Secondary battery and electrical device

Abstract

A secondary battery and an electrical device. The secondary battery comprises a housing, an electrode assembly and an adhesive member. The housing is provided with an accommodating cavity, and the electrode assembly is disposed within the accommodating cavity. In a first direction, the adhesive member is disposed between the housing and the electrode assembly, the first direction being the thickness direction of the electrode assembly. The adhesive member comprises a first adhesive layer bonded to the housing, a second adhesive layer bonded to the electrode assembly, and a base layer disposed between the first adhesive layer and the second adhesive layer. In the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1; among interfaces between the first adhesive layer and the housing, between the second adhesive layer and the electrode assembly, between the first adhesive layer and the base layer, and between the second adhesive layer and the base layer, the interface having the lowest peel strength is a first interface, and the peel strength of the first interface is τ2, where 1N / cm2<τ2≤τ1. This helps reduce the possibility of the electrode assembly impacting the housing and the risk of the electrode assembly being torn, thereby prolonging the service life of the secondary battery.

Description

Secondary batteries and electrical equipment

[0001] This application claims priority to Chinese Patent Application No. 202510314891.6, filed on March 17, 2025, 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] With the development of various electronic devices, rechargeable batteries have become an indispensable part of daily life. Commonly used devices such as mobile phones, tablets, laptops, and digital cameras all require rechargeable batteries to provide power for normal operation. However, during daily use, rechargeable batteries are inevitably subject to drops or vibrations, which significantly increases the risk of battery failure. Summary of the Invention

[0004] Regarding existing secondary batteries, the inventors discovered that one reason for battery failure is that the electrode assembly is typically fixed within the housing cavity by adhesive components. Drop energy or vibration energy is transferred to the electrode assembly through these adhesive components. Therefore, when the secondary battery experiences a significant drop or vibration, the electrode assembly is prone to tearing under the influence of the drop or vibration energy, leading to battery failure.

[0005] In view of the above situation, it is necessary to provide a secondary battery that can reduce the possibility of electrode assembly tearing, thereby improving the service life of the secondary battery.

[0006] This application provides a secondary battery, including a casing, an electrode assembly, and an adhesive. The casing has a receiving cavity, and the electrode assembly is disposed within the receiving cavity. An adhesive is disposed between the casing and the electrode assembly along a first direction, the first direction being the thickness direction of the electrode assembly. The adhesive includes a first adhesive layer bonded to the casing, a second adhesive layer bonded to the electrode assembly, and a base layer disposed between the first adhesive layer and the second adhesive layer. Along a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1. The interface with the lowest peel strength among the first adhesive layer and the casing, the second adhesive layer and the electrode assembly, the first adhesive layer and the base layer, and the second adhesive layer and the base layer is the first interface, and the peel strength of the first interface is τ2, 1 N / cm². 2 <τ2≤τ1.

[0007] Set to 1N / cm 2<τ2, the electrode assembly and the casing can be bonded and fixed together using adhesives. This helps reduce the possibility of the electrode assembly impacting the casing when the secondary battery is dropped or vibrated. Furthermore, setting τ2 ≤ τ1 allows the adhesives to peel off from the casing or electrode assembly before tearing, or the first or second adhesive layer to peel off from the base layer, when the drop or vibration intensity is high. This reduces the risk of drop or vibration energy being transferred to the electrode assembly through the adhesives, thus reducing the risk of tearing the electrode assembly and improving the lifespan of the secondary battery.

[0008] In one or more of the above embodiments, the bonding area between the second adhesive layer and the electrode assembly is greater than or equal to the bonding area of ​​the first interface; or, the bonding areas between the first adhesive layer and the shell, the first adhesive layer and the base layer, the second adhesive layer and the base layer, and the second adhesive layer and the electrode assembly are all equal.

[0009] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode of the electrode assembly. Along the first direction, the projections of the first adhesive layer, the second adhesive layer, and the base layer coincide, and the projection of the outermost electrode covers the projection of the adhesive. The projected area of ​​the outermost electrode is S1, and the projected area of ​​the second adhesive layer is S2, where 0.35 ≤ S2 / S1 ≤ 1. Setting 0.35 ≤ S2 / S1 ≤ 1 ensures that the bonding area between the adhesive and the casing and the electrode assembly is not too small, which helps to increase the value of τ2. Therefore, when the secondary battery is dropped or vibrated, it helps to further reduce the possibility of the electrode assembly impacting the casing.

[0010] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode of the electrode assembly. Along a direction perpendicular to the first direction, the minimum distance between the edge of the adhesive and the edge of the outermost electrode is d, where 10mm ≤ d. Setting 10mm ≤ d ensures that the edge of the adhesive is far from the edges of the outermost electrode and the outer shell, thereby making it less likely for the adhesive to peel off from the outermost electrode and the outer shell, further reducing the possibility of the electrode assembly impacting the outer shell.

[0011] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode of the electrode assembly. Along the first direction, the center of the circumcircle of the adhesive projection coincides with the center of the circumcircle of the outermost electrode projection. In this case, the distance between the edge of the adhesive and the edges of the outermost electrode and the shell is relatively uniform along different directions perpendicular to the first direction. This improves the peel strength between the adhesive and the outermost electrode and the shell along different directions perpendicular to the first direction, which is beneficial for increasing the value of τ2, thereby further reducing the possibility of the electrode assembly impacting the shell.

[0012] In one or more of the above embodiments, the materials of the first adhesive layer and / or the second adhesive layer each independently include a matrix resin, a tackifying resin, and a polyether polyol. Based on the total mass of the first adhesive layer and / or the second adhesive layer, the mass percentage of the matrix resin is 50% to 80%, the mass percentage of the tackifying resin is 20% to 45%, and the mass percentage of the polyether polyol is 0% to 6%. By including the above-mentioned materials in the materials of the first adhesive layer and / or the second adhesive layer, and by controlling the mass percentage of the above-mentioned materials in the first adhesive layer and / or the second adhesive layer within the above-mentioned range, the peel strength between the first adhesive layer and the shell and the base layer, and / or between the second adhesive layer and the electrode assembly and the base layer, can be adjusted, thereby facilitating the achievement of 1 N / cm... 2 <τ2≤τ1.

[0013] In one or more of the above embodiments, along the first direction, the thickness of the first adhesive layer is D1, 3μm≤D1≤10μm; and / or, the thickness of the second adhesive layer is D2, 3μm≤D2≤10μm. Setting 3μm≤D1 and / or 3μm≤D2 ensures that the first adhesive layer and / or the second adhesive layer are not too thin, which is beneficial to increasing the value of τ2, thereby reducing the possibility of the electrode assembly impacting the casing. Setting D1≤10μm and / or D2≤10μm ensures that the first adhesive layer and / or the second adhesive layer are not too thick, which is beneficial to increasing the energy density of the secondary battery.

[0014] In one or more of the above embodiments, τ1-τ2≤3N / cm 2 Set τ1-τ2≤3N / cm 2 Under the premise that the adhesive component tears and peels off from the housing or electrode assembly before the electrode assembly, τ2 can be kept from being too small, thereby reducing the possibility of the electrode assembly impacting the housing.

[0015] In one or more of the above embodiments, the minimum peel strength among the first adhesive layer and the outer shell, the first adhesive layer and the base layer, and the second adhesive layer and the base layer is less than the peel strength between the second adhesive layer and the electrode assembly. In this case, when the drop intensity or vibration intensity is high, the adhesive can peel off from the outer shell first, or the first adhesive layer or the second adhesive layer can peel off from the base layer first. Compared to the adhesive being peeled off from the electrode assembly first, this helps reduce the wear of the adhesive on the electrode assembly after peeling, thereby further improving the service life of the secondary battery.

[0016] In one or more of the above embodiments, 4N / cm 2 <τ2. Set to 4N / cm 2 <τ2, when the secondary battery is dropped or vibrated, it helps to further reduce the possibility of the electrode assembly impacting the casing.

[0017] In one or more of the above embodiments, the maximum value of the peel strength between the first adhesive layer and the outer shell, and between the second adhesive layer and the electrode assembly, is less than the minimum value of the peel strength between the first adhesive layer and the base layer, and between the second adhesive layer and the base layer. In this case, when the drop strength or vibration intensity is high, the adhesive can peel off from the outer shell or the electrode assembly first, and the internal structure of the adhesive can maintain good integrity, which helps to reduce the possibility of the adhesive being easily damaged and failing during the adhesive friction process.

[0018] In one or more of the above embodiments, the electrode assembly includes a negative electrode sheet, a positive electrode sheet, and a separator, with the separator separating the negative electrode sheet and the positive electrode sheet. The negative electrode sheet includes a negative current collector and a negative active material layer, the negative active material layer being disposed on two opposing sides of the negative current collector along its thickness direction. The positive electrode sheet includes a positive current collector and a positive active material layer, the positive active material layer being disposed on two opposing sides of the positive current collector along its thickness direction. The material of the negative active material layer includes styrene-butadiene rubber and carboxymethyl cellulose, with the styrene-butadiene rubber accounting for 1% to 2% of its mass and the carboxymethyl cellulose accounting for 1% to 2% of its mass. And / or, the material of the positive active material layer includes polyvinylidene fluoride, with the polyvinylidene fluoride accounting for 1% to 2% of its mass.

[0019] By including the aforementioned materials in the negative electrode active material layer and controlling the mass percentage of these materials within the negative electrode active material layer within the aforementioned range, the peel strength between the negative electrode active material layer and the separator and negative electrode current collector can be adjusted, thereby making it easier to ensure that τ2 ≤ τ1. Similarly, by including the aforementioned materials in the positive electrode active material layer and controlling the mass percentage of these materials within the positive electrode active material layer within the aforementioned range, the peel strength between the positive electrode active material layer and the separator and positive electrode current collector can be adjusted, thereby making it easier to ensure that τ2 ≤ τ1.

[0020] A second aspect of this application provides an electrical device including a secondary battery as described in the first aspect of this application. The secondary battery has a longer service life, which helps to extend the service life of the electrical device. Attached Figure Description

[0021] Figure 1 is a front view of a secondary battery provided in an embodiment of this application.

[0022] Figure 2 is a top view of a secondary battery provided in an embodiment of this application.

[0023] Figure 3 is a cross-sectional view along section line AA in Figure 1.

[0024] Figure 4 is a diagram showing the positional relationship between the second adhesive layer and the outermost electrode sheet provided in an embodiment of this application.

[0025] Figure 5 is a cross-sectional view along section line BB in Figure 2.

[0026] Figure 6 is a cross-sectional view along section line CC in Figure 2.

[0027] Figure 7 is an overall schematic diagram of an electrical device provided in an embodiment of this application.

[0028] Key component symbols: 1000, Electrical equipment; 100, Secondary battery; 10, Outer shell; 101, Receiving cavity; 11, First shell; 111, Bottom wall; 112, Side wall; 12, Second shell; 20, Electrode assembly; 21, Negative electrode plate; 211, Negative current collector; 212, Negative active material layer; 22, Positive electrode plate; 221, Positive current collector; 222, Positive active material layer; 23, Separator; 30, Adhesive; 31, Base layer; 32, First adhesive layer; 33, Second adhesive layer; 40, Negative electrode tab; 50, Negative electrode tab bundle; 60, Positive electrode tab; 70, Positive electrode tab bundle; 80, Terminal post; 90, Insulator; X, First direction; Y, Second direction; Z, Third direction. Detailed Implementation

[0029] 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.

[0030] 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.

[0031] Unless otherwise stated, the term "multiple" as used herein refers to two or more.

[0032] 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.

[0033] 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.

[0034] This application provides a secondary battery, including a casing, an electrode assembly, and an adhesive. The casing has a receiving cavity, and the electrode assembly is disposed within the receiving cavity. An adhesive is disposed between the casing and the electrode assembly along a first direction, the first direction being the thickness direction of the electrode assembly. The adhesive includes a first adhesive layer bonded to the casing, a second adhesive layer bonded to the electrode assembly, and a base layer disposed between the first and second adhesive layers. Along a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1. The interface with the lowest peel strength among the first adhesive layer and the casing, the second adhesive layer and the electrode assembly, the first adhesive layer and the base layer, and the second adhesive layer and the base layer is the first interface, and the peel strength of the first interface is τ2, 1 N / cm². 2 <τ2≤τ1.

[0035] In the secondary battery of this application, 1 N / cm is set. 2 <τ2, the electrode assembly and the casing can be bonded and fixed together using adhesives. This helps reduce the possibility of the electrode assembly impacting the casing when the secondary battery is dropped or vibrated. Furthermore, setting τ2 ≤ τ1 allows the adhesives to peel off from the casing or electrode assembly before tearing, or the first or second adhesive layer to peel off from the base layer, when the drop or vibration intensity is high. This reduces the risk of drop or vibration energy being transferred to the electrode assembly through the adhesives, thus reducing the risk of tearing the electrode assembly and improving the lifespan of the secondary battery.

[0036] 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.

[0037] Please refer to Figures 1 to 3. An embodiment of this application provides a secondary battery 100, including a housing 10, an electrode assembly 20, and an adhesive member 30. The electrode assembly 20 is housed within the housing 10. The adhesive member 30 is bonded to both the housing 10 and the electrode assembly 20, thereby bonding and fixing the electrode assembly 20 to the housing 10 via the adhesive member 30.

[0038] Please refer to Figure 3. The outer casing 10 is provided with a receiving cavity 101, which is filled with an electrolyte, including electrolyte salts.

[0039] In some embodiments, the material of the housing 10 includes, but is not limited to, aluminum-plastic film or steel.

[0040] In some embodiments, please refer to FIG1, the outer casing 10 includes a first casing 11 and a second casing 12, the first casing 11 and the second casing 12 are connected to form a receiving cavity 101.

[0041] In some embodiments, when the outer casing 10 is made of aluminum-plastic film, the first casing 11 and the second casing 12 can be fused together. When the outer casing 10 is made of steel, the first casing 11 and the second casing 12 can be welded together.

[0042] In some embodiments, the first housing 11 and the second housing 12 are connected along a first direction X, where the first direction X is the thickness direction of the electrode assembly 20.

[0043] In some embodiments, the first housing 11 is the body of the outer casing 10, and the second housing 12 is the cover of the outer casing 10. Referring to FIG3, the first housing 11 includes a bottom wall 111 and a side wall 112. The side wall 112 surrounds the periphery of the bottom wall 111 and forms a recess with the bottom wall 111. The side wall 112 is connected to the second housing 12. In some other embodiments, the second housing 12 may also have a recess.

[0044] Please refer to Figure 3. The electrode assembly 20 is disposed in the receiving cavity 101. The electrode assembly 20 includes a negative electrode 21, a positive electrode 22, and a separator 23, which separates the negative electrode 21 from the positive electrode 22.

[0045] In some embodiments, the negative electrode 21 and the positive electrode 22 are respectively bonded to the separator 23.

[0046] In some embodiments, please refer to FIG3, the electrode assembly 20 is a stacked structure, with multiple negative electrode plates 21 and multiple positive electrode plates 22 alternately stacked, and the separator 23 is disposed between any adjacent negative electrode plates 21 and positive electrode plates 22.

[0047] In some other embodiments, the electrode assembly 20 has a wound structure, in which a single negative electrode 21 and a single positive electrode 22 are stacked and wound together, and a diaphragm 23 is disposed between the negative electrode 21 and the positive electrode 22.

[0048] In some embodiments, the negative electrode 21 includes a negative current collector 211 and a negative active material layer 212, the negative active material layer 212 being disposed on two opposing sides of the negative current collector 211 along the thickness direction. The positive electrode 22 includes a positive current collector 221 and a positive active material layer 222, the positive active material layer 222 being disposed on two opposing sides of the positive current collector 221 along the thickness direction.

[0049] In some embodiments, when the electrode assembly 20 is a stacked structure, if the negative electrode 21 or the positive 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.

[0050] In some embodiments, the negative current collector 211 is made of copper foil, and the positive current collector 221 is made of aluminum foil.

[0051] In some embodiments, the negative electrode active material layer 212 may be formed by coating the negative electrode active material onto the negative electrode current collector 211, and the negative electrode active material layer 212 may be adhered to the negative electrode current collector 211. The positive electrode active material layer 222 may be formed by coating the positive electrode active material onto the positive electrode current collector 221, and the positive electrode active material layer 222 may be adhered to the positive electrode current collector 221.

[0052] 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.

[0053] Referring to Figure 3, along the first direction X, the adhesive 30 is disposed between the housing 10 and the electrode assembly 20. The adhesive 30 includes a base layer 31, a first adhesive layer 32, and a second adhesive layer 33, with the base layer 31 disposed between the first adhesive layer 32 and the second adhesive layer 33. The first adhesive layer 32 is bonded to the housing 10, and the second adhesive layer 33 is bonded to the electrode assembly 20. In some embodiments, the adhesive 30 is bonded to the second housing 12 and the outermost electrode of the electrode assembly 20. The first adhesive layer 32 is bonded to the second housing 12, and the second adhesive layer 33 is bonded to the outermost electrode of the electrode assembly 20. It should be understood that when the electrode assembly 20 has a laminated structure, the outermost electrode refers to the electrode closest to the adhesive 30 among several electrodes 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 electrode is the flat area located between the bending areas and close to the adhesive 30 of the outermost wound electrode.

[0054] Along a direction perpendicular to the first direction X, the tear strength of the electrode assembly 20 is τ1. The interface with the lowest peel strength among the first adhesive layer 32 and the outer shell 10, the second adhesive layer 33 and the electrode assembly 20, the first adhesive layer 32 and the base layer 31, and the second adhesive layer 33 and the base layer 31 is the first interface, and its peel strength is τ2, 1 N / cm². 2 <τ2≤τ1. The direction perpendicular to the first direction X includes the second direction Y and the third direction Z, and the first direction X, the second direction Y, and the third direction Z are mutually perpendicular. In some embodiments, the second direction Y can be the width direction of the electrode assembly 20, and the third direction Z can be the length direction of the electrode assembly 20.

[0055] The term τ1 refers to the shear stress required to completely tear the electrode assembly 20 under a load perpendicular to the first direction X. The tearing of the electrode assembly 20 may occur in various ways, including but not limited to: peeling of the negative electrode active material layer 212 from the separator 23; peeling of the negative electrode active material layer 212 from the negative electrode current collector 211; peeling of the positive electrode active material layer 222 from the separator 23; peeling of the positive electrode active material layer 222 from the positive electrode current collector 221; tearing of the separator 23 itself; tearing of the negative electrode active material layer 212 or the negative electrode current collector 211 itself; and tearing of the positive electrode active material layer 222 or the positive electrode current collector 221 itself.

[0056] The term τ2 refers to the shear stress required to completely peel off the first adhesive layer 32 from the outer shell 10, the second adhesive layer 33 from the electrode assembly 20, the first adhesive layer 32 from the base layer 31, or the second adhesive layer 33 from the base layer 31 under a load perpendicular to the first direction X. The load perpendicular to the first direction X may be caused by a drop or vibration of the secondary battery 100.

[0057] The above setting is 1N / cm 2 <τ2, the electrode assembly 20 and the outer casing 10 can be bonded and fixed together by the adhesive 30. When the secondary battery 100 is dropped or vibrated, this helps reduce the possibility of the electrode assembly 20 impacting the outer casing 10. Furthermore, setting τ2≤τ1, when the drop intensity or vibration intensity is high, the adhesive 30 can peel off from the outer casing 10 or the electrode assembly 20 before tearing, or the first adhesive layer 32 or the second adhesive layer 33 can peel off from the base layer 31 first. This reduces the risk of drop energy or vibration energy being transferred to the electrode assembly 20 through the adhesive 30, leading to tearing of the electrode assembly 20, thereby improving the service life of the secondary battery 100. It should be understood that by reducing the possibility of the electrode assembly 20 impacting the outer casing 10, when the first casing 11 and the second casing 12 are connected separately, it helps reduce the risk of the second casing 100 leaking and failing due to separation of the first casing 11 and the second casing 12.

[0058] It should be understood that when the drop intensity or vibration intensity is high, after the adhesive 30 peels off from the outer shell 10 or the electrode assembly 20, the adhesive 30 can reduce the drop energy or vibration energy through adhesive friction.

[0059] In some embodiments, the interface with the smallest bonding area among the first adhesive layer 32 and the outer shell 10, the second adhesive layer 33 and the electrode assembly 20, the first adhesive layer 32 and the base layer 31, and the second adhesive layer 33 and the base layer 31 is the first interface as described above. That is, the first interface has the smallest peel strength and bonding area.

[0060] In some embodiments, the bonding area between the second adhesive layer 33 and the electrode assembly 20 is greater than the bonding area between the first interface.

[0061] In some embodiments, the bonding area between the second adhesive layer 33 and the electrode assembly 20 is equal to the bonding area of ​​the first interface. Without affecting the purpose of this invention, and considering factors such as manufacturing precision, when there is a 5% error between the bonding area between the second adhesive layer 33 and the electrode assembly 20 and the bonding area of ​​the first interface, it can also be considered that the bonding area between the second adhesive layer 33 and the electrode assembly 20 is equal to the bonding area of ​​the first interface.

[0062] In some embodiments, the bonding areas of the first adhesive layer 32 with the outer shell 10, the first adhesive layer 32 with the base layer 31, the second adhesive layer 33 with the base layer 31, and the second adhesive layer 33 with the electrode assembly 20 are all equal. Without affecting the purpose of this invention, and considering the precision of manufacturing processes, when there is a 10% error between the minimum and maximum bonding areas of the first adhesive layer 32 with the outer shell 10, the first adhesive layer 32 with the base layer 31, the second adhesive layer 33 with the base layer 31, and the second adhesive layer 33 with the electrode assembly 20, the bonding areas of the first adhesive layer 32 with the outer shell 10, the first adhesive layer 32 with the base layer 31, the second adhesive layer 33 with the base layer 31, and the second adhesive layer 33 with the electrode assembly 20 can also be considered equal.

[0063] In some embodiments, the projections of the base layer 31, the first adhesive layer 32, and the second adhesive layer 33 all coincide along the thickness direction of the adhesive member 30. Coincidence, as used herein, means that, among the projections of the base layer 31, the first adhesive layer 32, and the second adhesive layer 33, up to 10% of the projection is allowed not to coincide with the projection of the smallest. The thickness direction of the adhesive member 30 may be parallel to the first direction X.

[0064] In some embodiments, 4N / cm 2 <τ2. Set to 4N / cm 2 <τ2, when the secondary battery 100 is dropped or vibrated, it helps to further reduce the possibility of the electrode assembly 20 impacting the outer casing 10.

[0065] In some embodiments, τ1-τ2≤3N / cm 2 Set τ1-τ2≤3N / cm 2 Under the premise that the adhesive 30 tears before the electrode assembly 20 and peels off from the housing 10 or the electrode assembly 20, τ2 can be kept from being too small, thereby reducing the possibility of the electrode assembly 20 impacting the housing 10.

[0066] In some embodiments, the minimum peel strength among the first adhesive layer 32 and the outer shell 10, the first adhesive layer 32 and the base layer 31, and the second adhesive layer 33 and the base layer 31 is less than the peel strength between the second adhesive layer 33 and the electrode assembly 20. In this case, when the drop intensity or vibration intensity is high, the adhesive 30 can peel off from the outer shell 10 first, or the first adhesive layer 32 or the second adhesive layer 33 can peel off from the base layer 31 first. Compared to the adhesive 30 peeling off from the electrode assembly 20 first, this helps to reduce the wear of the adhesive 30 on the electrode assembly 20 after peeling, thereby further improving the service life of the secondary battery 100.

[0067] In some embodiments, the maximum value of the peel strength between the first adhesive layer 32 and the outer shell 10, and between the second adhesive layer 33 and the electrode assembly 20, is less than the minimum value of the peel strength between the first adhesive layer 32 and the base layer 31, and between the second adhesive layer 33 and the base layer 31. In this case, when the drop intensity or vibration intensity is high, the adhesive component 30 can peel off from the outer shell 10 or the electrode assembly 20 first, and the internal structure of the adhesive component 30 can maintain better integrity, which helps to reduce the possibility of the adhesive component 30 being easily damaged and failing during the adhesive friction process. In some embodiments, the bonding area between the second adhesive layer 33 and the electrode assembly 20 is larger than the bonding area between the first adhesive layer 32 and the outer shell 10, which facilitates a larger peel strength between the second adhesive layer 33 and the electrode assembly 20, thereby facilitating the peeling of the adhesive component 30 from the outer shell 10 first when the drop intensity or vibration intensity is high.

[0068] In some embodiments, the thickness of the adhesive 30 is from 11 μm to 30 μm. For example, the thickness of the adhesive 30 is 11 μm, 13 μm, 17 μm, 20 μm, 25 μm, 30 μm or any value between the listed endpoint values.

[0069] In some embodiments, the thickness of the base layer 31 along the first direction X is 5 μm to 10 μm. For example, the thickness of the base layer 31 is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or any value between the listed endpoint values.

[0070] In some embodiments, the thickness of the first adhesive layer 32 along the first direction X is D1, where 3 μm ≤ D1 ≤ 10 μm. For example, D1 is 3 μm, 4 μm, 5 μm, 7 μm, 10 μm, or any value between the listed endpoints. Setting 3 μm ≤ D1 prevents the first adhesive layer 32 from being too thin, which is beneficial for increasing the value of τ2, thereby reducing the possibility of the electrode assembly 20 impacting the housing 10. Setting D1 ≤ 10 μm prevents the first adhesive layer 32 from being too thick, which is beneficial for increasing the energy density of the secondary battery 100.

[0071] In some embodiments, the thickness of the second adhesive layer 33 along the first direction X is D2, where 3 μm ≤ D2 ≤ 10 μm. For example, D2 is 3 μm, 4 μm, 5 μm, 7 μm, 10 μm, or any value between the listed endpoints. Setting D2 to 3 μm ≤ D2 prevents the second adhesive layer 33 from being too thin, which is beneficial for increasing the value of τ2, thereby reducing the possibility of the electrode assembly 20 impacting the housing 10. Setting D2 ≤ 10 μm prevents the second adhesive layer 33 from being too thick, which is beneficial for increasing the energy density of the secondary battery 100.

[0072] In some embodiments, the material of the first adhesive layer 32 includes a base resin, a tackifying resin, and a polyether polyol. Based on the total mass of the first adhesive layer 32, the mass percentage of the base resin is 50% to 80%, the mass percentage of the tackifying resin is 20% to 45%, and the mass percentage of the polyether polyol is 0% to 6%. By including the above-mentioned materials in the material of the first adhesive layer 32 and controlling the mass percentage of the above-mentioned materials in the first adhesive layer 32 within the above-mentioned range, the peel strength between the first adhesive layer 32 and the shell 10 and the base layer 31 can be adjusted, thereby making it easier to achieve a peel strength of 1 N / cm. 2 <τ2≤τ1.

[0073] In some embodiments, the material of the second adhesive layer 33 includes a base resin, a tackifying resin, and a polyether polyol. Based on the total mass of the second adhesive layer 33, the mass percentage of the base resin is 50% to 80%, the mass percentage of the tackifying resin is 20% to 45%, and the mass percentage of the polyether polyol is 0% to 6%. By including the above-mentioned materials in the material of the second adhesive layer 33 and controlling the mass percentage of the above-mentioned materials in the second adhesive layer 33 within the above-mentioned range, the peel strength between the second adhesive layer 33 and the electrode assembly 20 and the base layer 31 can be adjusted, thereby making it easier to achieve a peel strength of 1 N / cm. 2 <τ2≤τ1.

[0074] In some embodiments, the matrix resin comprises a SIS block copolymer (i.e., a triblock copolymer composed of polystyrene-polyisoprene-polystyrene), wherein the block ratio of polystyrene and polyisoprene can be appropriately adjusted according to the desired rigidity and mechanical strength of the first adhesive layer 32 and the second adhesive layer 33. For example, the block ratio of polystyrene can be increased, thereby improving the rigidity and mechanical strength of the first adhesive layer 32 and the second adhesive layer 33. The tackifying resin comprises hydrogenated resins, and the mass percentage of the tackifying resin can be increased, thereby improving the peel strength of the first adhesive layer 32 to the base layer 31 and the shell 10, and the second adhesive layer 33 to the base layer 31 and the electrode assembly 20. The polyether polyol is prepared by addition polymerization of an initiator (i.e., a compound containing active hydrogen groups) with ethylene oxide, propylene oxide, and butane oxide, etc., under catalysis.

[0075] In some embodiments, the negative electrode active material layer 212 is made of styrene-butadiene rubber and carboxymethyl cellulose, wherein the mass percentage of styrene-butadiene rubber is 1% to 2% and the mass percentage of carboxymethyl cellulose is 1% to 2%. By making the negative electrode active material layer 212 comprise the above-mentioned materials and controlling the mass percentage of the above-mentioned materials in the negative electrode active material layer 212 within the above-mentioned range, the peel strength between the negative electrode active material layer 212 and the separator 23 and the negative electrode current collector 211 can be adjusted, thereby making it easier to make τ2 ≤ τ1.

[0076] In some embodiments, the positive electrode active material layer 222 is made of polyvinylidene fluoride (PVDF), with a mass percentage of PVDF ranging from 1% to 2%. By including the above-mentioned material in the positive electrode active material layer 222 and controlling the mass percentage of the above-mentioned material in the positive electrode active material layer 222 within the above-mentioned range, the peel strength between the positive electrode active material layer 222 and the separator 23 and the positive electrode current collector 221 can be adjusted, thereby making it easier to ensure that τ2 ≤ τ1.

[0077] In some embodiments, along the first direction X, the projections of the first adhesive layer 32, the second adhesive layer 33, and the base layer 31 coincide, the projection of the outermost electrode covers the projection of the adhesive member 30, the projected area of ​​the outermost electrode is S1, the projected area of ​​the adhesive member 30 is S2, and 0.35≤S2 / S1≤1. For example, the value of S2 / S1 can be 0.35, 0.5, 0.6, 0.75, and 1. Setting 0.35≤S2 / S1≤1 ensures that the bonding area between the adhesive member 30 and the housing 10 and the electrode assembly 20 is not too small, which is beneficial to increasing the value of τ2. Therefore, when the secondary battery 100 is dropped or vibrated, it is beneficial to further reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0078] In some embodiments, referring to FIG4, the minimum distance between the edge of the adhesive 30 and the edge of the outermost electrode of the electrode assembly 20 along a direction perpendicular to the first direction X is d, where 10 mm ≤ d. For example, the value of d can be 10 mm, 11 mm, 13 mm, and 15 mm. Setting 10 mm ≤ d allows the edge of the adhesive 30 to be farther from the edges of the outermost electrode and the housing 10, thereby making it less likely for the adhesive 30 to peel off from the outermost electrode and the housing 10, which helps to further reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0079] It should be understood that the distance between the edge of the adhesive 30 and the edge of the outermost electrode of the electrode assembly 20 can be equal or unequal along different directions perpendicular to the first direction X, but all must satisfy 10mm≤d. Furthermore, since space needs to be reserved for the installation of the adhesive 30, the value of d should not be too large.

[0080] In some embodiments, referring to FIG4, the center of the circumcircle of the projection of the adhesive 30 coincides with the center of the circumcircle of the projection of the outermost electrode sheet along the first direction X. This coincidence means that the distance between the center of the circumcircle of the projection of the adhesive 30 and the center of the circumcircle of the projection of the outermost electrode sheet is 0 mm to 1 mm. In this case, the distance between the edge of the adhesive 30 and the edges of the outermost electrode sheet and the housing 10 is more uniform along different directions perpendicular to the first direction X. This improves the peel strength between the adhesive 30 and the outermost electrode sheet and the housing 10 along different directions perpendicular to the first direction X, which is beneficial to increasing the value of τ2, thereby further reducing the possibility of the electrode assembly 20 impacting the housing 10.

[0081] In some embodiments, please refer to FIG5, the secondary battery 100 includes a negative electrode tab 40, which is connected to a negative electrode current collector 211 and extends the negative electrode current collector 211 along a third direction Z.

[0082] In some embodiments, the negative electrode tab 40 and the negative electrode current collector 211 are integrally formed. In some embodiments, the negative electrode tab 40 and the negative electrode current collector 211 are welded together.

[0083] In some embodiments, referring to FIG5, a plurality of negative electrode tabs 40 are stacked sequentially along a first direction X and welded to form a negative electrode tab bundle 50. The negative electrode tab bundle 50 is bent in the opposite direction to the stacking direction of the plurality of negative electrode tabs 40 and then electrically connected to the housing 10.

[0084] In some embodiments, the negative electrode tab bundle 50 is welded to the housing 10. In some embodiments, the negative electrode tab bundle 50 is welded to the first housing 11.

[0085] In some embodiments, referring to FIG6, the secondary battery 100 includes a positive electrode tab 60, which is connected to a positive current collector 221 and extends the positive current collector 221 along a third direction Z.

[0086] In some embodiments, the positive electrode tab 60 and the positive electrode current collector 221 are integrally formed. In some embodiments, the positive electrode tab 60 and the positive electrode current collector 221 are welded together.

[0087] In some embodiments, referring to FIG6, a plurality of positive electrode tabs 60 are stacked sequentially along a first direction X and welded to form a positive electrode tab bundle 70. The positive electrode tab bundle 70 is bent in the opposite direction to the stacking direction of the plurality of positive electrode tabs 50 and then insulatedly connected to the housing 10.

[0088] In some embodiments, please refer to FIG6, the secondary battery 100 includes a terminal post 80, which is insulated and fixed to the housing 10, and the positive electrode tab bundle 70 is electrically connected to the terminal post 80.

[0089] In some embodiments, the positive electrode tab bundle 70 is connected to the electrode post 80 via an adapter (not shown), and the adapter is made of one or more conductive materials such as copper, aluminum, nickel, and nickel alloys.

[0090] In some embodiments, the terminal post 80 is insulated and fixed to the first housing 11. Referring to FIG6, the secondary battery 100 includes an insulating member 90 disposed on the first housing 11. Along a first direction X and a third direction Z, the terminal post 80 and the first housing 11 are spaced apart by at least a portion of the insulating member 90.

[0091] Please refer to Figure 7. One embodiment of this application provides an electrical device 1000, including the secondary battery 100 as described above. The secondary battery 100 has a long service life, 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.

[0092] To verify the influence of the relationship between τ1 and τ2 in this application on the secondary battery 100, the inventors of this application conducted the following experiments, which included 8 sets of comparative examples and 9 sets of exemplary examples. Each set of comparative examples and exemplary examples included 20 secondary batteries 100. In the secondary batteries 100 used in the comparative examples and exemplary examples, the outer shell 10 was made of steel. The first shell 11 and the second shell 12 were welded together, and the first shell 11 was the body of the outer shell 10, while the second shell 12 was the cover of the outer shell 10. The electrode assembly 20 in the secondary battery 100 had a stacked structure, and the outermost electrode of the electrode assembly 20 was a single-sided negative electrode 21. In the secondary battery 100, the adhesive 30 is centrally located relative to the outermost electrode of the electrode assembly 20. The first adhesive layer 32 is bonded to the shell cover (i.e., the second shell 12) of the outer casing 10, and the second adhesive layer 33 is bonded to the outermost electrode of the electrode assembly 20. Along the thickness direction of the adhesive 30, the projections of the base layer 31, the first adhesive layer 32, and the second adhesive layer 33 all coincide, and the projected area S2 of the adhesive 30 is equal to the projected area S1 of the outermost electrode (a 10% error is allowed between S1 and S2).

[0093] In this application, the required experimental τ2 can be obtained by changing the mass percentage of each material in the first adhesive layer 32 and the second adhesive layer 33. Similarly, the required experimental τ1 can be obtained by changing the mass percentage of each material in the negative electrode 21, the positive electrode 22, and the separator 23. The methods for determining τ1 and τ2 are as follows:

[0094] 1) Sample preparation: According to the required τ1 and τ2, take out the peeling sample where the adhesive 30 is bonded to the outermost electrode of the second shell 12 and the electrode assembly 20, and the tearing sample where the separator 23 is bonded to the negative electrode 21 and the positive electrode 22 from the finished secondary battery 100. Use a blade to cut peel test sample and tear test sample with a test area of ​​1cm×1cm in the different samples taken out.

[0095] 2) Testing: Fix the peel test sample and tear test sample onto the test fixture of the high-speed rail tensile testing machine in sequence. When fixing, make the thickness direction of the peel test sample and tear test sample perpendicular to the force direction of the high-speed rail tensile testing machine. Select the shearing mode, set the shearing angle to 0 degrees, and set the shearing speed to 25±2mm / min until the shearing interface of the peel test sample is completely peeled or the shearing interface of the tear test sample is completely torn.

[0096] 3) Values: Take the value of τ2 as the ratio of the maximum tensile force when the shear interface of the peel test sample is completely peeled off to the test area, and take the value of τ1 as the ratio of the maximum tensile force when the shear interface of the tear test sample is completely torn.

[0097] In this application, the impact of the relationship between τ1 and τ2 on the secondary battery 100 can be reflected by the drop pass rate of the secondary battery 100 and the tearing rate of the electrode assembly 20. The drop pass rate refers to the proportion of secondary batteries 100 that do not leak or catch fire after a drop test, and the tearing rate refers to the proportion of secondary batteries 100 whose electrode assembly 20 tears after a drop test. The drop test method is as follows:

[0098] 1) Take 20 secondary batteries 100 from each comparative example and embodiment as a group, place the 20 secondary batteries 100 in a special clamp in sequence, and drop them freely from a height of 1.5 meters onto the marble surface; each secondary battery 100 drops three times, and the order of the secondary battery 100 facing the marble surface in each drop is: upper shell cover - lower bottom wall - upper right corner - lower right corner - upper left corner - lower left corner;

[0099] 2) After each round of drops, check the appearance of the secondary battery 100. If the secondary battery 100 of the current round leaks or catches fire, stop the drop immediately.

[0100] 3) After all 20 secondary batteries 100 in each group have been dropped, the secondary batteries 100 are disassembled. The number of secondary batteries 100 that did not leak or catch fire is N, and the number of secondary batteries 100 that had their electrode assembly 20 torn is F. Then the drop pass rate of the secondary batteries 100 in this group is N / 20, and the tearing rate of the electrode assembly 20 is F / 20.

[0101] After the test, the experimental results were recorded as shown in Table 1:

[0102] Table 1

[0103] In Table 1, the drop pass rate and tearing rate of Comparative Examples 1 to 3 were both 0%, because τ2 < 1 N / cm. 2 When τ2 is relatively small, the adhesive 30 is prone to peeling off from the housing 10 or the electrode assembly 20 during drop testing, causing the electrode assembly 20 to impact the housing 10 and leak. In this case, regardless of whether τ2≤τ1 or τ2>τ1, the drop energy cannot be transferred to the electrode assembly 20 through the adhesive 30, and thus the electrode assembly 20 does not tear.

[0104] In Table 1, the drop pass rates of Comparative Examples 4 to 6 are all close to 0%, which is due to τ2 = 1 N / cm. 2 During drop tests, the adhesive 30 still easily peels off from the housing 10 or the electrode assembly 20, causing the electrode assembly 20 to impact the housing 10 and leak. The tearing rate in Comparative Example 4 is comparable to the drop pass rate because τ2 > τ1. In the portion of the secondary battery 100 that passed the drop test, the drop energy is transferred to the electrode assembly 20 through the adhesive 30, causing the electrode assembly 20 to tear. The tearing rates in Comparative Examples 5 and 6 are lower than those in Comparative Example 4 because τ2 ≤ τ1. In the portion of the secondary battery 100 that passed the drop test, the likelihood of drop energy being transferred to the electrode assembly 20 through the adhesive 30 is lower, thus reducing the likelihood of the electrode assembly 20 tearing.

[0105] In Table 1, the drop pass rates of Comparative Examples 7 and 8 are significantly higher than those of Comparative Examples 1 to 6. This is because τ2 > 1 N / cm 2 During drop tests, the adhesive 30 is less likely to peel off from the housing 10 or the electrode assembly 20, reducing the possibility of leakage caused by the electrode assembly 20 impacting the housing 10. The tearing rate in Comparative Examples 7 and 8 is comparable to the drop pass rate. This is because τ2 > τ1; in the portion of the secondary battery 100 that passes the drop test, the drop energy is transferred to the electrode assembly 20 through the adhesive 30, causing the electrode assembly 20 to tear.

[0106] In Table 1, the drop pass rates of Examples 1 to 9 are significantly higher than those of Comparative Examples 1 to 6, and the drop pass rates of Examples 7 to 9 are significantly higher than those of Examples 1 to 6. In other words, this application achieves this by setting τ2 > 1 N / cm. 2 This reduces the possibility of leakage caused by the electrode assembly 20 impacting the housing 10. Furthermore, by setting τ2 > 4 N / cm...2 This can further reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0107] In Table 1, the tearing rates of Examples 3 and 4 are significantly lower than those of Comparative Example 7, and the tearing rates of Examples 7 and 8 are significantly lower than those of Comparative Example 8. In other words, by setting τ2≤τ1, this application helps to reduce the risk of the electrode assembly 20 being torn.

[0108] In Table 1, the drop pass rates of Examples 4, 6, 8, and 9 are all significantly higher than that of Example 2. In other words, this application achieves higher drop pass rates by setting τ1-τ2≤3N / cm. 2 This helps reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0109] 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 has a receiving cavity; An electrode assembly disposed within the receiving cavity; An adhesive component, along a first direction, is disposed between the housing and the electrode assembly, the first direction being the thickness direction of the electrode assembly; the adhesive component includes a first adhesive layer bonded to the housing, a second adhesive layer bonded to the electrode assembly, and a base layer disposed between the first adhesive layer and the second adhesive layer; Along a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1. The interface with the lowest peel strength among the first adhesive layer and the outer shell, the second adhesive layer and the electrode assembly, the first adhesive layer and the base layer, and the second adhesive layer and the base layer is the first interface, and the peel strength of the first interface is τ2, 1 N / cm. 2 <τ2≤τ1.

2. The secondary battery according to claim 1, characterized in that, The bonding area between the second adhesive layer and the electrode assembly is greater than or equal to the bonding area of ​​the first interface; or, the bonding areas between the first adhesive layer and the shell, the first adhesive layer and the base layer, the second adhesive layer and the base layer, and the second adhesive layer and the electrode assembly are all equal.

3. The secondary battery according to claim 2, characterized in that, The adhesive is bonded to the outermost electrode of the electrode assembly. The projection of the outermost electrode covers the projection of the adhesive. The projected area of ​​the outermost electrode is S1, and the projected area of ​​the adhesive is S2. 0.35≤S2 / S1≤1.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The adhesive is bonded to the outermost electrode of the electrode assembly; the minimum distance between the edge of the adhesive and the edge of the outermost electrode in a direction perpendicular to the first direction is d, where 10mm≤d.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The adhesive is bonded to the outermost electrode of the electrode assembly; along the first direction, the center of the circumcircle of the projection of the adhesive coincides with the center of the circumcircle of the projection of the outermost electrode.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The materials of the first adhesive layer and / or the second adhesive layer each independently include a base resin, a tackifying resin, and a polyether polyol. Based on the total mass of the first adhesive layer and / or the second adhesive layer, the mass percentage of the base resin is 50% to 80%, the mass percentage of the tackifying resin is 20% to 45%, and the mass percentage of the polyether polyol is 0% to 6%.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, Along the first direction, the thickness of the first adhesive layer is D1, 3μm≤D1≤10μm; and / or, the thickness of the second adhesive layer is D2, 3μm≤D2≤10μm.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, τ1-τ2≤3N / cm 2 。 9. The secondary battery according to any one of claims 1 to 8, characterized in that, The minimum of the peel strengths of the first adhesive layer to the outer shell, the first adhesive layer to the base layer, and the second adhesive layer to the base layer is less than the peel strength of the second adhesive layer to the electrode assembly.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, 4N / cm 2 <τ2。 11. The secondary battery according to any one of claims 1 to 10, characterized in that, The maximum value of the peel strength between the first adhesive layer and the outer shell, and between the second adhesive layer and the electrode assembly, is less than the minimum value of the peel strength between the first adhesive layer and the base layer, and between the second adhesive layer and the base layer.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The electrode assembly includes a negative electrode, a positive electrode, and a separator, the separator separating the negative electrode and the positive electrode; the negative electrode includes a negative current collector and a negative active material layer, the negative active material layer being disposed on two opposing sides of the negative current collector along the thickness direction; the positive electrode includes a positive current collector and a positive active material layer, the positive active material layer being disposed on two opposing sides of the positive current collector along the thickness direction. The negative electrode active material layer is made of styrene-butadiene rubber and carboxymethyl cellulose, wherein the mass percentage of styrene-butadiene rubber is 1% to 2% and the mass percentage of carboxymethyl cellulose is 1% to 2%; and / or, the positive electrode active material layer is made of polyvinylidene fluoride, wherein the mass percentage of polyvinylidene fluoride is 1% to 2%.

13. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 12.

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