Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery comprises a packaging pouch, an electrode assembly and a conductive plate. The packaging pouch comprises an accommodating portion and a first sealing edge, wherein the electrode assembly is arranged in the accommodating portion, and the conductive plate is electrically connected to the electrode assembly and extends out of the packaging pouch. The electrode assembly comprises positive electrode sheets, negative electrode sheets and separators, wherein the positive electrode sheets, the separators and the negative electrode sheets are sequentially stacked to form a stacked structure. The accommodating portion comprises a first side wall and a second side wall arranged opposite each other in a third direction, wherein the first sealing edge is connected to the first side wall, and comprises a first segment connected to the first side wall and a second segment connected to the first segment in the extension direction of the first sealing edge. The edge region of at least one separator extends beyond the negative electrode sheets and is arranged in the first segment, such that the thickness of the second segment is less than that of the first segment. The present application can ensure both high energy density and safety performance.

Description

Secondary batteries and electronic devices Technical Field

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

[0002] With the increasing popularity of consumer electronics products such as laptops, mobile phones, handheld game consoles, tablets, power banks, and drones, people are demanding more and more stringent requirements for the energy density and safety performance of secondary batteries (such as pouch batteries).

[0003] Pouch batteries typically consist of a packaging bag and electrode assemblies housed within it. To improve the energy density of the battery, the distance between the electrode assemblies and the inner surface of the packaging bag can be reduced. However, if this distance is too small, part of the separator membrane from the electrode assemblies may penetrate into the area to be sealed within the packaging bag. Once this area is sealed, the separator membrane that has entered the sealing area may damage the packaging bag, leading to leakage, increased boundary voltage (IV value), and other safety hazards. Therefore, achieving a balance between high energy density and safety performance in pouch batteries is a pressing issue that needs to be addressed. Summary of the Invention

[0004] In view of this, it is necessary to provide a secondary battery that can balance high energy density and safety performance, as well as an electronic device having the above-mentioned secondary battery.

[0005] This application provides a secondary battery, including a packaging bag, an electrode assembly, and a conductive plate. The packaging bag includes a receiving portion and a first seal. The electrode assembly is disposed within the receiving portion, and the conductive plate is electrically connected to the electrode assembly and extends out of the packaging bag. The direction from the electrode assembly to the conductive plate is a first direction. The electrode assembly includes a positive electrode, a negative electrode, and a separator, which are sequentially stacked in a second direction to form a laminated structure. The electrode assembly includes N layers of separator in the second direction, and the N layers of separator include n layers of first separator, where n ≤ N. The first separator includes a main body region and a first edge region connected in a third direction. Viewed from the second direction, the main body region overlaps with the negative electrode, and the first edge region extends from the main body region and beyond the negative electrode. The receiving portion includes a first sidewall and a second sidewall disposed opposite to each other in a third direction, and the first seal is connected to the first sidewall. The first seal includes a first segment connected to the first sidewall and a second segment connected to the first segment along the extension direction of the first seal. At least a portion of each first edge region is disposed within the first segment. Define the thickness of the first segment as H1, the thickness of the second segment as H2, and H2

[0006] ​In this application, the first segment has a larger thickness, resulting in lower encapsulation pressure and / or temperature. This reduces the risk of the metal layer being exposed due to damage to the first adhesive layer within the first sealing edge, thereby reducing the risk of the metal layer contacting and being corroded by the electrolyte. This mitigates potential hazards such as leakage from the packaging bag and increased edge voltage, improving the safety performance of the secondary battery. Simultaneously, the second segment has a smaller thickness, allowing for higher encapsulation pressure and / or temperature, resulting in higher overall encapsulation strength for the first sealing edge. This further reduces the risk of leakage from the packaging bag. Moreover, since the first edge region is at least partially located within the first segment, the risk of leakage and increased edge voltage is reduced. Therefore, the gap between the negative electrode and the first sidewall of the packaging bag can be reduced accordingly, thereby increasing the energy density of the secondary battery. Thus, the secondary battery of this application achieves a balance between high safety performance and high energy density. In addition, since the first edge region is at least partially located within the first segment, the electrode assembly can be fixed inside the packaging bag. This reduces the shaking of the electrode assembly inside the packaging bag during mechanical abuse and further reduces the risk of short circuit between the positive and negative electrode plates caused by the first separator folding or wrinkling during mechanical abuse, thereby further improving the safety performance of the secondary battery.

[0007] Based on the first aspect, in one or more of the above possible implementations, 0.11mm ≤ H1 ≤ 0.40mm, and 0.10mm ≤ H2 ≤ 0.20mm. If the thickness H1 of the first segment is too large, it means that the packaging pressure and / or temperature used to encapsulate the first segment is too low. This may result in insufficient restraint on the first edge region, failing to properly fix the electrode assembly inside the packaging bag, thus failing to improve the safety performance of the secondary battery under mechanical abuse. If H1 is too small, it means that the packaging pressure and / or temperature used to encapsulate the first segment is too high. This will cause the first adhesive layer in the first segment to be damaged, resulting in potential hazards such as leakage from the packaging bag and increased edge voltage. Therefore, limiting H1 within the above range can balance the restraint effect of the first segment on the first edge region with the protection of the first adhesive layer within the first segment, thereby enabling the secondary battery to have higher safety performance. If the thickness H2 of the second segment is too large, it means that the encapsulation pressure and / or temperature used to package the second segment is too low. This will result in insufficient encapsulation strength and inadequate encapsulation pull, potentially leading to leakage. If H2 is too small, it means that the encapsulation pressure and / or temperature used to package the second segment is too high. This may cause damage to the first adhesive layer within the second segment, leading to problems such as increased edge voltage. Therefore, limiting H2 within the above range can balance the encapsulation reliability and safety performance of the secondary battery.

[0008] Based on the first aspect, in one or more of the above possible implementations, along the extension direction of the first sealing edge, the length of the first segment is L1, the length of the second segment is L2, and 0.8mm≤L1≤2mm, 0.8mm≤L2≤2mm. Limiting the lengths of the first and second segments within the above range can reduce the impact on the energy density of the secondary battery when the length of the first or second segment is too large. Moreover, since L1 is not less than 0.8mm, the first edge region can fully enter the first segment, thereby more firmly fixing the electrode assembly to the packaging bag. In the event of mechanical abuse of the secondary battery, the shaking of the electrode assembly within the packaging bag can be further reduced, and the risk of short circuit between the positive and negative electrode plates due to folding or wrinkling of the first separator during mechanical abuse can also be further reduced. At the same time, L2 is not less than 0.8mm, which allows the first sealing edge to have high overall sealing strength, further reducing the risk of leakage from the packaging bag.

[0009] Based on the first aspect, in one or more of the above possible implementations, along the extension direction of the first sealing edge, the length of the first edge region within the first segment is L3, where 0.4mm ≤ L3 ≤ L1. This can further reduce the gap between the negative electrode and the first sidewall of the packaging bag, thereby further improving the energy density of the secondary battery. Moreover, since the first edge region can fully enter the first segment, the electrode assembly is better fixed to the packaging bag. In the event of mechanical abuse of the secondary battery, the shaking of the electrode assembly within the packaging bag can be further reduced, and the risk of short circuit between the positive and negative electrode due to folding or wrinkling of the first separator during mechanical abuse can also be further reduced.

[0010] Based on the first aspect, in one or more of the above possible implementations, the first release film includes a substrate layer, which includes a first substrate region located in the main body region and a second substrate region located in the first edge region. The packaging bag includes a first sealing film and a second sealing film disposed opposite to each other, which are bonded together to form a first edge seal. The first edge seal includes a first protective layer, a first metal layer, a first adhesive layer, a second metal layer, and a second protective layer stacked sequentially, with the second substrate region bonded to the first adhesive layer. Since both the substrate layer and the first adhesive layer are polymer materials, it facilitates full fusion and bonding between the first edge region and the first adhesive layer, thereby improving the bonding strength between the first edge region and the first segment.

[0011] Based on the first aspect, in one or more of the above possible implementations, the first separator further includes an insulating layer containing inorganic particles. The insulating layer is disposed on the first substrate region, and the second substrate region extends beyond the insulating layer. The insulating layer on the first substrate region can improve the electrolyte wetting effect in the main body region, and since no insulating layer is disposed on the second substrate region within the first segment, both the substrate layer and the first adhesive layer are polymer materials, which facilitates the full fusion and adhesion between the first edge region and the first adhesive layer, thereby improving the bonding strength between the first edge region and the first segment.

[0012] Based on the first aspect, in one or more of the above possible implementations, the first separator further includes an insulating layer containing inorganic particles. The insulating layers are respectively disposed on the first substrate region and the second substrate region. The insulating layer disposed on the second substrate region is bonded to the first adhesive layer. The insulating layer on the first substrate region can improve the electrolyte wetting effect in the main body region, and an insulating layer is also disposed on the first edge region within the first segment. Therefore, the main body region and the first edge region of the first separator can be integrally formed, thereby simplifying the process.

[0013] Based on the first aspect, in one or more of the above possible implementations, the first separator further includes a first adhesive layer, which is disposed on the side of the insulating layer away from the substrate layer. The first adhesive layer can improve the adhesion between the first separator and the positive or negative electrode sheet, reducing the risk of damage to the electrode assembly structure during mechanical abuse. Moreover, no insulating layer or first adhesive layer is disposed on the first edge region within the first sealing edge. The first edge region is bonded to the first adhesive layer through the second substrate region. Both the substrate layer and the first adhesive layer are polymer materials, which facilitates the full fusion and bonding of the first edge region and the first adhesive layer, thereby improving the bonding strength between the first edge region and the first segment.

[0014] Based on the first aspect, in one or more of the above possible implementations, the first separator further includes a first adhesive layer. The first adhesive layer is disposed on the side of the insulating layer away from the substrate layer. The first adhesive layer disposed on the second substrate region is bonded to the first adhesive layer. The first adhesive layer can improve the adhesion between the first separator and the positive or negative electrode sheet, reduce the risk of damage to the electrode assembly structure during mechanical abuse, and since the insulating layer and the first adhesive layer are also disposed on the first edge region within the first sealing edge, the main body region and the first edge region of the first separator can be integrally formed, thereby simplifying the process.

[0015] Based on the first aspect, in one or more of the above possible implementation manners, the first adhesive layer includes a first polymer material, the substrate layer includes a second polymer material, and the first polymer material and the second polymer material are each independently selected from at least one of polyethylene, polypropylene, polyurethane, and polyimide. Therefore, the substrate layer and the first adhesive layer have the same or similar properties, which is more conducive to the full fusion and bonding of the first edge region and the first adhesive layer.

[0016] Based on the first aspect, in one or more of the above possible implementation manners, the first polymer material and the second polymer material are the same material. Therefore, the substrate layer and the first adhesive layer have the same properties, which is more conducive to the full fusion and bonding of the first edge region and the first adhesive layer.

[0017] Based on the first aspect, in one or more of the above possible implementation manners, H1 = d1 + d2 + n×S + X1, H2 = d1 + d2 + X2. Where d1 is the thickness of the first encapsulation film located in the accommodating part, d2 is the thickness of the second encapsulation film located in the accommodating part, S is the thickness of the main body region, and X1 and X2 are adjustment coefficients, -2mm ≤ X1 < 0mm, -2mm ≤ X2 < 0mm. By setting the adjustment coefficients, the first segment and the second segment can respectively have the required thickness, which can not only reduce the risk of the metal layer being exposed due to the breakage of the first adhesive layer in the first sealing edge, reduce potential hazards such as liquid leakage and edge voltage rise of the packaging bag, but also the overall first sealing edge can have a high packaging strength, so the risk of liquid leakage of the packaging bag can be further reduced.

[0018] Based on the first aspect, in one or more of the above possible implementation manners, n < N, and the outermost side of the electrode assembly in the second direction is the first isolation film. Therefore, the outermost first isolation film can play a role in restraining at least part of the positive electrode sheet and the negative electrode sheet while firmly fixing the electrode assembly to the packaging bag, and further reducing the晃动 of the electrode assembly in the packaging bag when the secondary battery undergoes mechanical abuse.

[0019] Based on the first aspect, in one or more of the above possible implementation manners, the edges of two adjacent first edge regions in the second direction are directly connected within the first sealing edge. Therefore, the first isolation film can play a role in restraining at least part of the positive electrode sheet and the negative electrode sheet while firmly fixing the electrode assembly to the packaging bag, further reducing the晃动 of the electrode assembly in the packaging bag when the secondary battery undergoes mechanical abuse, and further reducing the risk of the first isolation film flipping or generating wrinkles and causing contact short - circuit between the positive electrode sheet and the negative electrode sheet during mechanical abuse.

[0020] Based on the first aspect, in one or more of the above possible implementations, the packaging bag includes a second sealing film, and the second segment includes a first segment connected to the first segment and a second segment connected to the first segment along the extension direction of the first sealing edge. The second segment is bent toward the first segment in a direction away from the second sealing film. Therefore, the size of the secondary battery in the third direction can be reduced, further improving the energy density of the secondary battery. Moreover, the bending point is located in the thinner second segment, which facilitates bending the second segment and also reduces the risk of the second segment opening up compared to the first segment. In addition, it can also reduce the risk that the exposed metal layer at the edge of the second segment is easily short-circuited to the outside, further improving the safety performance of the secondary battery.

[0021] Based on the first aspect, in one or more of the above possible implementations, the secondary battery further includes a first adhesive member, through which the second segment is adhered to the first segment. Therefore, the risk of the second segment opening apart relative to the first segment can be further reduced.

[0022] Based on the first aspect, in one or more of the above possible implementations, the first segment is bent toward the first sidewall in a direction away from the second encapsulation film, and the second segment is disposed between the first segment and the first sidewall in a third direction. Therefore, the size of the secondary battery in the third direction can be further reduced, thereby further improving the energy density of the secondary battery.

[0023] Based on the first aspect, in one or more of the above possible implementations, the secondary battery further includes a second adhesive member, through which the second segment is adhered to the first sidewall. The second adhesive member can reduce the risk of the first segment opening relative to the first sidewall.

[0024] Based on the first aspect, in one or more of the above possible implementations, the distance between the negative electrode and the first sidewall in the third direction is D, 0.2mm≤D≤2mm, which can reduce the gap between the negative electrode and the first sidewall, thereby enabling the secondary battery to have a higher energy density.

[0025] Based on the first aspect, in one or more of the above possible implementation manners, the packaging bag further includes a second sealing edge connected to the second side wall. The second sealing edge includes a third segment connected to the second side wall and a fourth segment connected to the third segment along the extending direction of the second sealing edge. The first separator film further includes a second edge region, and the first edge region, the main body region, and the second edge region are sequentially connected in the third direction. When observed from the second direction, the second edge region extends from the main body region and extends beyond the negative electrode tab. At least a part of each second edge region is disposed within the third segment. Define the thickness of the third segment as H3 and the thickness of the fourth segment as H4, and H4 < H3. By setting the thickness of the third segment to be smaller, the corresponding packaging pressure and / or temperature used are smaller, which can reduce the risk of the second adhesive layer within the second sealing edge being damaged and the metal layer being exposed, thereby reducing the risk of the metal layer coming into contact with the electrolyte and being corroded by the electrolyte, thus reducing potential hazards such as liquid leakage from the packaging bag and increase in edge voltage, and further improving the safety performance of the secondary battery. At the same time, the thickness of the fourth segment is smaller, and the corresponding packaging pressure and / or temperature used are larger, so the fourth segment can have a higher packaging strength relative to the third segment, and thus the risk of liquid leakage from the packaging bag can be further reduced. Moreover, since at least a part of the second edge region is disposed within the third segment, the risk of liquid leakage from the packaging bag, increase in edge voltage, etc. can be reduced, so the gap between the negative electrode tab and the second side wall of the packaging bag can be correspondingly reduced, thereby further improving the energy density of the secondary battery. In addition, since at least a part of the second edge region is disposed within the third segment, when the secondary battery undergoes mechanical abuse, the shaking of the electrode assembly within the packaging bag can be further reduced, and the risk of short circuit between the positive electrode tab and the negative electrode tab caused by the folding or wrinkling of the first separator film during mechanical abuse can also be further reduced, thereby further improving the safety performance of the secondary battery.

[0026] The second aspect of the present application further provides an electronic device, which includes a battery compartment and the secondary battery as described above. The secondary battery is disposed within the battery compartment. The electronic device is powered by the above secondary battery, and the secondary battery can balance high energy density and safety performance. Description of the Drawings

[0027] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0028] FIG. 1 is a schematic structural view of a secondary battery provided by an embodiment of the present application when observed from the second direction.

[0029] FIG. 2 is a cross-sectional view of the secondary battery shown in FIG. 1 along the cutting line II-II in some embodiments.

[0030] FIG. 3 is a partial enlarged view of the secondary battery shown in FIG. 2.

[0031] FIG. 4 is another partial enlarged view of the secondary battery shown in FIG. 2.

[0032] Figure 5 is a schematic diagram of the secondary battery shown in Figure 1 before packaging.

[0033] Figure 6 is a cross-sectional view of the first sealing film of the packaging bag for the secondary battery shown in Figure 5.

[0034] Figure 7 is a cross-sectional view of the second sealing film of the packaging bag for the secondary battery shown in Figure 5.

[0035] Figure 8 is a cross-sectional view of the secondary battery shown in Figure 1 in some other embodiments.

[0036] Figure 9 is a cross-sectional view of the secondary battery shown in Figure 1 in some other embodiments.

[0037] Figure 10 is a cross-sectional view of the separator of the secondary battery shown in Figure 2 or Figure 3 in some embodiments.

[0038] Figure 11 is a cross-sectional view of the separator of the secondary battery shown in Figure 2 or Figure 3 in some embodiments.

[0039] Figure 12 is a cross-sectional view of the separator of the secondary battery shown in Figure 2 or Figure 3 in some embodiments.

[0040] Figure 13 is a cross-sectional view of the separator of the secondary battery shown in Figure 2 or Figure 3 in some embodiments.

[0041] Figure 14 is a cross-sectional view of the separator of the secondary battery shown in Figure 2 or Figure 3 in some embodiments.

[0042] Figure 15 is a cross-sectional view of a secondary battery provided in another embodiment of this application.

[0043] Figure 16 is a cross-sectional view of a secondary battery provided in another embodiment of this application.

[0044] Figure 17 is a schematic diagram of the structure of an electronic device provided in one embodiment of this application.

[0045] Key Component Symbols: Electronic Device 1; Packaging Bag 10; First Seal 11; First Edge 11A; Second Edge 11B; Second Seal 12; Third Seal 13; Receiving Part 14; Electrode Assembly 20; First End 20A; Second End 20B; Positive Electrode 21; Negative Electrode 22; Separator 23; First Separator 23A; First Conductive Plate 30; Second Conductive Plate 40; Tail Wrap 50; First Adhesive 60; Second Adhesive 70; Secondary Battery 100, 200, 300; First Encapsulation Film 101; Second Encapsulation Film 102; First Adhesive Layer 110; First Segment 111; Second Segment 112; Third Segment 121; Fourth Segment 122; Second Adhesive Layer 120; First Sidewall 141; Second Sidewall 142; First Endwall 143; Second Endwall 144; Positive Current Collector 210; Positive Active Material Layer 211; Negative Current Collector 220; Negative Active Material Layer 221; Main Body Area 230; First Edge Area 231 Second edge region 232 Substrate layer 233 Insulating layer 234 First adhesive layer 235 Battery compartment1001 First protective layer 1011 First metal layer 1012 First polymer layer 1013 Second protective layer 1021 Second metal layer 1022 Second polymer layer 1023 First segment 1121 Second segment 1122 First substrate region 2331 Second substrate region 2332 Third substrate region 2333 Distance D, T Thickness H1, H2, H3, H4, d1, d2, S Length L1, L2, L3 First direction X Second direction Y Third direction Z

[0046] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0047] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. 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 in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0048] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to provide a thorough and detailed understanding of this application to those skilled in the art.

[0049] Additionally, for brevity and clarity, the dimensions or thicknesses of various components and layers may be enlarged in the accompanying drawings. Throughout the text, the same numerical values ​​refer to the same elements. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more of the associated enumerated items. Furthermore, it should be understood that when element A is referred to as "connecting" element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0050] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".

[0051] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0052] Spatial terms, such as "above," may be used herein for convenience in describing the relationship between one element or feature and another element (or feature) or feature (or feature) illustrated in the figures. It should be understood that, in addition to the directions depicted in the figures, spatial terms are intended to include different orientations of the device or apparatus during use or operation. For example, if the device in the figure is flipped, an element described as "above" or "on" other elements or features would be oriented "below" or "under" other elements or features. Therefore, the exemplary term "above" can include both above and below orientations. It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, a first element, component, region, layer, or portion discussed below may be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0053] In this application, the design relationships of greater than, less than, or not equal to parameter values ​​need to exclude reasonable errors of the measuring equipment.

[0054] Please refer to Figures 1 to 4. One embodiment of this application provides a secondary battery 100, which includes a packaging bag 10, an electrode assembly 20, an electrolyte (not shown), and a conductive plate. The electrode assembly 20 and the electrolyte are disposed inside the packaging bag 10. The conductive plate may include a first conductive plate 30 and a second conductive plate 40, both of which are electrically connected to the electrode assembly 20 and extend out of the packaging bag 10. The first conductive plate 30 and the second conductive plate 40 can be connected to external components (not shown). A three-dimensional coordinate system is established based on two mutually perpendicular first directions X, second directions Y, and a third direction Z, wherein the direction from the electrode assembly 20 to the first conductive plate 30 or the second conductive plate 40 is the first direction X, the thickness direction of the electrode assembly 20 is the second direction Y, and in some embodiments, the direction from the first conductive plate 30 to the second conductive plate 40 is the third direction Z.

[0055] As shown in Figure 1, the packaging bag 10 includes a receiving portion 14 and a first sealing edge 11. The electrode assembly 20 and electrolyte are disposed within the receiving portion 14. In the third direction Z, the receiving portion 14 includes a first sidewall 141 and a second sidewall 142 disposed opposite to each other. The surface of the first sidewall 141 extends in the first direction X and the second direction Y, and the surface of the second sidewall 142 extends in the first direction X and the second direction Y. In the first direction X, the receiving portion 14 includes a first endwall 143 and a second endwall 144 disposed opposite to each other. The surface of the first endwall 143 extends in the second direction Y and the third direction Z, and the surface of the second endwall 144 extends in the second direction Y and the third direction Z. The first sealing edge 11 is connected to the first endwall 143. In some embodiments, the packaging bag 10 may further include a second sealing edge 12, and the second sealing edge 12 is connected to the second sidewall 142. The packaging bag 10 may further include a third sealing edge 13, and the third sealing edge 13 is connected to the first endwall 143. The first conductive plate 30 and the second conductive plate 40 can both extend out of the packaging bag 10 from the third sealing edge 13.

[0056] Please refer to Figure 5, which is a structural schematic diagram of the secondary battery 100 before encapsulation. The packaging bag 10 includes a first encapsulation film 101 and a second encapsulation film 102 disposed opposite to each other in the second direction Y. In some embodiments, the first encapsulation film 101 and the second encapsulation film 102 are integral structures before encapsulation, and the first encapsulation film 101 and the second encapsulation film 102 are obtained by folding a single encapsulation film. The materials of the first encapsulation film 101 and the second encapsulation film 102 are both multilayer sheets. As shown in Figure 6, the first encapsulation film 101 may include a first protective layer 1011, a first metal layer 1012, and a first polymer layer 1013 stacked sequentially. The first polymer layer 1013 is closer to the electrode assembly 20 than the first protective layer 1011. The material of the first protective layer 1011 can be a polymer resin, which can be used to protect the first metal layer 1012, reduce the risk of the first metal layer 1012 being damaged by external forces, and at the same time delay the air infiltration from the external environment, maintaining the internal environment of the secondary battery 100 in a normal operating environment. In some embodiments, the material of the first protective layer 1011 may be selected from at least one of polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyamide, and polyimide. The first metal layer 1012 may be used to delay the penetration of moisture from the external environment and reduce damage to the electrode assembly 20 caused by external forces. In some embodiments, the first metal layer 1012 may be an aluminum foil layer or a steel foil layer. The first polymer layer 1013 has the property of melting upon heating, can be used for encapsulation, and can reduce the risk of the multilayer sheet being dissolved or swollen by organic solvents in the electrolyte. The first polymer layer 1013 may also be used to reduce the risk of corrosion of the metal layer due to contact between the electrolyte in the electrolyte and the first metal layer 1012. In some embodiments, the first polymer layer 1013 includes a first polymer material, which may be selected from at least one of polyethylene, polypropylene, polyurethane, and polyimide.

[0057] As shown in Figure 7, the second encapsulation film 102 may include a second protective layer 1021, a second metal layer 1022, and a second polymer layer 1023 stacked sequentially. It can be understood that when the first encapsulation film 101 and the second encapsulation film 102 are obtained by folding a single encapsulation film, the materials of the second protective layer 1021, the second metal layer 1022, and the second polymer layer 1023 are the same as the materials of the first protective layer 1011, the first metal layer 1012, and the first polymer layer 1013, respectively.

[0058] As shown in Figures 3 to 5, when preparing the packaging bag 10, the sealing head of the sealing equipment can simultaneously apply a certain temperature and pressure to the edges of the first sealing film 101 and the second sealing film 102, causing the first polymer layer 1013 and the second polymer layer 1023 to melt and bond together, resulting in a first adhesive layer 110, a second adhesive layer 120, and a third adhesive layer (not shown). The first adhesive layer 110 is located inside the first sealing edge 11, the second adhesive layer 120 is located inside the second sealing edge 12, and the third adhesive layer is located inside the third sealing edge 13. That is, as shown in Figure 3, the first sealing edge 11 includes a first protective layer 1011, a first metal layer 1012, a first adhesive layer 110, a second metal layer 1022, and a second protective layer 1021 stacked sequentially. As shown in Figure 4, the second sealing edge 12 includes a first protective layer 1011, a first metal layer 1012, a second adhesive layer 120, a second metal layer 1022, and a second protective layer 1021 stacked sequentially. The third edge seal 13 comprises a first protective layer 1011, a first metal layer 1012, a third adhesive layer, a second metal layer 1022, and a second protective layer 1021, which are stacked sequentially. Each adhesive layer comprises the aforementioned first polymer material, namely at least one of polyethylene, polypropylene, polyurethane, and polyimide. In this application, each adhesive layer refers to the portion of the first polymer layer 1013 and the second polymer layer 1023 that is melted and bonded together within the corresponding edge seal. The unbonded portions of the first polymer layer 1013 and the second polymer layer 1023 that separate within the receiving portion 14 are not included in each adhesive layer.

[0059] As shown in Figures 2 and 3, in some embodiments, the first sealing edge 11 does not need to be bent. The surface where the first sealing edge 11 is located may be substantially perpendicular to the surface where the first sidewall 141 is located. Viewed from the first direction X, the first sealing edge 11 has a first edge 11A connected to the first sidewall 141 and a second edge 11B opposite to the first edge 11A. The first sealing edge 11 extends from the first edge 11A in a direction away from the receiving portion 14. Therefore, the extension direction of the first sealing edge 11 is opposite to the third direction Z, such that the first sealing edge 11 is substantially perpendicular to the first sidewall 141. In other embodiments, when the first sealing edge 11 is not bent, the extension direction of the first sealing edge 11 may also deviate from the third direction Z.

[0060] The electrode assembly 20 has a stacked structure and includes multiple positive electrode plates 21, multiple negative electrode plates 22, and at least one separator 23. In the stacked structure, the positive electrode plates 21 and negative electrode plates 22 are stacked alternately, with one negative electrode plate 22 in every two adjacent positive electrode plates 21 and one positive electrode plate 21 in every two adjacent negative electrode plates 22. The separator 23 is disposed between adjacent positive electrode plates 21 and negative electrode plates 22. Each positive electrode plate 21 includes a positive current collector 210 and a positive active material layer 211 disposed on the positive current collector 210, and a first conductive plate 30 is electrically connected to the positive current collector 210. Each negative electrode plate 22 includes a negative current collector 220 and a negative active material layer 221 disposed on the negative current collector 220, and a second conductive plate 40 is electrically connected to the negative current collector 220.

[0061] As shown in Figures 2 and 3, in some embodiments, the electrode assembly 20 includes N independent insulating films 23, each insulating film 23 disposed between adjacent positive electrode plates 21 and negative electrode plates 22. The electrode assembly 20 is stacked sequentially in the second direction Y in the order of positive electrode plate 21, insulating film 23, negative electrode plate 22, positive electrode plate 21, insulating film 23, negative electrode plate 22, and so on. As shown in Figure 8, in other embodiments, the electrode assembly 20 may also include an insulating film 23. This insulating film 23 is a one-piece structure and is formed into a Z-shaped structure by alternating bending and folding in both directions. In this case, the insulating film 23 includes N insulating films 23 in the second direction Y, and the edges of adjacent insulating films 23 are connected to each other.

[0062] The N-layer separator 23 includes n layers of first separator 23A, where n and N are both positive integers greater than 1, and n can be equal to or less than N. As shown in Figure 3, the first separator 23A includes a main body region 230 and a first edge region 231 connected in the third direction Z. In the third direction Z, the first edge region 231 is closer to the first edge 11 than the second sealing edge 12. Viewed from the second direction Y, the main body region 230 overlaps with the negative electrode 22, and the first edge region 231 extends from the main body region 230 and beyond the negative electrode 22. The first edge region 231 reduces the risk of short circuit between the positive electrode 21 and the negative electrode 22. As shown in Figure 4, in some embodiments, the first separator 23A may also include a second edge region 232. Referring to Figures 3 and 4, the first edge region 231, the main body region 230, and the second edge region 232 are connected sequentially in the third direction Z. Viewed from the second direction Y, the second edge region 232 extends from the main body region 230 and beyond the negative electrode 22. The second edge region 232 further reduces the risk of short circuit between the positive electrode 21 and the negative electrode 22.

[0063] The first sealing edge 11 includes a first segment 111 connected to the first sidewall 141 and a second segment 112 connected to the first segment 111. The second segment 112 is connected to the first segment 111 along the extending direction of the first sealing edge 11 (in some embodiments, the opposite direction of the third direction Z). At least a portion of each first edge region 231 is disposed within the first segment 111. After encapsulation, at least a portion of the first edge region 231 is fused and bonded to the first adhesive layer 110. In some embodiments, after encapsulation, only a portion of the first edge region 231 is fused and bonded to the first adhesive layer 110. The thickness of the first segment 111 is defined as H1, and the thickness of the second segment 112 is defined as H2.

[0064] During encapsulation, the first segment 111 containing the first edge region 231 can be encapsulated first, and then the second segment 112 can be encapsulated. The pressure and / or temperature of the sealing head during the first encapsulation is lower than that during the second encapsulation, resulting in a greater thickness for the first segment 111 than for the second segment 112. The above example illustrates the use of two encapsulations for the first edge 11; however, the encapsulation order of the first segment 111 and the second segment 112 can be reversed. In another embodiment, the first segment 111 and the second segment 112 can also be encapsulated using two sealing heads in the same encapsulation step. The pressure and / or temperature of the sealing head used to encapsulate the first segment 111 is lower, resulting in a thicker first segment 111 after encapsulation. In other embodiments, the first segment 111 and the second segment 112 can also be encapsulated using irregularly shaped sealing heads in the same encapsulation step. The distance between the upper and lower sealing heads used to encapsulate the first segment 111 is relatively large, resulting in a thicker first segment 111 after encapsulation.

[0065] ​Wherein, 0.11mm≤H1≤0.40mm, 0.10mm≤H2≤0.20mm. If the thickness H1 of the first segment 111 is too large, it means that the encapsulation pressure and / or temperature used to encapsulate the first segment 111 is too low. This may result in insufficient restraint of the first segment 111 on the first edge region 231, failing to properly fix the electrode assembly 20 inside the packaging bag 10, thus failing to improve the safety performance of the secondary battery 100 under mechanical abuse. If H1 is too small, it means that the encapsulation pressure and / or temperature used to encapsulate the first segment 111 is too high. This will cause the first adhesive layer 110 in the first segment 111 to be damaged, resulting in potential hazards such as leakage of the packaging bag 10 and increased edge voltage. Generally speaking, an edge voltage between -0.3V and 0.95V is within the normal range, and a value higher than 0.95V is considered an excessively high edge voltage. The edge voltage can be obtained by measuring the potential difference between the metal layer of the packaging bag 10 and the tabs of the secondary battery 100 using a multimeter. Therefore, limiting H1 to the above range can balance the binding effect of the first segment 111 on the first edge region 231 and prevent the first adhesive layer 110 in the first segment 111 from being damaged, thereby giving the secondary battery 100 higher safety performance.

[0066] If the thickness H2 of the second segment 112 is too large, it means that the encapsulation pressure and / or temperature used to encapsulate the second segment 112 is too low. This will result in insufficient encapsulation strength of the secondary battery 100, posing a risk of leakage. Encapsulation strength can be quantified by encapsulation tensile force, which can be obtained by testing with a tensile testing instrument. The encapsulated secondary battery 100 is placed on the stage of the tensile testing instrument. Two clamps hold the first encapsulation film 101 and the second encapsulation film 102 of the second segment 112, respectively. Then, the two clamps are pulled in opposite directions until the first encapsulation film 101 and the second encapsulation film 102 of the second segment 112 are completely separated. The tensile force at this point is the encapsulation tensile force of the second segment 112. The encapsulation tensile force can be used to characterize the encapsulation strength of the second segment 112. The greater the encapsulation tensile force, the higher its encapsulation reliability. Generally speaking, to ensure sufficient encapsulation reliability of the secondary battery 100, the encapsulation tensile force at the encapsulation edge needs to meet the standard of greater than 7N. If the encapsulation tensile force is less than 7N, it can be considered that there is a significant risk of leakage. If H2 is too small, it means that the packaging pressure and / or temperature used to encapsulate the second segment 112 is too high. This could lead to the destruction of the first adhesive layer 110 within the second segment 112, resulting in problems such as increased edge voltage. Therefore, limiting H2 within the above range can balance the packaging reliability and safety performance of the secondary battery 100.

[0067] In this application, the measurement steps for H1 and H2 may be as follows: (1) Take the first sealing edge 11 from the packaging bag 10 as a sample; (2) Prepare a resin composition, which is made of a crystal resin matrix (such as epoxy resin), a catalyst and a curing agent in a certain proportion; (3) Pour the resin composition into a mold and place the sample in the mold so that the sample is completely immersed in the resin composition, and then let it stand until the resin composition solidifies; (4) Cut the sample covered with the resin composition along a section perpendicular to the first direction X and polish the cut surface to obtain the cross section of the sample; (5) Use a suitable measuring tool (such as a micrometer) to measure the values ​​of H1 and H2 in the above cross section respectively.

[0068] If the thickness of the first segment 111 containing the first edge region 231 is equal to the thickness of the second segment 112 (e.g., the first segment 111 and the second segment 112 use the same encapsulation pressure or temperature), the first adhesive layer 110 inside the first sealing edge 11 is prone to damage, exposing the metal layer (e.g., aluminum layer). The metal layer may be continuously consumed by the electrolyte corrosion, causing the packaging bag 10 to leak. Furthermore, the electrolyte and the metal layer will generate ion channels after contact, leading to an increase in edge voltage and causing safety hazards. In this application, the thickness of the first segment 111 is relatively large (this can be achieved by reducing the pressure and / or temperature during the encapsulation of the first segment 111, but this application is not limited to this), which reduces the risk of the metal layer being exposed due to damage to the first adhesive layer 110 within the first sealing edge 11. This, in turn, reduces the risk of the metal layer coming into contact with the electrolyte and being corroded by the electrolyte, thereby reducing potential hazards such as leakage of the packaging bag 10 and increased edge voltage, and improving the safety performance of the secondary battery 100. At the same time, the thickness of the second segment 112 is relatively small, allowing the first sealing edge 11 to have higher overall encapsulation strength, thus further reducing the risk of leakage of the packaging bag 10. Moreover, since the first edge region 231 is at least partially located within the first segment 111, the risks of leakage of the packaging bag 10 and increased edge voltage are reduced. Therefore, the gap between the negative electrode 22 and the first sidewall 141 of the packaging bag 10 can be reduced accordingly, thereby increasing the energy density of the secondary battery 100. Therefore, the secondary battery 100 of this application can achieve both high safety performance and high energy density. In some embodiments, the distance between the negative electrode 22 and the first sidewall 141 in the third direction Z can be set to D, where 0.2mm ≤ D ≤ 2mm. This reduces the gap between the negative electrode 22 and the first sidewall 141, thereby enabling the secondary battery 100 to have a higher energy density.

[0069] Furthermore, since the first edge region 231 is at least partially located within the first segment 111, the electrode assembly 20 can be fixed to the packaging bag 10. When the secondary battery 100 is subjected to mechanical abuse (drop, impact, or shaking), the shaking of the electrode assembly 20 within the packaging bag 10 can be reduced, thereby reducing the risk of the packaging bag 10 being opened and causing leakage, and also reducing the risk of the electrode assembly 20 being damaged during shaking. Therefore, this application can omit the hot melt adhesive between the electrode assembly 20 and the inner surface of the packaging bag 10, which is beneficial for reducing costs and further improving the energy density of the secondary battery 100. Moreover, since the first edge region 231 is at least partially located within the first segment 111, the risk of short circuit between the positive electrode 21 and the negative electrode 22 caused by the first separator 23A folding or wrinkling during mechanical abuse can also be reduced, thereby further improving the safety performance of the secondary battery 100.

[0070] It is understood that the first edge region 231 is at least partially located within the first segment 111. This not only eliminates the need for hot melt adhesive between the electrode assembly 20 and the inner surface of the packaging bag 10, but also reduces the risk of the first edge region 231 folding or shrinking due to its fixation within the first segment 111. Furthermore, it eliminates the need for side wrapping adhesive on the electrode assembly 20, thereby facilitating a further increase in the energy density of the secondary battery 100. As shown in FIG1, in some embodiments, the electrode assembly 20 includes a first end 20A and a second end 20B disposed opposite each other in the first direction X. In the first direction X, the first end 20A is closer to the third sealing edge 13 than the second end 20B. Viewed from the second direction Y, the first conductive plate 30 extends beyond the first end 20A. The secondary battery 100 also includes a tail wrapping adhesive 50 located at the second end 20B, which adheres to the edge of the separator 23 in the first direction X, thereby reducing the risk of short circuit between the positive electrode 21 and the negative electrode 22 due to folding or shrinking of the separator 23. In some embodiments, the edge of the separator 23 can be fixed by wrapping the tail with adhesive 50, which helps to further improve the energy density of the secondary battery 100.

[0071] As shown in Figure 3, in some embodiments, along the extension direction of the first sealing edge 11 (in some embodiments, the opposite direction of the third direction Z), the length of the first segment 111 is L1, and the length of the second segment 112 is L2, where 0.8mm≤L1≤2mm and 0.8mm≤L2≤2mm. By setting the length of the first segment 111, the gap between the negative electrode 22 and the first sidewall 141 of the packaging bag 10 can be further reduced, thereby further improving the energy density of the secondary battery 100. Moreover, since L1 is not less than 0.8mm, the first edge region 231 can fully enter the first segment 111, thereby more firmly fixing the electrode assembly 20 to the packaging bag 10. In the event of mechanical abuse of the secondary battery 100, the shaking of the electrode assembly 20 within the packaging bag 10 can be further reduced, and the risk of short circuit between the positive electrode 21 and the negative electrode 22 due to folding or wrinkling of the first separator 23A during mechanical abuse can also be further reduced. By setting the length L2 of the second segment 112 to be no less than 0.8 mm, the first sealing edge 11 can have high overall sealing strength, thus further reducing the risk of leakage from the packaging bag 10. At the same time, setting L1 and L2 to be no greater than 2 mm can reduce the impact on the energy density of the secondary battery 100 when the length of the first segment 111 or the second segment 112 is too large.

[0072] In some embodiments, along the extending direction of the first sealing edge 11, the length of the first edge region 231 within the first segment 111 is L3, where 0.4mm ≤ L3 ≤ L1. Therefore, the gap between the negative electrode 22 and the first sidewall 141 of the packaging bag 10 can be further reduced, thereby further improving the energy density of the secondary battery 100. Moreover, since the first edge region 231 can fully enter the first segment 111, the electrode assembly 20 is better fixed to the packaging bag 10. This further reduces the shaking of the electrode assembly 20 within the packaging bag 10 during mechanical abuse of the secondary battery 100, and also further reduces the risk of short circuits caused by folding or wrinkling of the first separator 23A during mechanical abuse, which could lead to contact between the positive electrode 21 and the negative electrode 22.

[0073] In this application, the measurement steps for L1, L2, and L3 can be as follows: after obtaining the cross-section of the first sealing edge 11 using the above method, the values ​​of L1, L2, and L3 in the cross-section are measured using appropriate measuring tools. Although a portion of the first edge region 231 is fused and bonded to the first adhesive layer 110 after encapsulation, the boundary between the first edge region 231 and the first adhesive layer 110 can still be observed from the cross-section.

[0074] As shown in Figures 2 to 4, in some embodiments, the number n of first separators 23A disposed within the first sealing edge 11 is less than the total number N of separators 23 in the second direction Y. Furthermore, the outermost layer of the electrode assembly 20 in the second direction Y is the first separator 23A. Therefore, the outermost first separator 23A can bind at least a portion of the positive electrode 21 and the negative electrode 22 while securing the electrode assembly 20 relatively firmly to the packaging bag 10, further reducing the shaking of the electrode assembly 20 within the packaging bag 10 in the event of mechanical abuse of the secondary battery 100.

[0075] As shown in Figure 8, when the separator 23 forms a Z-shaped structure by alternating bending and folding in both directions, the edges of two adjacent first edge regions 231 in the second direction Y are directly connected within the first sealing edge 11. Therefore, the separator 23 can bind at least part of the positive electrode 21 and the negative electrode 22 while also securing the electrode assembly 20 to the packaging bag 10 more securely. In the event of mechanical abuse of the secondary battery 100, it can further reduce the shaking of the electrode assembly 20 within the packaging bag 10, and further reduce the risk of short circuits caused by the first separator 23A folding or wrinkling during mechanical abuse, which could lead to contact between the positive electrode 21 and the negative electrode 22.

[0076] As shown in Figure 9, in some embodiments, the number n of the first separators 23A within the first segment 111 is equal to the total number N of separators 23 in the second direction Y, meaning all separators 23 are present in the first segment 111. Therefore, this facilitates a more secure fixation of the electrode assembly 20 to the packaging bag 10, further reducing the shaking of the electrode assembly 20 within the packaging bag 10 during mechanical abuse of the secondary battery 100. It also further reduces the risk of short circuits caused by folding or wrinkling of all separators 23 during mechanical abuse, which could lead to contact between the positive electrode 21 and the negative electrode 22.

[0077] As shown in Figure 10, in some embodiments, the first release film 23A includes a substrate layer 233, which includes a first substrate region 2331 located in the main body region 230 and a second substrate region 2332 located in the first edge region 231. The second substrate region 2332 is bonded to the first adhesive layer 110 of the first edge seal 11. Since the first edge region 231 is bonded to the first adhesive layer 110 of the first edge seal 11 through the second substrate region 2332, and both the substrate layer 233 and the first adhesive layer 110 are polymer materials with similar or identical properties, it is more conducive to the full fusion and bonding of the first edge region 231 and the first adhesive layer 110 of the first edge seal 11 (shown in Figure 3), thereby improving the bonding strength between the first edge region 231 and the first edge seal 11. In some embodiments, the substrate layer 233 may further include a third substrate region 2333 located in the second edge region 232, and the second substrate region 2332, the first substrate region 2331, and the third substrate region 2333 are connected sequentially. In some embodiments, the substrate layer 233 includes a second polymer material, each of which is independently selected from at least one of polyethylene, polypropylene, polyurethane, and polyimide. Therefore, the second polymer material of the substrate layer 233 has the same or similar properties as the first polymer material of the first adhesive layer 110. To better fuse and bond the substrate layer 233 with the first adhesive layer 110, the second polymer material of the substrate layer 233 may be the same as the first polymer material of the first adhesive layer 110.

[0078] Referring to Figures 3 and 10, H1 = d1 + d2 + n × S + X1, H2 = d1 + d2 + X2, where d1 is the thickness of the first encapsulation film 101 located in the receiving portion 14, d2 is the thickness of the second encapsulation film 102 located in the receiving portion 14, S is the thickness of the main body region 230 (i.e., the thickness of the first substrate region 2331), and X1 and X2 are adjustment coefficients, -2mm ≤ X1 < 0mm, -2mm ≤ X2 < 0mm. The adjustment coefficients can be set by adjusting the encapsulation pressure and / or temperature of the first segment 111 and the second segment 112, so that the first segment 111 and the second segment 112 each have the required thickness. This not only reduces the risk of the metal layer being exposed due to damage to the first adhesive layer 110 within the first sealing edge 11, reducing potential hazards such as leakage and increased edge voltage in the packaging bag 10, but also ensures that the first sealing edge 11 as a whole has high encapsulation strength, thus further reducing the risk of leakage in the packaging bag 10.

[0079] As shown in Figure 11, in some embodiments, the first separating membrane 23A may also include a substrate layer 233 and an insulating layer 234 stacked together, and the insulating layer 234 contains inorganic particles. The substrate layer 233 includes a first substrate region 2331 located in the main body region 230 and a second substrate region 2332 located in the first edge region 231. The insulating layer 234 is disposed on the first substrate region 2331 but not on the insulating layer 234, and the second substrate region 2332 extends beyond the insulating layer 234. In this case, in the above formula H1=d1+d2+n×S+X1, S is the thickness of the first substrate region 2331. By providing an insulating layer 234 containing inorganic particles on the main body region 230, it is beneficial to improve the wetting effect of the electrolyte in the main body region 230. Meanwhile, no insulating layer 234 is provided on the first edge region 231 within the first segment 111. That is, the first edge region 231 is bonded to the first adhesive layer 110 of the first edge sealing 11 through the second substrate region 2332. Since both the substrate layer 233 and the first adhesive layer 110 are polymer materials with similar or identical properties, it is more conducive to the full fusion and bonding of the first edge region 231 and the first adhesive layer 110 of the first edge sealing 11. In some embodiments, the insulating layer 234 may be provided on one surface of the first substrate region 2331 or on two opposite surfaces of the first substrate region 2331. The inorganic particles are selected from at least one of alumina, silicon dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.

[0080] As shown in Figure 12, the insulating layer 234 can also be disposed on the first substrate region 2331 and the second substrate region 2332 respectively. In this case, the insulating layer 234 disposed on the second substrate region 2332 is bonded to the first adhesive layer 110. In the above formula H1=d1+d2+n×S+X1, S is the sum of the thicknesses of the first substrate region 2331 and the insulating layer 234. In this case, the main body region 230 and the first edge region 231 of the first separator 23A can be integrally formed, thereby simplifying the process.

[0081] As shown in Figure 13, in some embodiments, the first separating membrane 23A may also include a substrate layer 233, an insulating layer 234, and a first adhesive layer 235 stacked together. The first adhesive layer 235 is disposed on the side of the insulating layer 234 opposite to the first substrate layer 233. The substrate layer 233 includes a first substrate region 2331 located in the main body region 230 and a second substrate region 2332 located in the first edge region 231. The insulating layer 234 is disposed on the first substrate region 2331 but not on the second substrate region 2332, and the second substrate region 2332 extends beyond the insulating layer 234 in the third direction Z. The first adhesive layer 235 is disposed on the side of the insulating layer 234 opposite to the substrate layer 233. In this case, in the above formula H1=d1+d2+n×S+X1, S is the thickness of the first substrate region 2331. The first adhesive layer 235 can improve the adhesion between the first separator 23A and the positive electrode 21 or the negative electrode 22, reducing the risk of damage to the electrode assembly 20 structure during mechanical abuse. Meanwhile, no insulating layer 234 and the first adhesive layer 235 are provided on the first edge region 231 within the first sealing edge 11. That is, the first edge region 231 is bonded to the first adhesive layer 110 of the first sealing edge 11 via the second substrate region 2332. Since both the substrate layer 233 and the first adhesive layer 110 are polymer materials with similar or identical properties, it is more conducive to the full fusion and bonding of the first edge region 231 and the first adhesive layer 110 of the first sealing edge 11. In some embodiments, the adhesive material of the first adhesive layer 235 may be selected from at least one of the following: a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of vinylidene fluoride-trichloroethylene, polymethyl methacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, a copolymer of ethylene and vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, amylopectin, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, a copolymer of acrylonitrile-styrene-butadiene, polyvinyl alcohol, polyvinyl ether, polytetrafluoroethylene, polyhexafluoropropylene, a copolymer of styrene-butadiene, or polyvinylidene fluoride. These polymers can produce a strong adhesive effect, bonding the first separator 23A to the positive electrode 21 or the negative electrode 22.

[0082] As shown in FIG. 14, when the insulating layer 234 is provided on the first substrate region 2331 and the second substrate region 2332 respectively, the first adhesive layer 235 is provided on the side of the insulating layer 234 away from the substrate layer 233, that is, the first adhesive layer 235 can also be provided on the first substrate region 2331 and the second substrate region 2332 respectively. At this time, the first adhesive layer 235 provided on the second substrate region 2332 is bonded to the first adhesive layer 110. In the formula H1 = d1 + d2 + n×S + X1, S is the sum of the thicknesses of the first substrate region 2331, the insulating layer 234, and the first adhesive layer 235. Therefore, the main region 230 and the first edge region 231 of the first separator 23A can be integrally formed, thereby simplifying the process.

[0083] As shown in FIGS. 2 and 4, in some embodiments, the second sealing edge 12 includes a third section 121 connected to the second side wall 142 and a fourth section 122 connected to the third section 121 along the extending direction of the second sealing edge 12 (in some embodiments, it is the third direction Z). At least part of each second edge region 232 is provided within the third section 121. After encapsulation, at least part of the second edge region 232 is fused and bonded to the second adhesive layer 120. In some embodiments, after encapsulation, only part of the second edge region 232 is fused and bonded to the second adhesive layer 120. Define the thickness of the third section 121 as H3 and the thickness of the fourth section 122 as H4, and H4 < H3. Among them, when the second sealing edge 12 extends along the third direction Z, the thickness of the third section 121 or the fourth section 122 is its thickness in the second direction Y.

[0084] By setting the third section 121 to have a larger thickness, the corresponding encapsulation pressure and / or temperature used are smaller, which can reduce the risk of the second adhesive layer 120 in the second sealing edge 12 being damaged and the metal layer being exposed. Furthermore, it can reduce the risk of the metal layer contacting the electrolyte and being corroded by the electrolyte, thereby reducing potential hazards such as liquid leakage from the packaging bag 10 and side voltage increase, improving the safety performance of the secondary battery 100. At the same time, the fourth section 122 has a smaller thickness, and the corresponding encapsulation pressure and / or temperature used are larger, making the second sealing edge 12 as a whole have a higher encapsulation strength. Therefore, the risk of liquid leakage from the packaging bag 10 can be further reduced. Moreover, since the risk of liquid leakage from the packaging bag 10, side voltage increase, etc. is reduced after at least part of the second edge region 232 is provided within the third section 121, the gap between the negative electrode plate 22 and the second side wall 142 of the packaging bag 10 can be correspondingly reduced, thereby further improving the energy density of the secondary battery 100. In some embodiments, the distance between the negative electrode plate 22 and the second side wall 142 in the third direction Z can be set as T, where 0.2 mm ≤ T ≤ 2 mm, so that the secondary battery 100 has a higher energy density.

[0085] In addition, since the second edge region 232 is at least partially located within the third segment 121, the shaking of the electrode assembly 20 within the packaging bag 10 can be further reduced when the secondary battery 100 is subjected to mechanical abuse. It can also further reduce the risk of short circuit between the positive electrode 21 and the negative electrode 22 caused by the first separator 23A being folded or wrinkled during mechanical abuse, thereby further improving the safety performance of the secondary battery 100.

[0086] The length settings of the third segment 121 and the fourth segment 122 of the second edge sealing 12 can be referenced to the length settings of the first segment 111 and the second segment 112. The length setting of the second edge region 232 located within the third segment 121 can be referenced to the length setting of the first edge region 231 located within the first segment 111.

[0087] Referring to Figure 15, another embodiment of this application also provides a secondary battery 200. The difference from the secondary battery 100 described above is that the first sealing edge 11 is bent to form a single-fold structure. Specifically, the second segment 112 includes a first segment 1121 connected to the first segment 111 and a second segment 1122 connected to the first segment 1121 along the extension direction of the first sealing edge 11. The second segment 1122 is bent toward the first segment 1121 in a direction away from the second encapsulation film 102. Viewed from the second direction Y, the first segment 1121 and the second segment 1122 overlap. In this case, the first sealing edge 11 first extends along the opposite direction of the third direction Z and then along the third direction Z again, where H2 is the thickness of the first segment 1121 or the second segment 1122 in the second direction Y. Since the second segment 1122 is bent toward the first segment 1121, the size of the secondary battery 200 in the third direction Z can be reduced, further improving the space utilization and energy density of the secondary battery 200. Furthermore, the bending point is located in the thinner second segment 112, which facilitates bending the second segment 112 and reduces the risk of the second segment 1122 opening up compared to the first segment 1121. In addition, it also reduces the risk of the exposed metal layer at the edge of the second segment 1122 easily short-circuiting with the outside, further improving the safety performance of the secondary battery 200.

[0088] To further reduce the risk of the second segment 1122 opening apart compared to the first segment 1121, the secondary battery 200 also includes a first adhesive member 60, and the second segment 1122 is bonded to the first segment 1121 via the first adhesive member 60. The first adhesive member 60 can be double-sided tape or hot melt adhesive. The adhesive layer material in the double-sided tape can be selected from one or more of acrylate, polyurethane, rubber, and silicone. The hot melt adhesive can be selected from one or more of polyolefin hot melt adhesives, polyurethane hot melt adhesives, ethylene and its copolymers hot melt adhesives, polyester hot melt adhesives, polyamide hot melt adhesives, and styrene and its block copolymers hot melt adhesives.

[0089] Referring to Figure 16, another embodiment of this application provides a secondary battery 300. The difference from the secondary battery 100 described above is that the first sealing edge 11 is bent to form a double-folded edge structure. Specifically, the second segment 112 includes a first segment 1121 connected to the first segment 111 and a second segment 1122 connected to the first segment 1121 along the extending direction of the first sealing edge 11. The second segment 1122 is bent toward the first segment 1121 in a direction away from the second encapsulation film 102. Furthermore, the first segment 111 is bent toward the first sidewall 141 in a direction away from the second encapsulation film 102, and the second segment 1122 is disposed between the first segment 1121 and the first sidewall 141 in the third direction Z. This can further reduce the size of the secondary battery 300 in the third direction Z, thereby further improving the space utilization and energy density of the secondary battery 300. At this point, the first sealing edge 11 extends successively along the first direction X and the opposite direction of the first direction X. H1 is the thickness of the first segment 111 in the third direction Z, and H2 is the thickness of the first segment 1121 or the second segment 1122 in the third direction Z. After encapsulation, the second segment 112 can be bent for the first time to form the first segment 1121 and the second segment 1122, thereby protecting the exposed metal layer at the edge of the second segment 112, reducing the risk of short circuits with the outside after the metal layer is exposed, and improving safety. Then, the first segment 111 is bent for the second time onto the first sidewall 141. In some other embodiments, the bending sequence of the double-folded edge structure can also be: the first segment 111 can be bent for the first time onto the first sidewall 141, and then part of the second segment 112 can be bent for the second time to form the first segment 1121 and the second segment 1122, thereby protecting the exposed metal layer at the edge of the second segment 112. The order of the two bending can be selected according to the actual situation, and this application does not impose any restrictions. Therefore, the size of the secondary battery 300 in the third direction Z can be reduced, further improving the space utilization and energy density of the secondary battery 300. Moreover, the bending point is located in the second segment 112, which has a smaller thickness, thus facilitating the bending of the second segment 112 and reducing the risk of the second segment 1122 opening up compared to the first segment 1121.

[0090] To reduce the risk of the first segment 111 opening apart from the first sidewall 141, the secondary battery 300 also includes a second adhesive member 70, and the second segment 1122 is bonded to the first sidewall 141 via the second adhesive member 70. The second adhesive member 70 can be double-sided tape or hot melt adhesive. The adhesive layer material in the double-sided tape can be selected from one or more of acrylate, polyurethane, rubber, and silicone. The hot melt adhesive can be selected from one or more of polyolefin hot melt adhesives, polyurethane hot melt adhesives, ethylene and its copolymers hot melt adhesives, polyester hot melt adhesives, polyamide hot melt adhesives, and styrene and its block copolymers hot melt adhesives.

[0091] The secondary batteries 100, 200, and 300 in this application can be lithium secondary batteries, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0092] Please refer to Figure 17. One embodiment of this application also provides an electronic device 1, which includes a battery compartment 1001 and the aforementioned secondary battery 100 (or secondary batteries 200, 300) disposed within the battery compartment 101. The secondary battery 100 of this application is applicable to electronic devices 1 in various fields. The electronic device 1 is powered by the aforementioned secondary battery 100, which balances high energy density and safety performance. In one embodiment, the electronic device 1 of this application may be, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable C-type devices, mini CD-ROMs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors, etc.

[0093] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with this application are still within the scope of this application.

Claims

1. A secondary battery, comprising a packaging bag, an electrode assembly, and a conductive plate. The packaging bag includes a receiving portion and a first sealing edge. The electrode assembly is disposed within the receiving portion. The conductive plate is electrically connected to the electrode assembly and extends out of the packaging bag. The direction from the electrode assembly to the conductive plate is the first direction. Among them, the electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate, the separator, and the negative electrode plate are sequentially laminated in the second direction to form a laminated structure. The electrode assembly includes N layers of separators in the second direction. The N layers of separators include n layers of first separators, where n ≤ N; the first separator includes a main region and a first edge region connected in the third direction. When observed from the second direction, the main region overlaps with the negative electrode plate, and the first edge region extends from the main region and extends beyond the negative electrode plate; the receiving portion includes a first side wall and a second side wall oppositely disposed in the third direction. The first sealing edge is connected to the first side wall. The first sealing edge includes a first segment connected to the first side wall and a second segment connected to the first segment along the extending direction of the first sealing edge. At least a part of each first edge region is disposed within the first segment. Define the thickness of the first segment as H1, and the thickness of the second segment as H2, where H2 < H1. Among them, the first direction, the second direction, and the third direction are perpendicular to each other pairwise.

2. The secondary battery as described in claim 1, wherein, 0.11 mm ≤ H1 ≤ 0.40 mm, 0.10 mm ≤ H2 ≤ 0.20 mm.

3. The secondary battery as described in claim 1 or 2, wherein, Along the extending direction of the first sealing edge, the length of the first segment is L1, and the length of the second segment is L2. 0.8 mm ≤ L1 ≤ 2 mm, 0.8 mm ≤ L2 ≤ 2 mm.

4. The secondary battery according to claim 3, wherein, Along the extending direction of the first sealing edge, the length of the first edge region disposed within the first segment is L3. 0.4 mm ≤ L3 ≤ L1.

5. The secondary battery as described in any one of claims 1 to 4, wherein, the first separator includes a base material layer. The base material layer includes a first base material region located in the main region and a second base material region located in the first edge region. The packaging bag includes a first packaging film and a second packaging film disposed oppositely. The first packaging film and the second packaging film are bonded to form the first sealing edge. The first sealing edge includes a first protective layer, a first metal layer, a first adhesive layer, a second metal layer, and a second protective layer stacked in sequence. The second base material region is bonded to the first adhesive layer.

6. The secondary battery as described in claim 5, wherein, the first separator further includes an insulating layer containing inorganic particles. The insulating layer is disposed on the first base material region, and the second base material region extends beyond the insulating layer.

7. The secondary battery as described in claim 5, wherein, the first separator further includes an insulating layer containing inorganic particles. The insulating layer is respectively disposed on the first base material region and the second base material region. The insulating layer disposed on the second base material region is bonded to the first adhesive layer.

8. The secondary battery as described in claim 6, wherein, the first separator further includes a first adhesive layer. The first adhesive layer is disposed on the side of the insulating layer away from the base material layer.

9. The secondary battery as described in claim 7, wherein, The first isolation film further includes a first adhesive layer, the first adhesive layer is disposed on a side of the insulating layer away from the base material layer, and the first adhesive layer disposed on the second base material region is adhered to the first adhesive layer.

10. The secondary battery according to any one of claims 5 to 9, wherein, The first adhesive layer includes a first polymer material, the base material layer includes a second polymer material, and the first polymer material and the second polymer material are each independently selected from at least one of polyethylene, polypropylene, polyurethane, and polyimide.

11. The secondary battery as claimed in claim 10, wherein, The first polymer material and the second polymer material are the same material.

12. The secondary battery according to any one of claims 5, 7, and 9, wherein, H1 = d1 + d2 + n×S + X1, H2 = d1 + d2 + X2, where d1 is the thickness of the first encapsulation film in the accommodation part, d2 is the thickness of the second encapsulation film in the accommodation part, S is the thickness of the main body region, and X1 and X2 are adjustment coefficients, -2 mm ≤ X1 < 0 mm, -2 mm ≤ X2 < 0 mm.

13. The secondary battery according to any one of claims 1 to 12, wherein, n < N, and the outermost side of the electrode assembly in the second direction is the first isolation film.

14. The secondary battery according to any one of claims 1 to 13, wherein, Edges of two adjacent first edge regions in the second direction are directly connected within the first sealing edge.

15. The secondary battery according to any one of claims 1 to 14, wherein, The packaging bag includes a second encapsulation film, the second segment includes a first segment connected to the first segment and a second segment connected to the first segment along the extending direction of the first sealing edge, and the second segment is bent towards the first segment along a direction away from the second encapsulation film.

16. The secondary battery as claimed in claim 15, wherein, The secondary battery further includes a first bonding member, and the second segment is adhered to the first segment through the first bonding member.

17. The secondary battery as claimed in claim 15 or 16, wherein, The first segment is bent towards the first side wall along a direction away from the second encapsulation film, and the second segment is disposed between the first segment and the first side wall in the third direction.

18. The secondary battery as claimed in claim 17, wherein, The secondary battery further includes a second bonding member, and the second segment is adhered to the first side wall through the second bonding member.

19. The secondary battery according to any one of claims 1 to 18, wherein, The distance between the negative electrode sheet and the first side wall in the third direction is D, 0.2 mm ≤ D ≤ 2 mm.

20. The secondary battery according to any one of claims 1 to 19, wherein, The packaging bag further includes a second sealing edge connected to the second side wall, the second sealing edge includes a third segment connected to the second side wall and a fourth segment connected to the third segment along the extending direction of the second sealing edge; the first isolation film further includes a second edge region, the first edge region, the main body region, and the second edge region are sequentially connected in the third direction, and from the second direction view, the second edge region extends from the main body region and extends beyond the negative electrode sheet; At least a part of each second edge region is disposed within the third segment, define the thickness of the third segment as H3, the thickness of the fourth segment as H4, and H4 < H3.

21. An electronic device comprising a battery compartment, wherein, The electronic device further includes a secondary battery as described in any one of claims 1 to 20, and the secondary battery is disposed in the battery compartment.

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