Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery comprises a shell, an electrode assembly arranged in the shell and a sealing element for sealing the shell, the shell comprises a first shell body and a second shell body, the first shell body comprises a first wall and a first side wall connected with the first wall, the second shell body comprises a second wall and a second side wall connected with the second wall, the first side wall is provided with a first face facing the second side wall, and the second side wall is provided with a second face facing the first side wall. The first face and the second face are oppositely arranged in the assembling direction of the first shell and the second shell, and a gap is formed between the first face and the second face. The sealing piece comprises a first part arranged on the periphery of the first side wall in a winding mode, a second part arranged on the periphery of the second side wall in a winding mode and a third part connected with the first part and the second part, and the third part is arranged in the gap in a folding and unfolding mode. And when the electrode assembly expands, the third part can be correspondingly expanded, and when the electrode assembly contracts, the third part can correspondingly contract, so that the risk of liquid leakage and failure of the secondary battery can be reduced.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Art

[0002] Current secondary batteries include steel-cased batteries and soft-pack batteries. Generally speaking, both steel-cased batteries and soft-pack batteries include an outer shell and an electrode assembly disposed within the outer shell. The outer shell of a steel-cased battery includes a first shell and a second shell, which are sealed together by welding or a sealant. Summary of the Invention

[0003] For secondary batteries sealed with seals in the prior art, the electrode assembly expands when the secondary battery is charged and contracts when the secondary battery is discharged. The inventors discovered that the expansion or contraction of the electrode assembly exerts opposing forces on the first and second shells along their assembly direction. Because the first and second shells are encapsulated by the seal, as the number of charge and discharge cycles increases, the force generated by the expansion or contraction of the electrode assembly will repeatedly impact the sealing interface between the seal and the first and second shells, making the seal susceptible to failure and, consequently, causing the secondary battery to leak.

[0004] In view of the above situation, it is necessary to provide a secondary battery that is conducive to reducing the risk of leakage failure.

[0005] The first aspect of the present application provides a secondary battery, comprising a housing, an electrode assembly and a seal. The housing comprises a first shell and a second shell, the first shell and the second shell together forming a receiving chamber, and the receiving chamber is filled with an electrolyte. The first shell comprises a first wall and a first side wall connected to the periphery of the first wall, the second shell comprises a second wall and a second side wall connected to the periphery of the second wall, the first side wall is provided with a first surface facing the second side wall on a side away from the first wall, the second side wall is provided with a second surface facing the first side wall on a side away from the second wall, along a first direction, the first surface and the second surface are arranged opposite to each other and have a gap, and the first direction is the assembly direction of the first shell and the second shell. The electrode assembly is arranged in the receiving chamber, and along the first direction, the electrode assembly comprises a negative electrode sheet, a positive electrode sheet and a diaphragm, the negative electrode sheet and the positive electrode sheet are arranged alternately, and the diaphragm is arranged between adjacent negative electrode sheets and positive electrode sheets. The seal seals the gap, and the seal includes a first part, a second part and a third part. The first part is arranged around the outer periphery of the first side wall, the second part is arranged around the outer periphery of the second side wall, and the third part connects the first part and the second part, and the third part is retractably arranged in the gap.

[0006] By making the third part expandable and retractable in the gap, when the electrode assembly expands, the third part can expand accordingly, and when the electrode assembly contracts, the third part can contract accordingly, which is beneficial to reducing the impact on the packaging interface between the seal and the first shell and the second shell, making the packaging of the seal effective for a long time, thereby helping to reduce the risk of leakage failure of the secondary battery.

[0007] In one or more of the above embodiments, the secondary battery includes an adhesive member, which is adhered between the first wall and the electrode assembly and between the second wall and the electrode assembly along the first direction. The adhesive member can fix the first shell and the second shell to the electrode assembly respectively, which helps to reduce the possibility of the first shell and the second shell moving relative to each other and pulling the seal, resulting in the sealing failure of the seal. In addition, when the first shell and the second shell are electrically connected to different polarities of the electrode assembly, it helps to reduce the possibility of the first shell and the second shell moving relative to each other and contacting each other, resulting in a contact short circuit in the secondary battery.

[0008] In one or more of the above embodiments, the spacing between the first sidewall and the second sidewall along the first direction is D1, and the thickness of the third portion in the flattened state is H3, where 20μm≤H3≤0.5D1. By setting 20μm≤H3, the third portion is not too thin, which helps reduce the possibility of leakage due to damage to the third portion and the possibility of a short circuit between the first and second shells due to contact with burrs. By setting H3≤0.5D1, the third portion can be easily retracted and arranged in the gap.

[0009] In one or more of the above embodiments, 28 μm ≤ H3 ≤ 0.5D1. By setting 28 μm ≤ H3, the third portion can be made thicker, which is beneficial to further reduce the possibility of leakage caused by damage to the third portion and the possibility of short circuit caused by burr contact between the first shell and the second shell.

[0010] In one or more of the above embodiments, the thickness of the secondary battery along the first direction is H1, and the dimension of the third portion when flattened along the first direction is W3, where 0.05H1≤W3. Setting 0.05H1≤W3 facilitates ensuring that the flattened third portion is at least compatible with the expansion of the electrode assembly during charging of the secondary battery, thereby reducing the impact on the sealing interface between the seal and the first and second shells, and reducing the risk of leakage and failure of the secondary battery.

[0011] In one or more of the above embodiments, along the direction perpendicular to the first direction, the minimum spacing between the negative electrode pole piece and the shell is D2, the smaller value of the wall thickness of the first side wall and the wall thickness of the second side wall is H2, and 0.08H1≤W3≤2(D2+H2). By setting 0.08H1≤W3, it is convenient to make the flattened third part at least able to adapt to the degree of expansion of the electrode assembly when the secondary battery is charged after multiple cycles, which is beneficial to further ensure that the impact on the packaging interface between the seal and the first shell and the second shell is reduced, and further reduce the risk of leakage failure of the secondary battery. By setting W3≤2(D2+H2), the possibility of the third part squeezing the negative electrode pole piece can be reduced, and the possibility of the negative electrode pole piece being squeezed and deformed, resulting in burrs piercing the diaphragm and contacting the positive electrode pole piece, can be reduced, which is beneficial to reduce the risk of short circuit in the secondary battery.

[0012] In one or more of the above embodiments, the third portion is folded and disposed in the gap. Alternatively, the third portion is arcuate and disposed in the gap. When the electrode assembly expands or contracts, the folded third portion facilitates corresponding expansion or contraction. When the electrode assembly expands and contracts multiple times, the arcuate third portion reduces the possibility of damage or leakage from the third portion due to repeated expansion and contraction.

[0013] In one or more of the above embodiments, the seal includes a first adhesive layer and a metal layer. The first adhesive layer is adhered to the outer periphery of the first and second side walls, and the metal layer is disposed on the side of the first adhesive layer facing away from the first and second side walls. The first, second, and third parts each include a portion of the first adhesive layer, and the first, second, and third parts each include a portion of the metal layer. The adhesion of the first adhesive layer to the first and second side walls helps improve the stability of the adhesion between the seal and the housing. The provision of the metal layer on the side of the first adhesive layer facing away from the first and second side walls helps improve the sealing performance of the seal against the first and second shells. Furthermore, the good plasticity of the metal layer helps keep the third part in a retractable state.

[0014] In one or more of the above embodiments, the seal further includes a second adhesive layer, which is disposed on a side of the metal layer facing away from the first adhesive layer. The first portion, the second portion, and the third portion each include a portion of the second adhesive layer. The second adhesive layer disposed on the side of the metal layer facing away from the first adhesive layer protects the metal layer, thereby reducing the risk of failure due to corrosion or damage to the metal layer.

[0015] In one or more of the above embodiments, the first portion, the second portion and the third portion are integrally provided, which is beneficial to improving the sealing performance of the sealing member to the housing.

[0016] In one or more of the above embodiments, the negative electrode plate is electrically connected to the first shell, the positive electrode plate is electrically connected to the second shell, and the third portion protrudes from the gap toward the receiving cavity. This helps ensure insulation between the first shell and the second shell, reducing the risk of contact short circuits in the secondary battery.

[0017] The second aspect of the present application provides an electrical device comprising the secondary battery of the first aspect of the present application. The secondary battery is less likely to fail due to leakage, which is beneficial for extending the service life of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A top view of a secondary battery provided in accordance with an embodiment of the present application.

[0019] Figure 2 This is a front view of a secondary battery provided in one embodiment of the present application.

[0020] Figure 3 An exploded view of a secondary battery provided in one embodiment of the present application.

[0021] Figure 4 For the first embodiment of this application Figure 1 Cross-section along the midline AA.

[0022] Figure 5 The second embodiment of this application is Figure 1 Cross-section along the midline AA.

[0023] Figure 6 This is an overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0024] Description of main component symbols 1000. Electrical equipment; 100. Secondary battery; 10. Casing; 101. Receiving cavity; 11. First shell; 111. First wall; 112. First side wall; 1121. First surface; 12. Second shell; 121. Second wall; 122. Second side wall; 1221. Second surface; 20. Electrode assembly; 201. Negative ear; 202. Positive ear; 21. Negative electrode sheet; 22. Positive electrode sheet; 23. Diaphragm; 30. Seal; 301. First part; 302. Second part; 303. Third part; 31. First adhesive layer; 32. Metal layer; 33. Second adhesive layer; 40. Adhesive; X, first direction. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0026] It should be noted that when an element is considered to be “connected” to another element, it may be directly connected to the other element or there may be a centrally disposed element. When an element is considered to be “disposed on” another element, it may be directly disposed on the other element or there may be a centrally disposed element.

[0027] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0028] The terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implying the quantity, specific order or primary and secondary relationship of the technical features indicated.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] It should be understood that, taking into account actual manufacturing tolerances, in the technical solution of this application, when two components are arranged parallel or perpendicularly, the angle between the two components is allowed to have a tolerance of within 10% relative to the angle corresponding to the parallel or perpendicular arrangement. In the technical solution of this application, when two parameters are equal, a tolerance of within 10% is allowed between the two parameters.

[0031] The present application provides a secondary battery, comprising a housing, an electrode assembly and a seal. The housing comprises a first shell and a second shell, the first shell and the second shell together forming a receiving cavity, and the receiving cavity is filled with an electrolyte. The first shell comprises a first wall and a first side wall connected to the periphery of the first wall, the second shell comprises a second wall and a second side wall connected to the periphery of the second wall, the first side wall is provided with a first surface facing the second side wall on a side away from the first wall, the second side wall is provided with a second surface facing the first side wall on a side away from the second wall, along a first direction, the first surface and the second surface are arranged opposite to each other and have a gap, and the first direction is the assembly direction of the first shell and the second shell. The electrode assembly is arranged in the receiving cavity, and along the first direction, the electrode assembly comprises a negative electrode sheet, a positive electrode sheet and a diaphragm, the negative electrode sheet and the positive electrode sheet are arranged alternately, and the diaphragm is arranged between adjacent negative electrode sheets and positive electrode sheets. The seal seals the gap, and the seal includes a first part, a second part and a third part. The first part is arranged around the outer periphery of the first side wall, the second part is arranged around the outer periphery of the second side wall, and the third part connects the first part and the second part, and the third part is retractably arranged in the gap.

[0032] In the secondary battery of the present application, by making the third part expandable and retractable in the gap, when the electrode assembly expands, the third part can expand accordingly, and when the electrode assembly contracts, the third part can contract accordingly, which is beneficial to reducing the impact on the packaging interface between the seal and the first shell and the second shell, making the packaging of the seal effective for a long time, thereby helping to reduce the risk of leakage failure of the secondary battery.

[0033] The following will describe some embodiments of the present application in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0034] See also Figures 1 to 3 An embodiment of the present application provides a secondary battery 100 including a housing 10 , an electrode assembly 20 and a seal 30 . The electrode assembly 20 is accommodated in the housing 10 . The seal 30 is provided on the outer wall of the housing 10 and is used to seal the housing 10 .

[0035] See also Figure 4 and Figure 5 The housing 10 includes a first shell 11 and a second shell 12. The first shell 11 and the second shell 12 together form a receiving cavity 101. The receiving cavity 101 is filled with electrolyte, and the electrode assembly 20 is arranged in the receiving cavity 101. The housing 10 includes but is not limited to a metal housing, and the material of the first shell 11 and the material of the second shell 12 may be the same or different, and this application does not impose any restrictions on this. The electrode assembly 20 includes a negative electrode sheet 21, a positive electrode sheet 22 and a separator 23. The negative electrode sheet 21 and the positive electrode sheet 22 are arranged alternately, and the separator 23 separates the negative electrode sheet 21 and the positive electrode sheet 22. The assembly direction of the first shell 11 and the second shell 12 is defined as a first direction X, and the thickness direction of the electrode assembly 20 is parallel to the first direction X. In some embodiments, the housing 10 is a metal housing, the negative electrode sheet 21 is electrically connected to the first shell 11, and the positive electrode sheet 22 is electrically connected to the second shell 12. At this time, the first shell 11 and the second shell 12 are insulated. In some embodiments, the shell 10 is a metal shell, and the first shell 11 and the second shell 12 are insulated and provided with poles (not shown in the figure), the negative pole piece 21 is electrically connected to the pole provided on the first shell 11, and the positive pole piece 22 is electrically connected to the pole provided on the second shell 12. At this time, the first shell 11 and the second shell 12 are not limited to insulating settings or conductive settings.

[0036] See also Figure 3The first shell 11 includes a first wall 111 and a first side wall 112, and the second shell 12 includes a second wall 121 and a second side wall 122. The first side wall 112 connects to the periphery of the first wall 111, and the second side wall 122 connects to the periphery of the second wall 121. The first side wall 112 can be inclined or perpendicular to the first wall 111, and the second side wall 122 can be inclined or perpendicular to the second wall 121. This application does not impose any restrictions on this. The side of the first side wall 112 away from the first wall 111 is provided with a first surface 1121 facing the second side wall 122, and the side of the second side wall 122 away from the second wall 121 is provided with a second surface 1221 facing the first side wall 112. Along the first direction X, the first surface 1121 and the second surface 1221 are arranged to face each other.

[0037] In some embodiments, the electrode assembly 20 has a stacked structure, wherein the negative electrode sheets 21 and the positive electrode sheets 22 are alternately stacked, wherein the separator 23 is disposed between any adjacent negative electrode sheets 21 and positive electrode sheets 22. In some embodiments, the electrode assembly 20 has a wound structure, wherein the negative electrode sheets 21 and the positive electrode sheets 22 are alternately wound, wherein the separator 23 is disposed between the negative electrode sheets 21 and the positive electrode sheets 22.

[0038] In some embodiments, the negative electrode plate 21 includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is provided on two opposite sides of the negative electrode current collector along the thickness direction. The positive electrode plate 22 includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is provided on two opposite sides of the positive electrode current collector along the thickness direction. In some embodiments, the material of the negative electrode current collector includes at least one of copper, nickel, tantalum, and titanium, and the material of the positive electrode current collector includes at least one of aluminum, nickel, tantalum, and titanium. In some embodiments, the material of the negative electrode active material layer includes at least one of graphite, hard carbon, soft carbon, silicon, silicon oxide material, and silicon carbon material. The material of the positive electrode active material layer includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide.

[0039] In some embodiments, the diaphragm 23 is made of insulating film materials such as polyethylene film, polypropylene film, polyester film, or polyimide film.

[0040] In some embodiments, when the negative electrode sheet 21 is the outermost sheet of the electrode assembly 20, a hollow foil region is provided on the side of the negative electrode current collector facing away from the interior of the electrode assembly 20, and the negative electrode current collector is in direct contact and connection with the first wall 111 via the hollow foil region. When the positive electrode sheet 22 is the outermost sheet of the electrode assembly 20, a hollow foil region is provided on the side of the positive electrode current collector facing away from the interior of the electrode assembly 20, and the positive electrode current collector is in direct contact and connection with the second wall 121 via the hollow foil region. It should be understood that when the electrode assembly 20 is a stacked structure, the outermost sheet is the sheet closest to the first wall 111 or the second wall 121 among the several sheets of the electrode assembly 20 along the thickness direction of the electrode assembly 20. When the electrode assembly 20 is a wound structure, the outermost sheet is the flat area of the outermost winding sheet located between the bending regions and close to the first wall 111 or the second wall 121.

[0041] See also Figure 3 In some embodiments, the electrode assembly 20 is provided with a negative electrode tab 201 for conducting the negative electrode polarity and a positive electrode tab 202 for conducting the positive electrode polarity. The negative electrode tab 201 is connected to the first side wall 112, and the positive electrode tab 202 is connected to the second side wall 122. This facilitates the connection of the negative electrode tab 201 to the first shell 11 and the positive electrode tab 202 to the second shell 12, thereby improving the convenience of manufacturing the secondary battery 100. When the first wall 111 and the second wall 121 are arranged opposite each other along the thickness direction of the secondary battery 100, the connection of the negative electrode tab 201 to the first side wall 112 and the connection of the positive electrode tab 202 to the second side wall 122 also help reduce the space occupied by the secondary battery 100 along the thickness direction. In some embodiments, multiple negative electrode tabs 201 are gathered to form a negative electrode tab bundle, which is directly connected to the first side wall 112. Multiple positive electrode tabs 202 are gathered to form a positive electrode tab bundle, which is directly connected to the second side wall 122.

[0042] There is a gap between the first surface 1121 and the second surface 1221, and the sealing member 30 seals the gap. Figure 4 and Figure 5 The sealing member 30 includes a first portion 301, a second portion 302 and a third portion 303. The first portion 301 is disposed around the periphery of the first side wall 112, the second portion 302 is disposed around the periphery of the second side wall 122, and the third portion 303 connects the first portion 301 and the second portion 302. The third portion 303 is retractably disposed in the gap. Figure 3The third portion 303 of the seal 30 is shown unfolded to a flattened state along the first direction X. When the electrode assembly 20 expands, the third portion 303 can expand accordingly. When the electrode assembly 20 contracts, the third portion 303 can contract accordingly, which helps to reduce the impact on the packaging interface between the seal 30 and the first shell 11 and the second shell 12, making the packaging of the seal 30 effective for a long time, thereby helping to reduce the risk of leakage failure of the secondary battery 100. In some embodiments, along the wall thickness direction of the first side wall 112, the projection of the negative electrode tab bundle is located within the projection of the first side wall 112. Along the wall thickness direction of the second side wall 122, the projection of the positive electrode tab bundle is located within the projection of the second side wall 122 to avoid the third portion 303.

[0043] In some embodiments, the negative electrode tab 21 is electrically connected to the first housing 11, the positive electrode tab 22 is electrically connected to the second housing 12, and the third portion 303 protrudes from the gap toward the receiving cavity 101. This helps ensure insulation between the first housing 11 and the second housing 12, reducing the risk of contact short circuits in the secondary battery 100.

[0044] In some embodiments, the first portion 301, the second portion 302 and the third portion 303 are integrally provided. This is beneficial for improving the sealing performance of the sealing member 30 to the housing 10. Figure 4 In some embodiments, the third portion 303 is folded and disposed in the gap. When the electrode assembly 20 expands or contracts, the third portion 303 can be expanded or contracted accordingly. The folded shape referred to herein can be a regular or irregular folded or stacked state. Figure 5 In some embodiments, the third portion 303 is arranged in an arc shape in the gap. When the electrode assembly 20 expands and contracts multiple times, the possibility of the third portion 303 being damaged and leaking due to repeated expansion and contraction can be reduced.

[0045] In some embodiments, the thickness of the third portion 303 in the flattened state is H3. The thickness of the third portion 303 refers to the dimension of the third portion 303 along the thickness direction of the seal 30 in the flattened state, and 20 μm ≤ H3. For example, H3 is 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, or any value between the listed endpoints. By setting 20 μm ≤ H3, the third portion 303 is not too thin, which helps reduce the possibility of leakage caused by damage to the third portion 303 and the possibility of short circuits caused by contact between the first shell 11 and the second shell 12 due to burrs. In some embodiments, the thickness of the first portion 301, the second portion 302, and the third portion 303 are equal.

[0046] In some embodiments, 28 μm ≤ H3. By setting 28 μm ≤ H3, the third portion 303 can be made thicker, which is beneficial to further reduce the possibility of leakage caused by damage to the third portion 303 and the possibility of short circuit caused by burr contact between the first shell 11 and the second shell 12.

[0047] In some embodiments, the distance between the first sidewall 112 and the second sidewall 122 along the first direction X is D1, and H3≤0.5D1. By setting H3≤0.5D1, the third portion 303 can be easily and retractably disposed in the gap.

[0048] In some embodiments, 40 μm ≤ D1 ≤ 3000 μm. For example, D1 is 40 μm, 100 μm, 200 μm, 500 μm, 1000 μm, 2000 μm, 3000 μm, or any value between the listed endpoints. Setting 40 μm ≤ D1 helps reduce the possibility of a short circuit between the first shell 11 and the second shell 12 due to burr contact. Setting D1 ≤ 3000 μm helps reduce the loss of energy density of the secondary battery 100.

[0049] In some embodiments, the thickness of the secondary battery 100 along the first direction X is H1, and the dimension of the third portion 303 when flattened along the first direction X is W3, where 0.05H1 ≤ W3. For example, W3 is 0.05H1, 0.06H1, 0.07H1, 0.08H1, 0.09H1, 0.1H1, or any value between the listed endpoints. By setting 0.05H1 ≤ W3, the flattened third portion 303 is at least able to adapt to the expansion of the electrode assembly 20 during charging of the secondary battery 100, which helps to reduce the impact on the sealing interface between the seal 30 and the first shell 11 and the second shell 12, thereby reducing the risk of leakage failure of the secondary battery 100.

[0050] In some embodiments, 1 mm ≤ H1 ≤ 15 mm. For example, H1 is 1 mm, 3 mm, 5 mm, 10 mm, 15 mm, or any value between the listed endpoints.

[0051] In some embodiments, 0.08H1≤W3. By setting 0.08H1≤W3, the flattened third portion 303 can at least adapt to the expansion degree of the electrode assembly 20 during charging of the secondary battery 100 after multiple cycles of use, which is conducive to further ensuring that the impact on the packaging interface between the seal 30 and the first shell 11 and the second shell 12 is reduced, and further reducing the risk of leakage failure of the secondary battery 100.

[0052] In some embodiments, the minimum spacing between the negative electrode tab 21 and the housing 10 along a direction perpendicular to the first direction X is D2, the thickness of the first side wall 112 or the thickness of the second side wall 122 is H2, whichever is smaller, and W3 ≤ 2(D2 + H2). By setting W3 ≤ 2(D2 + H2), the possibility of the third portion 303 squeezing the negative electrode tab 21 can be reduced, and the possibility of burrs on the negative electrode tab 21 being squeezed and deformed, causing them to pierce the separator 23 and contact the positive electrode tab 22, can be reduced, thereby reducing the risk of a short circuit in the secondary battery 100.

[0053] In some embodiments, 0 mm < D2 ≤ 0.5 mm. For example, D2 is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, or any value between the listed endpoints.

[0054] In some embodiments, 0.03 mm ≤ H2 ≤ 0.5 mm. For example, H2 is 0.03 mm, 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, or any value between the listed endpoints.

[0055] See Figure 4 and Figure 5 In some embodiments, the seal 30 includes a first adhesive layer 31, which is adhered to the outer periphery of the first side wall 112 and the second side wall 122, thereby improving the stability of the adhesion between the seal 30 and the housing 10. The first portion 301, the second portion 302, and the third portion 303 each include a portion of the first adhesive layer 31.

[0056] In some embodiments, the first adhesive layer 31 can melt or lose adhesion when heated, and forms part of a pressure relief channel connected to the receiving cavity 101. When the secondary battery 100 experiences thermal runaway, the melting or loss of adhesion of the first adhesive layer 31 can promptly relieve pressure in the receiving cavity 101, thereby improving the safety of the secondary battery 100.

[0057] In some embodiments, the melting point of the first adhesive layer 31 is between 95°C and 130°C. For example, the melting point of the first adhesive layer 31 is 95°C, 100°C, 110°C, 130°C, or any value between the listed endpoints. By setting the melting point of the first adhesive layer 31 to between 95°C and 130°C, the possibility of premature melting or loss of adhesion of the first adhesive layer 31 before thermal runaway of the secondary battery 100 occurs can be reduced, which helps maintain the sealing effect of the seal 30 on the outer shell 10. Furthermore, it can ensure that the first adhesive layer 31 melts or loses adhesion in time to relieve pressure in the receiving cavity 101 when thermal runaway of the secondary battery 100 occurs, which helps improve the safety of the secondary battery 100.

[0058] In some embodiments, the material of the first adhesive layer 31 comprises an electrolyte-resistant polymer. The polymer comprises at least one of polyolefin, fluororubber, and polyurethane. Polyolefins may include polypropylene and polyethylene, among others. This allows the first adhesive layer 31 to have high resistance to electrolyte corrosion. In some embodiments, the first adhesive layer 31 comprises a single layer or multiple layers of the polymer.

[0059] See also Figure 4 and Figure 5 In some embodiments, the seal 30 includes a metal layer 32, which is disposed on the side of the first adhesive layer 31 facing away from the first sidewall 112 and the second sidewall 122. The first portion 301, the second portion 302, and the third portion 303 each include a portion of the metal layer 32. The metal layer 32 has a superior water barrier to that of the first adhesive layer 31, which helps improve the sealing performance of the seal 30 between the first and second housings 11, 12. Furthermore, the metal layer 32 has good plasticity, which helps keep the third portion 303 in a retractable state.

[0060] In some embodiments, the material of metal layer 32 includes at least one of steel, aluminum, nickel, silver, copper, and alloys thereof. In some embodiments, metal layer 32 is a single layer or a multilayer structure. For example, the multilayer structure includes a steel layer plus an aluminum layer, or a nickel layer plus a copper layer.

[0061] See also Figure 4 and Figure 5 In some embodiments, the seal 30 includes a second adhesive layer 33, which is disposed on a side of the metal layer 32 facing away from the first adhesive layer 31. The first portion 301, the second portion 302, and the third portion 303 each include a portion of the second adhesive layer 33. The second adhesive layer 33 protects the metal layer 32, thereby reducing the risk of failure due to corrosion or breakage of the metal layer 32.

[0062] In some embodiments, the melting point of the second adhesive layer 33 is greater than the melting point of the first adhesive layer 31. In some embodiments, the difference in melting point between the second adhesive layer 33 and the first adhesive layer 31 is greater than 10°C.

[0063] In some embodiments, the melting point of the second adhesive layer 33 is 140° C. to 500° C. For example, the melting point of the second adhesive layer 33 is 140° C., 160° C., 200° C., 250° C., 300° C., 500° C., or any value therebetween.

[0064] In some embodiments, the material of the second adhesive layer 33 comprises an electrolyte-resistant polymer. The polymer may include at least one of polyolefins, fluoropolymers, polyetheretherketones, fluororubbers, and polyurethanes. Polyolefins may include polypropylene and polyethylene, while fluoropolymers may include polytetrafluoroethylene. This allows the second adhesive layer 33 to have high resistance to electrolyte corrosion. In some embodiments, the second adhesive layer 33 comprises a single or multiple layers of the polymer.

[0065] It should be understood that when the seal 30 includes a first adhesive layer 31, a metal layer 32, and a second adhesive layer 33, the first adhesive layer 31 and the second adhesive layer 33 are respectively disposed on either side of the metal layer 32 along the thickness direction of the metal layer 32. In some embodiments, the first adhesive layer 31 and the metal layer 32, as well as the second adhesive layer 33 and the metal layer 32, are fixed by gluing, so that the first adhesive layer 31, the metal layer 32, and the second adhesive layer 33 are fixed by hot pressing, so that the first adhesive layer 31, the metal layer 32, and the second adhesive layer 33 are fixed by hot pressing, so that the first adhesive layer 31, the metal layer 32, and the second adhesive layer 33 are fixed by hot pressing. This helps maintain the sealing performance of the seal 30 against the first shell 11 and the second shell 12 during long-term use of the secondary battery 100.

[0066] In some embodiments, along the thickness direction of the sealant 30, the first adhesive layer 31 has a thickness d1, the metal layer 32 has a thickness d2, and the second adhesive layer 33 has a thickness d3. The following conditions are met: 7 μm ≤ d1 ≤ 500 μm, 7 μm ≤ d2 ≤ 250 μm, and 6 μm ≤ d3 ≤ 500 μm. For example, d1 is 7 μm, 10 μm, 20 μm, 50 μm, 100 μm, 200 μm, 500 μm, or any value therebetween; d2 is 7 μm, 10 μm, 20 μm, 50 μm, 100 μm, 150 μm, 250 μm, or any value therebetween; and d3 is 6 μm, 8 μm, 20 μm, 50 μm, 100 μm, 200 μm, 500 μm, or any value therebetween. By setting d1 to 7μm ≤ d1, d2 to 7μm ≤ d2, and d3 to 6μm ≤ d3, the first adhesive layer 31, metal layer 32, and second adhesive layer 33 are kept from being too thin, thereby reducing the risk of first adhesive layer 31 being corroded and failing by the electrolyte. This also reduces the risk of second adhesive layer 33 breaking after the secondary battery 100 is dropped, leading to damage and failure of the metal layer 32, or corrosion and failure of the metal layer 32. By setting d1 to 500μm ≤ 250μm, and d3 to 500μm, the first adhesive layer 31, metal layer 32, and second adhesive layer 33 are kept from being too thick, thereby increasing the energy density of the secondary battery 100.

[0067] In some embodiments, 10μm ≤ d1 ≤ 200μm, 10μm ≤ d2 ≤ 150μm, and 8μm ≤ d3 ≤ 200μm. By setting 10μm ≤ d1, 10μm ≤ d2, and 8μm ≤ d3, the first adhesive layer 31, metal layer 32, and second adhesive layer 33 can be made thicker, further reducing the risk of first adhesive layer 31 being corroded and failing by the electrolyte. This also helps reduce the risk of second adhesive layer 33 being damaged after the secondary battery 100 is dropped, leading to damage and failure of the metal layer 32, or failure of the metal layer 32 due to corrosion. By setting d1 ≤ 200μm, d2 ≤ 150μm, and d3 ≤ 200μm, the energy density of the secondary battery 100 can be further improved while ensuring that the thickness of the first adhesive layer 31 is substantially sufficient to prevent failure due to electrolyte corrosion, the thickness of the second adhesive layer 33 is sufficient to withstand most drops, and the thickness of the metal layer 32 is substantially sufficient to prevent failure due to damage or corrosion.

[0068] In some embodiments, the thickness of the first adhesive layer 31 can be uniform or non-uniform. In some embodiments, the thickness of the metal layer 32 can be uniform or non-uniform. In some embodiments, the thickness of the second adhesive layer 33 can be uniform or non-uniform. In some embodiments, the thickness of the seal 30 can be uniform or non-uniform, and the thickness of the seal 30 is equal to the sum of the thicknesses of the first adhesive layer 31, the metal layer 32, and the second adhesive layer 33.

[0069] See also Figure 4 and Figure 5 In some embodiments, the secondary battery 100 includes an adhesive member 40, which is adhered between the first wall 111 and the electrode assembly 20 and between the second wall 121 and the electrode assembly 20 along the first direction X. The adhesive member 40 can fix the first shell 11 and the second shell 12 to the electrode assembly 20 respectively, which helps to reduce the possibility of the first shell 11 and the second shell 12 moving relative to each other and pulling the seal 30, resulting in packaging failure of the seal 30. In addition, when the first shell 11 and the second shell 12 are electrically connected to different polarities of the electrode assembly 20, it helps to reduce the possibility of the first shell 11 and the second shell 12 moving relative to each other and contacting each other, resulting in a contact short circuit in the secondary battery 100. In some embodiments, the adhesive member 40 is a hot melt adhesive.

[0070] See also Figure 6 One embodiment of the present application provides an electric device 1000, comprising the aforementioned secondary battery 100. The secondary battery 100 is less susceptible to leakage failure, thereby extending the service life of the electric device 1000. The electric device 1000 includes, but is not limited to, electronic devices such as e-book players, mobile phones, fax machines, copiers, printers, headphones, video recorders, LCD televisions, tape recorders, radios, cameras, tablet computers, and laptop computers.

[0071] In addition, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the substantive scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, characterized in that: include: The housing comprises a first shell and a second shell, the first shell and the second shell together forming a receiving cavity, the receiving cavity being filled with an electrolyte; the first shell comprises a first wall and a first side wall connected to a periphery of the first wall, the second shell comprises a second wall and a second side wall connected to a periphery of the second wall, a first surface facing the second side wall is provided on a side of the first side wall away from the first wall, and a second surface facing the first side wall is provided on a side of the second side wall away from the second wall, the first surface and the second surface being arranged opposite to each other with a gap therebetween along a first direction, the first direction being the assembly direction of the first shell and the second shell; an electrode assembly disposed in the receiving cavity, wherein along the first direction, the electrode assembly comprises a negative electrode sheet, a positive electrode sheet, and a separator, wherein the negative electrode sheets and the positive electrode sheets are alternately disposed, and the separator is disposed between adjacent negative electrode sheets and positive electrode sheets; A seal seals the gap; the seal includes a first part, a second part and a third part, the first part is arranged around the outer periphery of the first side wall, the second part is arranged around the outer periphery of the second side wall, and the third part connects the first part and the second part; the third part is retractably arranged in the gap.

2. The secondary battery according to claim 1, wherein The secondary battery includes an adhesive member, and along the first direction, the adhesive member is adhered between the first wall and the electrode assembly and between the second wall and the electrode assembly.

3. The secondary battery according to claim 2, wherein A distance between the first side wall and the second side wall along the first direction is D1, and a thickness of the third portion in a flattened state is H3; 20 μm≤H3≤0.5D1.

4. The secondary battery according to claim 3, wherein 28μm≤H3≤0.5D1.

5. The secondary battery according to claim 1, wherein The thickness of the secondary battery along the first direction is H1, the size of the third portion in a flattened state along the first direction is W3, and 0.05H1≤W3.

6. The secondary battery according to claim 5, characterized in that Along a direction perpendicular to the first direction, the minimum distance between the negative electrode sheet and the shell is D2, the smaller value of the wall thickness of the first side wall and the wall thickness of the second side wall is H2, and 0.08H1≤W3≤2(D2+H2).

7. The secondary battery according to claim 1, wherein The third portion is arranged in the gap in a folded shape; or, the third portion is arranged in the gap in an arc shape.

8. The secondary battery according to any one of claims 1 to 7, characterized in that The sealing member includes a first adhesive layer and a metal layer, wherein the first adhesive layer is adhered to the outer periphery of the first side wall and the second side wall, and the metal layer is provided on a side of the first adhesive layer away from the first side wall and the second side wall; The first portion, the second portion, and the third portion each include a portion of the first adhesive layer, and the first portion, the second portion, and the third portion each include a portion of the metal layer.

9. The secondary battery according to claim 8, characterized in that The sealing member further includes a second adhesive layer, which is provided on a side of the metal layer away from the first adhesive layer; Wherein, the first part, the second part and the third part each include a portion of the second adhesive layer.

10. The secondary battery according to claim 1, wherein The first part, the second part and the third part are integrally arranged.

11. The secondary battery according to claim 1, wherein The negative electrode plate is electrically connected to the first shell, the positive electrode plate is electrically connected to the second shell, and the third portion protrudes from the gap toward the receiving cavity.

12. An electrical device, characterized in that: The secondary battery according to any one of claims 1 to 11 is included.

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