearing force and the tearing of the connecting portion 103 is reduced.

[0073] In the embodiments of this application, the first adhesive layer 50 can disperse the stress of the packaging bag 10 located at the first notch 64, and the first adhesive layer 50 can also prevent the torsional deformation of this part, improve the strength and tear resistance of this part, thereby reducing the leakage of the secondary battery 100 during circulation. At the same time, the provision of the first adhesive layer 50 can improve the sealing strength of the sealing structure of the packaging bag 10, and can effectively reduce the possibility of the packaging bag 10 being punctured at the notch. Furthermore, by limiting 0° to α to β to 180°, the angle between the two ends of the first adhesive layer 50 is larger, resulting in more uniform stress distribution. When the electrode assembly 20 expands, the first adhesive layer 50 can preferentially bear the stress, replacing the tear at the notch of the packaging bag 10, thereby reducing the risk of leakage of the secondary battery 100. Moreover, β to 180° makes it easier for stress to be distributed to the second notch 50a of the first adhesive layer 50, which facilitates preferential 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 high energy density.

[0074] Secondly, this application also proposes an electronic device including the secondary battery 100 described in any embodiment of the first aspect. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, electronic devices include, but are not limited to, Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0075] In the embodiments of this application, a lithium-ion battery is used as an example to perform cycle testing.

[0076] Example 1

[0077] Preparation of lithium-ion batteries

[0078] (1) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of a 12 μm thick aluminum foil for the positive electrode current collector, and dried to obtain a positive electrode sheet with a single-sided positive electrode active layer. The above steps were repeated on the other surface of the aluminum foil for the positive electrode current collector to obtain a positive electrode sheet with a double-sided positive electrode active layer. The electrode sheet was then cold-pressed and cut into L-shapes for later use.

[0079] (2) Preparation of the negative electrode sheet: Graphite was used as the negative electrode active material. The negative electrode active material graphite, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 96:2:2. Deionized water was added as a solvent to prepare a slurry with a solid content of 70 wt%, and the mixture was stirred evenly. Copper foil was selected as the negative electrode current collector. The slurry was uniformly coated on one surface of a 10 μm thick copper foil current collector, and then dried to obtain a negative electrode sheet with a single-sided negative electrode active layer. The above steps were repeated on the other surface of the copper foil current collector to obtain a negative electrode sheet with a double-sided negative electrode active layer. After cold pressing, the negative electrode sheet was cut into L-shapes for later use.

[0080] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are 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) is 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 the separator: A porous polyethylene membrane is used as the substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one side of the substrate layer as a separator (CCS). The mass percentage of alumina ceramic in the ceramic layer is 95%.

[0082] (5) Electrode assembly preparation: Aluminum sheet is selected as the positive electrode tab and welded to the aluminum foil of the positive electrode sheet. Nickel sheet is selected as the negative electrode tab and directly welded to the copper foil of the negative electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are stacked alternately in sequence, with a separator between adjacent positive and negative electrode sheets to form an electrode assembly for later use.

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

[0084] (7) Electrode assembly assembly: Place the L-shaped aluminum-plastic film with the pitted surface facing up in the assembly fixture, place the electrode assembly in the pit, and set the low-density polyethylene sealing part at the two electrode tabs. Then, cover the electrode assembly with the pitted surface facing down on another aluminum-plastic film with the pitted surface facing down. Heat seal the two aluminum-plastic films around the perimeter by hot pressing to obtain an L-shaped aluminum-plastic film packaging bag with a notch. The sealing structure of the packaging bag forms a first notch at the notch. The opening angle of the first notch is the first included angle α, which is 60°. Adhere the first adhesive layer to the corresponding notch of the L-shaped sealing structure. Cut a second notch from the first adhesive layer. The opening of the second notch faces the opening of the first notch, and the opening angle of the first notch is the second included angle β, which is 70°.

[0085] (8) Liquid injection and encapsulation: Electrolyte is injected into the assembled electrode assembly, and after vacuum encapsulation, standing, hot pressing formation, shaping and other processes, a lithium-ion battery is obtained.

[0086] Examples 2 to 20 and Comparative Examples 1 to 5, wherein the relevant data for Comparative Example 1, in which no first adhesive layer was provided, are shown in Table 1 below.

[0087] Cyclic test: At room temperature (25℃), the secondary battery is charged at a constant current of 0.5C to the full charge voltage of the system, then charged at a constant voltage of 0.05C, and discharged at a constant current of 0.5C to 3.0V. This constitutes one cycle. A total of 700 cycles are performed, and 100 tests are conducted to check for tearing at the first notch of the lithium-ion battery.

[0088] According to Table 1 above, and in conjunction with Examples 1 to 20 and Comparative Example 1, it can be seen that when a first adhesive layer is used, tearing at the first notch of the packaging bag can be effectively reduced. The first adhesive layer can disperse the stress of the packaging bag at the first notch, and can also prevent torsional deformation of this part, improving its strength and tear resistance, thereby reducing the leakage of the secondary battery during cycles. At the same time, the first adhesive layer can improve the sealing strength of the packaging bag's sealing structure, effectively reducing the chance of the packaging bag being punctured at the notch.

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

[0090] In Examples 2 to 4, the tear reduction effect is significantly better than that in Examples 1 and 5; in Examples 6 to 10, the tear reduction effect is significantly better than that in Example 11; in Examples 12 and 13, it is better than that in Example 16; and it is better than that in Examples 17 to 20. In Examples 5, 11, 16, and 17 to 20, β > 90°; in Example 1, α = 20° < 30°. Combining Examples 2 to 4, Examples 6 to 10, and Examples 12 and 13, it is preferable to have 30° ≤ α < β ≤ 90°, ensuring that the first adhesive layer is given priority in bearing the force, making it easier for the first adhesive layer to block tearing at the first notch; at the same time, it further reduces the impact of the first adhesive layer on the outer dimensions of the packaging bag.

[0091] The relevant test parameters for Examples 21 to 27 are shown in Table 2 below. For the peel strength test between the adhesive layer and the packaging bag, and the cohesive strength test of the packaging bag, please refer to the above.

[0092] Table 2

[0093] According to Table 2 above, and 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. After multiple charge-discharge cycles, the bonding strength between the first adhesive layer and the packaging bag may weaken, resulting in reduced protection of the packaging bag by the first adhesive layer and decreased tear resistance. After multiple cycles, the expansion and compression of the electrode assembly may cause tearing at the first notch. 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 bonding strength between the first adhesive layer and the packaging bag remains high, directly improving the tear resistance at the notch. Therefore, in the embodiments of this application, a > b is selected.

[0094] Tear resistance test: Disassemble the finished secondary battery and use a cutting fixture to obtain the first notch in the packaging bag, with both the length and width of the first notch being 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 the measurement. Set the machine's pulling speed to 60mm / min. Record the tensile force after the first notch tears. For specific methods, please refer to the tear resistance test section above.

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

[0096] Table 3

[0097] According to Table 3 above, and in conjunction with Examples 28 to 34, in Examples 28 and 29, the tear resistance of the substrate layer is less than that of the first and second walls; while in Examples 30 to 34, the tear resistance of the substrate layer is greater than that of the first and second walls. The effect of reducing tearing at the notch in Examples 30 to 34 is significantly better than in Examples 28 to 30. This is because the stronger tear resistance of the substrate layer improves the tear resistance at the first notch, and the substrate layer preferentially bears the stress, thus protecting the first notch and reducing tearing damage at it. 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 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, comprising a packaging bag and an electrode assembly housed within the packaging bag, the secondary battery having a notch, the packaging bag having a sealing structure, the sealing structure having a first notch at the notch, characterized in that, The secondary battery further includes a first adhesive layer, which is disposed on the 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 has a second notch. When viewed along 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 within the first notch. The opening angle of the first notch is the first included angle α, and the opening angle of the second notch is the 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 substrate layer and an adhesive layer stacked together, wherein the adhesive layer is bonded between the sealing structure and the substrate 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 substrate layer is cN; At the first gap, the tear resistance of the sealing 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, c>1.2×d×(x / 5)×(y / 0.08).

7. The secondary battery according to claim 3, characterized in that, The substrate layer includes at least one of polyvinyl chloride, polyethylene terephthalate, polypropylene, polyimide, or polyethylene; The adhesive layer includes at least one of epoxy resin, polyoxyethylene, or polyvinyl acetate.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The edge sealing structure includes a first wall portion, a second wall portion, and a connecting portion connecting the first wall portion and the second wall portion; The angle between the first wall portion and the second wall portion is the first included angle α. The first notch is formed by the first wall portion, the second wall portion, and the connecting portion together enclosing it. Viewed 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.

9. The secondary battery according to claim 8, characterized in that, The connecting part is in the shape of an arc that is concave towards the inside of the packaging bag, and the radius of the arc-shaped connecting part is r mm; Viewed along the thickness direction of the second battery, the first adhesive layer is in an arc shape that is concave towards 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, characterized in that, The center distance between the first adhesive layer and the connecting part is D mm, where 0 ≤ D ≤ 0.

3.

11. The secondary battery according to claim 1, characterized in that, Viewed along 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, characterized in that, Viewed along the thickness direction of the secondary battery, the apex of the second notch is located inside the first notch, and the two bottom corners of the second notch are located on the sealing structure.

13. The secondary battery according to claim 12, characterized in that, The apex of the second notch has an arc-shaped transition.

14. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 13.

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