Secondary batteries and electronic devices

Abstract

This application discloses a secondary battery and an electronic device. The secondary battery includes an electrode assembly, tabs, and a packaging bag. The tabs connect to the electrode assembly. The packaging bag includes a main body and a first sealing part. The main body is cylindrical, and the electrode assembly is disposed within the main body. The main body includes a top wall, and the first sealing part is connected to the top wall. The tabs extend from the first sealing part into the packaging bag. A first crease is formed between the first sealing part and the main body. The first sealing part is bent towards the surface of the top wall along the first crease. The first sealing part has a first sealing area, which is separate from the first crease. Along a direction perpendicular to the surface of the top wall, the orthographic projection of the first sealing part does not exceed the orthographic projection of the top wall, reducing the impact of bending the first sealing area on the sealing performance of the first sealing part, improving drop performance, reducing the space occupied by the first sealing part after bending, and thus improving energy density.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] With the widespread adoption of consumer electronics such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, people are placing increasingly stringent demands on the energy density and safety of rechargeable batteries. Pouch cells require bending the sealing edges to reduce space usage. For pouch cylindrical cells, bending the top sealing edge folds part of the sealing area, reducing sealing reliability and affecting the cell's drop performance. Utility Model Content

[0003] In view of this, it is necessary to provide a secondary battery and electronic device that improves drop performance and increases energy density.

[0004] Embodiments of this application provide a secondary battery, including an electrode assembly, tabs, and a packaging bag. The tabs connect to the electrode assembly. The packaging bag includes a main body and a first sealing portion. The main body is cylindrical, and the electrode assembly is disposed within the main body. The main body includes a top wall, and the first sealing portion connects to the top wall. The tabs extend from the first sealing portion into the packaging bag. A first crease is formed between the first sealing portion and the main body. The first sealing portion is bent toward the surface of the top wall along the first crease. The first sealing portion has a first sealing area, which is separate from the first crease. The orthographic projection of the first sealing portion does not exceed the orthographic projection of the top wall in a direction perpendicular to the top wall surface. By bending the first sealing portion toward the top wall surface along the first crease, and separating the first sealing area from the first crease, the impact of bending the first sealing area on the sealing performance of the first sealing portion is reduced, improving drop performance. By ensuring that the orthographic projection of the first sealing portion does not exceed the orthographic projection of the top wall in a direction perpendicular to the top wall surface, the space occupied by the bent first sealing portion is reduced, which is beneficial for increasing energy density.

[0005] In one or more of the above optional embodiments, the first sealing area includes an arc-shaped segment, which includes a first arc-shaped edge and a second arc-shaped edge. The distance between the first and second arc-shaped edges along the radial direction of the circle containing the arc-shaped segment is L1, and the radius of the circle containing the first sealing portion is R1, where 0.15 ≤ L1 / R1 ≤ 0.25. By ensuring L1 / R1 ≥ 0.15, the sealing width of the arc-shaped segment is increased, improving sealing strength and reducing the risk of leakage and / or moisture entering the packaging bag. When the sealing width of the arc segment is too large, it affects the flatness of the seal and easily causes protrusions. During the hot sealing process, the outermost protruding part of the packaging bag is easily burned, leading to leakage and / or moisture entering the packaging bag. Furthermore, the concave part corresponding to the outermost protruding part does not melt sufficiently, affecting the sealing performance of the packaging bag. By using L1 / R1≤0.25, while meeting the sealing width requirements of the arc segment, the sealing width of the arc segment is controlled, reducing the risk of leakage and / or moisture entering the packaging bag, improving the sealing performance of the packaging bag, and thus improving drop performance.

[0006] In one or more of the above optional embodiments, 0.18 ≤ L1 / R1 ≤ 0.22. By ensuring L1 / R1 ≥ 0.18, the sealing width of the arc segment is further increased, thereby improving the sealing strength and reducing the risk of leakage and / or moisture entering the packaging bag. By ensuring L1 / R1 ≤ 0.22, while meeting the sealing width requirement of the arc segment, the sealing width of the arc segment is further controlled, further reducing the risk of leakage and / or moisture entering the packaging bag, further improving the sealing performance of the packaging bag, and further enhancing drop performance.

[0007] In one or more of the above optional embodiments, the first sealing portion includes a third arc-shaped edge located on the outermost side, and a first arc-shaped edge located between the third arc-shaped edge and the second arc-shaped edge. The distance between the third arc-shaped edge and the first arc-shaped edge is L2, where 0.04 ≤ L2 / R1 ≤ 0.09. By increasing the distance between the third arc-shaped edge and the first arc-shaped edge by L2 / R1 ≥ 0.04, the risk of a reduction in the sealing width of the arc-shaped segment due to the sealing head being biased outward is reduced. By controlling the distance L2 by L2 / R1 ≤ 0.09, the situation where the sealing head cannot be completely heat-pressed onto the insulating component due to the sealing head being biased inward is reduced, thereby improving the sealing performance of the packaging bag and improving drop performance.

[0008] In one or more of the above optional embodiments, 0.06 ≤ L2 / R1 ≤ 0.08. By having L2 / R1 ≥ 0.06, the distance between the third arc-shaped edge and the first arc-shaped edge is further increased, further reducing the risk of a reduction in the packaging width of the arc-shaped segment due to the end cap being biased outwards. By having L2 / R1 ≤ 0.08, the distance L2 is further controlled, further reducing the possibility that the end cap may not be fully heat-pressed onto the insulating component due to the end cap being biased inwards, further improving the sealing performance of the packaging bag, and further improving drop performance.

[0009] In one or more of the above optional embodiments, the first sealing area includes a straight section, which includes a first segment and a second segment. The first segment overlaps with the end of the arc-shaped segment, and the second segment connects to the first segment and extends along the length direction of the first crease. The maximum length of the second segment is L2.

[0010] In one or more of the above optional embodiments, the radius of the circle containing the top wall is R2, and 0.8 ≤ R1 / R2 ≤ 1. With R1 / R2 ≥ 0.8, it is beneficial for the insulating component to cover the overlapping portion of the electrode tab and the first sealing part, reducing the risk of contact between the electrode tab and the metal layer of the packaging bag, leading to corrosion or even short circuits. With R1 / R2 ≤ 1, the radial distance of the first sealing part beyond the top wall after bending is reduced, thus minimizing the impact on the energy density of the secondary battery.

[0011] In one or more of the above optional embodiments, an insulating element is further included. The insulating element covers a portion of the electrode tab. A portion of the insulating element is located within the first sealing portion, and another portion of the insulating element protrudes from the first sealing portion. The radius of the circle containing the insulating element is R3, and the radius of the circle containing the top wall is R2, where 0.95 ≤ R3 / R2 ≤ 1.05. By ensuring R3 / R2 ≥ 0.95, it is beneficial for the insulating element to cover the portion overlapping the electrode tab and the first sealing portion, reducing the risk of contact between the electrode tab and the metal layer of the packaging bag, leading to corrosion or even short circuits. By ensuring R3 / R2 ≤ 1.05, the radial distance of the insulating element extending beyond the top wall in the circle containing the top wall is reduced, thus minimizing the impact on the energy density of the secondary battery.

[0012] In one or more of the above optional embodiments, the area of ​​the first sealing area is S1, the area of ​​the first sealing part is S2, and 0.5 ≤ S1 / S2 ≤ 0.9. By ensuring S1 / S2 ≥ 0.5, the sealing area of ​​the first sealing area is increased, reducing the risk of leakage and / or moisture entering the packaging bag. By ensuring S1 / S2 ≤ 0.9, the sealing area of ​​the first sealing area is controlled while still meeting the requirements, reducing the risk of leakage and / or moisture entering the packaging bag due to an excessively large first sealing area affecting its flatness. This improves the sealing performance of the packaging bag and enhances its drop resistance.

[0013] In one or more of the above optional embodiments, the second segment includes a first edge facing away from the first crease. The first edge connects the first arcuate edge and the third arcuate edge. Along a direction perpendicular to the length extension direction of the first crease, the distance between the first crease and the first edge is L3, where 1.2mm ≤ L3 ≤ 1.3mm. By increasing L3 ≥ 1.2mm, the sealing width of the second segment is increased, improving sealing strength and reducing the risk of leakage and / or moisture entering the packaging bag. When the sealing width of the second segment is too large, it affects the flatness of the seal, easily causing protrusions. During hot sealing, the outermost protruding part of the packaging bag is easily burned, leading to leakage and / or moisture entering the packaging bag. Furthermore, the corresponding concave part of the outermost protruding part does not melt sufficiently, affecting the sealing performance of the packaging bag. By using L3 ≤ 1.3mm, while satisfying the sealing width requirement of the second segment, the sealing width of the second segment is controlled, reducing the risk of leakage and / or moisture entering the packaging bag, improving the sealing performance of the packaging bag, and enhancing drop performance.

[0014] Embodiments of this application provide an electronic device including the secondary battery in any of the above embodiments.

[0015] The aforementioned secondary battery and electronic device, by bending the first sealing portion toward the top wall surface with a first crease, and with the first sealing area separated from the first crease, reduces the impact of bending the first sealing area on the sealing performance of the first sealing portion and improves drop performance. By ensuring that the orthographic projection of the first sealing portion does not exceed the orthographic projection of the top wall in a direction perpendicular to the top wall surface, the space occupied by the first sealing portion after bending is reduced, which is beneficial to improving energy density. Attached Figure Description

[0016] Figure 1 Schematic diagrams of the secondary battery structure are shown in some embodiments.

[0017] Figure 2 A schematic diagram of the secondary battery structure after bending is shown in some embodiments.

[0018] Figure 3 Schematic diagrams of the electronic devices in some embodiments are shown.

[0019] Explanation of key component symbols: Secondary battery 100 Packaging bag 10 First casing 10A Second shell 10B Main body 11 Top Wall 111 First sealing part 12 First Sealed Area 12A Arc segment 121 First arc-shaped edge 1211 Second curved edge 1212 The third arc edge 120 Straight section 122 First paragraph 1221 Second paragraph 1222 First edge 1222A JE20 Electrode assembly 30 Insulating component 40 First crease 101 Electronic devices 200 The following specific embodiments will further illustrate this application in conjunction with the above-described accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0021] When a component is considered to be "located" on another component, it can be directly on the other component or may also be interspersed with other components. When a component is considered to be "connected" to another component, it can be directly connected to the other component or may also be interspersed with other components.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] It is understandable that the term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components can exist in a state that is approximately perpendicular or equal to each other. For example, combined with numerical description, perpendicularity can refer to the angle between two straight lines within the range of 90° ± 10°, the dihedral angle between two planes within the range of 90° ± 10°, or the angle between a straight line and a plane within the range of 90° ± 10°. The two components described as "perpendicular" do not have to be absolutely straight lines or planes; they can be approximately straight lines or planes. From a macroscopic perspective, if the overall direction of extension is a straight line or plane, the component can be considered a "straight line" or "plane".

[0024] Unless otherwise defined, the term "multiple" in this document, when used to describe the number of components, specifically means that the component is two or more.

[0025] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] Please see Figure 1 and Figure 2 One embodiment of this application provides a secondary battery 100, including a packaging bag 10, tabs 20, and an electrode assembly 30. The electrode assembly 30 is disposed inside the packaging bag 10, and the tabs 20 are connected to the electrode assembly 30.

[0027] The packaging bag 10 includes a main body 11 and a first sealing part 12. The main body 11 is cylindrical, and the electrode assembly 30 is disposed within the main body 11. The main body 11 includes a top wall 111, and the first sealing part 12 is connected to the top wall 111. The electrode tab 20 extends out of the packaging bag 10 from the first sealing part 12. A first crease 101 is formed between the first sealing part 12 and the main body 11, and the first sealing part 12 is bent toward the surface of the top wall 111 along the first crease 101. The first sealing part 12 has a first sealing area 12A, which is separate from the first crease 101. Along a direction perpendicular to the surface of the top wall 111, the orthographic projection of the first sealing part 12 does not exceed the orthographic projection of the top wall 111.

[0028] This application achieves improved drop performance by bending the first sealing portion 12 towards the surface of the top wall 111 with the first crease 101, and separating the first sealing area 12A from the first crease 101. This reduces the impact of bending the first sealing area 12A on the sealing performance of the first sealing portion 12. Furthermore, by ensuring that the orthographic projection of the first sealing portion 12 does not exceed the orthographic projection of the top wall 111 along a direction perpendicular to the surface of the top wall 111, the space occupied by the bent first sealing portion 12 is reduced, which is beneficial for increasing energy density.

[0029] In some embodiments, the electrode assembly 30 includes a first electrode (not shown), a second electrode (not shown), and a separator (not shown) disposed between the first electrode and the second electrode. The polarity of the first electrode is opposite to that of the second electrode. Optionally, the first electrode, the separator, and the second electrode are stacked sequentially and arranged in a wound structure.

[0030] The first electrode includes a first current collector and a first active material layer disposed on at least a portion of the first current collector.

[0031] The second electrode includes a second current collector and a second active material layer disposed on at least a portion of the second current collector.

[0032] In some embodiments, the first electrode is a negative electrode and the second electrode is a positive electrode. Correspondingly, the first current collector is a negative current collector, and the first active material layer includes a first active material, which is a negative active material; the second current collector is a positive current collector, and the second active material layer includes a second active material, which is a positive active material. In other embodiments, the first electrode may also be a positive electrode and the second electrode may be a negative electrode.

[0033] The positive electrode current collector can be made of aluminum foil or nickel foil, and the negative electrode current collector can be made of at least one of copper foil, nickel foil or carbon-based current collector.

[0034] The separator includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.

[0035] In some embodiments, the packaging bag 10 includes two first sealing portions 12 and two tabs 20, one tab 20 being electrically connected to a first current collector and the other tab 20 being electrically connected to a second current collector. The tabs 20 can be connected to external components (not shown). The main body 11 includes two top walls 111, one of the first sealing portions 12 being connected to one of the top walls 111 and the other first sealing portion 12 being connected to the other top wall 111. One tab 20 extends out of the packaging bag 10 from one of the first sealing portions 12, and the other tab 20 extends out of the packaging bag 10 from the other first sealing portion 12.

[0036] In some embodiments, the packaging bag 10 includes a first housing 10A and a second housing 10B. The first housing 10A has a first receiving portion, and a first extension portion extends outward from the periphery of the first housing 10A. The second housing 10B has a second receiving portion, and a second extension portion extends outward from the periphery of the second housing 10B. An electrode assembly 30 is disposed in the first receiving portion and the second receiving portion. The first housing 10A is connected to the second housing 10B, and two first sealing portions 12 and two second sealing portions 13 are formed by hot-pressing the first extension portion and the second extension portion with a sealing head. The two first sealing portions 12 are located on the two end faces of the main body portion 11, and the two second sealing portions 13 are disposed opposite each other on the circumferential side surfaces of the main body portion 11.

[0037] In some embodiments, the secondary battery 100 includes an insulating member 40 that covers a portion of the tab 20. A portion of the insulating member 40 is located within a first sealing portion 12, while another portion protrudes from the first sealing portion 12. This reduces the risk of contact between the tab 20 and the metal layer of the packaging bag 10, thus mitigating the risk of corrosion or even a short circuit. Optionally, the insulating member includes insulating adhesive.

[0038] In some embodiments, the radius of the circle containing the first sealing portion 12 is R1, and the radius of the circle containing the top wall 111 is R2, with 0.8 ≤ R1 / R2 ≤ 1. By having R1 / R2 ≥ 0.8, it is beneficial for the insulating member 40 to cover the portion where the tab 20 overlaps with the first sealing portion 12, reducing the risk of contact between the tab 20 and the metal layer of the packaging bag 10, which could lead to corrosion or even a short circuit. By having R1 / R2 ≤ 1, the distance by which the first sealing portion 12 extends radially beyond the top wall 111 after bending is reduced, thus minimizing the impact on the energy density of the secondary battery 100.

[0039] Optionally, the ratio of R1 / R2 can be any one of 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, or any value within a range of any two of these values.

[0040] In some embodiments, the radius of the circle containing the insulating element 40 is R3, and the radius of the circle containing the top wall 111 is R2, with 0.95 ≤ R3 / R2 ≤ 1.05. By having R3 / R2 ≥ 0.95, it is beneficial for the insulating element 40 to cover the portion overlapping the tab 20 and the first sealing portion 12, reducing the risk of contact between the tab 20 and the metal layer of the packaging bag 10, which could lead to corrosion or even a short circuit. By having R3 / R2 ≤ 1.05, the radial distance of the insulating element 40 extending beyond the top wall 111 in the circle containing the top wall 111 is reduced, thus minimizing the impact on the energy density of the secondary battery 100.

[0041] Optionally, the ratio of R3 / R2 can be any one of 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, or any value within a range of any two of these values.

[0042] In some embodiments, the length of the insulating member 40 protruding from the top wall 111 along the radial direction of the circle containing the insulating member 40 is W, where 0.2mm ≤ W ≤ 2mm. By having W ≥ 0.2mm, the risk of corrosion or even short circuit due to contact between the tab 20 and the metal layer of the packaging bag 10 is reduced. By having W ≤ 2mm, while the insulating member 40 covers the portion overlapping the tab 20 and the first sealing portion 12, the distance by which the insulating member 40 extends radially beyond the top wall 111 along the circle containing the top wall 111 is reduced, thus minimizing the impact on the energy density of the secondary battery 100.

[0043] Optionally, W can be any one or a range of any two of the following: 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, and 2.0mm, or any value within a range of any two of these values. In some embodiments, the first sealing area 12A includes an arc-shaped segment 121, which includes a first arc-shaped edge 1211 and a second arc-shaped edge 1212. The first arc-shaped edge 1211 and the second arc-shaped edge 1212 are spaced apart along the radial direction of the circle containing the arc-shaped segment 121. The distance between the first arc-shaped edge 1211 and the second arc-shaped edge 1212 is L1, and the radius of the circle containing the first sealing portion 12 is R1, where 0.15 ≤ L1 / R1 ≤ 0.25. By ensuring L1 / R1 ≥ 0.15, the sealing width of the arc-shaped segment 121 is increased, improving the sealing strength and reducing the risk of leakage and / or moisture entering the packaging bag 10. When the sealing width of the arc segment 121 is too large, it affects the flatness of the seal of the arc segment 121 and is prone to protrusion. During the hot sealing process, the outermost protruding part of the packaging bag 10 is easily burned, resulting in leakage and / or moisture entering the packaging bag 10. In addition, the concave part corresponding to the outermost protruding part is not fully melted, affecting the sealing performance of the packaging bag 10. By using L1 / R1≤0.25, while meeting the sealing width of the arc segment 121, the sealing width of the arc segment 121 is controlled, reducing the risk of leakage and / or moisture entering the packaging bag 10, improving the sealing performance of the packaging bag 10, and helping to improve drop performance.

[0044] Optionally, the ratio of L1 / R1 can be any one of 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, or any value within a range of any two of these values.

[0045] In some embodiments, 0.18 ≤ L1 / R1 ≤ 0.22. By having L1 / R1 ≥ 0.18, the sealing width of the arc segment 121 is further increased, the sealing strength is further improved, and the risk of leakage and / or moisture entering the packaging bag 10 is further reduced. By having L1 / R1 ≤ 0.22, the sealing width of the arc segment 121 is further controlled while meeting the sealing requirements, further reducing the risk of leakage and / or moisture entering the packaging bag 10, further improving the sealing performance of the packaging bag 10, and further improving drop performance.

[0046] In some embodiments, the first sealing portion 12 includes a third arcuate edge 120 located at the outermost edge, and a first arcuate edge 1211 located between the third arcuate edge 120 and the second arcuate edge 1212. The distance between the third arcuate edge 120 and the first arcuate edge 1211 is L2, where 0.04 ≤ L2 / R1 ≤ 0.09. By increasing the distance between the third arcuate edge 120 and the first arcuate edge 1211 by L2 / R1 ≥ 0.04, the risk of a reduction in the encapsulation width of the arcuate segment 121 due to the end cap being biased outward is reduced. By controlling the distance L2 by L2 / R1 ≤ 0.09, the situation where the end cap cannot be completely heat-pressed onto the insulating member 40 due to the end cap being biased inward is reduced, thereby improving the sealing performance of the packaging bag 10 and improving drop performance.

[0047] Optionally, the ratio of L2 / R1 can be any one of 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or any value within a range of any two of these values.

[0048] In some embodiments, 0.06 ≤ L2 / R1 ≤ 0.08. By having L2 / R1 ≥ 0.06, the distance between the third arcuate edge 120 and the first arcuate edge 1211 is further increased, further reducing the risk of a reduction in the encapsulation width of the arcuate segment 121 due to the end cap being biased outwards. By having L2 / R1 ≤ 0.08, the distance of L2 is further controlled, further reducing the possibility that the end cap may not be fully heat-pressed onto the insulating member 40 due to the end cap being biased inwards, further improving the sealing performance of the packaging bag 10, and further enhancing drop performance.

[0049] Please see Figure 1 and 2 In some embodiments, the first sealing area 12A includes a straight segment 122, which includes a first segment 1221 and a second segment 1222. The first segment 1221 overlaps with the end of the arc-shaped segment 121, and the second segment 1222 connects to the first segment 1221. The maximum length of the second segment 1222 is L2 along the length extension direction of the first crease 101.

[0050] In some embodiments, the second segment 1222 includes a first edge 1222A that faces away from the first crease 101, and the first edge 1222A connects the first arcuate edge 1211 and the third arcuate edge 120. Along a direction perpendicular to the length extension direction of the first crease 101, the distance between the first crease 101 and the first edge 1222A is L3, where 1.2mm ≤ L3 ≤ 1.3mm. By increasing L3 ≥ 1.2mm, the encapsulation width of the second segment 1222 is increased, enhancing the encapsulation strength and reducing the risk of leakage and / or moisture entering the packaging bag 10. When the width of the second segment 1222 is too large, it affects the flatness of the seal and is prone to protrusion. During hot sealing, the outermost protruding part of the packaging bag 10 is easily burned, leading to leakage and / or moisture entering the packaging bag 10. Furthermore, the concave part corresponding to the outermost protruding part is not fully melted, affecting the sealing performance of the packaging bag 10. By keeping L3 ≤ 1.3mm, the width of the second segment 1222 is controlled while meeting the requirements, reducing the risk of leakage and / or moisture entering the packaging bag 10, improving the sealing performance of the packaging bag 10, and improving drop performance.

[0051] Optionally, L3 can be any one or any combination of two of the following: 1.2mm, 1.21mm, 1.22mm, 1.23mm, 1.24mm, 1.25mm, 1.26mm, 1.27mm, 1.28mm, 1.29mm, and 1.3mm, or any value within a range of two of these values.

[0052] In some embodiments, the area of ​​the first sealing area 12A is S1, the area of ​​the first sealing portion 12 is S2, and 0.5 ≤ S1 / S2 ≤ 0.9. By ensuring S1 / S2 ≥ 0.5, the sealing area of ​​the first sealing area 12A is increased, reducing the risk of leakage and / or moisture entering the packaging bag 10. By ensuring S1 / S2 ≤ 0.9, the sealing area of ​​the first sealing area 12A is controlled while still meeting the requirements, reducing the risk of leakage and / or moisture entering the packaging bag 10 due to an excessively large first sealing area 12A affecting its flatness. This improves the sealing performance of the packaging bag 10 and enhances its drop resistance.

[0053] In some embodiments, a portion of the first segment 1221 overlaps with a portion of the arc segment 121 to reduce the risk of leakage and / or moisture entering the packaging bag 10 due to a leak at the connection between the first segment 1221 and the arc segment 121.

[0054] Please see Figure 3This application also provides an electronic device 200 employing the aforementioned secondary battery 100. In one embodiment, the electronic device 200 of this application may be, but is not limited to, electronic devices, drones, backup power supplies, electric vehicles, electric motorcycles, electric-assisted bicycles, power tools, large household battery modules, etc.

[0055] The present application will be described in detail below through specific embodiments and comparative examples. Specifically, a wound cylindrical lithium-ion secondary battery, a first electrode as a negative electrode, and a second electrode as a positive electrode are used as examples to illustrate the present application, along with specific preparation processes and testing methods. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0056] Example 1 Preparation of the positive electrode sheet: Lithium cobalt oxide (positive electrode active material), conductive carbon black (conductive agent), and polyvinylidene fluoride (PVDF) (binder) are dissolved in an N-methylpyrrolidone (NMP) solution at a weight ratio of 97.5:1:1.5 to form a positive electrode slurry. Aluminum foil is used as the positive electrode current collector. The positive electrode slurry is coated onto the current collector, and after drying, cold pressing, and slitting, the positive electrode sheet is obtained.

[0057] Preparation of negative electrode sheet: The negative electrode active material artificial graphite, the thickener sodium carboxymethyl cellulose (CMC), and the binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; dried, and then cold-pressed, cut, and slit to obtain the negative electrode sheet.

[0058] Preparation of the isolation membrane: A polyethylene (PE) membrane with a thickness of 5 μm was selected.

[0059] Preparation of electrolyte: In a dry argon atmosphere glove box, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2, and lithium salt LiPF6 was added. After mixing evenly, the electrolyte was obtained, wherein the mass percentage concentration of LiPF6 was 12.5%.

[0060] Electrode assembly fabrication: The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound together.

[0061] Assembly: Place the perforated aluminum-plastic film in the assembly fixture with the perforated surface facing upwards, place the electrode assembly in the perforation, and apply external force to press it firmly. Then, cover the electrode assembly with another perforated aluminum-plastic film with the perforated surface facing downwards, and heat-seal the two aluminum-plastic films around their perimeter using a hot-pressing method to obtain the assembled electrode assembly.

[0062] Electrolyte injection encapsulation: Electrolyte is injected into the assembled electrode assembly, and after vacuum encapsulation, standing, hot pressing formation, shaping and other processes, a secondary battery is obtained.

[0063] Comparative Example 1, The difference from Example 1 is that the first sealing area of ​​Comparative Example 1 is bent. It should be noted that, apart from the differences mentioned above, all other parameters of Comparative Example 1 are the same as those of Example 1.

[0064] Examples 2-28, The differences from Example 1 are as follows: the values ​​of L1 / R1, L2 / R1, R1 / R2, R3 / R2, S1 / S2, and L3 are specifically recorded in Table 1. It should be noted that, except for the differences mentioned above, all other parameters in Examples 2-28 are the same as in Example 1.

[0065] Then, 100 secondary batteries from each embodiment were taken and subjected to drop tests, sealing tests, and volumetric energy density tests. The values ​​of L1 / R1, L2 / R1, R1 / R2, R3 / R2, S1 / S2, and L3 were measured using a CCD microscope.

[0066] Drop test method: 1) Battery cell 100 was placed in an environment of 20℃ (±5℃) and left to stand for 60 minutes. Then, it was charged as follows: discharged at a constant current of 0.7C to 3.0V, left to stand for 10 minutes, charged at a constant current of 0.5C to 4.5V, and charged at a constant voltage of 0.02C. The initial voltage of battery cell 100 before the drop test was tested. It was then dropped freely from a position 1m above a marble floor in the following order: head-tail-four sides-right corner of head-right corner of tail-left corner of head-left corner of tail (angle: 45±15°), repeated 5 times. The drop test pass criteria were: no leakage, no fire, no explosion, and the open circuit voltage after the test ≥ 90% of the initial voltage. Otherwise, the drop test was considered a failure. 100 secondary batteries were tested; the number of secondary batteries that passed the test was X1, and the pass rate was X1 / 100×100%. Sealing test method: 1) Immerse the battery cell in red ink for 12 hours. Remove the battery cell from the red ink and use aqua regia to etch the nylon layer in the encapsulation film at the top seal. Use hydrochloric acid solution to etch away the metal layer in the encapsulation film at the top seal, exposing the polymer layer in the encapsulation film. Rinse with water and use an optical microscope to observe whether the polymer layer in the encapsulation film at the top seal has been penetrated by red ink. If it has been penetrated by red ink, it indicates that there is a leakage channel in the polymer layer of the encapsulation film at the top seal, and it is judged as NG (Not Good). If it has not been penetrated by red ink, it is judged as OK. 100 battery cells are tested in each example and comparative example. The number of battery cells that pass the test is X2, and the test pass rate is X2 / 100×100%. Volumetric energy density test method: Under 25℃ conditions, the secondary battery was left to stand for 10 min, then charged at a constant current of 0.2C to the charging limit voltage, charged at a constant voltage to 0.02C, and left to stand for 5 min; then discharged at a constant current of 0.2C to the discharge cutoff voltage, and left to stand for 5 min. The discharge capacity C0 was recorded. The volumetric energy density was calculated using the following formula: Volumetric energy density = Plateau voltage × C0 / Volume of secondary battery.

[0067] Table 1 As can be seen from Comparative Example 1 and Examples 1-28, the first sealing part is bent towards the top wall surface with the first crease, and the first sealing area is separated from the first crease, which reduces the impact of bending the first sealing area on the sealing performance of the first sealing part and improves drop performance. By ensuring that the orthographic projection of the first sealing part does not exceed the orthographic projection of the top wall in a direction perpendicular to the top wall surface, the space occupied by the first sealing part after bending is reduced, which is beneficial to improving energy density.

[0068] As shown in Examples 1-7, the distance between the first and second arc-shaped edges is L1, and the radius of the circle containing the first sealing part is R1, satisfying 0.15≤L1 / R1≤0.25. Increasing the sealing width of the arc segment improves sealing strength while ensuring the flatness of the arc segment reduces the risk of leakage and / or moisture entering the packaging bag, thus improving the bag's sealing performance and enhancing drop performance. When 0.18≤L1 / R1≤0.22, the sealing performance of the packaging bag is improved while simultaneously enhancing drop performance. When L1 / R1≤0.15, the flatness of the arc segment improves, enhancing the bag's sealing performance, but the sealing width of the arc segment decreases, leading to reduced drop performance. When L1 / R1≥0.25, the sealing width of the arc segment increases, improving drop performance, but the flatness of the arc segment decreases, reducing the bag's sealing performance.

[0069] From Examples 1 and 8-13, it can be seen that the radius of the circle containing the first sealing part is R1, and the distance between the third arc-shaped edge 120 and the first arc-shaped edge is L2, where 0.04 ≤ L2 / R1 ≤ 0.09. Increasing the distance between the third arc-shaped edge and the first arc-shaped edge reduces the risk of a decrease in the sealing width of the arc segment due to the sealing head being biased outwards. It also reduces the possibility of the sealing head not being able to be completely heat-pressed onto the insulating component due to the sealing head being biased inwards, thus improving the sealing performance of the packaging bag and improving drop performance. When 0.06 ≤ L2 / R1 ≤ 0.08, the sealing performance of the packaging bag is improved while also considering the improvement of drop performance. When L2 / R1 ≤ 0.04, the sealing width of the arc segment decreases, leading to a decrease in drop performance. When L2 / R1 ≥ 0.09, the sealing head cannot be completely heat-pressed onto the insulating component, resulting in a decrease in the sealing performance of the packaging bag.

[0070] As can be seen from Examples 1 and 14-17, the radius of the circle containing the first sealing part is R1, and the radius of the circle containing the top wall is R2. 0.8 ≤ R1 / R2 ≤ 1 reduces the risk of corrosion and even short circuits caused by contact between the tab 20 and the metal layer of the packaging bag 10, thus reducing the impact on the energy density of the secondary battery 100. When R1 / R2 ≤ 0.8, the insulation is insufficiently exposed, posing a risk of corrosion and even short circuits due to contact between the tab and the metal layer of the packaging bag. When R1 / R2 ≥ 1, the space occupied by the first sealing part increases, reducing the energy density of the secondary battery.

[0071] From Examples 1 and 18-21, it can be seen that the radius of the circle containing the insulating component is R3, and the radius of the circle containing the top wall is R2, with 0.95 ≤ R3 / R2 ≤ 1.05. This reduces the risk of corrosion and even short circuits caused by contact between the tab and the metal layer of the packaging bag, thus reducing the impact on the energy density of the secondary battery. When R3 / R2 ≤ 0.95, the insulating component is insufficiently exposed, posing a risk of corrosion and even short circuits due to contact between the tab and the metal layer of the packaging bag. When R3 / R2 ≥ 1.05, the space occupied by the insulating component increases, reducing the energy density of the secondary battery.

[0072] From Examples 1 and 22-25, it can be seen that the area of ​​the first sealing area is S1, the area of ​​the first sealing part is S2, and 0.5 ≤ S1 / S2 ≤ 0.9. By controlling the sealing area of ​​the first sealing area while ensuring its adequate size, the risk of leakage and / or moisture entering the packaging bag is reduced due to an excessively large first sealing area affecting its flatness. This improves the sealing performance and drop resistance of the packaging bag. When S1 / S2 ≤ 0.5, the sealing area of ​​the packaging bag decreases, leading to reduced drop resistance. When S1 / S2 ≥ 0.9, the sealing area of ​​the packaging bag increases, improving drop resistance, but reducing the flatness of the curved section and thus decreasing the sealing performance of the packaging bag.

[0073] As can be seen from Examples 1 and 26-28, the distance between the first crease and the first edge is L3 along the direction perpendicular to the length of the first crease, where 1.2mm ≤ L3 ≤ 1.3mm. Increasing the width of the second segment improves the sealing strength, reduces the risk of leakage and / or moisture entering the packaging bag, improves the bag's airtightness, and enhances drop performance. When L3 ≤ 1.2mm, the sealing width of the second segment decreases, reducing the sealing strength and consequently decreasing drop performance. When L3 ≥ 1.3mm, the sealing area of ​​the packaging bag increases, improving drop performance, but reducing the flatness of the curved segment and decreasing the bag's airtightness.

[0074] Those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the spirit and essence of this application fall within the scope of this application's disclosure.

Claims

1. A secondary battery, characterized in that, include: Electrode assembly; The tab connects to the electrode assembly; A packaging bag includes a main body and a first sealing part. The main body is cylindrical, and the electrode assembly is disposed inside the main body. The main body includes a top wall, and the first sealing part is connected to the top wall. The electrode tab extends out of the packaging bag from the first sealing part. A first crease is formed between the first sealing part and the main body. The first sealing part is bent toward the surface of the top wall along the first crease. The first sealing part has a first sealing area, which is separate from the first crease. Along a direction perpendicular to the surface of the top wall, the orthographic projection of the first sealing portion does not exceed the orthographic projection of the top wall.

2. The secondary battery as described in claim 1, characterized in that, The first sealing area includes an arc segment, which includes a first arc edge and a second arc edge. The distance between the first arc edge and the second arc edge along the radial direction of the circle containing the arc segment is L1, and the radius of the circle containing the first sealing part is R1, where 0.15≤L1 / R1≤0.

25.

3. The secondary battery as described in claim 2, characterized in that, 0.18≤L1 / R1≤0.

22.

4. The secondary battery as described in claim 2, characterized in that, The first sealing portion includes a third arc-shaped edge located on the outermost side, the first arc-shaped edge being located between the third arc-shaped edge and the second arc-shaped edge, and the distance between the third arc-shaped edge and the first arc-shaped edge being L2, where 0.04≤L2 / R1≤0.

09.

5. The secondary battery as described in claim 4, characterized in that, 0.06≤L2 / R1≤0.

08.

6. The secondary battery as described in claim 4, characterized in that, The first sealing area includes a straight section, which includes a first segment and a second segment. The first segment overlaps with the end of the arc-shaped segment, and the second segment connects to the first segment and extends along the length direction of the first crease. The maximum length of the second segment is L2.

7. The secondary battery as described in claim 2 or 4, characterized in that, The radius of the circle containing the top wall is R2, and 0.8 ≤ R1 / R2 ≤ 1.

8. The secondary battery as described in claim 1, characterized in that, It also includes an insulating component, which covers part of the tab, a portion of the insulating component is located inside the first sealing portion, and another portion of the insulating component protrudes from the first sealing portion. The radius of the circle containing the insulating component is R3, and the radius of the circle containing the top wall is R2, where 0.95≤R3 / R2≤1.

05.

9. The secondary battery as described in claim 1, characterized in that, The area of ​​the first sealing area is S1, the area of ​​the first sealing part is S2, and 0.5≤S1 / S2≤0.

9.

10. The secondary battery as described in claim 6, characterized in that, The second segment includes a first edge that is away from the first crease. The first edge connects the first arcuate edge and the third arcuate edge. The distance between the first crease and the first edge is L3, where 1.2mm≤L3≤1.3mm.

11. An electronic device, characterized in that, The electronic device includes a secondary battery as described in any one of claims 1 to 10.

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