Secondary battery and electric device

Abstract

The present application discloses a secondary battery and an electric device. The secondary battery comprises a housing, an electrode assembly and a sealing member. The housing comprises a first shell and a second shell, and the first shell and the second shell are connected in a first direction and together form an accommodating cavity. The accommodating cavity is filled with an electrolyte, and the electrode assembly is disposed in the accommodating cavity. The sealing member is disposed around the periphery of the first shell and the second shell, and seals the joint between the first shell and the second shell. The sealing member comprises a first adhesive layer, a second adhesive layer, and a metal layer. In the thickness direction of the metal layer, the first adhesive layer and the second adhesive layer are respectively disposed on two sides of the metal layer. The first adhesive layer is bonded to the first shell and the second shell. By means of the first adhesive layer, the bonding stability between the sealing member and the housing can be improved. The metal layer helps to improve the sealing performance of the sealing member for the first shell and the second shell. The second adhesive layer helps to reduce the risk of damage and failure of the metal layer, and helps to maintain the sealing performance of the sealing member for the first shell and the second shell.

Description

Secondary batteries and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202411958781.5, filed on December 28, 2024, entitled "Secondary Battery and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of energy storage technology, and in particular to a secondary battery and electrical equipment. Background Technology

[0003] Current secondary batteries include steel-cased batteries and pouch batteries. Generally, both steel-cased and pouch batteries include a casing and electrode components housed within the casing. The casing of a steel-cased battery comprises a first shell and a second shell, which are sealed together by welding. Summary of the Invention

[0004] Regarding existing secondary batteries, the inventors discovered that stress is generated during the sealing connection of the first and second shells by welding. This stress can easily lead to defects such as cracks in the weld, thereby affecting the sealing performance of the secondary battery.

[0005] In view of the above situation, it is necessary to provide a secondary battery that is beneficial to improving the sealing performance of the first and second housings.

[0006] This application provides a secondary battery, including a casing, an electrode assembly, and a seal. The casing includes a first housing and a second housing, which are connected along a first direction and together form a receiving cavity. The receiving cavity is filled with an electrolyte, and the electrode assembly is disposed within the receiving cavity. The seal is disposed around the outer periphery of the first housing and the second housing, and seals the connection between the first housing and the second housing. The seal includes a first adhesive layer, a second adhesive layer, and a metal layer. Along the thickness direction of the metal layer, the first adhesive layer and the second adhesive layer are respectively disposed on both sides of the metal layer, and the first adhesive layer is bonded to the first housing and the second housing.

[0007] The seal includes a first adhesive layer, which is bonded to both the first and second housings. The first adhesive layer improves the stability of the bond between the seal and the housing. The seal also includes a metal layer located on the side of the first adhesive layer away from the housing. The metal layer has better water resistance than the first adhesive layer, which improves the seal's sealing performance against the first and second housings. Finally, the seal includes a second adhesive layer located on the side of the metal layer away from the first adhesive layer. The second adhesive layer protects the metal layer, reducing the risk of failure due to metal layer damage. This helps maintain the seal's effectiveness against the first and second housings during the long-term use of the secondary battery.

[0008] In one or more of the above embodiments, the sealing member includes a first fixing portion and a second fixing portion disposed at two ends along its own extending direction. Along the thickness direction of the sealing member, the projection of the first fixing portion overlaps with the projection of the second fixing portion. A first adhesive layer of the second fixing portion is fixed to a second adhesive layer of the first fixing portion.

[0009] In this case, the first fixing part and the second fixing part are stacked along the thickness direction of the seal. The fixing method of the first adhesive layer to the second adhesive layer can reduce the risk of electrolyte corrosion of the metal layer, which may lead to the failure of the fixing between the first adhesive layer or the second adhesive layer and the metal layer. This can make the seal more stable, which is beneficial to improving the sealing effect of the seal on the shell, thereby reducing the risk of secondary battery leakage failure.

[0010] In one or more of the above embodiments, the first adhesive layer of the second fixing part is fused and fixed to the second adhesive layer of the first fixing part. Compared with the direct bonding method, the fusion fixing method is beneficial to improving the stability of the seal. Furthermore, during fusion, the first adhesive layer of the second fixing part melts while the second adhesive layer of the first fixing part does not melt. This reduces the possibility that the second adhesive layer may adhere to the heating instrument, and that the seal may be pulled when the heating instrument is removed, leading to a decrease in the adhesion between the first adhesive layer and the first and second housings. It also reduces the possibility that the second adhesive layer may be deformed under tension, leading to a decrease in the protective effect on the metal layer. This further improves the sealing effect of the seal on the outer shell.

[0011] In one or more of the above embodiments, the first adhesive layer is configured to melt or de-adhere upon heating, and forms part of a pressure relief channel communicating with the receiving cavity. The melting point of the first adhesive layer is T1, and the melting point of the second adhesive layer is T2, where T2 > T1. When the secondary battery experiences thermal runaway, the melting or de-adhesion of the first adhesive layer can promptly relieve pressure in the receiving cavity, which is beneficial to improving the safety of the secondary battery. T2 > T1 facilitates the process of melting the first adhesive layer of the second fixing part while the second adhesive layer of the first fixing part does not melt during welding.

[0012] In one or more of the above embodiments, T2-T1 ≥ 10℃. The melting point difference between the first adhesive layer and the second adhesive layer is greater than 10℃, which facilitates more convenient control of the melting of the first adhesive layer of the second fixing part, while the second adhesive layer of the first fixing part does not melt.

[0013] In one or more of the above embodiments, 95℃≤T1≤130℃. 95℃≤T1 ensures that the first adhesive layer will not melt or lose adhesion prematurely before thermal runaway of the secondary battery, which helps maintain the sealing effect of the sealant on the outer casing. T1≤130℃ ensures that the first adhesive layer melts or loses adhesion in time when thermal runaway of the secondary battery occurs, allowing for pressure relief of the receiving cavity, which further improves the safety of the secondary battery.

[0014] In one or more of the above embodiments, the thickness of the seal is d0, where 20μm ≤ d0 ≤ 1000μm. With 20μm ≤ d0, the seal is not too thin, ensuring high overall strength and reducing the risk of seal breakage and leakage failure after a secondary battery drop. With d0 ≤ 1000μm, the seal is not too thick, ensuring sufficient overall strength while reducing the space required for the seal, thus minimizing energy density loss in the secondary battery.

[0015] In one or more of the above embodiments, 28μm≤d0≤300μm. 28μm≤d0 results in higher overall strength of the seal, which helps to further reduce the risk of seal breakage and subsequent leakage failure of the secondary battery after a drop. d0≤300μm ensures that the overall strength of the seal meets most drop conditions while further reducing the space required for the seal, which helps to further reduce the loss of energy density in the secondary battery.

[0016] In one or more of the above embodiments, the thickness of the first adhesive layer is d1, the thickness of the second adhesive layer is d2, and the thickness of the metal layer is d3, where 7μm≤d1≤500μm, 6μm≤d2≤500μm, and 7μm≤d3≤250μm. In this configuration, the first adhesive layer, the second adhesive layer, and the metal layer are not too thin, which helps reduce the risk of the first adhesive layer failing due to electrolyte corrosion, and also helps reduce the risk of the second adhesive layer breaking after a drop, leading to metal layer failure or corrosion. Furthermore, the first adhesive layer, the second adhesive layer, and the metal layer are not too thick, which helps reduce the thickness of the seal, thereby reducing the loss of energy density in the secondary battery.

[0017] In one or more of the above embodiments, 10μm≤d1≤200μm and 8μm≤d2≤200μm. 10μm≤d1 and 8μm≤d2 allow for thicker first and second adhesive layers, which helps to further reduce the risk of the first adhesive layer failing due to electrolyte corrosion and further reduces the risk of the second adhesive layer breaking after a drop, leading to metal layer failure or corrosion. d1≤200μm and d2≤200μm ensure that the thickness of the first adhesive layer is sufficient to prevent electrolyte corrosion and the thickness of the second adhesive layer is sufficient for most drop scenarios, while further reducing the loss of energy density in the secondary battery.

[0018] In one or more of the above embodiments, 10μm≤d3≤150μm. 10μm≤d3 allows for a thicker metal layer, which helps to further reduce the risk of metal layer failure due to breakage or corrosion after the second adhesive layer is damaged. d3≤150μm ensures that the metal layer thickness is sufficient to prevent failure due to breakage or corrosion, while further reducing the loss of energy density in the secondary battery.

[0019] In one or more of the above embodiments, the first adhesive layer includes a first portion bonded to the first housing and a second portion bonded to the second housing. Along the first direction, the minimum dimension of the first portion is W1, and the minimum dimension of the second portion is W2, where 0.1mm ≤ W1 ≤ 3mm and 0.1mm ≤ W2 ≤ 3mm. The dimensions 0.1mm ≤ W1 and 0.1mm ≤ W2 allow for a larger bonding area between the first adhesive layer and the first and second housings, making it less likely for the electrolyte to erode the first adhesive layer in a direction parallel to the first direction. This helps reduce the risk of premature leakage failure of the secondary battery in a direction parallel to the first direction, thereby extending the battery's lifespan. The dimensions W1 ≤ 3mm and W2 ≤ 3mm prevent the first adhesive layer from extending beyond the housing in a direction parallel to the first direction, thus reducing the energy density loss of the secondary battery.

[0020] In one or more of the above embodiments, 0.3mm≤W1≤1.5mm and 0.3mm≤W2≤1.5mm. 0.3mm≤W1 and 0.3mm≤W2 allow for a larger bonding area between the first adhesive layer and the first and second housings, making it less likely for the electrolyte to erode the first adhesive layer in a direction parallel to the first direction. This further reduces the risk of premature leakage failure of the secondary battery in a direction parallel to the first direction, thereby extending the battery's lifespan. W1≤1.5mm and W2≤1.5mm make it less likely for the first adhesive layer to extend beyond the outer casing in a direction parallel to the first direction, further reducing the energy density loss of the secondary battery.

[0021] In one or more of the above embodiments, the positive electrode of the electrode assembly is electrically connected to the first housing, and the negative electrode of the electrode assembly is electrically connected to the second housing. The first housing and the second housing are insulated from each other. This helps to reduce the risk of short circuits in the secondary battery.

[0022] In one or more of the above embodiments, the first housing includes a first wall and a first sidewall connecting the periphery of the first wall, and the second housing includes a second wall and a second sidewall connecting the periphery of the second wall. Along a first direction, the first sidewall and the second sidewall are disposed opposite to each other and have a gap. This facilitates the bonding of the first adhesive layer to the first housing and the second housing.

[0023] In one or more of the above embodiments, the secondary battery further includes an insulating member disposed in the gap and connecting the first sidewall and the second sidewall. The insulating member facilitates the installation of insulation between the first housing and the second housing.

[0024] In one or more of the above embodiments, the insulating component is integrally formed with the first adhesive layer. In this case, the insulating component can be directly formed by melting a portion of the first adhesive layer, inserting it into the gap between the first and second sidewalls, and then cooling it. This simplifies the assembly process of the secondary battery and helps to streamline the manufacturing process of the secondary battery. Furthermore, the integral formation of the insulating component with the first adhesive layer allows it to fully fit the gap between the first and second sidewalls, which helps to further improve the sealing performance of the sealing component for the first and second housings.

[0025] In one or more of the above embodiments, the material of the first adhesive layer includes at least one selected from polyolefin, fluororubber, and polyurethane. The material of the second adhesive layer includes at least one selected from polyolefin, fluoropolymer, polyetheretherketone, fluororubber, and polyurethane. This allows both the first and second adhesive layers to have high resistance to electrolyte corrosion, which helps reduce the possibility of electrolyte corrosion of the first adhesive layer, leading to the first adhesive layer peeling off from the outer casing, or the first adhesive layer of the second fixing part peeling off from the second adhesive layer of the first fixing part. This helps reduce the risk of leakage failure in the secondary battery. Furthermore, it also helps reduce the risk of electrolyte corrosion of the metal layer after the first adhesive layer has been corroded.

[0026] The second aspect of this application provides an electrical device, including the secondary battery of the first aspect of this application. The secondary battery has better sealing performance, and the electrolyte is less prone to leakage, which helps to extend the service life of the electrical device. Attached Figure Description

[0027] Figure 1 is a top view of a secondary battery provided in an embodiment of this application.

[0028] Figure 2 is a front view of a secondary battery provided in an embodiment of this application.

[0029] Figure 3 is an exploded view of a secondary battery provided in an embodiment of this application.

[0030] Figure 4 is a cross-sectional view along section line AA in Figure 1 according to an embodiment of this application.

[0031] Figure 5 is a cross-sectional view along section line BB in Figure 2 of an embodiment of this application.

[0032] Figure 6 is an overall schematic diagram of an electrical device provided in an embodiment of this application.

[0033] Key component symbols: 1000, Electrical equipment; 100, Secondary battery; 10, Housing; 101, Receiving cavity; 102, Corner; 103, Adhesive component; 11, First housing; 111, First wall; 112, First side wall; 12, Second housing; 121, Second wall; 122, Second side wall; 20, Electrode assembly; 201, First electrode bundle; 202, Second electrode bundle; 21, First electrode; 22, Second electrode; 23, Diaphragm; 30, Sealing component; 301, First fixing part; 302, Second fixing part; 31, First adhesive layer; 311, First part; 312, Second part; 32, Second adhesive layer; 33, Metal layer; 40, Insulating component; X, First direction. Detailed Implementation

[0034] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0035] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have a component that is centrally located. When a component is considered to be "set" on another component, it can be directly set on the other component or may also have a component that is centrally located.

[0036] Unless otherwise stated, the term "multiple" as used herein refers to two or more.

[0037] The terms “first”, “second”, etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implying the quantity, specific order, or primary and secondary relationship of the indicated technical features.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0039] It should be understood that, considering the actual machining tolerance, in the technical solution of this application, when the two components are set in parallel / perpendicular directions, they are set in the same direction, and there may be a certain angle between the two components. The tolerance between the two components is allowed to be 0-±10%, and the tolerance between the two components is allowed to be greater than, equal to or less than 0-±10%.

[0040] This application provides a secondary battery, including a casing, an electrode assembly, and a seal. The casing includes a first housing and a second housing, which are connected along a first direction and together form a receiving cavity. The receiving cavity is filled with an electrolyte, and the electrode assembly is disposed within the receiving cavity. The seal is disposed around the outer periphery of the first housing and the second housing, sealing the connection between the first housing and the second housing. The seal includes a first adhesive layer, a second adhesive layer, and a metal layer. Along the thickness direction of the metal layer, the first adhesive layer and the second adhesive layer are respectively disposed on both sides of the metal layer, and the first adhesive layer is bonded to the first housing and the second housing.

[0041] In the secondary battery of this application, the sealing element includes a first adhesive layer, which is bonded to both the first and second housings. The first adhesive layer improves the stability of the bond between the sealing element and the housing. The sealing element also includes a metal layer disposed on the side of the first adhesive layer away from the housing. The water resistance of the metal layer is superior to that of the first adhesive layer, thus improving the sealing performance of the sealing element to both the first and second housings. Finally, the sealing element includes a second adhesive layer disposed on the side of the metal layer away from the first adhesive layer. The second adhesive layer protects the metal layer, reducing the risk of failure due to metal layer damage. Therefore, during the long-term use of the secondary battery, the sealing performance of the sealing element to both the first and second housings is maintained.

[0042] Some embodiments of this application will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0043] Please refer to Figures 1 to 4. An embodiment of this application provides a secondary battery 100, including a housing 10, an electrode assembly 20, and a sealing element 30, wherein the electrode assembly 20 is housed within the housing 10. The sealing element 30 refers to the component that seals the housing 10.

[0044] Please refer to Figure 4. The outer casing 10 is provided with a receiving cavity 101, which is filled with electrolyte. The electrode assembly 20 is disposed in the receiving cavity 101.

[0045] In some embodiments, referring to Figures 3 and 4, the outer casing 10 includes a first casing 11 and a second casing 12, the first casing 11 and the second casing 12 being connected along a first direction X and together forming a receiving cavity 101.

[0046] In some embodiments, the first direction X is parallel to the thickness direction of the housing 10. In other embodiments, the first direction X is parallel to the length direction or width direction of the housing 10.

[0047] In some embodiments, the first housing 11 is insulated from the second housing 12. In other embodiments, the first housing 11 and the second housing 12 are electrically connected.

[0048] In some embodiments, the outer casing 10 is a metal casing, and the material of the outer casing 10 includes at least one selected from steel alloy, aluminum alloy, and copper alloy. The first casing 11 and the second casing 12 are made of at least one selected from steel alloy, aluminum alloy, and copper alloy.

[0049] In some embodiments, referring to FIG3, the first housing 11 includes a first wall 111 and a first side wall 112, and the second housing 12 includes a second wall 121 and a second side wall 122. The first side wall 112 is connected to the periphery of the first wall 111, and the second side wall 122 is connected to the periphery of the second wall 121. Along the first direction X, the first side wall 112 and the second side wall 122 are disposed opposite to each other and have a gap.

[0050] In some embodiments, please refer to FIG3, the housing 10 includes a corner portion 102, a portion of which is disposed on the first sidewall 112, and another portion of which is disposed on the second sidewall 122.

[0051] Please refer to Figure 3. The electrode assembly 20 includes a first electrode 21, a second electrode 22, and a diaphragm 23. The second electrode 22 has the opposite polarity to the first electrode 21, and the diaphragm 23 separates the first electrode 21 from the second electrode 22.

[0052] In some embodiments, please refer to Figures 3 and 4. The electrode assembly 20 has a stacked structure, with a plurality of first electrodes 21 and a plurality of second electrodes 22 alternately stacked, and a diaphragm 23 disposed between any adjacent first electrodes 21 and second electrodes 22.

[0053] In some embodiments, the electrode assembly 20 is a wound structure, in which a single first electrode 21 and a single second electrode 22 are stacked and wound together, and a diaphragm 23 is disposed between the first electrode 21 and the second electrode 22.

[0054] In some embodiments, the first electrode 21 is a negative electrode and the second electrode 22 is a positive electrode. In some embodiments, the first electrode 21 is a positive electrode and the second electrode 22 is a negative electrode. Wherein, along the thickness direction of the electrode assembly 20, the projection of the negative electrode overlaps the projection of the positive electrode.

[0055] In some embodiments, the first electrode 21 includes a first current collector and a first active material layer, with the first current collector disposed on two opposing sides of the first active material layer along its thickness direction. The second electrode 22 includes a second current collector and a second active material layer, with the second current collector disposed on two opposing sides of the second active material layer along its thickness direction. In some embodiments, when the first electrode 21 or the second electrode 22 is the outermost electrode of the electrode assembly 20, the side of the current collector facing away from the interior of the electrode assembly 20 may not have an active material layer.

[0056] In some embodiments, the material of the first current collector includes at least one of copper, nickel, tantalum, and titanium, and the material of the second current collector includes at least one of aluminum, nickel, tantalum, and titanium.

[0057] In some embodiments, the first active material layer is made of at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen materials, and silicon-carbon materials. The second active material layer is made of 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.

[0058] In some embodiments, the diaphragm 23 is an insulating membrane material such as a polyethylene membrane, a polypropylene membrane, a polyester membrane, or a polyimide membrane.

[0059] In some embodiments, the positive electrode of the electrode assembly 20 is electrically connected to the first housing 11, and the negative electrode of the electrode assembly 20 is electrically connected to the second housing 12. The first housing 11 and the second housing 12 are insulated from each other, which helps to reduce the risk of short circuit in the secondary battery 100.

[0060] In some embodiments, referring to FIG3, the secondary battery 100 further includes a plurality of first tabs connected to the first electrode 21, the plurality of first tabs being gathered together to form a first tab bundle 201. The secondary battery 100 also includes a plurality of second tabs connected to the second electrode 22, the plurality of second tabs being gathered together to form a second tab bundle 202. One of the first tab bundle 201 and the second tab bundle 202 is electrically connected to the first housing 11, and the other of the first tab bundle 201 and the second tab bundle 202 is electrically connected to the second housing 12.

[0061] In some embodiments, referring to FIG4, the secondary battery 100 further includes an insulating member 40. The insulating member 40 is disposed in the gap between the first sidewall 112 and the second sidewall 122, and connects the first sidewall 112 and the second sidewall 122. The insulating member 40 facilitates the installation of insulation between the first housing 11 and the second housing 12.

[0062] In some embodiments, one of the positive and negative electrodes of the electrode assembly 20 is electrically connected to the housing 10, and the other of the positive and negative electrodes of the electrode assembly 20 is insulated from the housing 10, wherein the first housing 11 is electrically connected to the second housing 12. For example, one of the positive and negative electrodes of the electrode assembly 20 is electrically connected to the housing 10, and the other of the positive and negative electrodes of the electrode assembly 20 is electrically connected to a terminal (not shown), which is insulated from the housing 10.

[0063] Referring to Figures 1 to 4, the sealing element 30 is disposed around the outer periphery of the first housing 11 and the second housing 12, and seals the junction of the first housing 11 and the second housing 12. Along the thickness direction of the sealing element 30, the projection of the sealing element 30 at least partially overlaps with the projections of the first housing 11 and the second housing 12.

[0064] In some embodiments, along the first direction X, the projections of the first housing 11 and the second housing 12 are both located within the enclosed area bounded by the projection of the seal 30. In other embodiments, along the first direction X, the projection of the first housing 11 is located within the enclosed area bounded by the projection of the seal 30, and the projection of the second housing 12 at least partially overlaps with the projection of the seal 30.

[0065] Please refer to Figures 4 and 5. The seal 30 includes a first adhesive layer 31, a second adhesive layer 32, and a metal layer 33. Along the thickness direction of the metal layer 33, the first adhesive layer 31 and the second adhesive layer 32 are respectively disposed on both sides of the metal layer 33. The first adhesive layer 31 is bonded to the first housing 11 and the second housing 12. It should be understood that the metal layer 33 is disposed on the side of the first adhesive layer 31 facing away from the outer housing 10, and the second adhesive layer 32 is disposed on the side of the metal layer 33 facing away from the first adhesive layer 31.

[0066] In some embodiments, the first adhesive layer 31 is bonded to the first sidewall 112 of the first housing 11 and the second sidewall 122 of the second housing 12. This facilitates the bonding of the first adhesive layer 31 to the first housing 11 and the second housing 12.

[0067] In some embodiments, referring to FIG4, the first adhesive layer 31 includes a first portion 311 and a second portion 312. The first portion 311 is bonded to the first housing 11, and the second portion 312 is bonded to the second housing 12. Along the first direction X, the minimum dimension of the first portion 311 is W1, and the minimum dimension of the second portion 312 is W2, where 0.1mm ≤ W1 ≤ 3mm and 0.1mm ≤ W2 ≤ 3mm. The dimensions 0.1mm ≤ W1 and 0.1mm ≤ W2 allow for a larger bonding area between the first adhesive layer 31 and the first housing 11 and the second housing 12. This makes it less likely for the electrolyte to erode the first adhesive layer 31 in a direction parallel to the first direction X, thus reducing the risk of premature leakage failure of the secondary battery 100 in a direction parallel to the first direction X, and consequently extending the service life of the secondary battery 100. The dimensions W1 ≤ 3mm and W2 ≤ 3mm prevent the first adhesive layer 31 from extending beyond the outer casing 10 in a direction parallel to the first direction X, thereby reducing the energy density loss of the secondary battery 100.

[0068] In some embodiments, 0.3mm ≤ W1 ≤ 1.5mm and 0.3mm ≤ W2 ≤ 1.5mm. 0.3mm ≤ W1 and 0.3mm ≤ W2 allow for a larger bonding area between the first adhesive layer 31 and the first housing 11 and the second housing 12. This makes it less likely for the electrolyte to erode the first adhesive layer 31 in a direction parallel to the first direction X, further reducing the risk of premature leakage failure of the secondary battery 100 in the direction parallel to the first direction X, thereby extending the service life of the secondary battery 100. W1 ≤ 1.5mm and W2 ≤ 1.5mm make it less likely for the first adhesive layer 31 to extend beyond the outer casing 10 in a direction parallel to the first direction X, further reducing the energy density loss of the secondary battery 100.

[0069] In some embodiments, referring to FIG4, the secondary battery 100 further includes an adhesive 103, which bonds the outer casing 10 to the electrode assembly 20. This helps reduce the risk of the electrode assembly 20 moving within the receiving cavity 101, causing the first casing 11 and / or the second casing 12 to peel off from the first adhesive layer 31. In some embodiments, the adhesive 103 is disposed between the outer casing 10 and the electrode assembly 20 along the thickness direction of the electrode assembly 20.

[0070] In some embodiments, the first adhesive layer 31 and the metal layer 33, and the second adhesive layer 32 and the metal layer 33 are fixed together by adhesive bonding, so that the first adhesive layer 31, the second adhesive layer 32 and the metal layer 33 are composited into a whole. In some embodiments, the first adhesive layer 31 and the metal layer 33, and the second adhesive layer 32 and the metal layer 33 are fixed together by hot pressing, so that the first adhesive layer 31, the second adhesive layer 32 and the metal layer 33 are composited into a whole.

[0071] In some embodiments, the first adhesive layer 31 is bonded to the first housing 11 and the second housing 12 after being activated at high temperature. In some embodiments, the sealing element 30 is clamped by a heating instrument, and heat is transferred to the sealing element 30, causing the first adhesive layer 31 to melt and be activated at high temperature. The heating temperature or power of the heating instrument is adjustable. It should be understood that high temperature refers to a temperature greater than or equal to the melting point of the first adhesive layer 31, but should not be too high to reduce the impact on the second adhesive layer 32, the metal layer 33, etc. In other embodiments, the first adhesive layer 31 is directly bonded to the first housing 11 and the second housing 12.

[0072] The aforementioned sealing element 30 includes a first adhesive layer 31, which is bonded to the first housing 11 and the second housing 12. The first adhesive layer 31 helps improve the stability of the bond between the sealing element 30 and the housing 10. The sealing element 30 includes a metal layer 33, which is disposed on the side of the first adhesive layer 31 away from the housing 10. The water resistance of the metal layer 33 is better than that of the first adhesive layer 31, which helps improve the sealing performance of the sealing element 30 to the first housing 11 and the second housing 12. The sealing element 30 includes a second adhesive layer 32, which is disposed on the side of the metal layer 33 away from the first adhesive layer 31. The second adhesive layer 32 can protect the metal layer 33, which helps reduce the risk of failure due to metal layer 33 breakage. Therefore, during the long-term use of the secondary battery 100, it helps maintain the sealing performance of the sealing element 30 to the first housing 11 and the second housing 12.

[0073] In some embodiments, the insulating member 40 is integrally formed with the first adhesive layer 31. In this case, the insulating member 40 can be directly formed by melting a portion of the first adhesive layer 31 and then cooling it into the gap between the first sidewall 112 and the second sidewall 122. This simplifies the assembly process of the secondary battery 100 and helps to streamline the manufacturing process of the secondary battery 100. Furthermore, the integral formation of the insulating member 40 with the first adhesive layer 31 allows it to fully fit the gap between the first sidewall 112 and the second sidewall 122, which further improves the sealing performance of the sealing member 30 for the first housing 11 and the second housing 12.

[0074] In some other embodiments, the insulating element 40 is separately disposed from the first adhesive layer 31. In this case, the insulating element 40 is not dependent on the melting state of the first adhesive layer 31, and the sealing element 30 can be disposed after the insulating element 40 is disposed between the first housing 11 and the second housing 12, which can make the insulation reliability between the first housing 11 and the second housing 12 higher.

[0075] In some embodiments, referring to FIG5, along the extending direction of the seal 30, the seal 30 includes a first fixing portion 301 and a second fixing portion 302 disposed at two ends.

[0076] In some embodiments, along the thickness direction of the seal 30, the projection of the first fixing part 301 overlaps with the projection of the second fixing part 302, and the first adhesive layer 31 of the second fixing part 302 is fixed to the second adhesive layer 32 of the first fixing part 301. In this case, the first fixing part 301 and the second fixing part 302 are stacked along the thickness direction of the seal 30. The way in which the first adhesive layer 31 fixes the second adhesive layer 32 can reduce the risk of electrolyte corrosion of the metal layer 33, which could lead to failure of the fixation between the first adhesive layer 31 or the second adhesive layer 32 and the metal layer 33. This can make the seal 30 have higher stability, which is beneficial to improving the sealing effect of the seal 30 on the outer casing 10, thereby helping to reduce the risk of leakage failure of the secondary battery 100.

[0077] In some embodiments, the first fixing part 301 and the second fixing part 302 are stacked on the corner part 102, which can utilize part of the space of the corner part 102 and help reduce the loss of energy density of the secondary battery 100.

[0078] In some other embodiments, along the thickness direction of the seal 30, the projection of the first fixing portion 301 is separate from the projection of the second fixing portion 302, and the first adhesive layer 31, the metal layer 33, and the second adhesive layer 32 are each a continuous annular structure. The seal 30 is heat-shrinkable; before sealing, the seal 30 has a larger size to fit over the junction of the first housing 11 and the second housing 12; after sealing, the size of the seal 30 is reduced to seal the junction of the first housing 11 and the second housing 12.

[0079] In some embodiments, the first adhesive layer 31 of the second fixing part 302 is directly bonded to the second adhesive layer 32 of the first fixing part 301.

[0080] In some embodiments, the first adhesive layer 31 of the second fixing part 302 is fused and fixed to the second adhesive layer 32 of the first fixing part 301. Compared with direct bonding, fusion fixing is beneficial to improving the stability of the seal 30. Furthermore, during fusion, the first adhesive layer 31 of the second fixing part 302 melts while the second adhesive layer 32 of the first fixing part 301 does not melt. This reduces the possibility that the second adhesive layer 32 may adhere to the heating instrument, and that the seal 30 may be pulled when the heating instrument is removed, leading to a decrease in the adhesion between the first adhesive layer 31 and the first housing 11 and the second housing 12. It also reduces the possibility that the second adhesive layer 32 may be deformed under tension, leading to a decrease in the protective effect on the metal layer 33. This further improves the sealing effect of the seal 30 on the outer shell 10.

[0081] In some embodiments, the first adhesive layer 31 can be heated to melt or de-adhere, forming part of a pressure relief channel communicating with the receiving cavity 101. When the secondary battery 100 experiences thermal runaway, the melting or de-adhesion of the first adhesive layer 31 can promptly relieve pressure in the receiving cavity 101, which helps improve the safety of the secondary battery 100.

[0082] In some embodiments, the melting point of the first adhesive layer 31 is T1, and the melting point of the second adhesive layer 32 is T2, where T2 > T1. This facilitates welding so that the first adhesive layer 31 of the second fixing part 302 melts while the second adhesive layer 32 of the first fixing part 301 does not melt.

[0083] In some embodiments, T2-T1 ≥ 10°C. The melting point difference between the first adhesive layer 31 and the second adhesive layer 32 is greater than 10°C, which facilitates more convenient control of the melting of the first adhesive layer 31 of the second fixing part 302, while the second adhesive layer 32 of the first fixing part 301 does not melt.

[0084] In some embodiments, 95℃≤T1≤130℃. For example, T1 is 95℃, 100℃, 110℃, and 130℃. 95℃≤T1 ensures that the first adhesive layer 31 will not melt or lose adhesion prematurely before the secondary battery 100 experiences thermal runaway, which helps maintain the sealing effect of the sealant 30 on the outer casing 10. T1≤130℃ ensures that the first adhesive layer 31 melts or loses adhesion in time when the secondary battery 100 experiences thermal runaway, allowing for pressure relief of the receiving cavity 101, which further improves the safety of the secondary battery 100.

[0085] In some embodiments, 140°C ≤ T2 ≤ 500°C. For example, T2 can be 140°C, 150°C, 200°C, 300°C, or 500°C. 140°C ≤ T2 ensures that the melting point difference between the first adhesive layer 31 and the second adhesive layer 32 is greater than 10°C. T2 ≤ 500°C prevents the melting point of the second adhesive layer 32 from being too high, allowing at least a portion of the material to be applied to the second adhesive layer 32.

[0086] In some embodiments, the first adhesive layer 31 is made of an electrolyte-resistant polymer, and the polymer of the first adhesive layer 31 includes at least one selected from polyolefins, fluororubber, and polyurethane. The second adhesive layer 32 is made of an electrolyte-resistant polymer, and the polymer of the second adhesive layer 32 includes at least one selected from polyolefins, fluoropolymers, polyetheretherketones, fluororubber, and polyurethane. The polyolefins may include polypropylene and polyethylene, and the fluoropolymers may be such as polytetrafluoroethylene. In this case, the first adhesive layer 31 and the second adhesive layer 32 can have high resistance to electrolyte corrosion, which helps reduce the possibility of electrolyte corrosion of the first adhesive layer 31, leading to the first adhesive layer 31 peeling off from the outer casing 10, or the first adhesive layer 31 of the second fixing part 302 peeling off from the second adhesive layer 32 of the first fixing part 301, thereby reducing the risk of leakage failure of the secondary battery 100. Furthermore, it also helps reduce the risk of electrolyte corrosion of the metal layer 33 after the first adhesive layer 31 is corroded.

[0087] In some embodiments, the first adhesive layer 31 comprises a single layer or multiple layers of polymer, and the second adhesive layer 32 comprises a single layer or multiple layers of polymer.

[0088] In some embodiments, referring to Figure 4, the thickness of the seal 30 is d0, where 20 μm ≤ d0 ≤ 1000 μm. For example, d0 can be 20 μm, 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, and 1000 μm. With 20 μm ≤ d0, the seal 30 is not too thin, resulting in higher overall strength and reducing the risk of leakage and failure of the secondary battery 100 due to seal breakage after a drop. With d0 ≤ 1000 μm, the seal 30 is not too thick, ensuring sufficient overall strength while reducing the space required for the seal 30, thus reducing energy density loss in the secondary battery 100.

[0089] In some embodiments, the thickness of the seal 30 may be non-uniform, with the thinnest part of the seal 30 having a thickness greater than or equal to 20 μm and the thickest part having a thickness less than or equal to 1000 μm.

[0090] In some embodiments, 28 μm ≤ d0 ≤ 300 μm. For example, d0 can be 28 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, and 300 μm. 28 μm ≤ d0 allows for higher overall strength of the seal 30, which helps to further reduce the risk of leakage and failure of the secondary battery 100 due to seal 30 breakage after a drop. d0 ≤ 300 μm allows the overall strength of the seal 30 to meet most drop conditions while further reducing the space required for the seal 30, which helps to further reduce the energy density loss of the secondary battery 100.

[0091] In some embodiments, the thickness of the seal 30 may be non-uniform, with the thinnest part of the seal 30 having a thickness greater than or equal to 28 μm and the thickest part having a thickness less than or equal to 300 μm.

[0092] In some embodiments, the thickness of the seal 30 is equal to the sum of the thicknesses of the first adhesive layer 31, the second adhesive layer 32, and the metal layer 33.

[0093] In some embodiments, the thickness of the first adhesive layer 31 is d1, the thickness of the second adhesive layer 32 is d2, and the thickness of the metal layer 33 is d3, wherein 7μm≤d1≤500μm, 6μm≤d2≤500μm, and 7μm≤d3≤250μm. For example, d1 can be 7μm, 50μm, 100μm, 200μm, 300μm, and 500μm; d2 can be 6μm, 50μm, 100μm, 200μm, 300μm, and 500μm; and d3 can be 7μm, 20μm, 50μm, 100μm, 200μm, and 250μm. In this configuration, the first adhesive layer 31, the second adhesive layer 32, and the metal layer 33 are not too thin, which helps reduce the risk of the first adhesive layer 31 failing due to electrolyte corrosion and reduces the risk of the second adhesive layer 32 breaking after the secondary battery 100 is dropped, leading to the failure of the metal layer 33 or its corrosion failure. Conversely, the first adhesive layer 31, the second adhesive layer 32, and the metal layer 33 are not too thick, which helps reduce the thickness of the seal 30, thereby reducing the energy density loss of the secondary battery 100. It should be understood that the first adhesive layer 31, the second adhesive layer 32, and the metal layer 33 are not all simultaneously at their maximum selectable thickness. For example, the thickness of the first adhesive layer 31 may be 500 μm, the thickness of the second adhesive layer 32 may be 250 μm, and the thickness of the metal layer 33 may be 250 μm.

[0094] In some embodiments, 10μm≤d1≤200μm and 8μm≤d2≤200μm. For example, d1 can be 10μm, 50μm, 100μm, 150μm, and 200μm, and d2 can be 8μm, 50μm, 100μm, 150μm, and 200μm. 10μm≤d1 and 8μm≤d2 allow for thicker first adhesive layer 31 and second adhesive layer 32, which helps to further reduce the risk of the first adhesive layer 31 being corroded and failing due to electrolyte corrosion, and further reduces the risk of the second adhesive layer 32 breaking after the secondary battery 100 is dropped, leading to the failure of the metal layer 33 or its corrosion failure. d1≤200μm and d2≤200μm allow the thickness of the first adhesive layer 31 to be basically sufficient to prevent corrosion failure by electrolyte, and the thickness of the second adhesive layer 32 to meet most drop conditions, while further reducing the energy density loss of the secondary battery 100.

[0095] In some embodiments, since the first adhesive layer 31 is more readily in contact with the electrolyte than the second adhesive layer 32, and the first adhesive layer 31 needs to be fused to the second adhesive layer 32, the thickness of the first adhesive layer 31 needs to be greater than the thickness of the second adhesive layer 32.

[0096] In some embodiments, 10 μm ≤ d3 ≤ 150 μm. For example, d3 can be 10 μm, 50 μm, 100 μm, and 150 μm. 10 μm ≤ d3 allows for a thicker metal layer 33, which helps to further reduce the risk of metal layer 33 failing due to breakage or corrosion after the second adhesive layer 32 is damaged. d3 ≤ 150 μm ensures that the thickness of the metal layer 33 is sufficient to prevent failure due to breakage or corrosion, while further reducing the energy density loss of the secondary battery 100.

[0097] In some embodiments, the metal layer 33 is made of at least one of steel, aluminum, nickel, silver, copper, and alloys thereof.

[0098] In some embodiments, the metal layer 33 is a single-layer or multi-layer structure. For example, a multi-layer structure can be a steel layer plus an aluminum layer or a nickel layer plus a copper layer, etc.

[0099] Please refer to Figure 6. One embodiment of this application provides an electrical device 1000, including the secondary battery 100 as described above. The secondary battery 100 has good sealing properties, and the electrolyte is not easily leaked, which helps to extend the service life of the electrical device 1000. The electrical device 1000 includes, but is not limited to, electronic devices such as mobile phones, tablets, and laptops.

[0100] Furthermore, those skilled in the art should recognize that the above embodiments are merely illustrative of this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the substantive scope of this application fall within the scope of this application.

Claims

1. A secondary battery, characterized in that, include: The outer casing includes a first housing and a second housing, the first housing and the second housing being connected along a first direction and together forming a receiving cavity; the receiving cavity is filled with an electrolyte. An electrode assembly disposed within the receiving cavity; A sealing element is disposed around the outer periphery of the first housing and the second housing, and seals the junction of the first housing and the second housing; the sealing element includes a first adhesive layer, a second adhesive layer and a metal layer, wherein the first adhesive layer and the second adhesive layer are respectively disposed on both sides of the metal layer along the thickness direction of the metal layer, and the first adhesive layer is bonded to the first housing and the second housing.

2. The secondary battery according to claim 1, characterized in that, The sealing element includes a first fixing part and a second fixing part disposed at two ends along its own extension direction. Along the thickness direction of the sealing element, the projection of the first fixing part overlaps with the projection of the second fixing part; the first adhesive layer of the second fixing part is fixed to the second adhesive layer of the first fixing part.

3. The secondary battery according to claim 2, characterized in that, The first adhesive layer of the second fixing part is fused and fixed to the second adhesive layer of the first fixing part.

4. The secondary battery according to claim 3, characterized in that, The first adhesive layer is configured to melt or lose its adhesiveness upon heating and forms part of a pressure relief channel communicating with the receiving cavity; the melting point of the first adhesive layer is T1, and the melting point of the second adhesive layer is T2, where T2 > T1.

5. The secondary battery according to claim 4, characterized in that, T2-T1≥10℃.

6. The secondary battery according to claim 5, characterized in that, 95℃≤T1≤130℃。 7. The secondary battery according to claim 1, characterized in that, The thickness of the seal is d0, where 20μm≤d0≤1000μm.

8. The secondary battery according to claim 7, characterized in that, 28μm≤d0≤300μm.

9. The secondary battery according to claim 7, characterized in that, The thickness of the first adhesive layer is d1, the thickness of the second adhesive layer is d2, and the thickness of the metal layer is d3. 7μm≤d1≤500μm, 6μm≤d2≤500μm, and 7μm≤d3≤250μm.

10. The secondary battery according to claim 9, characterized in that, 10μm≤d1≤200μm, 8μm≤d2≤200μm.

11. The secondary battery according to claim 9, characterized in that, 10μm≤d3≤150μm.

12. The secondary battery according to claim 1, characterized in that, The first adhesive layer includes a first portion bonded to the first housing and a second portion bonded to the second housing. Along the first direction, the minimum dimension of the first portion is W1, and the minimum dimension of the second portion is W2, where 0.1mm≤W1≤3mm and 0.1mm≤W2≤3mm.

13. The secondary battery according to claim 12, characterized in that, 0.3mm≤W1≤1.5mm, 0.3mm≤W2≤1.5mm.

14. The secondary battery according to claim 1, characterized in that, The positive electrode of the electrode assembly is electrically connected to the first housing, and the negative electrode of the electrode assembly is electrically connected to the second housing; the first housing and the second housing are insulated from each other.

15. The secondary battery according to claim 14, characterized in that, The first housing includes a first wall and a first side wall connecting the periphery of the first wall, and the second housing includes a second wall and a second side wall connecting the periphery of the second wall. Along the first direction, the first side wall and the second side wall are disposed opposite to each other and have a gap.

16. The secondary battery according to claim 15, characterized in that, The secondary battery also includes an insulating component, which is disposed in the gap and connects the first sidewall and the second sidewall.

17. The secondary battery according to claim 16, characterized in that, The insulating component is integrally formed with the first adhesive layer.

18. The secondary battery according to any one of claims 1 to 17, characterized in that, The material of the first adhesive layer includes at least one of polyolefin, fluororubber and polyurethane; the material of the second adhesive layer includes at least one of polyolefin, fluoropolymer, polyetheretherketone, fluororubber and polyurethane.

19. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 18.

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