Secondary battery, preparation method thereof and electronic device

Abstract

The invention discloses a secondary battery, a preparation method thereof and an electronic device. The secondary battery includes a packaging bag, an electrode assembly, and a tab. The packaging bag comprises a containing part and a first sealing edge. The tab is electrically connected with the electrode assembly and extends out of the packaging bag. The direction in which the tab protrudes out of the electrode assembly is a first direction, the thickness direction of the electrode assembly is a second direction, and the accommodating part comprises a first side wall and a second side wall which are oppositely arranged in a third direction. The first sealing edge comprises a first section connected to the first side wall and a second section connected to the first section in the extending direction of the first sealing edge. The second section is disposed between the first section and the first sidewall in the third direction. The packaging bag comprises a first packaging film and a second packaging film. And the first packaging film and the second packaging film in the first section are stacked. The first packaging film extends from the first section to the second section along the extending direction. A plurality of concave parts are integrally formed in the surface, facing the first side wall, of the second section, the second section is bonded to the first side wall through a first bonding piece, and at least part of the first bonding piece is arranged in the concave parts.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and particularly to a secondary battery, a preparation method of the secondary battery, and an electronic device having the secondary battery. Background Art

[0002] With the popularization of consumer electronic products such as laptop computers, mobile phones, handheld game consoles, tablet computers, mobile power supplies, and drones, people's requirements for the energy density and safety performance of secondary batteries (such as soft-pack secondary batteries) are becoming increasingly strict.

[0003] A soft-pack secondary battery generally includes a packaging bag and an electrode assembly disposed in the packaging bag. In related technologies, the side seal of the packaging bag is bent once or twice to improve the energy density of the soft-pack secondary battery. However, the sealing performance of the single-folded edge structure formed by one-time bending is relatively low, and it is easy to be opened after the secondary battery is dropped or collided, resulting in safety problems such as liquid leakage of the soft-pack secondary battery; the sealing performance of the double-folded edge structure formed by two-time bending is relatively improved, but it will increase the width of the soft-pack secondary battery and reduce the energy density. Therefore, how to make the soft-pack secondary battery have both high energy density and safety performance has become an urgent problem to be solved. Summary of the Invention

[0004] In view of this, it is necessary to provide a secondary battery and a preparation method thereof that can have both high energy density and safety performance. In addition, it is also necessary to provide an electronic device having the secondary battery.

[0005] In a first aspect of the present application, a secondary battery is provided, including a packaging bag, an electrode assembly, and a tab. The packaging bag includes a receiving portion and a first seal. The electrode assembly is disposed in the receiving portion, and the tab is electrically connected to the electrode assembly and extends out of the packaging bag. The direction in which the tab protrudes from the electrode assembly is a first direction, and the thickness direction of the electrode assembly is a second direction. The receiving portion includes a first side wall and a second side wall that are oppositely disposed in a third direction. The first seal includes a first section connected to the first side wall and a second section connected to the first section along the extending direction of the first seal. At least a part of the second section is disposed between the first section and the first side wall in the third direction. The first direction, the second direction, and the third direction are perpendicular to each other pairwise. The packaging bag includes a first packaging film and a second packaging film that are oppositely disposed. The first packaging film and the second packaging film in the first section are stacked. The first packaging film extends from the first section to the second section along the extending direction, and the second packaging film is not provided on the first packaging film in the second section. In the third direction, the second packaging film in the first section is located between the first packaging film in the first section and at least a part of the first packaging film in the second section. A plurality of concave portions are integrally provided on the surface of the second section facing the first side wall, and the concave portions are recessed along the direction away from the first side wall. The secondary battery further includes a first adhesive member, and the second section is adhered to the first side wall through the first adhesive member, and at least a part of the first adhesive member is disposed in the concave portions.

[0006] In this application, there is no second encapsulation film on the first encapsulation film in the second section. Compared with the traditional double-folded edge structure, the size of the first sealing edge in the third direction of this application is smaller, thereby improving the energy density of the secondary battery. At the same time, by providing a plurality of recesses on the surface of the second section and at least partially arranging the first adhesive members in the recesses, not only can the bonding strength between the first adhesive members and the second section be improved, but also a plurality of dispersed stress points can be formed between the first adhesive members and the second section to disperse the stress of the second section under mechanical abuse, improving the problem of stress concentration in the second section caused by the thickness difference between the first section and the second section. Therefore, it is beneficial to reduce the risk that the second section is prone to open relative to the first side wall, enabling the second section to exert a binding force towards the first side wall on the first section to increase the resistance to being flushed open between the first encapsulation film and the second encapsulation film of the first section, making the sealing performance of the first sealing edge higher, thereby improving the safety performance of the secondary battery under mechanical abuse (such as dropping, collision, etc.). Therefore, the secondary battery of this application can balance higher energy density and safety performance.

[0007] Based on the first aspect, in some possible implementation manners, the first encapsulation film includes a first encapsulation layer, a first metal layer, and a first protection layer that are stacked. The second encapsulation film includes a second encapsulation layer, a second metal layer, and a second protection layer that are stacked. At least a part of the first encapsulation layer and at least a part of the second encapsulation layer in the first section are adhered to each other. The recesses are integrally provided on the first protection layer. The plurality of recesses are arranged along the first direction and the second direction respectively. Therefore, it is beneficial to form a plurality of dispersed stress points between the first adhesive members and the second section and the stress is more dispersed, further reducing the risk that the second section is prone to open relative to the first side wall, making the sealing performance of the first sealing edge higher.

[0008] Based on the first aspect, in some possible implementation manners, the depth of the recess in the third direction is H, and the thickness of the first protection layer in the third direction is h, where 0.5h ≤ H ≤ 0.8h. On the one hand, it enables the first adhesive members to be fully filled in the recesses, improving the bonding strength between the first adhesive members and the second section to reduce the risk that the second section is prone to open relative to the first side wall, enabling the first sealing edge to maintain a high sealing performance; on the other hand, it can reduce the risk that the surface of the first polymer layer of the second section facing away from the first side wall simultaneously forms protrusions, resulting in an increase in the thickness of the second section, making the size of the first sealing edge in the third direction smaller, thereby improving the energy density of the secondary battery.

[0009] Based on the first aspect, in some possible implementation manners, the size of the recess in the first direction is W 1 , 0.5H ≤ W 1≤H. On the one hand, it enables the first adhesive member to be fully filled in the recess, improving the adhesive strength between the first adhesive member and the second segment; on the other hand, it enables more dispersed stress points to be formed on the surface of the second segment of a certain size to disperse the stress of the second segment under mechanical abuse. Both of these can reduce the risk that the second segment is prone to opening relative to the first sidewall, enabling the first edge seal to maintain a high sealing performance.

[0010] Based on the first aspect, in some possible implementation manners, the size of the recess in the second direction is W 2 , 0.5H ≤ W 2 ≤H. On the one hand, it enables the first adhesive member to be fully filled in the recess, improving the adhesive strength between the first adhesive member and the second segment; on the other hand, it enables more dispersed stress points to be formed on the surface of the second segment of a certain size to disperse the stress of the second segment under mechanical abuse. Both of these can reduce the risk that the second segment is prone to opening relative to the first sidewall, enabling the first edge seal to maintain a high sealing performance.

[0011] Based on the first aspect, in some possible implementation manners, the distance between two adjacent recesses in the first direction is S 1 , 0 < S 1 ≤ 0.3H. Therefore, it enables more dispersed stress points to be formed on the surface of the second segment of a certain size to disperse the stress of the second segment under mechanical abuse, reducing the risk that the second segment is prone to opening relative to the first sidewall, enabling the first edge seal to maintain a high sealing performance.

[0012] Based on the first aspect, in some possible implementation manners, the distance between two adjacent recesses in the second direction is S 2 , 0 < S 2 ≤ 0.3H. Therefore, it enables more dispersed stress points to be formed on the surface of the second segment of a certain size to disperse the stress of the second segment under mechanical abuse, reducing the risk that the second segment is prone to opening relative to the first sidewall, enabling the first edge seal to maintain a high sealing performance.

[0013] Based on the first aspect, in some possible implementation manners, the accommodating portion further includes a first transition region and a second transition region respectively connected to two edges of the first sidewall in the first direction. The first transition region is closer to the tab in the first direction than the second transition region. Both the first transition region and the second transition region are bent with respect to the first sidewall. Both the first transition region and the second transition region extend from the first sidewall in the direction close to the second sidewall. The orthographic projections of the plurality of recesses in the third direction are all located within the orthographic projection of the first sidewall in the third direction. Therefore, the recesses of the second segment can be fully attached to the first sidewall through the first adhesive member, facilitating the formation of more dispersed stress points between the first adhesive member and the second segment to disperse the stress under mechanical abuse, reducing the risk that the second segment is prone to opening relative to the first sidewall, enabling the first edge seal to maintain a high sealing performance.

[0014] Based on the first aspect, in some possible implementation manners, when observed from the second direction, the packaging bag includes a first edge and a second edge that are oppositely arranged in the first direction, and the tab is connected to the first edge. The first side wall includes a first connecting edge connected to the first transition region. The distance between the plurality of recesses and the first edge in the first direction is D 1 , and the distance between the first connecting edge and the first edge in the first direction is d 1 , d 1 < D 1 ≤1.1d 1 . Therefore, the recesses in the second section can be fully attached to the first side wall through the first adhesive, which is beneficial to forming more dispersed stress points between the first adhesive and the second section to disperse the stress under mechanical abuse, reducing the risk that the second section is prone to opening relative to the first side wall, and enabling the first seal to maintain a high sealing performance.

[0015] Based on the first aspect, in some possible implementation manners, when observed from the second direction, the packaging bag includes a first edge and a second edge that are oppositely arranged in the first direction, and the tab is connected to the first edge. The first side wall includes a second connecting edge connected to the second transition region. The distance between the plurality of recesses and the second edge in the first direction is D 2 , and the distance between the second connecting edge and the second edge in the first direction is d 2 , d 2 < D 2 ≤1.1d 2 . Therefore, the recesses in the second section can be fully attached to the first side wall through the first adhesive, which is beneficial to forming more dispersed stress points between the first adhesive and the second section to disperse the stress under mechanical abuse, reducing the risk that the second section is prone to opening relative to the first side wall, and enabling the first seal to maintain a high sealing performance.

[0016] Based on the first aspect, in some possible implementation manners, the first section includes a third connecting edge connected to the second section. The distance between the plurality of recesses and the third connecting edge along the extending direction is D 3 , the thickness of the first section in the third direction is H 1 , 3H 1 ≤D 3 ≤5H 1 . Therefore, the risk that the first packaging film of the second section is easily broken due to the bending of the second section in the area where the recesses are located can be reduced. Moreover, it is beneficial to form more dispersed stress points between the first adhesive and the second section to disperse the stress under mechanical abuse, both of which can reduce the risk that the second section is prone to opening relative to the first side wall, and enable the first seal to maintain a high sealing performance.

[0017] Based on the first aspect, in some possible implementation manners, the first segment includes a third connecting edge connected to the second segment. The second segment includes a fourth connecting edge disposed opposite to the third connecting edge along the extending direction. The distance between the plurality of concave portions and the fourth connecting edge in the second direction is D 4 , and the spacing between two adjacent concave portions in the second direction is S 2 , 0 < D 4 ≤ S 2 . Therefore, more concave portions can be arranged in the second direction, which is not only beneficial to improving the bonding strength between the first bonding member and the second segment, but also beneficial to forming more dispersed stress points between the first bonding member and the second segment to disperse the stress under mechanical abuse, reducing the risk that the second segment is prone to open relative to the first side wall, and enabling the first edge sealing to maintain a high sealing property.

[0018] Based on the first aspect, in some possible implementation manners, the length of the first segment along the extending direction is L 1 , and the length of the second segment along the extending direction is L 2 , L 2 ≤ L 1 . Therefore, the risk that the second segment is prone to fold over and increase the thickness of the secondary battery when the length of the second segment is relatively large can be reduced, which is beneficial to improving the energy density of the secondary battery. Moreover, the risk that the second segment abuts against the bending portion between the first segment and the first side wall when the length of the second segment is relatively large can also be reduced, making the second segment relatively flat, thereby improving the bonding strength between the first bonding member and the second segment.

[0019] Based on the first aspect, in some possible implementation manners, the length of the first segment along the extending direction is L 1 , and the thickness of the accommodating portion in the second direction is H 0 , 0.6H 0 ≤ L 1 ≤ 0.8H 0 . On the one hand, it can make the encapsulation strength between the first encapsulation film and the second encapsulation film of the first segment relatively high, further improving the safety performance of the secondary battery; on the other hand, it can reduce the risk that the first segment extends beyond the accommodating portion in the second direction and increases the thickness of the secondary battery, which is beneficial to improving the energy density of the secondary battery.

[0020] Based on the first aspect, in some possible implementation manners, the length of the second segment along the extending direction is L 2 , and the thickness of the accommodating portion in the second direction is H 0 , 0.6H 0 ≤ L 2 ≤ 0.8H 0On the one hand, the contact area between the second section and the first side wall can be increased, which is not only beneficial to improving the bonding strength between the first bonding member and the second section, but also conducive to forming more dispersed stress points between the first bonding member and the second section to disperse the stress under mechanical abuse, reducing the risk that the second section is prone to open relative to the first side wall, and enabling the first edge seal to maintain a high sealing performance. On the other hand, the risk of the second section being folded over and increasing the thickness of the secondary battery can be reduced, thereby facilitating the improvement of the energy density of the secondary battery.

[0021] Based on the first aspect, in some possible implementation manners, the positive projection of the concave portion in the third direction is circular or elliptical. Therefore, the stress existing in the second section under mechanical abuse can be distributed along the tangent direction of the contour of the concave portion, making the stress more dispersed, thereby further reducing the problem that the second section is prone to open relative to the first side wall, and making the sealing performance of the first edge seal higher.

[0022] In the second aspect of the present application, an electronic device is provided, which includes a battery compartment and the secondary battery as described above. The secondary battery is disposed in the battery compartment. The electronic device is powered by the above-mentioned secondary battery, and the secondary battery can take into account both high energy density and safety performance.

[0023] In the third aspect of the present application, a method for manufacturing the secondary battery as described above is provided, including the following steps: providing a packaging material, the packaging material includes a first packaging film and a second packaging film, the first packaging film includes a connected first main region and a first edge region, and the second packaging film includes a connected second main region and a second edge region; at least stamping the second main region to form a groove; electrically connecting the electrode assembly with the tab, and placing the electrode assembly with the tab in the groove; disposing the first packaging film and the second packaging film opposite to each other, and packaging the first edge region and the second edge region to form a first edge seal, the first main region and the second main region form a receiving portion, the first edge seal and the receiving portion constitute a packaging bag and the tab extends out of the packaging bag, wherein, the first packaging film and the second packaging film inside the first edge seal overlap to constitute a first section, and the first packaging film extends in a direction away from the receiving portion to exceed the second packaging film to constitute a second section; performing an embossing process on the surface of the second section to form a plurality of concave portions; secondarily bending the first edge seal so that at least a part of the second section is clamped between the first section and the first side wall, and bonding the second section to the first side wall through a first bonding member. The secondary battery manufactured by the above manufacturing method can take into account both high energy density and safety performance.

[0024] Based on the third aspect, in some possible implementation manners, the first encapsulation film further includes a third edge region, the first edge region, the first main body region, and the third edge region are connected in sequence, the second encapsulation film further includes a fourth edge region, the second edge region, the second main body region, and the fourth edge region are connected in sequence. When the first encapsulation film and the second encapsulation film are disposed opposite to each other, the third edge region and the fourth edge region overlap with each other to form an airbag edge. The manufacturing method further includes: performing formation treatment on the secondary battery and encapsulating the airbag edge; cutting off a part of the first encapsulation film and the second encapsulation film of the airbag edge to obtain a second sealing edge, the first encapsulation film and the second encapsulation film inside the second sealing edge overlap to form a third section, and the first encapsulation film extends beyond the second encapsulation film in a direction away from the accommodating portion to form a fourth section; performing an embossing process on the surface of the fourth section to form a plurality of recesses; bending the second sealing edge twice so that at least a part of the fourth section is clamped between the third section and the second side wall, and bonding the fourth section to the second side wall through a second bonding member. By providing the airbag edge, the gas generated during formation is released to the airbag edge, and by making the airbag edge into a second sealing edge with a structure similar to the first sealing edge, the energy density and safety performance of the secondary battery can be further improved. Description of the Drawings

[0025] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0026] Figure 1 is a schematic structural diagram of a secondary battery according to an embodiment of the present application when viewed from a second direction.

[0027] Figure 2 is Figure 1 a cross-sectional view of the secondary battery shown along the cutting line II-II.

[0028] Figure 3 is Figure 2 a partial enlarged view of the secondary battery shown at III.

[0029] Figure 4A is Figure 2 a cross-sectional view of the first sealing edge of the secondary battery shown after being unfolded.

[0030] Figure 4B is Figure 4A a schematic structural diagram of the secondary battery shown when viewed from a second direction.

[0031] Figure 5 is Figure 4A a schematic structural diagram of the first sealing edge shown after being bent once.

[0032] Figure 6 is Figure 4B a partial enlarged view of the first sealing edge shown at VI.

[0033] Figure 7 Flow chart of the manufacturing method of a secondary battery according to an embodiment of the present application.

[0034] Figure 8A is Figure 7 Cross-sectional view after laminating and encapsulating the first encapsulation film and the second encapsulation film to form the first seal edge in the manufacturing method of

[0035] Figure 8B is Figure 8A Schematic structural view of the secondary battery shown when observed from the second direction.

[0036] Figure 9A is for Figure 8A Cross-sectional view after encapsulating the airbag edge of the secondary battery shown.

[0037] Figure 9B is Figure 9A Schematic structural view of the secondary battery shown when observed from the second direction.

[0038] Figure 10A is for Figure 9A Cross-sectional view after cutting off the airbag edge shown.

[0039] Figure 10B is Figure 10A Schematic structural view of the secondary battery shown when observed from the second direction.

[0040] Figure 11A is for Figure 10A Cross-sectional view after cutting off the airbag edge shown.

[0041] Figure 11B is Figure 11A Schematic structural view of the secondary battery shown when observed from the second direction.

[0042] Figure 12 Schematic structural view of an electronic device according to an embodiment of the present application.

[0043] Description of main component symbols

[0044] Electronic device 1

[0045] Packaging bag 10

[0046] First edge 10A

[0047] Second edge 10B

[0048] First seal edge 11

[0049] Second seal edge 12

[0050] Third seal edge 13

[0051] Receiving part 14

[0052] Airbag edge 15

[0053] Electrode assembly 20

[0054] First tab 30

[0055] Second tab 40

[0056] First adhesive 50

[0057] Secondary battery 100

[0058] First encapsulation film 101

[0059] First protective layer 101A

[0060] First metal layer 101B

[0061] First polymer layer 101C

[0062] Second encapsulation film 102

[0063] Second protective layer 102A

[0064] Second metal layer 102B

[0065] Second polymer layer 102C

[0066] First section 111

[0067] Second section 112

[0068] Third section 121

[0069] Fourth section 122

[0070] First side wall 141

[0071] Second side wall 142

[0072] First end wall 143

[0073] Second end wall 144

[0074] First transition region 145

[0075] Second transition region 146

[0076] Edges 151, 152, 153

[0077] Battery compartment 1001

[0078] First edge region 1011

[0079] Third edge region 1012

[0080] The first main body area 1013

[0081] The second edge area 1021

[0082] The fourth edge area 1022

[0083] The second main body area 1023

[0084] The groove 1023A

[0085] The third connecting edge 1111

[0086] The fifth connecting edge 1112

[0087] The recess 1120

[0088] The fourth connecting edge 1121

[0089] The first connecting edge 1411

[0090] The second connecting edge 1412

[0091] The thickness h, H 1 , H 0

[0092] The depth H

[0093] The dimension W 1 , W 2

[0094] The encapsulation width W 3 , W 4

[0095] The spacing S 1 , S 2

[0096] The distance D 1 , D 2 , D 3 , D 4 , d 1 , d 2

[0097] The length L 1 , L 2

[0098] The cutting lines C1, C2, C3

[0099] The first direction X

[0100] The second direction Y

[0101] The third direction Z

[0102] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. Detailed implementation manners

[0103] The technical solutions in the embodiments of the present application will be described clearly and in detail below. Obviously, the described embodiments are some but not all of the embodiments of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0104] Hereinafter, the implementation manners of the present application will be described in detail. However, the present application can be embodied in many different forms and should not be construed as limited to the exemplary implementation manners set forth herein. Instead, these exemplary implementation manners are provided so that this application will be thorough and detailed and will convey to those skilled in the art.

[0105] In addition, for the sake of simplicity and clarity, in the drawings, the dimensions or thicknesses of various components and layers may be enlarged. Throughout the text, the same numerals refer to the same elements. As used herein, the terms "and / or", "as well as / or" include any and all combinations of one or more of the associated listed items. In addition, it should be understood that when element A is referred to as being "connected" to 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.

[0106] Furthermore, when describing the implementation manners of the present application, the use of "may" refers to "one or more implementation manners of the present application".

[0107] The professional terms used herein are for the purpose of describing specific implementation manners and are not intended to limit this application. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. It should be further understood that the term "comprises", when used in this specification, means the presence of the recited features, values, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0108] Spatial - related terms, such as "above", etc., may be used in this document for convenience of description to describe the relationship between an element or feature and another element(s) or feature(s) as illustrated in the figures. It should be understood that, in addition to the directions described in the figures, spatial - related terms are intended to include different directions during the use or operation of the device or apparatus. For example, if the device in the figure is flipped, an element described as "above" or "on" another element or feature will be oriented "below" or "beneath" the other element or feature. Thus, the exemplary term "above" can include both upward and downward directions. It should be understood that although terms such as first, second, third, etc. may be used in this document to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part without departing from the teachings of the exemplary embodiments.

[0109] In this application, for the design relationships of greater than, less than, or not equal to between parameter values, the reasonable errors of the measuring device need to be excluded.

[0110] Please refer to Figure 1 and Figure 2 An embodiment of this application provides a secondary battery 100, which includes a packaging bag 10, an electrode assembly 20, an electrolyte (not shown in the figure), and electrode tabs. The electrode assembly 20 and the electrolyte are disposed inside the packaging bag 10. The electrode tabs may include a first electrode tab 30 and a second electrode tab 40. Both the first electrode tab 30 and the second electrode tab 40 are electrically connected to the electrode assembly 20 and extend out of the packaging bag 10. The first electrode tab 30 and the second electrode tab 40 can be connected to external components (not shown in the figure). A three - dimensional coordinate system is established according to the first direction X, the second direction Y, and the third direction Z that are perpendicular to each other. The direction in which the first electrode tab 30 or the second electrode tab 40 protrudes from the electrode assembly 20 is the first direction X, the thickness direction of the electrode assembly 20 is the second direction Y. In some embodiments, the direction from the first electrode tab 30 to the second electrode tab 40 is the third direction Z.

[0111] As Figure 1As shown, the packaging bag 10 includes a housing portion 14 and a first edge seal 11. The electrode assembly 20 and the electrolyte are disposed in the housing portion 14. The housing portion 14 includes a first side wall 141 and a second side wall 142 disposed opposite to each other in the third direction Z, and also includes a first end wall 143 and a second end wall 144 disposed opposite to each other in the first direction X. The surface of the first side wall 141 extends in the first direction X and the second direction Y, and the surface of the second side wall 142 extends in the first direction X and the second direction Y. The first edge seal 11 is connected to the first side wall 141. The surface of the first end wall 143 extends in the second direction Y and the third direction Z, and the surface of the second end wall 144 extends in the second direction Y and the third direction Z. In some embodiments, the packaging bag 10 may further include a second edge seal 12 and a third edge seal 13, wherein the second edge seal 12 is connected to the second side wall 142, and the third edge seal 13 is connected to the first end wall 143. The first pole tab 30 and the second pole tab 40 may both extend out of the packaging bag 10 from the third edge seal 13.

[0112] The packaging bag 10 further includes a first edge 10A and a second edge 10B that are arranged opposite to each other in the first direction X. The first edge 10A is the edge of the third edge seal 13 that is away from the receiving portion 14 in the first direction X. The second edge 10B is the edge of the receiving portion 14 that is away from the third edge seal 13 in the first direction X. In some embodiments, the second edge 10B overlaps with the positive projection of the second end wall 144 in the second direction Y. Since the first pole tab 30 and the second pole tab 40 can both extend out of the packaging bag 10 from the third edge seal 13, when viewed from the second direction Y, the first pole tab 30 and the second pole tab 40 are connected to the first edge 10A.

[0113] Further, the accommodating portion 14 may also include a first transition zone 145 and a second transition zone 146 respectively connected to two edges of the first side wall 141 in the first direction X. The first transition zone 145 is closer to the first pole tab 30 or the second pole tab 40 than the second transition zone 146 in the first direction X. The first transition zone 145 is connected to the first side wall 141 and the first end wall 143, and the second transition zone 146 is connected to the first side wall 141 and the second end wall 144. The first transition zone 145 and the second transition zone 146 are both bent compared to the first side wall 141. The first transition zone 145 and the second transition zone 146 both extend from the first side wall 141 in a direction close to the second side wall 142. Optionally, when viewed from the second direction Y, the first transition zone 145 and the second transition zone 146 are both arc-shaped.

[0114] like Figure 2 and Figure 3 As shown, the first edge seal 11 is bent twice to form a double edge structure. The first edge seal 11 includes a first section 111 connected to the first side wall 141 and an extension direction of the first edge seal 11 (such as Figure 2 and Figure 3As shown, the extending direction of the first sealing edge 11 is a bent direction, and the second section 112 is connected to the first section 111. At least a part of the second section 112 is disposed between the first section 111 and the first side wall 141 in the third direction Z. When observed from the third direction Z, there is an overlap between the first section 111 and the second section 112. Since the first sealing edge 11 is bent, the size of the secondary battery 100 in the third direction Z can be reduced, and the space utilization rate and energy density of the secondary battery 100 can be improved.

[0115] The packaging bag 10 includes a first packaging film 101 and a second packaging film 102 that are oppositely disposed in the second direction Y. The first packaging film 101 and the second packaging film 102 in the first section 111 are stacked. The first packaging film 101 extends from the first section 111 to the second section 112 along the extending direction of the first sealing edge 11, but the second packaging film 102 does not extend to the second section 112. That is, the second packaging film 102 is not provided on the first packaging film 101 in the second section 112. After the first sealing edge 11 is bent twice, in the third direction Z, the second packaging film 102 of the first section 111 is located between the first packaging film 101 of the first section 111 and at least a part of the first packaging film 101 of the second section 112. Since the second packaging film 102 is not provided on the first packaging film 101 in the second section 112, the thickness of the second section 112 in the third direction Z is smaller than that of the first section 111. Therefore, compared with the traditional double-folded edge structure, the thickness of the first sealing edge 11 of the present application in the third direction Z is smaller, thereby further improving the space utilization rate and energy density of the secondary battery 100.

[0116] With reference to Figure 4A and Figure 4B , where Figure 4A and Figure 4B are schematic structural diagrams of the first sealing edge 11 when it is unfolded to a straight state. Among them, the first section 111 includes a third connecting edge 1111 connected to the second section 112 and a fifth connecting edge 1112 connected to the first side wall 141. The second section 112 includes a fourth connecting edge 1121 that is oppositely disposed to the third connecting edge 1111 along the extending direction of the first sealing edge 11. It can be understood that the third connecting edge 1111 is the boundary where the double-layer packaging film transitions to the single-layer packaging film along the extending direction of the first sealing edge 11. When the first sealing edge 11 is bent relative to the first side wall 141, an arc segment will be formed at the bending position, and the fifth connecting edge 1112 is the position where the first packaging film 101 or the second packaging film 102 is connected to the arc segment (that is, the arc segment formed by the bending of the non-overlapped first packaging film 101 and second packaging film 102 in the first section 111). The fourth connecting edge 1121 is the trailing edge of the first sealing edge 11 along its extending direction.

[0117] In some embodiments, the first encapsulation film 101 and the second encapsulation film 102 are an integral structure 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 multi-layer sheets. As Figure 3 shown, the first encapsulation film 101 may include a first protective layer 101A, a first metal layer 101B, and a first polymer layer 101C that are sequentially stacked. The first polymer layer 101C is closer to the electrode assembly 20 than the first protective layer 101A. The material of the first protective layer 101A may be a polymer resin, which can be used to protect the first metal layer 101B, reduce the risk of damage to the first metal layer 101B due to external forces, and at the same time delay the penetration of air in the external environment to maintain a normal operating environment inside the secondary battery 100. In some embodiments, the material of the first protective layer 101A may be selected from at least one of polyethylene terephthalate, polybutylene terephthalate, polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyamide, and polyimide. The first metal layer 101B can be used to delay the penetration of moisture in the external environment and reduce the damage caused by external forces to the electrode assembly 20. In some embodiments, the first metal layer 101B may be an aluminum foil layer or a steel foil layer. The first polymer layer 101C has the property of heating and melting, can be used for encapsulation, and can reduce the risk of the multi-layer sheet being dissolved or swollen by organic solvents in the electrolyte. The first polymer layer 101C can also be used to reduce the risk of the electrolyte in the electrolyte contacting the first metal layer 101B and causing corrosion of the metal layer. In some embodiments, the first polymer layer 101C includes a first polymer material, which may be selected from at least one of polyethylene, polypropylene, polyurethane, and polyimide.

[0118] The second encapsulation film 102 may include a second protective layer 102A, a second metal layer 102B, and a second polymer layer 102C that are sequentially stacked. 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 102A, the second metal layer 102B, and the second polymer layer 102C are the same as the materials of the first protective layer 101A, the first metal layer 101B, and the first polymer layer 101C, respectively. When preparing the packaging bag 10, a certain temperature and pressure can be applied to at least a part of the first encapsulation film 101 in the first section 111 and at least a part of the second encapsulation film 102 in the first section 111 by using the sealing head of the encapsulation device, so that at least a part of the first polymer layer 101C in the first section 111 and at least a part of the second polymer layer 102C in the first section 111 are melted and bonded together.

[0119] As Figure 3As shown, on the surface of the second section 112 facing the first sidewall 141, a plurality of recesses 1120 are integrally provided. The recesses 1120 are recessed in a direction away from the first sidewall 141. Among them, when the first encapsulation film 101 includes a first protective layer 101A, a first metal layer 101B, and a first polymer layer 101C that are sequentially stacked, the recesses 1120 are integrally provided on the first protective layer 101A. When manufacturing the recesses 1120, an embossing process can be performed on the surface of the first protective layer 101A of the second section 112 facing the first sidewall 141 through a pressing roller, so that the surface of the first protective layer 101A of the second section 112 facing the first sidewall 141 is recessed in a direction away from the first sidewall 141 to form a plurality of recesses 1120. And through the embossing process, in addition to the surface of the first protective layer 101A of the second section 112 being recessed in a direction away from the first sidewall 141, the surface of the first metal layer 101B of the second section 112 facing the first sidewall 141 and the surface of the first polymer layer 101C facing the first sidewall 141 may also be deformed synchronously in a direction away from the first sidewall 141. For example, the surface of the first metal layer 101B of the second section 112 facing the first sidewall 141 may be recessed in a direction away from the first sidewall 141.

[0120] As Figure 5 shown, among them, after the first edge 11 is encapsulated and embossed, the first edge 11 can be first bent for the first time, so that the second section 112 is stacked on the first section 111 in the second direction Y, thereby protecting the second metal layer 102B exposed at the edge of the second encapsulation film 102 of the first section 111, reducing the risk of easy short - circuiting with the outside after the second metal layer 102B is exposed, and improving safety. The bending position of the first bending is located at the second section 112 with a smaller thickness, so as to facilitate bending. Then, the first section 111 and the second section 112 that are stacked on each other are bent for the second time onto the first sidewall 141 to form Figure 2 the double - folded edge structure shown. In other embodiments, the bending sequence of the double - folded edge structure can also be: first, the entire first edge 11 is bent for the first time onto the first sidewall 141, and then the first edge 11 is bent for the second time, so that the second section 112 is stacked on the first section 111 in the third direction Z. The sequence of the two bends can be selected according to the actual situation, and the present application does not make any restrictions.

[0121] As Figure 3As shown, the secondary battery 100 further includes a first adhesive member 50. The second section 112 is adhered to the first side wall 141 through the first adhesive member 50, thereby reducing the risk of the second section 112 opening relative to the first side wall 141. Moreover, at least a part of the first adhesive member 50 is filled in the recess 1120. On the one hand, it is not only beneficial to form a strong mechanical biting effect between the first adhesive member 50 and the second section 112, but also beneficial to increase the bonding area between the first adhesive member 50 and the second section 112, thereby improving the bonding strength between the first adhesive member 50 and the second section 112 and reducing the risk of the second section 112 opening relative to the first side wall 141. On the other hand, the first adhesive members 50 disposed in the plurality of recesses 1120 can form a plurality of dispersed stress points between the first adhesive member 50 and the second section 112. The above-mentioned plurality of dispersed stress points are beneficial to disperse local stress under mechanical abuse, and improve the problem that the thickness difference between the first section 111 and the second section 112 causes stress concentration in the second section 112 and the second section 112 is prone to open relative to the first side wall 141 under stress. Optionally, the first adhesive member 50 is a hot melt adhesive. The material of the hot melt adhesive can be selected from one or several of polyolefin hot melt adhesives, polyurethane hot melt adhesives, ethylene and its copolymer hot melt adhesives, polyester hot melt adhesives, polyamide hot melt adhesives, styrene and its block copolymer hot melt adhesives. At least one additive such as a curing agent, a toughening agent, an antioxidant, an ultraviolet absorber, a filler, etc. can also be selectively added to the first adhesive member 50 according to actual needs.

[0122] In the present application, the first edge 11 is bent twice to form a double-edge structure, such that the second segment 112 is disposed between the first segment 111 and the first side wall 141 in the third direction Z. By arranging that the second encapsulation film 102 is not provided on the first encapsulation film 101 within the second segment 112, compared with the conventional double-edge structure, the size of the first edge 11 in the third direction Z of the present application is smaller, thereby improving the space utilization rate and energy density of the secondary battery 100. Meanwhile, by providing a plurality of recesses 1120 on the surface of the second segment 112 and at least part of the first bonding member 50 is disposed within the recesses 1120, not only can the bonding strength between the first bonding member 50 and the second segment 112 be improved, but also a plurality of dispersed stress points can be formed between the first bonding member 50 and the second segment 112 to disperse the stress of the second segment 112 under mechanical abuse, improving the problem of stress concentration in the second segment 112 caused by the thickness difference between the first segment 111 and the second segment 112. Therefore, it is beneficial to reduce the risk that the second segment 112 is prone to open relative to the first side wall 141, such that the second segment 112 can apply a binding force towards the first side wall 141 to the first segment 111 to increase the resistance to being burst open between the first encapsulation film 101 and the second encapsulation film 102 of the first segment 111, making the sealing performance of the first edge 11 higher, thereby improving the safety performance of the secondary battery 100 under mechanical abuse (such as dropping, collision, etc.). Therefore, the secondary battery 100 of the present application can balance high energy density and safety performance.

[0123] As Figure 2 shown, it can be understood that, in order to further improve the energy density and safety performance of the secondary battery 100, the second edge 12 can be arranged to have a structure similar to that of the first edge 11. For example, the second edge 12 can be bent twice to form a double-edge structure, such that the second edge 12 includes a third segment 121 connected to the second side wall 142 and a fourth segment 122 connected to the third segment 121 along the extending direction of the second edge 12. The fourth segment 122 is provided with recesses (not shown in the figure), and after being bent twice, the fourth segment 122 is located between the third segment 121 and the second side wall 142 in the third direction Z, and the fourth segment 122 is bonded to the second side wall 142 by a second bonding member 60.

[0124] As Figure 3 shown, in some embodiments, the plurality of recesses 1120 can be arranged along the first direction X and the second direction Y respectively. For example, the plurality of recesses 1120 can be arranged in an array. As Figure 6 shown, wherein Figure 6It is a partial enlarged view after the first edge 11 is unfolded to a flat state. It can be understood that when the first edge 11 is unfolded, a plurality of concave portions 1120 are arranged along the first direction X and the third direction Z respectively. Therefore, it is beneficial to form a plurality of dispersed stress points between the first bonding member 50 and the second section 112 and the stress is more dispersed, further reducing the risk that the second section 112 is prone to open relative to the first side wall 141, and making the sealing performance of the first edge 11 higher.

[0125] In some embodiments, the positive projection of the concave portion 1120 in the third direction Z can be circular, oval, triangular, square, trapezoidal, rhombic or other polygonal shapes. It can be understood that as Figure 6 shown, when the first edge 11 is unfolded, the positive projection of the concave portion 1120 in the second direction Y is circular, oval, triangular, square, trapezoidal, rhombic or other polygonal shapes. Optionally, the positive projection of the concave portion 1120 in the third direction Z is circular or oval. At this time, the stress existing in the second section 112 under mechanical abuse can be distributed along the tangent direction of the contour of the concave portion 1120, making the stress more dispersed, thereby further reducing the problem that the second section 112 is prone to open relative to the first side wall 141, and making the sealing performance of the first edge 11 higher. In this embodiment, the positive projection of the concave portion 1120 in the third direction Z is circular, thereby further dispersing the stress of the second section 112, reducing the risk that the second section 112 is prone to open relative to the first side wall 141, and making the sealing performance of the first edge 11 higher.

[0126] As Figure 3 shown, in some embodiments, the depth of the concave portion 1120 in the third direction Z is H, and the thickness of the first protective layer 101A in the third direction Z is h, 0.5h ≤ H ≤ 0.8h. By defining the lower limit of H, the first bonding member 50 can be fully filled in the concave portion 1120, improving the bonding strength between the first bonding member 50 and the second section 112 to reduce the risk that the second section 112 is prone to open relative to the first side wall 141, so that the first edge 11 can maintain a high sealing performance; by defining the upper limit of H, the risk of increasing the thickness of the second section 112 caused by the formation of protrusions on the surface of the first polymer layer 101C of the second section 112 away from the first side wall 141 (at this time, the second section 112 is bent as a whole) can be reduced, making the size of the first edge 11 in the third direction Z smaller, thereby improving the space utilization rate and energy density of the secondary battery 100.

[0127] In this application, the measuring steps for h and H can be as follows: (1) Discharge the secondary battery 100; (2) Prepare a resin composition, which is formulated by mixing a crystal glue resin matrix (such as epoxy resin), a catalyst, and a curing agent in a certain proportion; (3) Pour the resin composition into a mold, cut open the accommodating portion 14 of the packaging bag 10 of the secondary battery 100 and place it obliquely in the mold so that the resin composition slowly flows into the packaging bag 10 through the cut; (4) Adjust the secondary battery 100 to a horizontal position, discharge the excess air bubbles, and then let it stand until the resin composition solidifies; (5) Cut the secondary battery 100 along a cross-section perpendicular to the first direction X and passing through at least one recess 1120 and polish the cut surface to obtain a cross-section of the sample, and then use a suitable measuring tool (such as a micrometer) to measure the thickness h of the first protective layer 101A and the depth of the recess 1120 in the above cross-section; (6) Repeat to take multiple cross-sections and measure the depth of the recess 1120 in each cross-section, and the deepest measured depth is the value of H.

[0128] As Figure 6 shown, in some embodiments, the size of the recess 1120 in the first direction X is W 1 , 0.5H ≤ W 1 ≤ H. By defining the lower limit of W 1 , the first bonding member 50 can be fully filled in the recess 1120, improving the bonding strength between the first bonding member 50 and the second section 112; by defining the upper limit of W 1 , more dispersed stress points can be formed on the surface of the second section 112 of a certain size to disperse the stress of the second section 112 under mechanical abuse. This can reduce the risk that the second section 112 is prone to open relative to the first side wall 141, enabling the first seal 11 to maintain a high sealing performance. Similarly, when the size of the recess 1120 in the second direction Y is W 2 (as Figure 6 shown, W 2 is the size of the recess 1120 in the third direction Z when the first seal 11 is unfolded), 0.5H ≤ W 2 ≤ H can be set. Among them, when the positive projection of the recess 1120 in the third direction Z is circular, W 1 is approximately equal to W 2 . In this application, the measuring steps for W 1 and W 2 can be as follows: (1) Separate the second section 112 and the first bonding member 50 so that the surface of the second section 112 facing the first side wall 141 and the recess 1120 provided on this surface are exposed; (2) Then use a suitable measuring tool to measure the sizes of the recess 1120 along the first direction X and the second direction Y respectively, and the measured sizes are the values of W 1 and W 2 .

[0129] As Figure 6 shown, in some embodiments, the distance between two adjacent recesses 1120 in the first direction X is S 1 , 0 < S 1 ≤ 0.3H. Thus, more dispersed stress points can be formed on the surface of the second section 112 of a certain size to disperse the stress of the second section 112 under mechanical abuse, which can reduce the risk that the second section 112 is prone to open relative to the first sidewall 141, enabling the first seal 11 to maintain a high sealing performance. Similarly, when the distance between two adjacent recesses 1120 in the second direction Y is S 2 (as Figure 6 shown, S 2 is the distance between two adjacent recesses 1120 in the third direction Z when the first seal 11 is unfolded), 0 < S 2 ≤ 0.3H can be set. In this application, the measurement steps of S 1 and S 2 can be obtained by measuring with a suitable measuring tool after separating the second section 112 and the first adhesive member 50 by a similar method.

[0130] As Figure 4B shown, in some embodiments, when the accommodating portion 14 further includes a first transition region 145 and a second transition region 146, the orthographic projections of all the recesses 1120 in the third direction Z are located within the orthographic projection of the first sidewall 141 in the third direction Z. The orthographic projection of each recess 1120 in the third direction Z does not fall within the orthographic projection of the first transition region 145 or the second transition region 146 in the third direction Z. In this way, when the first seal 11 is bent twice to form a double-folded edge structure, the recesses 1120 of the second section 112 can be fully attached to the first sidewall 141 through the first adhesive member 50, which is conducive to forming more dispersed stress points between the first adhesive member 50 and the second section 112 to disperse the stress under mechanical abuse, reducing the risk that the second section 112 is prone to open relative to the first sidewall 141, enabling the first seal 11 to maintain a high sealing performance (it can be understood that if the orthographic projection of at least one recess 1120 in the third direction Z falls within the orthographic projection of the first transition region 145 or the second transition region 146 in the third direction Z, after the first seal 11 is bent twice to form a double-folded edge structure, since the first transition region 145 and the second transition region 146 are bent relative to the first sidewall 141, a part of the second section 112 provided with the above at least one recess 1120 fails to be fully attached to the first transition region 145 or the second transition region 146 through the first adhesive member 50, resulting in a relatively reduced number of stress points formed between the first adhesive member 50 and the second section 112, and also resulting in a relatively reduced bonding strength between the first adhesive member 50 and the second section 112).

[0131] As Figure 4BAs shown, among them, the first side wall 141 includes a first connecting edge 1411 connected to the first transition region 145 and a second connecting edge 1412 connected to the second transition region 146. The first connecting edge 1411 and the second connecting edge 1412 are the two edges of the first side wall 141 in the first direction X. The distance between all the recesses 1120 and the first edge 10A in the first direction X is D 1 , the distance between the first connecting edge 1411 and the first edge 10A in the first direction X is d 1 , d 1 < D 1 ≤ 1.1d 1 . In this way, it can also be ensured that the positive projection of each recess 1120 in the third direction Z does not fall within the positive projection of the first transition region 145 in the third direction Z. This is beneficial to forming more dispersed stress points between the first adhesive 50 and the second section 112 to disperse the stress under mechanical abuse, reducing the risk that the second section 112 is prone to opening relative to the first side wall 141, and enabling the first sealing edge 11 to maintain a high sealing performance. Further, when the distance between all the recesses 1120 and the second edge 10B in the first direction X is D 2 , and the distance between the second connecting edge 1412 and the second edge 10B in the first direction X is d 2 , it can also be set that d 2 < D 2 ≤ 1.1d 2 . In this way, it can also be ensured that the positive projection of each recess 1120 in the third direction Z does not fall within the positive projection of the second transition region 146 in the third direction Z. This is beneficial to forming more dispersed stress points between the first adhesive 50 and the second section 112 to disperse the stress under mechanical abuse, reducing the risk that the second section 112 is prone to opening relative to the first side wall 141, and enabling the first sealing edge 11 to maintain a high sealing performance. In this application, the measurement steps of D 1 and D 2 can be obtained by measuring with a suitable measuring tool after separating the second section 112 and the first adhesive 50 by a similar method

[0132] As Figure 3 and Figure 4B shown, in some embodiments, the distance between all the recesses 1120 and the third connecting edge 1111 along the extending direction of the first sealing edge 11 is D 3 , the thickness of the first section 111 in the third direction Z is H 1 , 3H 1 ≤ D 3 ≤ 5H 1In this way, the risk that the first encapsulation film 101 of the second section 112 is easily broken due to the bending of the second section 112 in the region where the concave portion 1120 is located can be reduced. Moreover, it is also beneficial to form more dispersed stress points between the first bonding member 50 and the second section 112 to disperse the stress under mechanical abuse. All of these can reduce the risk that the second section 112 is easily opened relative to the first side wall 141, so that the first sealing edge 11 can maintain a high sealing performance. As Figure 4B shown, in the present application, the measurement step of D 3 can be to separate the second section 112 and the first bonding member 50 by a similar method and then unfold the first sealing edge 11 to a flat state, and then use a suitable measuring tool to measure the distance between all the concave portions 1120 and the third connecting edge 1111 along the third direction Z. The measured distance is D 3 .

[0133] In some embodiments, the distance between all the concave portions 1120 and the fourth connecting edge 1121 in the second direction Y is D 4 , and the distance between two adjacent concave portions 1120 in the second direction Y is S 2 , 0 < D 4 ≤ S 2 . In this way, more concave portions 1120 can be arranged in the second direction Y, which is not only beneficial to improving the bonding strength between the first bonding member 50 and the second section 112, but also beneficial to forming more dispersed stress points between the first bonding member 50 and the second section 112 to disperse the stress under mechanical abuse, reducing the risk that the second section 112 is easily opened relative to the first side wall 141, so that the first sealing edge 11 can maintain a high sealing performance. As Figure 6 shown, in the present application, the measurement step of D 4 can be to separate the second section 112 and the first bonding member 50 by a similar method and then unfold the first sealing edge 11 to a flat state, and then use a suitable measuring tool to measure the distance between all the concave portions 1120 and the fourth connecting edge 1121 along the third direction Z. The measured distance is D 4 .

[0134] In some embodiments, the length of the first section 111 along the extending direction of the first sealing edge 11 is L 1 , and the length of the second section 112 along the extending direction of the first sealing edge 11 is L 2 , L 2 ≤ L 1Thus, the risk of the second section 112 being folded and causing an increase in the thickness of the secondary battery 100 can be reduced, which is conducive to improving the energy density of the secondary battery 100. Moreover, the risk of the second section 112 abutting against the bending portion between the first section 111 and the first side wall 141 when the length of the second section 112 is relatively large can also be reduced, making the second section 112 relatively flat, thereby improving the bonding strength between the first bonding member 50 and the second section 112. As Figure 4B shown, in this application, L 1 and L 2 can be measured by separating the second section 112 and the first bonding member 50 by a similar method and then unfolding the first sealing edge 11 to a flat state, and then using a suitable measuring tool to measure the lengths of the first section 111 and the second section 112 along the third direction Z respectively. The measured lengths are L 1 and L 2 .

[0135] When the thickness of the accommodating portion 14 in the second direction Y is H 0 (marked in Figure 2 ), it is also possible to set 0.6H 0 ≤L 1 ≤0.8H 0 . By defining the lower limit of L 1 , a relatively high encapsulation strength can be achieved between the first encapsulation film 101 and the second encapsulation film 102 of the first section 111, further improving the safety performance of the secondary battery 100. By defining the upper limit of L 1 , the risk of the first section 111 exceeding the accommodating portion 14 in the second direction Y and causing an increase in the thickness of the secondary battery 100 can be reduced, which is conducive to improving the energy density of the secondary battery 100.

[0136] Moreover, it is also possible to set 0.6H 0 ≤L 2 ≤0.8H 0 . By defining the lower limit of L 2 , the contact area between the second section 112 and the first side wall 141 can be increased, which is not only conducive to improving the bonding strength between the first bonding member 50 and the second section 112, but also conducive to forming more dispersed stress-bearing points between the first bonding member 50 and the second section 112 to disperse the stress under mechanical abuse, reducing the risk of the second section 112 being easily opened relative to the first side wall 141, and enabling the first sealing edge 11 to maintain a relatively high sealing performance. By defining the upper limit of L 2 , the risk of the second section 112 being folded and causing an increase in the thickness of the secondary battery 100 can be reduced, which is conducive to improving the energy density of the secondary battery 100.

[0137] Among them, the secondary battery 100 of the present application can be a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0138] Please refer to Figure 7 , an embodiment of the present application also provides a method for manufacturing the above secondary battery 100. According to different requirements, the order of steps of the manufacturing method can be changed, and some steps can be omitted or combined. The manufacturing method includes the following steps:

[0139] Step S1: Provide a packaging material, which includes a first packaging film 101 and a second packaging film 102.

[0140] Among them, as Figure 8A and Figure 8B shown, the first packaging film 101 includes a first edge area 1011, a first main area 1013, and a third edge area 1012 connected in sequence, and the second packaging film 102 includes a second edge area 1021, a second main area 1023, and a fourth edge area 1022 connected in sequence.

[0141] Step S2: At least stamp the second main area 1023 to form a groove 1023A.

[0142] Step S3: Electrically connect the electrode assembly 20 to the first pole ear 30 and the second pole ear 40, and place the electrode assembly 20 with the first pole ear 30 and the second pole ear 40 in the groove 1023A.

[0143] Step S4: Arrange the first packaging film 101 and the second packaging film 102 opposite to each other, and package the first edge area 1011 and the second edge area 1021 to form a first seal 11 of the packaging bag 10. The first main area 1013 and the second main area 1023 form a receiving portion 14 of the packaging bag 10, and the first pole ear 30 and the second pole ear 40 extend out of the packaging bag 10.

[0144] Among them, the first packaging film 101 and the second packaging film 102 of the first seal 11 overlap, and the first packaging film 101 extends from the overlapping area in a direction away from the first side wall 141 to exceed the second packaging film 102. The overlapping first packaging film 101 and second packaging film 102 constitute a first section 111 of the first seal 11, and the first packaging film 101 exceeding the second packaging film 102 constitutes a second section 112 of the first seal 11. Among them, the third seal 13 can be formed simultaneously with the first seal 11.

[0145] In some embodiments, the third edge area 1012 and the fourth edge area 1022 overlap each other to form an air bag edge 15 of the packaging bag 10. As Figure 8BAs shown, further, the airbag edge 15 can extend beyond the third sealing edge 13 in the first direction X (i.e., beyond the first edge 10A). During encapsulation, the edges 151 of the airbag edge 15 that extend beyond the third sealing edge 13 and the edge 152 facing away from the second sidewall 142 can be encapsulated synchronously. Figure 8B The filled-in lines in it show the encapsulated part between the first encapsulation film 101 and the second encapsulation film 102.

[0146] Step S5, perform formation treatment on the secondary battery 100 so that the gas generated during formation is released to the airbag edge 15, and then as Figure 9A and Figure 9B shown, encapsulate the edge 153 where the airbag edge 15 is connected to the second sidewall 142.

[0147] In some embodiments, as Figure 9B shown, in the third direction Z, the encapsulation width W of the edge 151 of the airbag edge 15 3 is less than the encapsulation width W of the edge 153 4 .

[0148] Step S6, as Figures 9A to 11B shown, cut off part of the first encapsulation film 101 and the second encapsulation film 102 of the airbag edge 15 to obtain the second sealing edge 12.

[0149] Among them, part of the airbag edge 15 can be cut three times. As Figure 9A and Figure 9B shown, the cutting line C1 of the first cut extends along the first direction X and is located between the edge 153 where the airbag edge 15 is connected to the second sidewall 142 and the edge 152 facing away from the second sidewall 142 in the third direction Z. The cutting line C2 of the second cut is flush with the first edge 10A and extends along the third direction Z, and is used to cut off the part of the airbag edge 15 that extends beyond the third sealing edge 13. Since it is set in step S4 that the airbag edge 15 extends beyond the third sealing edge 13 in the first direction X and the part of the airbag edge 15 that extends beyond the third sealing edge 13 is encapsulated, and since it is set in step S5 that the encapsulation width W of the edge 151 of the airbag edge 15 3 is less than the encapsulation width W of the edge 153 4 , therefore as Figure 10A shown, after the first cut and the second cut, the first encapsulation film 101 and the second encapsulation film 102 adjacent to the cutting lines C1 and C2 are not bonded. As Figure 11A and Figure 11B shown, the cutting line C3 of the third cut extends along the first direction X and is used to cut off the second encapsulation film 102 that is not bonded to the first encapsulation film 101.

[0150] At this time, as Figure 11A and Figure 11BAs shown, the remaining airbag edge 15 forms the second sealing edge 12. The first encapsulation film 101 and the second encapsulation film 102 inside the second sealing edge 12 overlap, and the first encapsulation film 101 extends from the overlapping area in a direction away from the second side wall 142 to extend beyond the second encapsulation film 102. The mutually overlapping first encapsulation film 101 and second encapsulation film 102 constitute the third section 121 of the second sealing edge 12, and the first encapsulation film 101 that extends beyond the second encapsulation film 102 constitutes the fourth section 122 of the second sealing edge 12.

[0151] Step S7, as Figure 4A and Figure 4B shown, an embossing process is performed on the surface of the second section 112 to form a plurality of recesses 1120.

[0152] In some embodiments, an embossing process may also be performed on the surface of the fourth section 122 to form a plurality of recesses (not shown in the figure).

[0153] Step S8, as Figure 2 shown, the first sealing edge 11 is bent twice to form a double-folded edge structure, and the second section 112 is bonded to the first side wall 141 through the first bonding member 50.

[0154] Among them, after the first sealing edge 11 is bent twice, the second section 112 is disposed between the first section 111 and the first side wall 141 in the third direction Z. In some embodiments, the second sealing edge 12 may also be bent twice to form a double-folded edge structure, and the fourth section 122 is bonded to the second side wall 142 through the second bonding member 60.

[0155] Please refer to Figure 12 , an embodiment of the present application further provides an electronic device 1. The electronic device 1 includes a battery compartment 1001 and the above-mentioned secondary battery 100 disposed in the battery compartment 101. Among them, the secondary battery 100 of the present application is applicable to electronic devices 1 in various fields. The electronic device 1 is powered by the above-mentioned secondary battery 100, and the secondary battery 100 can balance high energy density and safety performance. In one embodiment, the electronic device 1 of the present application may be, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal TV, a portable cleaner, a portable C machine, a mini disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a moped, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flash, a camera, a large household battery, and a lithium ion capacitor, etc.

[0156] The present application will be described in detail below through specific examples and comparative examples. Among them, taking the wound-type lithium-ion secondary battery as an example and combining with the specific preparation process and testing method to describe the present application. Those skilled in the art should understand that the preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application.

[0157] Example 1

[0158] (1) Preparation of the negative electrode sheet: The negative electrode active material artificial graphite, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed according to a weight ratio of 98:1:1, and deionized water is added as a solvent to prepare a slurry with a solid content of 50 wt%. The slurry is stirred evenly. The slurry is evenly coated on one surface of a copper foil with a thickness of 6 μm, and it should be noted that the coating is an intermittent coating, leaving an empty foil area. It is dried at 100 °C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side and a coating thickness of 95 μm. The above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a negative electrode active material layer coated on both sides.

[0159] (2) The positive electrode active material lithium cobaltate (LiCoO 2 ), conductive carbon black (Super P), carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) are mixed according to a weight ratio of 97.6:0.6:0.5:1.3, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 72 wt%. The slurry is stirred evenly. The slurry is evenly coated on one surface of an aluminum foil with a thickness of 10 μm, and it should be noted that the coating is an intermittent coating, leaving an empty foil area. It is dried at 95 °C to obtain a positive electrode sheet with a positive electrode active material layer thickness of 90 μm. The above coating steps are repeated on the other surface of the positive electrode current collector aluminum foil, leaving a coating area, to obtain a positive electrode sheet with a positive electrode active material layer coated on both sides.

[0160] (3) Preparation of the electrolyte: In a dry argon atmosphere, first, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 30:50:20, and then the lithium salt lithium hexafluorophosphate (LiPF 6 ) is added to the organic solvents and dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0161] (4) Assembly of the electrode assembly: The positive electrode tab and the negative electrode tab are respectively welded to the positive and negative current collectors by ultrasonic welding. The positive electrode tab is made of aluminum, and the negative electrode tab is made of nickel. Then, the positive and negative electrode plates and the separator are arranged in the order of positive electrode plate - separator - negative electrode plate - separator, and wound and assembled into a square electrode assembly. The separator is a polyethylene (PE) film with a thickness of 6 μm. Place the second encapsulation film (aluminum plastic film, with a thickness of 115 μm) formed with a pit into the assembly fixture with the pit surface facing up, and place the electrode assembly into the pit.

[0162] (5) Liquid injection and encapsulation: Inject the electrolyte into the groove of the second encapsulation film, set the first encapsulation film and the second encapsulation film opposite to each other, and encapsulate the first edge area and the second edge area to obtain the first seal. The third edge area and the fourth edge area are stacked on top of each other to form an air bag edge. Then, perform formation treatment on the secondary battery, and then encapsulate and cut off the air bag edge in sequence to obtain the second seal.

[0163] (6) Pressing and folding the edges: Perform embossing treatment and secondary bending on the first seal and the second seal respectively, and bond the first seal and the second seal to the first side wall and the second side wall respectively to obtain the secondary battery as shown in Figure 2 and Figure 3 shown.

[0164] Comparative Example 1

[0165] The difference from Example 1 is that the second section of the first seal contains the first encapsulation film and the encapsulation film stacked and bonded to each other, and no recess is provided in the second section.

[0166] Comparative Example 2

[0167] The difference from Example 1 is that the first seal is a single-folded edge structure, that is, the second section of the first seal is omitted, and the first section of the first seal is bonded to the first side wall through the first bonding member.

[0168] Then, perform energy density and safety performance tests on the secondary batteries obtained in each example and comparative example. The test results are recorded in Table 1.

[0169] The test steps for the energy density include: At a test temperature of 25 °C, charge the secondary battery at a constant current of 0.7C to 4.48V, then charge it at a constant voltage of 4.48V to 0.025C, let it stand for 5 min, discharge it at a constant current of 0.2C to 3.0V, and let it stand for 5 min to obtain the discharge capacity D of the secondary battery. The above secondary battery is charged at a constant current of 1C for 33 min, and then the length, width, and height of the secondary battery are measured with a laser thickness gauge to calculate the volume V of the secondary battery. The energy density (ED) = D × 3.87 / V, with the unit of Wh / L.

[0170] The safety performance is characterized by whether there is leakage at the first edge after the drop test. The drop test steps are as follows: 1) Under the environmental conditions of 23±2℃, record the open circuit voltage and internal resistance of the secondary battery (the test instrument is a voltage resistance tester, manufacturer: Dongguan Lijia Precision Instrument Co., Ltd., model: LNG-SY1-0020-DQ); 2) Put the secondary battery into the fixture bin, and use the automatic drop device to drop the fixture bin with the secondary battery from a position of 1m to the cement floor in a round-trip manner, with the bottom of the fixture bin head, the left side, the right side, the back, the front, and the top as a circle. A total of 3 rounds of drops, i.e. 18 times; 3) Then, the battery is dropped from a position of 1.5m to a cement bottom plate in a round of landing on the bottom, left side, right side, back side, front side and top side of the fixture head. A total of 3 rounds of drops, i.e. 18 times; 4) After each round of drops, the voltage of the secondary battery is measured. When the secondary battery catches fire or explodes, the drop is stopped; otherwise, the drop is continued; 5) Observe whether the first packaging film and the second packaging film of the first edge sealing are broken open. If not, the secondary battery is judged to have passed the drop test.

[0171] Table 1

[0172] Bending method of the first edge seal The second segment Energy density (Wh / L) Pass rate of the drop test Example 1 Secondary bending Does not include the first encapsulation film 598.483 10 / 10 Comparative Example 1 Secondary bending Includes the first encapsulation film 590.961 10 / 10 Comparative Example 2 Single bending / 606.199 5 / 10

[0173] In the above table, the drop test pass rate is 5 / 10, which means that 5 out of 10 batteries tested passed the test. The meanings of other ratio values ​​are similar.

[0174] It can be seen from the data in Table 1 that, compared with Comparative Example 1, the first edge seal of Example 1 has a smaller size in the third direction, and the energy density of the secondary battery is higher. Moreover, compared with Comparative Example 2, the setting of the recess in Example 1 can reduce the risk of the second section opening relative to the first side wall, thereby improving the sealing of the first edge seal. Therefore, the secondary battery can have a higher drop resistance performance.

[0175] Embodiment 2-5

[0176] The difference from Example 1 lies in the value of the depth H of the concave portion, which is specifically recorded in Table 2.

[0177] Table 2

[0178]

[0179] From the data in Table 2, it can be seen that the depth of the concave portion in Examples 1-3 satisfies 0.5h≤H≤0.8h. Compared with Example 5, Example 1-3 is conducive to improving the bonding strength between the first adhesive and the second section so that the first edge seal can maintain a higher sealing performance, so the secondary battery has a higher drop resistance performance, and compared with Example 4, Example 1-3 can also reduce the impact of the concave portion on the thickness of the second section, so the secondary battery can take into account a higher energy density.

[0180] Examples 6 - 13

[0181] Differences from Example 1 lie in the dimension W of the recess in the first direction 1 and the spacing S between two adjacent recesses in the first direction 1 , which are specifically recorded in Table 3

[0182] Table 3

[0183]

[0184] It can be seen from the data in Table 3 that for Examples 1, 6 - 7, the dimension of the recess in the first direction satisfies 0.5H ≤ W 1 ≤ H. Compared with Examples 8 - 9, Examples 1, 6 - 7 are conducive to improving the bonding strength between the first bonding member and the second section, and at the same time, more dispersed stress points can be formed on the surface of the second section of a certain size to disperse the stress of the second section under mechanical abuse. Therefore, the first edge sealing can maintain a high sealing performance, and the secondary battery has a high anti - drop performance. Compared with Example 13, for Examples 1, 10 - 12, the spacing between two adjacent recesses in the first direction satisfies 0 < S 1 ≤ 0.3H, so that more dispersed stress points can be formed on the surface of the second section of a certain size to disperse the stress of the second section under mechanical abuse. Therefore, the first edge sealing can maintain a high sealing performance, and the secondary battery has a high anti - drop performance

[0185] Examples 14 - 21

[0186] Differences from Example 1 lie in the distance D between all the recesses and the first edge 1 , the distance D between all the recesses and the third connecting edge 3 , and the distance between all the recesses and the fourth connecting edge is D 4 . They are specifically recorded in Table 4

[0187] Table 4

[0188]

[0189] It can be seen from the data in Table 4 that for Examples 1, 14 - 15, the distance between the recesses and the first edge satisfies d 1 < D 1 ≤ 1.1d 1 . Compared with Example 16, in Examples 1, 14 - 15, all the recesses can be fully attached to the first side wall through the first bonding member. Compared with Example 17, Examples 1, 14 - 15 are conducive to forming more dispersed stress points between the first bonding member and the second section to disperse the stress under mechanical abuse. Therefore, the first edge sealing can maintain a high sealing performance, and the secondary battery has a high anti - drop performance

[0190] In Embodiments 1, 18 - 19, the distance between the concave portion and the third connecting side satisfies 3H 1 ≤D 3 ≤5H 1 . Compared with Embodiment 20, Embodiments 1, 18 - 19 can reduce the risk that the first encapsulation film of the second section is easily broken due to the bending of the second section in the area where the concave portion is located, and compared with Embodiment 21, Embodiments 1, 18 - 19 are beneficial to forming more dispersed stress points between the first bonding member and the second section to disperse the stress under mechanical abuse. Therefore, the first sealing edge can maintain a high sealing performance, and the secondary battery has a high anti-drop performance.

[0191] Embodiments 22 - 29

[0192] The difference from Embodiment 1 lies in the length L of the first section 1 , and the length L of the second section 2 . Specifically recorded in Table 5.

[0193] Table 5

[0194]

[0195] From the data in Table 5, it can be seen that in Embodiments 1, 22 - 23, the length of the second section satisfies L 2 >L 1 and 0.6H 0 ≤L 2 ≤0.8H 0 . Compared with Embodiment 24, Embodiments 1, 22 - 23 can improve the bonding strength between the first bonding member and the second section, and form more dispersed stress points between the first bonding member and the second section to disperse the stress under mechanical abuse. Therefore, the first sealing edge can maintain a high sealing performance, and the secondary battery has a high anti-drop performance; and compared with Embodiment 25, Embodiments 1, 22 - 23 can reduce the risk of the thickness increase of the secondary battery caused by the folding of the second section and the risk of the second section abutting against the bending part of the first section and the first side wall. Therefore, the battery can take into account both a high energy density and an anti-drop performance.

[0196] In Embodiments 1, 26 - 27, the length of the first section satisfies 0.6H 0 ≤L 1 ≤0.8H 0 . Compared with Embodiment 28, Embodiments 1, 26 - 27 can make the encapsulation strength between the first encapsulation film and the second encapsulation film of the first section relatively high. Therefore, the secondary battery has a high anti-drop performance, and compared with Embodiment 29, Embodiments 1, 26 - 27 can reduce the risk of the thickness increase of the secondary battery caused by the longer first section and the risk of the second section abutting against the bending part of the first section and the first side wall. Therefore, the secondary battery also takes into account both a high energy density and an anti-drop performance.

[0197] The above disclosure is only the preferred embodiment of the present application. Of course, the present application cannot be limited thereby. Therefore, equivalent changes made according to the present application still fall within the scope covered by the present application.

Claims

1. A secondary battery, comprising a packaging bag, an electrode assembly and a tab, wherein the packaging bag comprises a receiving portion and a first edge seal, the electrode assembly is disposed in the receiving portion, the tab is electrically connected to the electrode assembly and extends out of the packaging bag, the direction in which the tab protrudes from the electrode assembly is a first direction, and the thickness direction of the electrode assembly is a second direction; wherein, The accommodating portion includes a first side wall and a second side wall arranged opposite to each other in a third direction, the first edge seal includes a first section connected to the first side wall and a second section connected to the first section along an extending direction of the first edge seal, at least a portion of the second section is arranged between the first section and the first side wall in the third direction, and the first direction, the second direction and the third direction are perpendicular to each other; The packaging bag comprises a first packaging film and a second packaging film arranged opposite to each other; the first packaging film and the second packaging film in the first section are stacked, the first packaging film extends from the first section to the second section along the extension direction, and the second packaging film is not provided on the first packaging film in the second section; in the third direction, the second packaging film of the first section is located between the first packaging film of the first section and at least a portion of the first packaging film of the second section; The surface of the second section facing the first side wall is integrally provided with a plurality of recesses, and the recesses are recessed in a direction away from the first side wall; the secondary battery also includes a first adhesive, the second section is bonded to the first side wall through the first adhesive, and at least part of the first adhesive is arranged in the recess.

2. The secondary battery according to claim 1, wherein The first packaging film includes a first packaging layer, a first metal layer and a first protective layer which are stacked, and the second packaging film includes a second packaging layer, a second metal layer and a second protective layer which are stacked; at least a portion of the first packaging layer and at least a portion of the second packaging layer in the first section are bonded together, the recess is integrally arranged in the first protective layer, and the multiple recesses are arranged along the first direction and the second direction, respectively.

3. The secondary battery according to claim 2, wherein: The depth of the concave portion in the third direction is H, the thickness of the first protective layer in the third direction is h, and 0.5h≤H≤0.8h.

4. The secondary battery according to claim 2 or 3, wherein: The recess satisfies at least one of the following conditions: (1) The dimension of the recess in the first direction is W1, 0.5H≤W1≤H; (2) The dimension of the recess in the second direction is W2, 0.5H≤W2≤H; (3) The distance between two adjacent concave portions in the first direction is S1, 0<S1≤0.3H; (4) The distance between two adjacent concave portions in the second direction is S2, and 0<S2≤0.3H.

5. The secondary battery according to claim 1, wherein The accommodating portion further includes a first transition region and a second transition region respectively connected to two edges of the first side wall in the first direction, the first transition region is closer to the pole ear than the second transition region in the first direction, the first transition region and the second transition region are both bent compared to the first side wall, and the first transition region and the second transition region both extend from the first side wall in a direction close to the second side wall; The orthographic projections of the plurality of recesses in the third direction are all located within the orthographic projection of the first side wall in the third direction.

6. The secondary battery according to claim 5, wherein: When viewed from the second direction, the packaging bag includes a first edge and a second edge arranged opposite to each other in the first direction, and the pole ear is connected to the first edge; the first side wall includes a first connecting edge connected to the first transition zone, the distance between the multiple recesses and the first edge in the first direction is D1, and the distance between the first connecting edge and the first edge in the first direction is d1, d1<D1≤1.1d1.

7. The secondary battery according to claim 5, wherein: Observed from the second direction, the packaging bag includes a first edge and a second edge arranged opposite to each other in the first direction, and the pole ear is connected to the first edge; the first side wall includes a second connecting edge connected to the second transition zone, the distance between the multiple recesses and the second edge in the first direction is D2, and the distance between the second connecting edge and the second edge in the first direction is d2, d2<D2≤1.1d2.

8. The secondary battery according to claim 1, wherein The first section includes a third connecting edge connected to the second section, a distance between the plurality of recesses and the third connecting edge along the extending direction is D3, a thickness of the first section in the third direction is H1, and 3H1≤D3≤5H1.

9. The secondary battery according to claim 1, wherein The first section includes a third connecting edge connected to the second section, the second section includes a fourth connecting edge arranged opposite to the third connecting edge along the extension direction, the distance between the multiple recesses and the fourth connecting edge in the second direction is D4, and the distance between two adjacent recesses in the second direction is S2, 0<D4≤S2.

10. The secondary battery according to claim 1, wherein The length of the first section along the extending direction is L1, the length of the second section along the extending direction is L2, and L2≤L1.

11. The secondary battery according to claim 1, wherein The length of the first section along the extending direction is L1, the length of the second section along the extending direction is L2, and the thickness of the accommodation portion in the second direction is H0; 0.6H0≤L1≤0.8H0, and / or, 0.6H0≤L2≤0.8H0.

12. The secondary battery according to claim 1, wherein The orthographic projection of the concave portion in the third direction is a circle or an ellipse.

13. An electronic device, comprising a battery compartment, wherein: The electronic device further comprises a secondary battery as claimed in any one of claims 1 to 12, wherein the secondary battery is disposed in the battery compartment.

14. A method for preparing a secondary battery according to any one of claims 1 to 12, wherein: The steps include: Providing a packaging material, the packaging material comprising a first packaging film and a second packaging film, the first packaging film comprising a first main body region and a first edge region connected to each other, the second packaging film comprising a second main body region and a second edge region connected to each other; stamping at least the second main body region to form a groove; Electrically connecting the electrode assembly to the electrode tab, and placing the electrode assembly with the electrode tab in the groove; The first packaging film and the second packaging film are arranged opposite to each other, and the first edge area and the second edge area are packaged to form a first edge seal, the first main body area and the second main body area form a receiving portion, the first edge seal and the receiving portion constitute a packaging bag, and the tab extends out of the packaging bag, wherein the first packaging film and the second packaging film in the first edge seal overlap to form a first section, and the first packaging film extends in a direction away from the receiving portion to exceed the second packaging film to form a second section; Performing an embossing process on the surface of the second section to form a plurality of recesses; and The first edge seal is bent twice so that at least a portion of the second section is sandwiched between the first section and the first side wall, and the second section is bonded to the first side wall through a first adhesive.

15. The method for preparing a secondary battery according to claim 14, wherein: The first packaging film further includes a third edge region, the first edge region, the first main region and the third edge region are connected in sequence, and the second packaging film further includes a fourth edge region, the second edge region, the second main region and the fourth edge region are connected in sequence; When the first packaging film and the second packaging film are arranged opposite to each other, the third edge area and the fourth edge area overlap with each other to form an air bag edge; The preparation method further comprises: Performing formation treatment on the secondary battery and packaging the air bag edge; Cutting off a portion of the first packaging film and the second packaging film of the air bag edge to obtain a second sealing edge, wherein the first packaging film and the second packaging film in the second sealing edge overlap to form a third section, and the first packaging film extends in a direction away from the accommodating portion to exceed the second packaging film to form a fourth section; Performing an embossing process on the surface of the fourth section to form a plurality of recessed portions; and The second edge seal is bent twice so that at least a portion of the fourth section is sandwiched between the third section and the second side wall, and the fourth section is bonded to the second side wall via a second adhesive.

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