Secondary battery, electronic device, and method for manufacturing secondary battery

Abstract

The invention relates to a secondary battery, electronic equipment and a manufacturing method of the secondary battery, the secondary battery comprises a shell and an electrode assembly, the shell comprises a packaging film, and the packaging film wraps the outer surface of the electrode assembly. The shell further comprises a plurality of adhesive layers, the adhesive layers are arranged on the surface, away from the electrode assembly, of the packaging film at intervals, and the tensile elongation at break phi 2 of the part, provided with the adhesive layers, of the shell is smaller than the tensile elongation at break phi 1 of the packaging film. According to the secondary battery, the electronic equipment and the manufacturing method of the secondary battery, the problem of short circuit of the secondary battery can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular, to a secondary battery, an electronic device, and a manufacturing method of the secondary battery. Background Art

[0002] As a power source of an electronic device, a secondary battery is crucial for ensuring the normal use of the electronic device. When the secondary battery is damaged by an external force, it is likely to cause an internal short circuit, leading to safety problems such as thermal runaway. Summary of the Invention

[0003] The inventors of the present application have found through research that when the secondary battery is damaged by an external force, the packaging film is easily extended to the fracture of the electrode tab by the external force, resulting in contact between the aluminum layer of the packaging film and the electrode tab, thus causing a short circuit. By coating an adhesive layer with a tensile fracture elongation lower than that of the packaging film on the outer surface of the packaging film of the finished secondary battery, the housing has the adhesive layer and the packaging film, so that the tensile fracture elongation of the part of the housing provided with the adhesive layer is lower than that of the original packaging film. When the secondary battery is damaged by an external force, the housing can break in advance, and the extension of the aluminum layer in the packaging film is reduced during the break, thereby reducing the possibility of the aluminum layer being greatly extended to contact the electrode tab and causing a short circuit.

[0004] The purpose of the present application is to provide a secondary battery, an electronic device, and a manufacturing method of the secondary battery, aiming to improve the problem of short circuit of the secondary battery.

[0005] According to a first aspect of the present application, there is provided a secondary battery, including a housing and an electrode assembly. The housing includes a packaging film that wraps around the outer surface of the electrode assembly. The housing further includes a plurality of adhesive layers that are spaced apart on the surface of the packaging film facing away from the electrode assembly. The tensile fracture elongation of the packaging film is The tensile fracture elongation of the part of the housing provided with the adhesive layer is

[0006] In the above technical solution, by spacing a plurality of adhesive layers on the surface of the packaging film facing away from the electrode assembly, the housing has the adhesive layer and the packaging film, and the tensile fracture elongation of the part of the housing provided with the adhesive layer is less than the tensile fracture elongation of the packaging film When the housing is damaged by an external force, it will break in advance, and the extension of the housing is small, which is beneficial to reducing the possibility of the housing being extended to the fracture of the electrode tab by the external force, and further reducing the possibility of the aluminum layer of the housing contacting the electrode tab and causing a short circuit.

[0007] In some preferred embodiments, the adhesive layer is arranged in a strip shape on the surface of the packaging film facing away from the electrode assembly, which is beneficial to improving the simplicity of preparing the adhesive layer.

[0008] In some preferred embodiments, the length direction of the adhesive layer is perpendicular to the length direction of the electrode assembly, which is beneficial to improving the simplicity of preparing the adhesive layer.

[0009] In some preferred embodiments, the length direction of the adhesive layer is perpendicular to the width direction of the electrode assembly, which is beneficial to improving the simplicity of preparing the adhesive layer.

[0010] In some preferred embodiments, the width of the adhesive layer is from 0.2 mm to 30 mm. When the width of the adhesive layer is less than 0.2 mm, due to the fluidity of the adhesive layer during the curing process of the adhesive layer, adjacent adhesive layers are likely to be connected. Also, due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the width of the adhesive layer, resulting in a relatively obvious short-circuit problem in the secondary battery. By setting the width of the adhesive layer ≥ 0.2 mm, it is beneficial to reduce the possibility of adjacent adhesive layers being connected and to improve the short-circuit problem of the secondary battery. When the width of the adhesive layer is greater than 30 mm, there are fewer stress concentration points on the housing when it is stressed, and it is not easy to generate stress concentration when the housing is stressed, resulting in the housing not being easily broken, and the short-circuit problem of the secondary battery being relatively obvious. By setting the width of the adhesive layer ≤ 30 mm, it is beneficial to increase the stress concentration points on the housing when it is stressed, and thus beneficial to the housing breaking in advance when it is subjected to an external force, and further beneficial to improving the short-circuit problem of the secondary battery.

[0011] In some preferred embodiments, the adhesive layer is arranged in a dot shape on the surface of the packaging film facing away from the electrode assembly, which is beneficial for the adhesive layer to meet different preparation methods.

[0012] In some preferred embodiments, on the surface of the packaging film, the diameter of the minimum circumscribed circle of the adhesive layer is from 0.5 mm to 10 mm. When the diameter of the minimum circumscribed circle of the adhesive layer is less than 0.5 mm, due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the diameter of the minimum circumscribed circle of the adhesive layer, resulting in a relatively obvious short-circuit problem in the secondary battery. By setting the diameter of the minimum circumscribed circle of the adhesive layer ≥ 0.5 mm, it is beneficial to improve the short-circuit problem of the secondary battery. When the diameter of the minimum circumscribed circle of the adhesive layer is greater than 10 mm, there are fewer stress concentration points on the housing when it is stressed, and it is not easy to generate stress concentration when the housing is stressed, resulting in the housing not being easily broken, and thus the short-circuit problem of the secondary battery being relatively obvious. By setting the diameter of the minimum circumscribed circle of the adhesive layer ≤ 10 mm, it is beneficial to increase the stress concentration points on the housing when it is stressed, and thus beneficial to the housing breaking in advance when it is subjected to an external force, and further beneficial to improving the short-circuit problem of the secondary battery.

[0013] In some preferred embodiments, the gap width between two adjacent adhesive layers is 0.2 mm to 10 mm. There is a gap between two adjacent adhesive layers. When the housing is subjected to stress, stress concentration is likely to occur, which is beneficial to further reducing the tensile fracture elongation of the part of the housing provided with the adhesive layer. The smaller the gap width between two adjacent adhesive layers, the easier it is for stress concentration to occur when the housing is subjected to stress, the lower the tensile fracture elongation of the part of the housing provided with the adhesive layer, and the better the improvement effect on the short-circuit problem of the secondary battery. If the gap width is greater than 10 mm, the stress concentration generated when the housing is subjected to stress is not obvious. By setting the gap width between two adjacent adhesive layers ≤ 10 mm, stress concentration is more likely to occur when the housing is subjected to stress, which is beneficial to further improving the short-circuit problem of the secondary battery. When the gap width between two adjacent adhesive layers is less than 0.2 mm, the adjacent adhesive layers are likely to be connected. And due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the gap width, and the short-circuit problem of the secondary battery is relatively obvious. By setting the gap width between two adjacent adhesive layers ≥ 0.2 mm, it is beneficial to reduce the possibility of connection between adjacent adhesive layers and is beneficial to improving the short-circuit problem of the secondary battery.

[0014] In some preferred embodiments, the thickness of the adhesive layer is 1 μm to 60 μm. The greater the thickness of the adhesive layer, the lower the tensile fracture elongation of the part of the housing provided with the adhesive layer, and the better the improvement effect on the short-circuit problem of the secondary battery. When the thickness of the adhesive layer is less than 1 μm, the reduction of the tensile fracture elongation of the part of the housing provided with the adhesive layer is not obvious. By setting the thickness of the adhesive layer ≥ 1 μm, the tensile fracture elongation of the part of the housing provided with the adhesive layer can be further reduced, thereby further improving the short-circuit problem of the secondary battery. However, the greater the thickness of the adhesive layer, the more energy density the secondary battery loses. When the thickness of the adhesive layer is 60 μm, continuing to increase the thickness of the adhesive layer, the improvement of the short-circuit problem of the secondary battery is not obvious, and more energy density of the secondary battery will be lost. Therefore, considering the short-circuit problem of the secondary battery and the energy density of the secondary battery comprehensively, it is preferred that the thickness of the adhesive layer ≤ 60 μm.

[0015] In some preferred embodiments, the adhesive layer includes a resin compound, and the resin compound includes at least one of epoxy resin and phenolic resin, which is beneficial to further reducing the tensile fracture elongation of the part of the housing provided with the adhesive layer.

[0016] In some preferred embodiments, the adhesive layer further includes a curing agent for the resin compound. The curing agent can connect the molecules or polymer chains of the resin compound to form a more stable network structure, thereby increasing the strength and hardness of the adhesive layer. The curing agent includes at least one of aliphatic amine, aromatic amine, modified amine, and maleic anhydride, which is beneficial to the curing agent and the resin compound to form a more stable network structure, thereby increasing the strength and hardness of the adhesive layer.

[0017] In some preferred embodiments, the mass percentage of the curing agent in the adhesive layer is 5% to 20%. When the mass percentage of the curing agent in the adhesive layer is less than 5%, the curing reaction between the lipid compound and the curing agent will be insufficient. By setting the mass percentage of the curing agent in the adhesive layer ≥ 5%, it is beneficial to improve the sufficiency of the curing reaction between the lipid compound and the curing agent. When the mass percentage of the curing agent is greater than 20%, the curing agent is in excess, which will reduce the cohesive force of the housing, and the elongation at break of the part of the housing provided with the adhesive layer will increase, resulting in a more obvious short-circuit problem of the secondary battery. By setting the mass percentage of the curing agent in the adhesive layer ≤ 20%, it is beneficial to improve the cohesive force of the housing, beneficial to reduce the elongation at break of the part of the housing provided with the adhesive layer, and thus beneficial to improve the short-circuit problem of the secondary battery.

[0018] In some preferred embodiments, the adhesive layer further includes inorganic fillers, and the inorganic fillers are beneficial to improving the tensile strength of the adhesive layer, and thus beneficial to improving the protection effect of the adhesive layer on the packaging film.

[0019] In some preferred embodiments, the inorganic filler includes glass fiber, which is beneficial to improving the tensile strength of the adhesive layer. The mass percentage of glass fiber in the adhesive layer is 10% to 50%. When the mass percentage of the inorganic filler is less than 10%, the improvement of the tensile strength of the adhesive layer is not obvious. When the mass percentage of the inorganic filler ≥ 10%, the tensile strength of the adhesive layer can be further improved. However, when the mass percentage of the inorganic filler is greater than 50%, the coating uniformity of the adhesive layer is poor. Therefore, considering the tensile strength of the adhesive layer and the coating uniformity of the adhesive layer, it is preferred that the mass percentage of the inorganic filler ≤ 50%.

[0020] In some preferred embodiments, the inorganic filler includes silica, which is beneficial to improving the tensile strength of the adhesive layer. The mass percentage of silica in the adhesive layer is 5% to 30%. When the mass percentage of the inorganic filler is less than 5%, the improvement of the tensile strength of the adhesive layer is not obvious. When the mass percentage of the inorganic filler ≥ 5%, the tensile strength of the adhesive layer can be further improved. However, when the mass percentage of the inorganic filler is greater than 30%, the coating uniformity of the adhesive layer is poor. Therefore, considering the tensile strength of the adhesive layer and the coating uniformity of the adhesive layer, it is preferred that the mass percentage of the inorganic filler ≤ 30%.

[0021] In some preferred embodiments, the larger, the elongation at break of the part of the housing provided with the adhesive layer the smaller, the better the effect of improving the short circuit between the aluminum layer of the housing and the electrode sheet, when it is less than 9.5%, the thickness of the adhesive layer is likely to be less than 1 μm, and the effect of improving the short circuit between the aluminum layer of the housing and the electrode sheet is not obvious. By setting the thickness of the adhesive layer can be ≥ 1 μm, and the possibility of short circuit between the aluminum layer of the housing and the electrode sheet can be reduced. When it is greater than 66%, the thickness of the adhesive layer is likely to be greater than 60 μm. Continuing to increase the effect of improving the short - circuit contact between the aluminum layer of the housing and the electrode tab is not significantly improved, and it is easy to lose more energy density of the secondary battery. By setting the thickness of the adhesive layer can be ≤60 μm, which can improve the energy density of the secondary battery.

[0022] In some preferred embodiments, the packaging film includes a first polymer layer, a first metal layer, a second polymer layer, and a third polymer layer stacked in sequence. A plurality of adhesive layers are provided at intervals on the surface of the third polymer layer facing away from the second polymer layer. The third polymer layer includes polyamide, which can improve the strength of the packaging film.

[0023] In a second aspect, the present application also proposes an electronic device, including the secondary battery according to any one of the embodiments in the first aspect above.

[0024] In a third aspect, the present application also proposes a manufacturing method of a secondary battery for preparing the secondary battery according to any one of the embodiments in the first aspect above, including: providing a packaging film and an electrode assembly, and wrapping the packaging film around the outer surface of the electrode assembly. Providing an adhesive layer and coating the adhesive layer on the surface of the packaging film facing away from the electrode assembly. Since the packaging film needs to be punched before wrapping the electrode assembly, the packaging film requires a certain tensile fracture elongation rate. By setting the adhesive layer after the packaging film wraps the electrode assembly, the tensile fracture elongation rate of the part of the composite packaging film (housing) formed by the packaging film and the adhesive layer with the adhesive layer can be reduced, without affecting the tensile fracture elongation rate of the packaging film before wrapping the electrode assembly, so that the packaging film can meet the punching requirements.

[0025] Additional aspects and advantages of the embodiments of the present application will be described, shown, or elucidated in part through the implementation of the embodiments of the present application in the following description. Description of the Drawings

[0026] One or more embodiments are exemplarily illustrated by corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements, unless otherwise stated, the dimensions in the drawings do not constitute a proportional limitation.

[0027] Figure 1 It is a schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0028] Figure 2 It is a schematic structural diagram of an electrode assembly according to some embodiments of the present application;

[0029] Figure 3 It is a schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0030] Figure 4Schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0031] Figure 5 Schematic structural diagram of a secondary battery according to some embodiments of the present application;

[0032] Figure 6 Schematic cross-sectional view of a secondary battery according to some embodiments of the present application;

[0033] Figure 7 Schematic structural diagram of a packaging film and an adhesive layer according to some embodiments of the present application.

[0034] Explanation of reference numerals:

[0035] 100, secondary battery; 10, housing; 11, packaging film; 111, first polymer layer; 112, first metal layer; 113, second polymer layer; 114, third polymer layer; 115, first wall; 116, second wall; 117, first side wall; 118, second side wall; 119, head wall; 120, tail wall; 12, adhesive layer; 121, gap; 20, electrode assembly; 20a, tab; 21, positive electrode sheet; 22, negative electrode sheet; 23, separator; X, length direction of the electrode assembly; Y, width direction of the electrode assembly; Z, thickness direction of the electrode assembly. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0037] Referring to "embodiments" in the present application means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0038] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, "a plurality of" means two or more, unless otherwise clearly and specifically defined.

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

[0040] The term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there can be a state approximately vertical between two components. For example, in combination with numerical descriptions, vertical can refer to the included angle range between two straight lines being between 90 ± 10°, vertical can also refer to the dihedral angle range between two planes being between 90 ± 10°, and vertical can also refer to the included angle range between a straight line and a plane being between 90 ± 10°. The two components described as "vertical" may not be absolute straight lines or planes, and may also be approximately straight lines or planes. From a macroscopic perspective, as long as the overall extension direction is a straight line or a plane, the components can be considered "straight lines" or "planes".

[0041] The length direction, width direction, and thickness direction of the present application are two-way directions, that is, the length direction includes the direction indicated by the arrow in the drawing and its opposite direction, the width direction includes the direction indicated by the arrow in the drawing and its opposite direction, and the thickness direction includes the direction indicated by the arrow in the drawing and its opposite direction.

[0042] The technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0043] In a first aspect, an embodiment of the present application provides a secondary battery 100. Please refer to Figure 1 , the secondary battery 100 includes a housing 10, an electrode assembly 20, and a tab 20a. The housing 10 can accommodate the electrode assembly 20 and an electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 20 within the housing 10. The tab 20a is connected to the electrode assembly 20, and the tab 20a extends out of the housing 10 in the length direction X of the electrode assembly 20 to assist the electrode assembly 20 in performing energy transfer with an external electronic device.

[0044] For the above electrode assembly 20, please refer to Figure 2 , Figure 2The laminated structure of the electrode assembly 20 is shown. The electrode assembly 20 includes a negative electrode sheet 22, a positive electrode sheet 21, and a separator 23. In the thickness direction Z of the electrode assembly 20, the positive electrode sheet 21 and the negative electrode sheet 22 are alternately stacked, and a separator 23 is provided between adjacent positive electrode sheets 21 and negative electrode sheets 22. The separator 23 is used to insulate and separate the positive electrode sheet 21 and the negative electrode sheet 22. In the embodiments of the present application, taking the electrode assembly 20 as a laminated structure as an example for illustration, in some other embodiments, the electrode assembly 20 can also be a wound structure and other structures. For example, after the positive electrode sheet 21, the separator 23, and the negative electrode sheet 22 are stacked in sequence, they are wound to form a wound electrode assembly 20. Among them, the thickness direction Z of the electrode assembly 20 is perpendicular to the length direction X of the electrode assembly 20.

[0045] Please refer to Figure 3 , the housing 10 includes a packaging film 11, and the packaging film 11 wraps the outer surface of the electrode assembly 20. When the secondary battery 100 is damaged by an external force, the packaging film 11 is easily extended to the pole piece fracture by the external force, resulting in the contact between the aluminum layer of the packaging film 11 and the pole piece, thus causing a short circuit.

[0046] To improve the above problems, in the embodiments of the present application, the housing 10 further includes a plurality of adhesive layers 12. The plurality of adhesive layers 12 are spaced apart on the surface of the packaging film 11 facing away from the electrode assembly 20. The tensile fracture elongation rate of the part of the housing 10 provided with the adhesive layer 12 is less than the tensile fracture elongation rate of the packaging film 11 By spacing a plurality of adhesive layers 12 on the surface of the packaging film 11 facing away from the electrode assembly 20, the housing 10 has the adhesive layer 12 and the packaging film 11. The tensile fracture elongation rate of the part of the housing 10 provided with the adhesive layer 12 is less than the tensile fracture elongation rate of the packaging film 11 When the housing 10 is damaged by an external force, it will break in advance, and the extension of the housing 10 is small, which is beneficial to reducing the possibility that the housing 10 is extended to the pole piece fracture by the external force, and further can reduce the possibility of contact short circuit between the aluminum layer of the housing 10 and the pole piece.

[0047] In some embodiments, the larger, the smaller the tensile fracture elongation rate of the part of the housing 10 provided with the adhesive layer 12 the better the effect of improving the contact short circuit between the aluminum layer of the housing and the pole piece, When it is less than 9.5%, the thickness of the adhesive layer 12 is likely to be less than 1 μm, and the effect of improving the contact short circuit between the aluminum layer of the housing 10 and the pole piece is not obvious. By setting the thickness of the adhesive layer 12 can be ≥1 μm, and the possibility of contact short circuit between the aluminum layer of the housing 10 and the pole piece can be reduced. When it is greater than 66%, the thickness of the adhesive layer 12 is likely to be greater than 60 μm. Continuing to increase The effect of improving the short - circuit problem of the aluminum layer of the housing 10 in contact with the electrode tab is not significantly improved, and it is easy to lose more energy density of the secondary battery 100. By setting the thickness of the adhesive layer 12 can be ≤ 60 μm, which can improve the energy density of the secondary battery 100.

[0048] In some embodiments, the adhesive layer 12 includes a resin compound, which is beneficial to further reduce the elongation at break of the adhesive layer 12, and further beneficial to reduce the elongation at break of the part of the housing 10 provided with the adhesive layer 12.

[0049] In some embodiments, the resin compound includes at least one of epoxy resin and phenolic resin, which is beneficial to further reduce the elongation at break of the adhesive layer 12.

[0050] In some embodiments, the adhesive layer 12 further includes a curing agent for the resin compound. The curing agent can connect the molecules or polymer chains of the resin compound to form a more stable network structure, thereby increasing the strength and hardness of the adhesive layer 12.

[0051] In some embodiments, the curing agent is an amine - type compound or an acid anhydride - type compound, which is beneficial for the curing agent and the resin compound to form a more stable network structure, thereby increasing the strength and hardness of the adhesive layer 12.

[0052] In some embodiments, the curing agent includes at least one of aliphatic amines, aromatic amines, modified amines, and maleic anhydride, which is beneficial for the curing agent and the resin compound to form a more stable network structure.

[0053] In some embodiments, the mass percentage of the curing agent in the adhesive layer 12 is 5% to 20%. When the mass percentage of the curing agent in the adhesive layer 12 is less than 5%, the curing reaction between the lipid compound and the curing agent will be insufficient. By setting the mass percentage of the curing agent in the adhesive layer 12 ≥ 5%, it is beneficial to improve the sufficiency of the curing reaction between the lipid compound and the curing agent. When the mass percentage of the curing agent is greater than 20%, the curing agent is in excess, which will reduce the cohesion of the housing 10, and the elongation at break of the part of the housing 10 provided with the adhesive layer 12 will increase, resulting in a more obvious short - circuit problem of the secondary battery 100. By setting the mass percentage of the curing agent in the adhesive layer 12 ≤ 20%, it is beneficial to the cohesion of the housing 10, beneficial to reduce the elongation at break of the part of the housing 10 provided with the adhesive layer 12, and further beneficial to improve the short - circuit problem of the secondary battery 100.

[0054] In some embodiments, the adhesive layer 12 includes acrylate, and acrylate can be used without adding a curing agent, which is beneficial to improve the simplicity of preparing the adhesive layer 12.

[0055] In some embodiments, the adhesive layer 12 is arranged in a strip shape on the surface of the packaging film 11 facing away from the electrode assembly 20, which is beneficial to improving the simplicity of preparing the adhesive layer 12.

[0056] In some embodiments, the length direction of the adhesive layer 12 is perpendicular to the length direction X of the electrode assembly 20, which is beneficial to improving the simplicity of preparing the adhesive layer 12.

[0057] In some embodiments, please refer to Figure 4 , the length direction of the adhesive layer 12 is perpendicular to the width direction Y of the electrode assembly 20, which is beneficial to improving the simplicity of preparing the adhesive layer 12. Wherein, the length direction X of the electrode assembly 20, the width direction Y of the electrode assembly 20 and the thickness direction Z of the electrode assembly 20 are perpendicular to each other in pairs.

[0058] In some embodiments, the width W1 of the adhesive layer 12 is 0.2 mm to 30 mm. When the width of the adhesive layer 12 is less than 0.2 mm, due to the fluidity of the adhesive layer 12 during the curing process of the adhesive layer 12, adjacent adhesive layers 12 are likely to be connected. And due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the width of the adhesive layer 12, resulting in a more obvious short-circuit problem of the secondary battery 100. By setting the width of the adhesive layer 12 ≥ 0.2 mm, it is beneficial to reduce the possibility of adjacent adhesive layers 12 being connected, and is beneficial to improving the short-circuit problem of the secondary battery 100. When the width of the adhesive layer 12 is greater than 30 mm, there are fewer stress concentration points on the housing 10 when it is stressed, and the housing 10 is not likely to generate stress concentration when stressed, resulting in the housing 10 not being easily broken, and the short-circuit problem of the secondary battery 100 is more obvious. By setting the width of the adhesive layer 12 ≤ 30 mm, it is beneficial to increase the stress concentration points on the housing 10 when it is stressed, and then it is beneficial to the housing 10 to break in advance when it is subjected to an external force, and then it is beneficial to improving the short-circuit problem of the secondary battery 100.

[0059] In some embodiments, please refer to Figure 5 , the adhesive layer 12 is arranged in a dot shape on the surface of the packaging film 11 facing away from the electrode assembly 20, which is beneficial for the adhesive layer 12 to meet different preparation methods.

[0060] In some embodiments, on the surface of the packaging film 11, the diameter of the minimum circumscribed circle of the adhesive layer 12 is 0.5 mm to 10 mm. When the diameter of the minimum circumscribed circle of the adhesive layer 12 is less than 0.5 mm, due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the diameter of the minimum circumscribed circle of the adhesive layer 12, resulting in a more obvious short-circuit problem of the secondary battery 100. By setting the diameter of the minimum circumscribed circle of the adhesive layer 12 ≥ 0.5 mm, it is beneficial to improve the short-circuit problem of the secondary battery 100. When the diameter of the minimum circumscribed circle of the adhesive layer 12 is greater than 10 mm, there are fewer stress concentration points where the housing 10 is stressed. When the housing 10 is stressed, it is not easy to generate stress concentration, resulting in that the housing 10 is not easy to break, and further resulting in a more obvious short-circuit problem of the secondary battery 100. By setting the diameter of the minimum circumscribed circle of the adhesive layer 12 ≤ 10 mm, it is beneficial to increase the stress concentration points where the housing 10 is stressed, and further beneficial to the housing 10 to break in advance when subjected to an external force, and further beneficial to improving the short-circuit problem of the secondary battery 100.

[0061] In some embodiments, the width T1 of the gap 121 between two adjacent adhesive layers 12 is 0.2 mm to 10 mm. There is a gap 121 between two adjacent adhesive layers 12. When the housing 10 is stressed, it is easy to generate stress concentration, which is beneficial to further reduce the tensile fracture elongation of the part of the housing 10 provided with the adhesive layer 12. The smaller the width of the gap between two adjacent adhesive layers 12, the easier it is for the housing 10 to generate stress concentration when stressed, the lower the tensile fracture elongation of the part of the housing 10 provided with the adhesive layer 12, and the better the improvement effect of the short-circuit problem of the secondary battery 100. If the gap width is greater than 10 mm, the stress concentration generated when the housing 10 is stressed is not obvious. By setting the gap width between two adjacent adhesive layers 12 ≤ 10 mm, it is easier for the housing 10 to generate stress concentration when stressed, which is beneficial to further improve the short-circuit problem of the secondary battery 100. When the width of the gap between two adjacent adhesive layers 12 is less than 0.2 mm, the adjacent adhesive layers 12 are easy to be connected. And due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the width of the gap 121, resulting in a more obvious short-circuit problem of the secondary battery 100. By setting the width of the gap between two adjacent adhesive layers 12 ≥ 0.2 mm, it is beneficial to reduce the possibility of the adjacent adhesive layers 12 being connected, and beneficial to improving the short-circuit problem of the secondary battery 100.

[0062] In some embodiments, please refer to Figure 6, the thickness H1 of the adhesive layer 12 is from 1 μm to 60 μm. The greater the thickness of the adhesive layer 12, the lower the elongation at break of the part of the housing 10 provided with the adhesive layer 12, and the better the improvement effect of the short - circuit problem of the secondary battery 100. When the thickness of the adhesive layer 12 is less than 1 μm, the reduction of the elongation at break of the part of the housing 10 provided with the adhesive layer 12 is not obvious. By setting the thickness of the adhesive layer 12 ≥ 1 μm, the elongation at break of the part of the housing 10 provided with the adhesive layer 12 can be further reduced, thereby further improving the short - circuit problem of the secondary battery 100. However, the greater the thickness of the adhesive layer 12, the more energy density the secondary battery 100 loses. When the thickness of the adhesive layer 12 is 60 μm, continuing to increase the thickness of the adhesive layer 12, the improvement of the short - circuit problem of the secondary battery 100 is not obvious, but more energy density of the secondary battery 100 will be lost. Therefore, considering both the short - circuit problem of the secondary battery 100 and the energy density of the secondary battery 100, it is preferred that the thickness of the adhesive layer 12 ≤ 60 μm.

[0063] In some embodiments, the adhesive layer 12 further includes inorganic fillers. The inorganic fillers are beneficial to improving the tensile strength of the adhesive layer 12, and thus are beneficial to enhancing the protection effect of the adhesive layer 12 on the packaging film 11.

[0064] In some embodiments, the inorganic filler includes glass fiber, which is beneficial to improving the tensile strength of the adhesive layer 12. The mass percentage of the glass fiber in the adhesive layer 12 is from 10% to 50%. When the mass percentage of the inorganic filler is less than 10%, the improvement of the tensile strength of the adhesive layer 12 is not obvious. When the mass percentage of the inorganic filler ≥ 10%, the tensile strength of the adhesive layer 12 can be further improved. However, when the mass percentage of the inorganic filler is greater than 50%, the coating uniformity of the adhesive layer 12 is poor. Therefore, considering both the tensile strength of the adhesive layer 12 and the coating uniformity of the adhesive layer 12, it is preferred that the mass percentage of the inorganic filler ≤ 50%.

[0065] In some embodiments, the inorganic filler includes silicon dioxide, which is beneficial to improving the tensile strength of the adhesive layer 12. The mass percentage of the silicon dioxide in the adhesive layer 12 is from 5% to 30%. When the mass percentage of the inorganic filler is less than 5%, the improvement of the tensile strength of the adhesive layer 12 is not obvious. When the mass percentage of the inorganic filler ≥ 5%, the tensile strength of the adhesive layer 12 can be further improved. However, when the mass percentage of the inorganic filler is greater than 30%, the coating uniformity of the adhesive layer 12 is poor. Therefore, considering both the tensile strength of the adhesive layer 12 and the coating uniformity of the adhesive layer 12, it is preferred that the mass percentage of the inorganic filler ≤ 30%.

[0066] In some embodiments, please refer to Figure 3 and Figure 6, the packaging film 11 includes a first wall 115, a first side wall 117, a second wall 116, and a second side wall 118 that are connected in sequence. The first wall 115 and the second wall 116 are oppositely arranged in the thickness direction Z of the electrode assembly 20, and the first side wall 117 and the second side wall 118 are oppositely arranged in the width direction Y of the electrode assembly 20. Since the first wall 115 and the second wall 116 are more easily extended to the electrode fragment fracture by external forces, an adhesive layer 12 is provided on the surface of the first wall 115 facing away from the electrode assembly 20, which is beneficial to reducing the tensile fracture elongation rate of the first wall 115. When the first wall 115 is damaged by external forces, it will fracture in advance, which is beneficial to reducing the possibility of the first wall 115 being extended to the electrode fragment fracture by external forces. An adhesive layer 12 is provided on the surface of the second wall 116 facing away from the electrode assembly 20, which is beneficial to reducing the tensile fracture elongation rate of the second wall 116. When the second wall 116 is damaged by external forces, it will fracture in advance, which is beneficial to reducing the possibility of the second wall 116 being extended to the electrode fragment fracture by external forces.

[0067] In some embodiments, the adhesive layer 12 is evenly distributed on the surface of the first wall 115 facing away from the electrode assembly 20, which is beneficial to improving the uniformity of the tensile fracture elongation rate of the first wall 115. It can be understood that the adhesive layer 12 being evenly distributed on the first wall 115 means that the adhesive layer 12 is roughly evenly distributed on the first wall 115. Due to processing errors, the adhesive layer 12 may not be completely evenly distributed.

[0068] In some embodiments, the adhesive layer 12 is evenly distributed on the surface of the second wall 116 facing away from the electrode assembly 20, which is beneficial to improving the uniformity of the tensile fracture elongation rate of the second wall 116. It can be understood that the adhesive layer 12 being evenly distributed on the second wall 116 means that the adhesive layer 12 is roughly evenly distributed on the second wall 116. Due to processing errors, the adhesive layer 12 may not be completely evenly distributed.

[0069] In some embodiments, there is a distance between the adhesive layer 12 and the first side wall 117, and there is a distance between the adhesive layer 12 and the second side wall 118. Since the first side wall 117 and the second side wall 118 of the packaging film 11 are easily collided and worn, if the tensile fracture elongation rates of the first side wall 117 and the second side wall 118 of the packaging film 11 are reduced, the first side wall 117 and the second side wall 118 are easily damaged. By setting a distance between the adhesive layer 12 and the first side wall 117, it is beneficial to reducing the possibility of the first side wall 117 being damaged due to a relatively low tensile fracture elongation rate. By setting a distance between the adhesive layer 12 and the second side wall 118, it is beneficial to reducing the possibility of the second side wall 118 being damaged due to a relatively low tensile fracture elongation rate.

[0070] In some embodiments, the packaging film 11 further includes a head wall 119 and a tail wall 120 oppositely disposed in the length direction X of the electrode assembly 20. The head wall 119 is connected to the first wall 115, the second wall 116, the first side wall 117, and the second side wall 118. The tail wall 120 is connected to the first wall 115, the second wall 116, the first side wall 117, and the second side wall 118. There is a distance between the adhesive layer 12 and the head wall 119, and there is a distance between the adhesive layer 12 and the tail wall 120. Since the head wall 119 and the tail wall 120 of the packaging film 11 are easily collided and worn, if the tensile fracture elongation rate of the head wall 119 and the tail wall 120 of the packaging film 11 is reduced, the head wall 119 and the tail wall 120 are easily damaged. By providing a distance between the adhesive layer 12 and the head wall 119, it is beneficial to reduce the possibility of damage due to the relatively low tensile fracture elongation rate of the head wall 119. By providing a distance between the adhesive layer 12 and the tail wall 120, it is beneficial to reduce the possibility of damage due to the relatively low tensile fracture elongation rate of the tail wall 120.

[0071] In some embodiments, please refer to Figure 7 , in the thickness direction of the packaging film 11, the packaging film 11 includes a first polymer layer 111, a first metal layer 112, a second polymer layer 113, and a third polymer layer 114 stacked in sequence. A plurality of adhesive layers 12 are spaced apart on the surface of the third polymer layer 114 facing away from the second polymer layer 113. The first polymer layer 111 includes polypropylene to make the packaging film 11 easy to encapsulate. The first metal layer 112 includes aluminum to enhance the plasticity of the packaging film 11. The second polymer layer 113 includes polyurethane to enhance the adhesion performance of the second polymer layer 113. The third polymer layer 114 includes polyamide to enhance the strength of the packaging film 11.

[0072] In a second aspect of the present application, an electronic device is further provided, including the secondary battery 100 according to any one of the embodiments of the first aspect above. The electronic device of the embodiments of the present application is not particularly limited, and it may be any electronic device known in the prior art. For example, the electronic device includes but is not limited to Bluetooth headsets, mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, ships, spacecraft, and the like. Among them, the electric toy may include stationary or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. The spacecraft may include airplanes, rockets, space shuttles, and spaceships, etc.

[0073] In a third aspect of the present application, a method for manufacturing a secondary battery 100 is further provided, which is used to prepare the secondary battery 100 according to any embodiment of the first aspect, and includes: providing a packaging film 11 and an electrode assembly 20, and wrapping the packaging film 11 around the outer surface of the electrode assembly 20. Providing an adhesive layer 12, and coating the adhesive layer 12 on the surface of the packaging film 11 facing away from the electrode assembly 20. Since the packaging film 11 needs to be dimpled before wrapping the electrode assembly 20, the packaging film 11 requires a certain tensile fracture elongation rate. By providing the adhesive layer 12 after the packaging film 11 wraps the electrode assembly 20, the tensile fracture elongation rate of the part of the composite packaging film 11 (the housing 10) formed by the packaging film 11 and the adhesive layer 12 where the adhesive layer 12 is provided can be reduced, without affecting the tensile fracture elongation rate of the packaging film 11 before the packaging film 11 wraps the electrode assembly 20, so that the packaging film 11 can meet the dimple requirement.

[0074] Test part:

[0075] 1. Tensile test of packaging film:

[0076] Take the packaging film without the adhesive layer as a sample, use a special tensile cutting knife to make a test sample with a length of 70 mm and a width of 15 mm from the sample, fix the test sample to the test fixture of a high-speed rail tensile testing machine, with a tensile speed of 50 ± 0.5 mm / min and a tensile spacing of 50 mm.

[0077] Tensile fracture elongation rate of packaging film = (displacement at the time of sample breakage / initial length of sample) × 100%.

[0078] 2. Tensile test of housing:

[0079] Take the housing as a sample. The housing includes a packaging film and a plurality of adhesive layers arranged at intervals on the surface of the packaging film. Use a special tensile cutting knife to make a test sample with a length of 70 mm and a width of 15 mm from the sample, fix the test sample to the test fixture of a high-speed rail tensile testing machine, with a tensile speed of 50 ± 0.5 mm / min and a tensile spacing of 50 mm.

[0080] Tensile fracture elongation rate of the part of the housing where the adhesive layer is provided = (displacement at the time of sample breakage / initial length of sample) × 100%.

[0081] 3. Nail test:

[0082] First, fully charge the secondary battery. Place the sample flat on the test table, and use a special nail with a diameter of 3 mm, a chamfer of 0.3, a nail tip length of 3 mm, and a nail body length of ≥ 100 mm to test from the center position of the sample at a speed of 150 ± 1.5 mm / s until the sample is completely pierced.

[0083] Passing criterion: After the test is completed, the secondary battery does not catch fire or explode.

[0084] Example 1

[0085] <Preparation of the positive electrode sheet>:

[0086] Using aluminum foil as the positive current collector, a layer of lithium cobalt oxide slurry is evenly coated on the surface of the aluminum foil. The slurry composition is a combination of 97.5 wt% lithium cobalt oxide (LiCoO2), 1.0 wt% carbon black (Super P), and 1.5 wt% polyvinylidene fluoride (PVDF). It is dried at 85 °C and then cold-pressed, sliced, and slit to prepare the positive electrode sheet.

[0087] <Preparation of the negative electrode sheet>:

[0088] Using copper foil as the negative current collector, a layer of graphite slurry is evenly coated on the surface of the copper foil. The slurry composition is a combination of 97.7 wt% artificial graphite, 1.3 wt% sodium carboxymethyl cellulose (CMC), and 1.0 wt% styrene-butadiene rubber (SBR). It is dried at 85 °C and then cold-pressed, sliced, and slit to prepare the negative electrode sheet.

[0089] <Preparation of the electrolyte>:

[0090] A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC) = 20:30:20:28:2, mass ratio) at a mass ratio of 8:92 is used as the electrolyte of the secondary battery.

[0091] <Preparation of the secondary battery>:

[0092] The positive electrode sheet and the negative electrode sheet are welded with tabs, and then the positive electrode sheet and the negative electrode sheet are stacked. The positive electrode sheet and the negative electrode sheet are separated by a polyethylene separator to prepare the electrode assembly.

[0093] Using an aluminum-plastic film with a thickness of 103 μm as the packaging film, the packaging film is wrapped around the outer surface of the electrode assembly. After top-side sealing, inkjet coding, vacuum drying, electrolyte injection, and high-temperature standing, formation and capacity measurement are carried out to obtain the preliminary secondary battery.

[0094] Mix 83.3 wt% of epoxy resin and 8.3 wt% of fatty amine (curing agent) in air for 3 - 5 min (the mass ratio of 83.3 wt% of epoxy resin to 8.3 wt% of fatty amine is approximately 10:1), coat it on the surface of the packaging film of the primary secondary battery facing away from the electrode assembly, and cure it in an 80°C oven for 1 h to form an adhesive layer. Among them, the shape of the adhesive layer is strip-shaped, the thickness of the adhesive layer is 10 μm, the width of the adhesive layer is 3 mm, the length of the adhesive layer is 60 mm, the length direction of the adhesive layer is perpendicular to the length direction of the electrode assembly (the direction in which the tab extends out of the housing), the number of adhesive layers ≥ 2, all the adhesive layers are evenly arranged on the surface of the packaging film facing away from the electrode assembly in the length direction of the electrode assembly, there is a gap between adjacent two adhesive layers, and the width of the gap is 1 mm. In the width direction of the secondary battery, the secondary battery includes a first side wall and a second side wall, the distance between the adhesive layer and the first side wall is 2 mm, and the distance between the adhesive layer and the second side wall is 2 mm. In the length direction of the secondary battery, the secondary battery includes a head wall and a tail wall, the distance between the adhesive layer closest to the head wall and the head wall is 2 mm, and the distance between the adhesive layer closest to the tail wall and the tail wall is 2 mm. The adhesive layer and the packaging film form a housing, the length of the secondary battery is 99 mm, and the width of the secondary battery is 66 mm.

[0095] The relevant parameters in Comparative Examples 1 and 2 and Examples 1 to 20 are shown in Table 1 below.

[0096] Among them, the housing of Comparative Example 1 is only the packaging film and does not include an adhesive layer.

[0097] The adhesive layer on the surface of the packaging film in Comparative Example 2 is fully coated and there is no gap in the adhesive layer.

[0098] The thicknesses of the adhesive layers in Examples 1 to 7 are different, the widths of the adhesive layers in Example 1 and Examples 8 to 11 are different, and the widths of the gaps between adjacent two adhesive layers in Example 1 and Examples 12 to 15 are different.

[0099] The shapes of the adhesive layers in Examples 16 to 20 are dot-shaped, and the diameters of the minimum circumscribed circles of the adhesive layers in Examples 16 to 20 are different.

[0100] Table 1

[0101]

[0102] Note: In Table 1, "\ " means not including this parameter.

[0103] According to Table 1 above, in combination with Comparative Examples 1 and 2 and Examples 1 to 20, it can be seen that by arranging a plurality of adhesive layers at intervals on the surface of the packaging film facing away from the electrode assembly, the housing has an adhesive layer and a packaging film, and the tensile fracture elongation of the part of the housing provided with the adhesive layer is less than that of the packaging film. When the housing is damaged by an external force, it will break in advance, and the extension of the housing is small, which is beneficial to reducing the possibility that the housing is extended to the fracture of the pole piece by an external force, and further reducing the possibility of short circuit between the aluminum layer of the housing and the pole piece. Therefore, the nail penetration rate will increase.

[0104] In combination with Examples 1 to 7, it can be seen that the greater the thickness of the adhesive layer, the lower the tensile fracture elongation of the part of the housing provided with the adhesive layer, and the higher the nail penetration rate of the secondary battery. When the thickness of the adhesive layer is less than 1μm, the reduction of the tensile fracture elongation of the part of the housing provided with the adhesive layer is not obvious. By setting the thickness of the adhesive layer ≥1μm, the tensile fracture elongation of the part of the housing provided with the adhesive layer can be further reduced, thereby further improving the nail penetration rate of the secondary battery. However, the greater the thickness of the adhesive layer, the more energy density the secondary battery will lose. When the thickness of the adhesive layer is 60μm, the secondary battery has a good nail penetration rate. Continuing to increase the thickness of the adhesive layer, the improvement of the nail penetration rate of the secondary battery is not obvious, and more energy density of the secondary battery will be lost. Therefore, considering the nail penetration rate of the secondary battery and the energy density of the secondary battery comprehensively, it is preferred that the thickness of the adhesive layer ≤60μm.

[0105] In combination with Example 1 and Examples 8 to 11, it can be seen that the width of the adhesive layer is 0.2mm to 30mm, and the part of the housing provided with the adhesive layer has a low tensile fracture elongation, and the secondary battery has a high nail penetration rate. When the width of the adhesive layer is less than 0.2mm, due to the fluidity of the adhesive layer during the curing process of the adhesive layer, adjacent adhesive layers are likely to be connected, and due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the width of the adhesive layer, resulting in poor nail penetration effect. When the width of the adhesive layer is greater than 30mm, there are fewer stress concentration points on the housing when it is stressed, and it is not easy to generate stress concentration when the housing is stressed, resulting in that the housing is not easy to break, and the nail penetration rate of the secondary battery will decrease.

[0106] Combined with Embodiment 1 and Embodiments 12 to 15, it can be seen that by setting a gap between two adjacent adhesive layers, stress concentration is likely to occur when the housing is under stress, which is beneficial to further reducing the tensile fracture elongation rate of the part of the housing provided with the adhesive layer, and further beneficial to reducing the possibility of short circuit between the aluminum layer of the housing and the electrode sheet. Therefore, the acupuncture passing rate will be further improved. The smaller the gap width between two adjacent adhesive layers, the easier it is for stress concentration to occur when the housing is under stress, the lower the tensile fracture elongation rate of the part of the housing provided with the adhesive layer, and the higher the acupuncture passing rate of the secondary battery. If the gap width is greater than 10 mm, the stress concentration generated when the housing is under stress is not obvious. By setting the gap width between two adjacent adhesive layers ≤ 10 mm, the acupuncture passing rate of the secondary battery can be further improved. When the gap width between two adjacent adhesive layers is less than 0.2 mm, the adjacent adhesive layers are likely to be connected, and due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the gap length. Therefore, it is preferred that the gap width between two adjacent adhesive layers ≥ 0.2 mm.

[0107] Combined with Embodiments 16 to 20, it can be seen that when the shape of the adhesive layer is dot-shaped and the diameter of the minimum circumscribed circle of the adhesive layer is 0.5 mm to 10 mm, the part of the housing provided with the adhesive layer has a lower tensile fracture elongation rate, and the secondary battery has a higher acupuncture passing rate. When the diameter of the minimum circumscribed circle of the adhesive layer is less than 0.5 mm, due to the limitation of processing accuracy, it is difficult to ensure the dimensional stability of the diameter of the minimum circumscribed circle of the adhesive layer, resulting in poor acupuncture effect. When the diameter of the minimum circumscribed circle of the adhesive layer is greater than 10 mm, there are fewer stress concentration points on the housing, and it is not easy for stress concentration to occur when the housing is under stress, resulting in that the housing is not easy to break, and the acupuncture passing rate of the secondary battery will decrease.

[0108] The relevant parameters in Embodiments 1 to 7 are shown in Table 2 below.

[0109] Among them, the thicknesses of the adhesive layers in Embodiments 1 to 7 are different.

[0110] Table 2

[0111]

[0112] According to Table 2 above, combined with Embodiments 1 to 7, it can be seen that the tensile fracture elongation rate of the packaging film is The tensile fracture elongation rate of the part of the housing provided with the adhesive layer is The larger it is, the higher the acupuncture passing rate of the secondary battery, When it is less than 9.5%, the thickness of the adhesive layer is likely to be less than 1 μm, and the acupuncture passing rate of the secondary battery is relatively low. By setting the thickness of the adhesive layer can be ≥ 1 μm, and the acupuncture passing rate of the secondary battery can be improved. When it is greater than 66%, the thickness of the adhesive layer is likely to be greater than 60 μm. Continuing to increase The increase in the puncture passing rate of the secondary battery is not obvious, and it is easy to lose more energy density of the secondary battery. By setting the thickness of the adhesive layer can be ≤ 60 μm, which can improve the energy density of the secondary battery.

[0113] The above are only the embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present application.

Claims

1. A secondary battery, comprising a housing and an electrode assembly, wherein the housing comprises a packaging film, and the packaging film is wrapped around the outer surface of the electrode assembly; It is characterized in that The shell also includes a plurality of adhesive layers, which are spaced apart on the surface of the packaging film away from the electrode assembly. The packaging film has a tensile elongation at break of φ1, and a tensile elongation at break of a portion of the shell where the adhesive layers are provided, φ2, φ2<φ1.

2. The secondary battery according to claim 1, characterized in that: The adhesive layer is arranged in a strip shape on a surface of the packaging film away from the electrode assembly.

3. The secondary battery according to claim 2, characterized in that: The length direction of the glue layer is perpendicular to the length direction of the electrode assembly; or, the length direction of the glue layer is perpendicular to the width direction of the electrode assembly.

4. The secondary battery according to claim 2, characterized in that: The width of the adhesive layer is 0.2 mm to 30 mm.

5. The secondary battery according to claim 1, characterized in that: The adhesive layer is arranged in a dotted shape on a surface of the packaging film away from the electrode assembly.

6. The secondary battery according to claim 5, characterized in that: On the surface of the packaging film, the diameter of the minimum circumscribed circle of the adhesive layer is 0.5 mm to 10 mm.

7. The secondary battery according to claim 1, characterized in that: The width of the gap between two adjacent adhesive layers is 0.2 mm to 10 mm.

8. The secondary battery according to claim 1, characterized in that: The thickness of the adhesive layer is 1 μm to 60 μm.

9. The secondary battery according to claim 1, characterized in that: The adhesive layer includes a resin compound, and the resin compound includes at least one of an epoxy resin and a phenolic resin.

10. The secondary battery according to claim 9, characterized in that: The adhesive layer further includes a curing agent for the resin compound, and the curing agent includes at least one of aliphatic amines, aromatic amines, modified amines, and maleic anhydride.

11. The secondary battery according to claim 10, characterized in that: The mass percentage of the curing agent in the adhesive layer is 5% to 20%.

12. The secondary battery according to claim 1, characterized in that: The adhesive layer also includes an inorganic filler; The inorganic filler includes glass fiber, and the mass percentage of the glass fiber in the adhesive layer is 10% to 50%; or, the inorganic filler includes silicon dioxide, and the mass percentage of the silicon dioxide in the adhesive layer is 5% to 30%.

13. The secondary battery according to claim 1, characterized in that: 9.5%≤φ1-φ2≤66%.

14. The secondary battery according to claim 1, characterized in that: The packaging film comprises a first polymer layer, a first metal layer, a second polymer layer and a third polymer layer stacked in sequence, a surface of the third polymer layer facing away from the second polymer layer is provided with a plurality of adhesive layers at intervals, and the third polymer layer comprises polyamide.

15. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 14.

16. A method for manufacturing a secondary battery, for preparing the secondary battery according to any one of claims 1 to 14, characterized in that: include: Providing the packaging film and the electrode assembly, and wrapping the packaging film on the outer surface of the electrode assembly; The glue layer is provided and coated on the surface of the packaging film facing away from the electrode assembly.

Images