Secondary battery and electric device

Abstract

Disclosed in the present application are a secondary battery and an electric 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 arranged within the accommodating cavity. The adhesive member is of a single-layer structure and comprises a first surface and a second surface arranged opposite each other in a first direction. The first surface is bonded to one of the housing and the electrode assembly. In the direction perpendicular to the first direction, the second surface can move relative to the other one of the housing and the electrode assembly, and can generate friction during relative movement. The first direction is the thickness direction of the adhesive member. In the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1, and the anti-slip strength between the second surface and the housing or between the second surface and the electrode assembly is τ2, where 1N / cm2<τ2≤τ1. Setting 1N / cm2<τ2 helps reduce the possibility of the electrode assembly impacting the housing. Setting τ2≤τ1 helps reduce 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. 202510315701.2, 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 their 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. Thus, 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. In particular, as the number of battery cycles increases, the expansion force generated by the secondary battery gradually increases, exacerbating the deformation of the electrode assembly and making it even more susceptible to tearing, thereby 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, the electrode assembly is disposed within the receiving cavity, and the adhesive is a single-layer structure including a first surface and a second surface disposed opposite to each other along a first direction. The first surface is bonded to one of the casing and the electrode assembly. The second surface is movable relative to the other of the casing and the electrode assembly along a direction perpendicular to the first direction, and is capable of generating friction during relative movement. The first direction is the thickness direction of the adhesive. Wherein, along the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1, and the anti-slip strength between the second surface and the casing or between the second surface and the electrode assembly is τ2, 1 N / cm. 2 <τ2≤τ1.

[0007] By bonding the adhesive component to one of the housing and the electrode assembly, and allowing relative movement between the adhesive component and the other of the housing and the electrode assembly, friction is generated during the relative movement between the adhesive component and the housing or between the adhesive component and the electrode assembly, thus creating a cushioning effect. By setting 1 N / cm... 2 If τ2 < τ1, the anti-slip strength between the second surface and the outer casing or the second surface and the electrode assembly will not be too low. Furthermore, when the secondary battery is subjected to drops or vibrations, the frictional buffering effect between the second surface and the outer casing or the second surface and the electrode assembly can reduce the drop energy or vibration energy, thus reducing the possibility of the electrode assembly impacting the outer casing. By setting τ2 ≤ τ1, the anti-slip strength between the second surface and the outer casing or the second surface and the electrode assembly will not be too high. When the drop intensity or vibration intensity is high, the second surface can slip relative to the outer casing or the electrode assembly before the electrode assembly tears, thus reducing the risk of the electrode assembly being torn and consequently improving the service life of the secondary battery.

[0008] In one or more of the above embodiments, 1N / cm 2 ≤τ1-τ2≤3N / cm 2 Considering that τ1 decreases with the increase of the number of secondary battery cycles, a setting of 1 N / cm is used. 2 Setting τ1-τ2 ≤ 3 N / cm reduces the likelihood that τ1 will decrease to less than τ2 after cycling, thus mitigating the risk of electrode assembly tearing in the event of drops or vibrations after cycling. 2 Under the premise of satisfying τ2≤τ1, τ2 can be made not too small, which helps to reduce the possibility of the electrode assembly impacting the outer shell.

[0009] In one or more of the above embodiments, the coefficient of friction between the second surface and the outer shell or electrode assembly is f, where 0.5 ≤ f ≤ 3. By setting 0.5 ≤ f, τ2 is prevented from being too small, which helps reduce the possibility of the electrode assembly impacting the outer shell. By setting f ≤ 3, τ2 is prevented from being too large, which helps reduce the risk of the electrode assembly being torn.

[0010] In one or more of the above embodiments, 0.8 ≤ f ≤ 2. Setting 0.8 ≤ f helps to further reduce the possibility of the electrode assembly impacting the housing. Setting f ≤ 2 helps to further reduce the risk of the electrode assembly being torn.

[0011] In one or more of the above embodiments, the shear modulus of the adhesive is G, where 200MPa≤G≤1000MPa. By setting G to 200MPa≤G, the rigidity of the adhesive is prevented from being too weak, which helps reduce the possibility of fatigue damage under continuous friction, thus helping the adhesive maintain its friction buffering effect. By setting G≤1000MPa, the rigidity of the adhesive is prevented from being too strong, which facilitates elastic deformation of the adhesive and helps reduce the possibility of the electrode assembly impacting the outer shell.

[0012] In one or more of the above embodiments, the thickness of the adhesive component along the first direction is D, where 9μm ≤ D ≤ 25μm. By setting 9μm ≤ D, the adhesive component is prevented from being too thin, which helps reduce the possibility of fatigue damage under continuous friction, thereby helping the adhesive component maintain its friction buffering effect. By setting D ≤ 25μm, the adhesive component is prevented from being too thick, which helps improve the energy density of the secondary battery.

[0013] In one or more of the above embodiments, along the first direction, the surface containing the minimum projected area of ​​the adhesive includes the second surface.

[0014] In one or more of the above embodiments, the first surface is bonded to the electrode assembly. The second surface is movable relative to the outer casing along a direction perpendicular to the first direction. Compared to a configuration where the first surface is bonded to the outer casing and the second surface moves relative to the electrode assembly, generating friction, this reduces wear on the electrode assembly, thus improving the lifespan of the secondary battery. Furthermore, it facilitates the treatment of the surface of the outer casing that rubs against the second surface, thereby easily adjusting the coefficient of friction between the second surface and the outer casing.

[0015] In one or more of the above embodiments, along the direction perpendicular to the first direction, the peel strength between the first surface and the electrode assembly is τ3, where τ3 ≥ τ2. Setting τ3 ≥ τ2, compared to setting τ3 < τ2, reduces the possibility of the first surface peeling off from the electrode assembly prematurely, which is beneficial for maintaining a frictional buffering effect between the second surface and the outer casing.

[0016] In one or more of the above embodiments, the first surface has staggered protrusions and recesses, at least some of which are bonded to the electrode assembly. Having protrusions and recesses on the first surface helps to increase τ3, making it easier for τ3 ≥ τ2.

[0017] In one or more of the above embodiments, τ3-τ2≤10N / cm 2 Under the premise that τ3≥τ2, τ3 can be kept from being too large, which is beneficial to improving the convenience of preparing adhesive parts.

[0018] In one or more of the above embodiments, the first surface is bonded to the outermost electrode of the electrode assembly. Along the first direction, the projected area of ​​the outermost electrode is S1, and the friction area of ​​the second surface is S2, where 0.5 ≤ S2 / S1 ≤ 1. Setting 0.5 ≤ S2 / S1 ≤ 1 ensures that the friction area between the second surface and the outer shell is not too small, which helps to increase the value of τ2 and further reduces the possibility of the electrode assembly impacting the outer shell.

[0019] In one or more of the above embodiments, the second surface contacts the housing or electrode assembly. This facilitates friction and provides a cushioning effect during relative movement.

[0020] In one or more of the above embodiments, the adhesive material includes polyacrylate and a curing agent, wherein the mass percentage of polyacrylate is 95% to 99%, and the mass percentage of the curing agent is 1% to 4%. By including the above materials in the adhesive material and controlling the mass percentage of the above materials in the adhesive within the above range, it is easier to achieve 1 N / cm 2 <τ2≤τ1.

[0021] 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

[0022] Figure 1 is a front view of a secondary battery provided in an embodiment of this application.

[0023] Figure 2 is a top view of a secondary battery provided in an embodiment of this application.

[0024] Figure 3 is a cross-sectional view along section line AA in Figure 1.

[0025] Figure 4 is a schematic diagram of the structure of an adhesive component provided in an embodiment of this application.

[0026] Figure 5 is a cross-sectional view along section line BB in Figure 2.

[0027] Figure 6 is a cross-sectional view along section line CC in Figure 2.

[0028] Figure 7 is an overall schematic diagram of an electrical device provided in an embodiment of this application.

[0029] 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; 211, Negative current collector; 212, Negative active material layer; 22, Positive electrode; 221, Positive current collector; 222, Positive active material layer; 23, Separator; 30, Adhesive; 31, First surface; 311, Protrusion; 312, Recess; 32, Second surface; 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

[0030] 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.

[0031] 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.

[0032] Unless otherwise stated, the term "multiple" as used herein refers to two or more.

[0033] 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.

[0034] 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.

[0035] This application provides a secondary battery, including a casing, an electrode assembly, and an adhesive. The casing has a receiving cavity, the electrode assembly is disposed within the receiving cavity, and the adhesive is a single-layer structure including a first surface and a second surface disposed opposite to each other along a first direction. The first surface is bonded to one of the casing and the electrode assembly, and the second surface is movable relative to the other of the casing and the electrode assembly along a direction perpendicular to the first direction, and is capable of generating friction during relative movement. The first direction is the thickness direction of the adhesive. The tear strength of the electrode assembly is τ1 along the direction perpendicular to the first direction, and the anti-slip strength of the second surface to the casing or the second surface to the electrode assembly is τ2, 1 N / cm². 2 <τ2≤τ1.

[0036] In the secondary battery of this application, an adhesive component is bonded to one of the casing and the electrode assembly, allowing relative movement with the other component. This relative movement between the adhesive component and the casing, or between the adhesive component and the electrode assembly, generates friction and provides a buffering effect. By setting a value of 1 N / cm... 2 If τ2 < τ1, the anti-slip strength between the second surface and the outer casing or the second surface and the electrode assembly will not be too low. Furthermore, when the secondary battery is subjected to drops or vibrations, the frictional buffering effect between the second surface and the outer casing or the second surface and the electrode assembly can reduce the drop energy or vibration energy, thus reducing the possibility of the electrode assembly impacting the outer casing. By setting τ2 ≤ τ1, the anti-slip strength between the second surface and the outer casing or the second surface and the electrode assembly will not be too high. When the drop intensity or vibration intensity is high, the second surface can slip relative to the outer casing or the electrode assembly before the electrode assembly tears, thus reducing the risk of the electrode assembly being torn and consequently improving the service life of the secondary battery.

[0037] 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.

[0038] 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 30. The electrode assembly 20 is housed within the housing 10. The adhesive 30 is bonded to one of the housing 10 and the electrode assembly 20, and is movable relative to the other of the housing 10 and the electrode assembly 20, and is capable of generating friction during relative movement.

[0039] Referring to Figure 3, the housing 10 has a receiving cavity 101, which is filled with an electrolyte, including an electrolyte salt. In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0040] In some embodiments, the material of the housing 10 includes, but is not limited to, aluminum-plastic film or steel.

[0041] In some embodiments, referring to FIG1, the housing 10 includes a first housing 11 and a second housing 12, the first housing 11 and the second housing 12 being connected to form a receiving cavity 101. In some embodiments, the first housing 11 and the second housing 12 are connected along the thickness direction of the electrode assembly 20.

[0042] 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.

[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 diaphragm 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 is 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, the adhesive 30 is a single-layer structure and includes a first surface 31 and a second surface 32 disposed opposite to each other along a first direction X, where X is the thickness direction of the adhesive 30. The first surface 31 is bonded to one of the housing 10 and the electrode assembly 20. The second surface 32 is movable relative to the other of the housing 10 and the electrode assembly 20 along a direction perpendicular to the first direction X, and can generate friction during relative movement. For example, the first surface 31 is bonded to the housing 10, and the second surface 32 is movable relative to the electrode assembly 20; or, the first surface 31 is bonded to the electrode assembly 20, and the second surface 32 is movable relative to the housing 10. The second surface 32 can be in pre-contact with the housing 10 or the electrode assembly 20 to facilitate friction and provide a buffering effect during relative movement. Alternatively, the second surface 32 can be in contact with the housing 10 or the electrode assembly 20 after the secondary battery 100 has undergone cyclic expansion. When the electrode assembly 20 and the housing 10 have a tendency to move relative to each other or when relative movement occurs, a buffering effect can be generated between the second surface 32 and the housing 10 or the electrode assembly 20. For example, the second surface 32 is in pre-contact with the housing 10 or the electrode assembly 20, so that friction is generated when the second surface 32 moves relative to the housing 10 or the electrode assembly 20, thus generating a buffering effect.

[0054] Along a direction perpendicular to the first direction X, the tear strength of the electrode assembly 20 is τ1, and the anti-slip strength between the second surface 32 and the outer shell 10 or between the second surface 32 and the electrode assembly 20 is τ2, 1 N / cm. 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 cause relative slippage between the second surface 32 and the outer casing 10 or between the second surface 32 and the electrode assembly 20 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 is achieved by setting 1N / cm 2 If τ2 < τ1, the anti-slip strength between the second surface 32 and the outer shell 10 or the electrode assembly 20 will not be too small. Furthermore, when the secondary battery 100 is dropped or vibrated, the frictional buffering effect between the second surface 32 and the outer shell 10 or the electrode assembly 20 can reduce the drop energy or vibration energy, thus reducing the possibility of the electrode assembly 20 impacting the outer shell 10. By setting τ2 ≤ τ1, the anti-slip strength between the second surface 32 and the outer shell 10 or the electrode assembly 20 will not be too large. When the drop intensity or vibration intensity is high, the second surface 32 can slide relative to the outer shell 10 or the electrode assembly 20 before the electrode assembly 20 tears, thus reducing the risk of the electrode assembly 20 being torn and 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 shell 10, when the first shell 11 and the second shell 12 are connected separately, it is beneficial to reduce the risk of the second shell 11 separating from the second shell 12, leading to leakage failure of the secondary battery 100.

[0058] In some embodiments, 1N / cm 2 ≤τ1-τ2≤3N / cm 2 Considering that τ1 decreases with the increase of 100 cycles of the secondary battery, by setting 1N / cm 2 Setting τ1-τ2 ≤ 3 N / cm reduces the likelihood that τ1 will decrease to less than τ2 after cycling, thus mitigating the risk of the electrode assembly 20 being torn in the event of a drop or vibration after cycling. 2Under the premise that τ2≤τ1 is satisfied, τ2 can be made not too small, which helps to reduce the possibility of the electrode assembly 20 impacting the outer shell 10.

[0059] In some embodiments, along the first direction X, the surface containing the minimum projected area of ​​the adhesive 30 includes the second surface 32.

[0060] In some embodiments, the coefficient of friction between the second surface 32 and the housing 10 or the electrode assembly 20 is f, where 0.5 ≤ f ≤ 3. For example, the value of f is 0.5, 0.8, 1.5, 2, 2.5, 3, or any value between the listed endpoints. By setting 0.5 ≤ f, τ2 is prevented from being too small, which helps to reduce the possibility of the electrode assembly 20 impacting the housing 10. By setting f ≤ 3, τ2 is prevented from being too large, which helps to reduce the risk of the electrode assembly 20 being torn.

[0061] In some embodiments, 0.8 ≤ f ≤ 2. Setting 0.8 ≤ f helps to further reduce the possibility of the electrode assembly 20 impacting the housing 10. Setting f ≤ 2 helps to further reduce the risk of the electrode assembly 20 being torn.

[0062] In some embodiments, the first surface 31 is bonded to the electrode assembly 20, and the second surface 32 is movable relative to the housing 10 along a direction perpendicular to the first direction X. Compared to the first surface 31 being bonded to the housing 10 and the second surface 32 moving relative to the electrode assembly 20 and generating friction, the wear on the electrode assembly 20 can be reduced, which is beneficial to improving the service life of the secondary battery 100. Furthermore, the surface of the housing 10 that rubs against the second surface 32 can be easily treated, thereby conveniently adjusting the coefficient of friction between the second surface 32 and the housing 10. For example, by laser roughening the surface of the housing 10 that rubs against the second surface 32, the surface roughness of the housing 10 can be increased, thereby increasing the coefficient of friction between the second surface 32 and the housing 10. In some embodiments, the second surface 32 is movable relative to the second housing 12.

[0063] In some embodiments, the peel strength between the first surface 31 and the electrode assembly 20 along a direction perpendicular to the first direction X is τ3, where τ3 ≥ τ2. τ3 refers to the shear stress required to completely peel the first surface 31 from the electrode assembly 20 under a load perpendicular to the first direction X. Setting τ3 ≥ τ2, rather than τ3 < τ2, reduces the possibility of premature peeling of the first surface 31 from the electrode assembly 20, which is beneficial for maintaining the frictional buffering effect between the second surface 32 and the outer casing 10.

[0064] In some embodiments, τ3-τ2≤10N / cm 2 Under the premise that τ3≥τ2, τ3 can be kept from being too large, which is beneficial to improving the convenience of preparing the adhesive part 30.

[0065] In some embodiments, referring to FIG4, the first surface 31 has staggered protrusions 311 and recesses 312, at least some of which are bonded to the electrode assembly 20. Having protrusions 311 and recesses 312 on the first surface 31 facilitates an increase in τ3, making it easier for τ3 ≥ τ2. In other embodiments, the second surface 32 has staggered protrusions 311 and recesses 312 to improve the coefficient of friction between the second surface 32 and the housing 10.

[0066] In some embodiments, referring to FIG4, the thickness of the adhesive 30 along the first direction X is D, where 9 μm ≤ D ≤ 25 μm. For example, the thickness of the adhesive 30 is 9 μm, 12 μm, 15 μm, 20 μm, 25 μm, or any value between the listed endpoints. By setting 9 μm ≤ D, the adhesive 30 is prevented from being too thin, which helps reduce the possibility of fatigue damage to the adhesive 30 under continuous friction, thereby helping the adhesive 30 maintain its friction buffering effect. By setting D ≤ 25 μm, the adhesive 30 is prevented from being too thick, which helps to improve the energy density of the secondary battery 100.

[0067] In some embodiments, the shear modulus of the adhesive 30 is G, where 200 MPa ≤ G ≤ 1000 MPa. For example, the value of G is 200 MPa, 300 MPa, 400 MPa, 500 MPa, 750 MPa, 1000 MPa, or any value between the listed endpoints. By setting G to 200 MPa ≤ G, the rigidity of the adhesive 30 is not too weak, which helps reduce the possibility of fatigue damage to the adhesive 30 under continuous friction, thereby helping the adhesive 30 maintain its friction buffering effect. By setting G ≤ 1000 MPa, the rigidity of the adhesive 30 is not too strong, which facilitates elastic deformation of the adhesive 30, which helps reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0068] In some embodiments, the adhesive 30 is made of polyacrylate and a curing agent, wherein the polyacrylate comprises 95% to 99% by mass and the curing agent comprises 1% to 4% by mass. The curing agent includes, but is not limited to, epoxy resin and polyamide. By including the above-described materials in the adhesive 30 and controlling the mass percentage of these materials within the above-described range, it is possible to achieve a 1 N / cm² curing agent. 2 <τ2≤τ1.

[0069] In some embodiments, the first surface 31 is bonded to the outermost electrode of the electrode assembly 20. Along the first direction X, the projected area of ​​the outermost electrode is S1, and the friction area of ​​the second surface 32 is S2, where 0.5 ≤ S2 / S1 ≤ 1. For example, the value of S2 / S1 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any value between the listed endpoints. Setting 0.5 ≤ S2 / S1 ≤ 1 ensures that the friction area between the second surface 32 and the housing 10 is not too small, which helps to increase the value of τ2 and further reduces the possibility of the electrode assembly 20 impacting the housing 10.

[0070] It should be understood that when the electrode assembly 20 is a stacked structure, the outermost electrode is the electrode closest to the adhesive 30 among the 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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 60 and then insulatedly connected to the housing 10.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] To verify the impact of the solution provided in this application on the secondary battery 100, the inventors of this application conducted the following experiments, which included 8 comparative examples and 20 implementation examples, each of which included 20 secondary batteries 100. In the secondary batteries 100 used in the comparative examples and implementation examples, the outer casing 10 was made of steel. The first casing 11 and the second casing 12 were welded together, with the first casing 11 being the body of the outer casing 10 and the second casing 12 being the cover of the outer casing 10. The electrode assembly 20 in the secondary battery 100 had a stacked structure, with the outermost electrode of the electrode assembly 20 being a single-sided negative electrode 21. The first surface 31 of the adhesive 30 was bonded to the outermost electrode of the electrode assembly 20, and the second surface 32 of the adhesive 30 contacted the cover of the outer casing 10 (i.e., the second casing 12), with the friction area S2 of the second surface 32 being equal to the projected area S1 of the outermost electrode (a 10% error is allowed between S1 and S2).

[0083] In this application, 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 method for determining τ1 is as follows:

[0084] 1) Sample preparation: Take out the separator 23, negative electrode 21 and positive electrode 22 that are kept bonded from the finished secondary battery 100 as the sample to be torn. Use a blade to cut a tear test sample with a test area of ​​1cm×1cm in the sample to be to be torn.

[0085] 2) Testing: Fix the tear test sample onto the test fixture of the high-speed rail tensile testing machine. When fixing, make the thickness direction of the 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. Start the test until the shearing interface of the tear test sample is completely torn.

[0086] 3) Value: The value of τ1 is the ratio of the maximum tensile force when the shear interface of the tear test sample is completely torn to the test area.

[0087] In this application, the required τ2 for the experiment can be obtained by changing the mass percentage of each material in the adhesive component 30. The method for determining τ2 is as follows:

[0088] 1) Place the finished secondary battery 100 in an environment of 25±1℃;

[0089] 2) Charge the secondary battery 100 with 3C constant current and discharge it with 1C constant current for 800 cycles, and then measure the expansion force generated by the secondary battery 100 using an expansion force tester.

[0090] 3) Take out the adhesive 30 and the outermost electrode from the secondary battery 100 as the sample to be slid, and take out the shell cover of the outer casing 10 as the sample to be slid. Use a blade to cut out a sliding test sample with a test area of ​​3cm×3cm in the sample to be slid.

[0091] 4) Fix the sliding test sample onto the test slider of the friction coefficient tester, wherein the outermost electrode is located between the adhesive 30 and the test slider, and the adhesive 30 is located on the outermost side away from the test slider. Fix the sliding sample to the horizontal test table, ensuring that the sliding test sample is parallel to the sliding sample on the horizontal test table. Set the slider speed to 60±2mm / min, start the test so that the sliding test sample starts to move on the sliding sample, and after stopping, the friction coefficient tester reading is the friction coefficient between the test samples.

[0092] 5) Repeat step 4 5 times and take the average value;

[0093] 6) Calculate the product of the expansion force generated by the secondary battery 100 and the coefficient of friction, and divide it by the friction area S2 of the second surface 32. The resulting ratio is the value of τ2.

[0094] 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:

[0095] 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;

[0096] 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.

[0097] 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.

[0098] After the test, the experimental results were recorded as shown in Tables 1 to 3:

[0099] Table 1

[0100] Table 2

[0101] Table 3

[0102] In Tables 1 to 3, the shear modulus G of Comparative Examples 1 to 8, Examples 1 to 9, and Examples 16 to 20 is 1100 MPa, but τ1 and τ2 are different. τ1 and τ2 in Examples 10 to 15 are the same as those in Example 2, but the shear modulus G in Examples 10 to 15 is different from that in Example 2. Compared to Comparative Examples 1 to 8 and Examples 1 to 15, Examples 16 to 20 underwent 800 cycles before the drop test.

[0103] In Table 1, the drop pass rates of Comparative Examples 1 to 6 are all close to 0%, which is because τ2 ≤ 1 N / cm 2During drop tests, the second surface 32 is prone to relative slippage with the outer casing 10, causing the electrode assembly 20 to impact the casing 10 and resulting in leakage. The tearing rate of Comparative Examples 1 and 4 is comparable to the drop pass rate. This is 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 rate of Comparative Examples 2 and 3 is lower than that of Comparative Example 1, and the tearing rate of Comparative Examples 5 and 6 is lower than that of Comparative Example 4. This is 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.

[0104] 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 second surface 32 is less likely to slip relative to the outer casing 10, reducing the possibility of leakage caused by the electrode assembly 20 impacting the outer casing 10. The tearing rate of 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.

[0105] In Table 1, the drop pass rates of Examples 1 to 9 are all significantly higher than those of Comparative Examples 1 to 6. That is, this application achieves higher drop pass rates by setting τ2 > 1 N / cm. 2 This can reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0106] 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.

[0107] 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.

[0108] In Table 2, the drop pass rates of Examples 10 and 11 are comparable, but the shear modulus of Example 11 is greater than that of Example 10. According to Examples 11 to 15 and Example 2, the drop pass rates of Examples 15 and 2 are comparable, but the shear modulus of Example 2 is greater than that of Example 15. When G ≤ 1000 MPa, the drop pass rate of the secondary battery 100 gradually increases as the shear modulus G gradually decreases. In other words, by setting G to 200 MPa ≤ G, this application helps reduce the possibility of fatigue damage to the adhesive 30 under continuous friction, thereby helping the adhesive 30 maintain its friction buffering effect. By setting G ≤ 1000 MPa, it helps reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0109] In Table 3, the tearing rate of the secondary battery in Example 16 after 800 cycles is significantly higher than that in Examples 17 to 20. The tearing rate of the secondary battery in Example 19 after 800 cycles is comparable to that in Example 20. In other words, this application achieves this by setting 1 N / cm... 2 ≤τ1-τ2≤3N / cm 2 This helps reduce the risk of the electrode assembly 20 being torn when the secondary battery 100 is dropped or vibrated after cycling.

[0110] 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, the adhesive component being a single-layer structure and including a first surface and a second surface disposed opposite to each other along a first direction, the first surface being bonded to one of the housing and the electrode assembly; Along a direction perpendicular to the first direction, the second surface is movable relative to the other of the housing and the electrode assembly, and is able to generate friction during relative movement; the first direction is the thickness direction of the adhesive; Wherein, along the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1, and the anti-slip strength between the second surface and the outer shell or between the second surface and the electrode assembly is τ2, 1 N / cm. 2 <τ2≤τ1.

2. The secondary battery according to claim 1, characterized in that, 1N / cm 2 ≤τ1-τ2≤3N / cm 2 。 3. The secondary battery according to claim 1 or 2, characterized in that, The coefficient of friction between the second surface and the outer shell or the electrode assembly is f, where 0.5 ≤ f ≤ 3.

4. The secondary battery according to claim 3, characterized in that, 0.8≤f≤2。 5. The secondary battery according to any one of claims 1 to 4, characterized in that, The shear modulus of the adhesive component is G, where 200MPa≤G≤1000MPa.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, Along the first direction, the thickness of the adhesive is D, where 9μm≤D≤25μm.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, Along the first direction, the surface containing the minimum projected area of ​​the adhesive includes the second surface.

8. The secondary battery according to claim 7, characterized in that, The first surface is bonded to the electrode assembly; the second surface is movable relative to the outer casing in a direction perpendicular to the first direction.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, Along a direction perpendicular to the first direction, the peel strength between the first surface and the electrode assembly is τ3, where τ3 ≥ τ2.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, The first surface has staggered protrusions and recesses, at least a portion of which are bonded to the electrode assembly.

11. The secondary battery according to claim 9, characterized in that, τ3-τ2≤10N / cm 2 。 12. The secondary battery according to claim 7 or 8, characterized in that, The first surface is bonded to the outermost electrode of the electrode assembly; along the first direction, the projected area of ​​the outermost electrode is S1, and the friction area of ​​the second surface is S2; 0.5≤S2 / S1≤1.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, The second surface is in contact with the housing or the electrode assembly.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The adhesive is made of polyacrylate and a curing agent, wherein the polyacrylate comprises 95% to 99% by mass and the curing agent comprises 1% to 4% by mass.

15. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 14.

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