Secondary battery and electric device

Abstract

The secondary battery comprises a shell, an electrode assembly and a bonding piece, the shell is provided with a containing cavity, the electrode assembly is arranged in the containing cavity, the bonding piece comprises a base layer, a bonding layer and a friction layer, and the bonding layer and the friction layer are arranged on the two opposite faces of the base layer in the first direction respectively. The adhesive layer is adhered to one of the case and the electrode assembly. In the direction perpendicular to the first direction, the friction layer can move relative to the other one of the shell and the electrode assembly, and friction can be generated during relative movement. The first direction is the thickness direction of the base layer. In the direction perpendicular to the first direction, the tearing strength of the electrode assembly is tau 1, the anti-sliding strength of the friction layer and the shell or the friction layer and the electrode assembly is tau 2, and 1 N / cm < 2 > < tau 2 < = tau 1. And by setting 1N / cm < 2 > < tau < 2 >, the possibility that the electrode assembly impacts the shell is reduced. By setting tau2 < = tau1, the risk of tearing the electrode assembly can be reduced, and the service life of the secondary battery can be prolonged.

Description

Technical Field

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

[0002] With the development of various electronic devices, secondary batteries have become an indispensable part of daily life. For example, commonly used mobile phones, tablets, laptops and digital cameras all require secondary batteries to provide power for normal operation. However, secondary batteries are inevitably dropped or vibrated during daily use, and the risk of secondary battery failure is high. Summary of the invention

[0003] For the secondary battery in the prior art, the inventor found that part of the reason for the failure of the secondary battery is that the electrode assembly is generally fixed in the receiving cavity by an adhesive, and the drop energy or vibration energy will be transmitted to the electrode assembly through the adhesive. In this way, when the secondary battery is dropped or vibrated with a large intensity, the electrode assembly is prone to tearing under the action of the drop energy or vibration energy. In particular, as the number of cycles of the secondary battery increases, the expansion force generated by the secondary battery gradually increases, the deformation degree of the electrode assembly is aggravated, and it is more likely to tear, thereby causing the secondary battery to fail.

[0004] In view of the above situation, it is necessary to provide a secondary battery that can reduce the possibility of tearing of the electrode assembly, thereby facilitating the improvement of the service life of the secondary battery.

[0005] In a first aspect, the present application provides a secondary battery, comprising a shell, an electrode assembly and an adhesive, wherein the shell has a receiving cavity, the electrode assembly is arranged in the receiving cavity, the adhesive comprises a base layer, an adhesive layer and a friction layer, along a first direction, the adhesive layer and the friction layer are respectively arranged on two opposite sides of the base layer, and the adhesive layer is bonded to one of the shell and the electrode assembly. In a direction perpendicular to the first direction, the friction layer and the other of the shell and the electrode assembly can move relative to each other, and can generate friction during relative movement. The first direction is the thickness direction of the base layer. In the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ 1 , the anti-slip strength between the friction layer and the shell or between the friction layer and the electrode assembly is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0006] By setting the bonding layer to be bonded to one of the housing and the electrode assembly, the friction layer and the other of the housing and the electrode assembly can move relative to each other, and friction and a buffering effect can be generated when the friction layer and the housing or the friction layer and the electrode assembly move relative to each other. 2 <τ2 , the anti-slip strength between the friction layer and the shell or between the friction layer and the electrode assembly is not too small, and when the secondary battery falls or vibrates, the friction buffering effect between the friction layer and the shell or between the friction layer and the electrode assembly can reduce the falling energy or vibration energy, which is beneficial to reduce the possibility of the electrode assembly impacting the shell. 2 ≤τ 1 The anti-slip strength between the friction layer and the shell or the friction layer and the electrode assembly is not too large. The friction layer can slide relative to the shell or the electrode assembly before the electrode assembly is torn, which is beneficial to reduce the risk of the electrode assembly being torn, thereby helping to increase the service life of the secondary battery.

[0007] In one or more of the above embodiments, 1N / cm 2 ≤τ 1 -τ 2 ≤3N / cm 2 . Considering that as the number of secondary battery cycles increases, τ 1 By setting 1N / cm 2 ≤τ 1 -τ 2 , which can reduce the τ of the secondary battery after cycling 1 Reduced to less than τ 2 This helps reduce the risk of the electrode assembly being torn when the secondary battery is dropped or vibrated after cycling. 1 -τ 2 ≤3N / cm 2 , when satisfying τ 2 ≤τ 1 Under the premise of 2 It is not too small, which helps to reduce the possibility of the electrode assembly impacting the shell.

[0008] In one or more of the above embodiments, the friction coefficient between the friction layer and the housing or the electrode assembly is f, 0.5≤f≤3. By setting 0.5≤f, τ 2 It is not too small, which is helpful to reduce the possibility of the electrode assembly impacting the shell. By setting f≤3, τ 2 It is not too large, which helps reduce the risk of the electrode assembly being torn.

[0009] In one or more of the above embodiments, 0.8≤f≤2. By setting 0.8≤f, the possibility of the electrode assembly impacting the housing is further reduced. By setting f≤2, the risk of the electrode assembly being torn is further reduced.

[0010] In one or more of the above embodiments, the base layer is provided with a through hole penetrating along the first direction, and the adhesive layer and the friction layer are connected through the through hole and are integrally arranged, which can reduce the possibility of separation of the adhesive layer or the friction layer from the base layer, and is conducive to improving the overall structural stability of the adhesive component, so that the friction layer maintains a friction buffering effect with the shell.

[0011] In one or more of the above embodiments, the shear modulus of the adhesive is G, 50MPa≤G≤1000MPa. By setting 50MPa≤G, the rigidity of the adhesive can be made not too weak, which is conducive to reducing the possibility of fatigue damage of the adhesive under continuous friction, thereby facilitating the friction layer to maintain the friction buffering effect. By setting G≤1000MPa, the rigidity of the adhesive can be made not too strong, which can facilitate elastic deformation of the adhesive, and is conducive to reducing the possibility of the electrode assembly impacting the shell.

[0012] In one or more of the above embodiments, along the first direction, the thickness of the adhesive is D, 9μm≤D≤65μm. By setting 9μm≤D, the adhesive can be made not too thin, which is conducive to reducing the possibility of fatigue damage of the adhesive under continuous friction, thereby facilitating the friction layer to maintain the friction buffering effect. By setting D≤65μm, the adhesive is not too thick, which is conducive to improving the energy density of the secondary battery.

[0013] In one or more of the above embodiments, along the first direction, the thickness of the base layer is d 1 The thickness of the bonding layer is d 2 The thickness of the friction layer is d 3 , 3μm≤d 1 ≤15μm,3μm≤d 2 ≤25μm,3μm≤d 3 ≤25μm. By setting 3μm≤d 1 、3μm≤d 2 and 3μm≤d 3 , which can make the base layer, bonding layer and friction layer not too thin, which is beneficial to reduce the possibility of fatigue damage of the bonding parts under continuous friction, and thus helps the friction layer to maintain the friction buffering effect. 1 ≤15μm, d 2 ≤25μm and d 3 ≤25μm, which can prevent the base layer, adhesive layer and friction layer from being too thick, and is beneficial to improving the energy density of the secondary battery.

[0014] In one or more of the above embodiments, the adhesive layer is bonded to one of the housing and the electrode assembly, and the friction layer is in contact with the other of the housing and the electrode assembly, so as to facilitate friction and buffering during relative movement.

[0015] In one or more of the above embodiments, the adhesive layer is bonded to the electrode assembly. The friction layer and the housing can move relative to each other in a direction perpendicular to the first direction. Compared with the bonding of the adhesive layer to the housing and the relative movement and friction between the friction layer and the electrode assembly, the wear of the electrode assembly can be reduced, which is conducive to improving the service life of the secondary battery. In addition, it is convenient to process the surface of the housing that rubs against the friction layer, so as to conveniently adjust the friction coefficient between the friction layer and the housing.

[0016] In one or more of the above embodiments, along the first direction, the bonding area of ​​the bonding layer is greater than or equal to the friction area of ​​the friction layer.

[0017] In one or more of the above embodiments, the bonding layer is bonded to the outermost electrode sheet of the electrode assembly. Along the first direction, the projection area of ​​the outermost electrode sheet is S 1 , the friction area of ​​the friction layer is S 2 , 0.5≤S 2 / S 1 ≤1. Set 0.5≤S 2 / S 1 ≤1, which can make the friction area between the friction layer and the outer shell not too small, which is beneficial to improve τ 2 The value of is beneficial to further reduce the possibility of the electrode assembly impacting the casing.

[0018] In one or more of the above embodiments, the peel strength between the adhesive layer and the electrode assembly along the direction perpendicular to the first direction is τ 3 , τ 3 ≥τ 2 . Relative to setting τ 3 <τ 2 , set τ 3 ≥τ 2 The possibility of premature separation of the adhesive layer from the electrode assembly can be reduced, which is beneficial for the friction layer to maintain a friction buffering effect with the shell.

[0019] In one or more of the above embodiments, τ 3 -τ 2 ≤10N / cm 2 . When satisfying τ 3 ≥τ 2 Under the premise of 3 It is not too large, which is beneficial to improving the convenience of preparing the adhesive layer.

[0020] In one or more of the above embodiments, the material of the adhesive layer includes a base resin, a tackifying resin, a polyether polyol and microcrystals, the mass percentage of the base resin is 30% to 40%, the mass percentage of the tackifying resin is 54% to 69%, the mass percentage of the polyether polyol is 0% to 5%, and the mass percentage of the microcrystals is 1% to 2%. The material of the friction layer includes polyacrylate and a curing agent, the mass percentage of the polyacrylate is 95% to 99%, and the mass percentage of the curing agent is 1% to 4%. The material of the adhesive layer includes the above materials and the mass percentage of the above materials in the adhesive layer is regulated within the above range, and / or the material of the friction layer includes the above materials and the mass percentage of the above materials in the friction layer is regulated within the above range, so that 1N / cm 2 <τ 2 ≤τ 1 .

[0021] The second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application. The secondary battery has a relatively long service life, which is beneficial to prolonging the service life of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A front view of a secondary battery provided in accordance with an embodiment of the present application.

[0023] Figure 2 A top view of a secondary battery provided in accordance with an embodiment of the present application.

[0024] Figure 3 For along Figure 1 Cross-section along the midline AA.

[0025] Figure 4 A schematic diagram of the structure of an adhesive member provided in one embodiment of the present application.

[0026] Figure 5 For along Figure 2 Cross-section along section line BB.

[0027] Figure 6 For along Figure 2 Cross-section along section line CC.

[0028] Figure 7 An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0029] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, 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 electrode current collector; 212, negative electrode active material layer; 22, positive electrode plate; 221, positive electrode current collector; 222, positive electrode active material layer; 23, diaphragm; 30, adhesive; 31, base layer; 311, through hole; 32, adhesive layer; 33, friction layer; 40, negative electrode tab; 50, negative electrode tab bundle; 60, positive electrode tab; 70, positive electrode tab bundle; 80, pole; 90, insulating member; X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0030] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be a centrally disposed element at the same time. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be a centrally disposed element at the same time.

[0031] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0032] The terms "first", "second", etc. are only used to distinguish different objects and shall not be understood 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 those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0034] An embodiment of the present application provides a secondary battery, including a shell, an electrode assembly and an adhesive, wherein the shell has a receiving cavity, the electrode assembly is arranged in the receiving cavity, the adhesive includes a base layer, an adhesive layer and a friction layer, along a first direction, the adhesive layer and the friction layer are respectively arranged on two opposite sides of the base layer, and the adhesive layer is bonded to one of the shell and the electrode assembly. Along a direction perpendicular to the first direction, the friction layer and the other of the shell and the electrode assembly can move relative to each other, and can generate friction during relative movement. The first direction is the thickness direction of the base layer. Among them, along the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1 , the anti-slip strength between the friction layer and the shell or between the friction layer and the electrode assembly is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0035] In the secondary battery of the present application, by setting the adhesive layer to be bonded to one of the outer shell and the electrode assembly, the friction layer and the other of the outer shell and the electrode assembly can move relative to each other, and friction and buffering can be generated when the friction layer and the outer shell or the friction layer and the electrode assembly move relative to each other. 2 <τ 2 , the anti-slip strength between the friction layer and the shell or between the friction layer and the electrode assembly is not too small, and when the secondary battery falls or vibrates, the friction buffering effect between the friction layer and the shell or between the friction layer and the electrode assembly can reduce the falling energy or vibration energy, which is beneficial to reduce the possibility of the electrode assembly impacting the shell. 2 ≤τ 1 The anti-slip strength between the friction layer and the outer shell or the friction layer and the electrode assembly is not too large. When the drop intensity or vibration intensity is large, the friction layer can slide relative to the outer shell or the electrode assembly before the electrode assembly is torn, which is beneficial to reduce the risk of the electrode assembly being torn, thereby helping to increase the service life of the secondary battery.

[0036] Some embodiments of the present application will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0037] See also Figures 1 to 3 The embodiment of the present application provides a secondary battery 100, including a housing 10, an electrode assembly 20 and an adhesive member 30, wherein the electrode assembly 20 is accommodated in the housing 10. The adhesive member 30 is bonded to one of the housing 10 and the electrode assembly 20, and can move relative to the other of the housing 10 and the electrode assembly 20.

[0038] See also Figure 3 The housing 10 is provided with a receiving chamber 101, and the receiving chamber 101 is filled with an electrolyte, and the electrolyte includes an electrolyte salt. In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[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, see Figure 1The housing 10 includes a first shell 11 and a second shell 12, and the first shell 11 and the second shell 12 are connected to form a receiving cavity 101. In some embodiments, the first shell 11 and the second shell 12 are connected along the thickness direction of the electrode assembly 20.

[0041] In some embodiments, when the material of the housing 10 is an aluminum-plastic film, the first housing 11 and the second housing 12 can be connected by melting. When the material of the housing 10 is steel, the first housing 11 and the second housing 12 can be connected by welding.

[0042] In some embodiments, the first housing 11 is the body of the housing 10, and the second housing 12 is the cover of the housing 10. Figure 3 The first housing 11 includes a bottom wall 111 and a side wall 112. The side wall 112 is disposed around 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 be formed with a recess.

[0043] See also Figure 3 The electrode assembly 20 is disposed in the receiving cavity 101. The electrode assembly 20 includes a negative electrode sheet 21, a positive electrode sheet 22 and a separator 23, and the separator 23 separates the negative electrode sheet 21 from the positive electrode sheet 22.

[0044] In some embodiments, the negative electrode sheet 21 and the positive electrode sheet 22 are respectively bonded to the separator 23 .

[0045] In some embodiments, see Figure 3 The electrode assembly 20 is a stacked structure, wherein a plurality of negative electrode sheets 21 and a plurality of positive electrode sheets 22 are alternately stacked, and a separator 23 is disposed between any adjacent negative electrode sheets 21 and positive electrode sheets 22 .

[0046] In some other embodiments, the electrode assembly 20 is a winding structure, in which a single negative electrode sheet 21 and a single positive electrode sheet 22 are stacked and wound, and the separator 23 is disposed between the negative electrode sheet 21 and the positive electrode sheet 22 .

[0047] In some embodiments, the negative electrode plate 21 includes a negative electrode current collector 211 and a negative electrode active material layer 212, and the negative electrode active material layer 212 is disposed on two opposite sides of the negative electrode current collector 211 along the thickness direction. The positive electrode plate 22 includes a positive electrode current collector 221 and a positive electrode active material layer 222, and the positive electrode active material layer 222 is disposed on two opposite sides of the positive electrode current collector 221 along the thickness direction.

[0048] In some embodiments, when the electrode assembly 20 is a stacked structure, if the negative electrode sheet 21 or the positive electrode sheet 22 is the outermost sheet of the electrode assembly 20 , the side of the current collector facing away from the interior of the electrode assembly 20 may not be provided with an active material layer.

[0049] In some embodiments, the negative electrode current collector 211 is made of copper foil, and the positive electrode current collector 221 is made of aluminum foil.

[0050] In some embodiments, the negative electrode active material layer 212 may be formed by coating the negative electrode active material on the negative electrode current collector 211, and the negative electrode active material layer 212 is bonded to the negative electrode current collector 211. The positive electrode active material layer 222 may be formed by coating the positive electrode active material on the positive electrode current collector 221, and the positive electrode active material layer 222 is bonded to the positive electrode current collector 221.

[0051] In some embodiments, the diaphragm 23 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0052] See also Figure 3 The adhesive member 30 includes a base layer 31, an adhesive layer 32 and a friction layer 33. The adhesive layer 32 and the friction layer 33 are respectively arranged on two opposite sides of the base layer 31 along the first direction X. The first direction X is the thickness direction of the base layer 31. In some embodiments, the adhesive layer 32 and the friction layer 33 are respectively bonded to the base layer 31. The adhesive layer 32 is bonded to one of the housing 10 and the electrode assembly 20. The friction layer 33 and the other of the housing 10 and the electrode assembly 20 can move relative to each other along the direction perpendicular to the first direction X, and can generate friction during the relative movement. For example, the adhesive layer 32 is bonded to the housing 10, and the friction layer 33 and the electrode assembly 20 can move relative to each other; or, the adhesive layer 32 is bonded to the electrode assembly 20, and the friction layer 33 and the housing 10 can move relative to each other. In some embodiments, the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 can be in contact in advance, which can facilitate the generation of friction and buffering effect during relative movement. Alternatively, the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 may contact each other after the secondary battery 100 undergoes cyclic expansion. When the electrode assembly 20 and the housing 10 have a tendency to move relative to each other or move relative to each other, a buffering effect can be generated between the friction layer 33 and the housing 10 or the electrode assembly 20. For example, the adhesive 30 is closely attached to the housing 10 and the electrode assembly 20, so that friction is generated when the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 move relative to each other, thereby generating a buffering effect.

[0053] In the direction perpendicular to the first direction X, the tear strength of the electrode assembly 20 is τ 1 , the anti-slip strength between the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 is τ 2 , 1N / cm 2 <τ 2 ≤τ 1The direction perpendicular to the first direction X includes a second direction Y and a third direction Z, and the first direction X, the second direction Y and the third direction Z are perpendicular to each other. In some embodiments, the second direction Y may be the width direction of the electrode assembly 20, and the third direction Z may be the length direction of the electrode assembly 20.

[0054] The so-called τ 1 It refers to the shear stress required to completely tear the electrode assembly 20 under the action of a load perpendicular to the first direction X. The tearing of the electrode assembly 20 includes, but is not limited to, the peeling of the negative electrode active material layer 212 and the separator 23, the peeling of the negative electrode active material layer 212 and the negative electrode current collector 211, the peeling of the positive electrode active material layer 222 and the separator 23, the peeling of the positive electrode active material layer 222 and the positive electrode current collector 221, the tearing of the separator 23 itself, the tearing of the negative electrode active material layer 212 or the negative electrode current collector 211 itself, and the tearing of the positive electrode active material layer 222 or the positive electrode current collector 221 itself.

[0055] The so-called τ 2 It refers to the shear stress required to enable relative slip between the friction layer 33 and the housing 10 or between the friction layer 33 and the electrode assembly 20 under the load perpendicular to the first direction X. The load perpendicular to the first direction X may be caused by the secondary battery 100 falling or vibrating.

[0056] The above is achieved by setting 1N / cm 2 <τ 2 , the anti-slip strength between the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 is not too small, and when the secondary battery 100 falls or vibrates, the friction buffering effect between the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 can reduce the falling energy or vibration energy, which is beneficial to reduce the possibility of the electrode assembly 20 impacting the housing 10. By setting τ 2 ≤τ 1 , the anti-slip strength between the friction layer 33 and the housing 10 or the friction layer 33 and the electrode assembly 20 is not too large. When the drop strength or vibration strength is large, the friction layer 33 can slide relative to the housing 10 or the electrode assembly 20 before the electrode assembly 20 is torn, which is conducive to reducing the risk of the electrode assembly 20 being torn, thereby facilitating the service life of the secondary battery 100. It should be understood that by reducing the possibility of the electrode assembly 20 impacting the housing 10, when the first housing 11 and the second housing 12 are separately arranged and connected, it is conducive to reducing the risk of the first housing 11 and the second housing 12 being separated, resulting in leakage failure of the secondary battery 100.

[0057] In some embodiments, 1N / cm 2≤τ 1 -τ 2 ≤3N / cm 2 . Considering that as the number of cycles of the secondary battery increases, τ 1 By setting 1N / cm 2 ≤τ 1 -τ 2 , which can reduce the secondary battery 100 after cycling τ 1 Reduced to less than τ 2 The possibility of the electrode assembly 20 being torn when the secondary battery 100 is dropped or vibrated after cycling is reduced. By setting τ 1 -τ 2 ≤3N / cm 2 , when satisfying τ 2 ≤τ 1 Under the premise of 2 It is not too small, which is helpful to reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0058] In some embodiments, the friction coefficient between the friction layer 33 and the housing 10 or the electrode assembly 20 is f, 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 endpoint values. By setting 0.5≤f, τ 2 It is not too small, which is helpful to reduce the possibility of the electrode assembly 20 impacting the housing 10. By setting f≤3, τ 2 It is not too large, which is beneficial to reduce the risk of tearing of the electrode assembly 20. In some embodiments, the friction coefficient between the friction layer 33 and the shell 10 is f.

[0059] In some embodiments, 0.8≤f≤2. By setting 0.8≤f, the possibility of the electrode assembly 20 impacting the housing 10 is further reduced. By setting f≤2, the risk of the electrode assembly 20 being torn is further reduced.

[0060] In some embodiments, the adhesive layer 32 is bonded to the electrode assembly 20. The friction layer 33 and the housing 10 can move relative to each other in a direction perpendicular to the first direction X. Compared with the bonding of the adhesive layer 32 to the housing 10 and the relative movement and friction between the friction layer 33 and the electrode assembly 20, the wear of the electrode assembly 20 can be reduced, which is conducive to improving the service life of the secondary battery 100. In addition, it is convenient to process the surface of the housing 10 that rubs against the friction layer 33, so as to conveniently adjust the friction coefficient between the friction layer 33 and the housing 10. For example, by laser roughening the surface of the housing 10 that rubs against the friction layer 33, the surface roughness of the housing 10 is increased, thereby increasing the friction coefficient between the friction layer 33 and the housing 10. In some embodiments, the friction layer 33 and the second housing 12 can move relative to each other and generate friction.

[0061] In some embodiments, the bonding layer 32 is bonded to the electrode assembly 20 . Along a direction perpendicular to the first direction X, the friction layer 33 and the housing 10 can move relative to each other and generate friction, and the bonding area of ​​the bonding layer 32 is larger than the friction area of ​​the friction layer 33 .

[0062] In some embodiments, the bonding layer 32 is bonded to the electrode assembly 20. Along the direction perpendicular to the first direction X, the friction layer 33 and the housing 10 can move relative to each other and generate friction, and the bonding area of ​​the bonding layer 32 is equal to the friction area of ​​the friction layer 33. Without affecting the purpose of the invention of the present application, considering the accuracy of production and processing, when there is a 5% error between the bonding area of ​​the bonding layer 32 and the friction area of ​​the friction layer 33, it can also be considered that the bonding area of ​​the bonding layer 32 is equal to the friction area of ​​the friction layer 33.

[0063] It should be understood that, considering that in actual applications, the bonding interface of the bonding layer 32 is not completely used for bonding, the bonding area of ​​the bonding layer 32 refers to the area of ​​the portion of the bonding interface of the bonding layer 32 used for bonding. Considering that in actual applications, the friction interface of the friction layer 33 is not completely used for friction, the friction area of ​​the friction layer 33 refers to the area of ​​the portion of the friction interface of the friction layer 33 used for friction.

[0064] In some embodiments, the bonding layer 32 is bonded to the outermost electrode sheet of the electrode assembly 20. Along the first direction X, the projection area of ​​the outermost electrode sheet is S 1 , the friction area of ​​the friction layer 33 is S 2 , 0.5≤S 2 / S 1 ≤1. For example, S 2 / S 1 The value of can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any value between the listed endpoints. Set 0.5≤S 2 / S1 ≤1, which can ensure that the friction area between the friction layer 33 and the housing 10 is not too small, which is beneficial to improve τ 2 The value of is beneficial to further reduce the possibility of the electrode assembly 20 impacting the shell 10.

[0065] It should be understood that when the electrode assembly 20 is a stacked structure, the outermost electrode sheet is the electrode sheet closest to the adhesive 30 among the electrode sheets of the electrode assembly 20 along the thickness direction of the electrode assembly 20. When the electrode assembly 20 is a wound structure, the outermost electrode sheet is the flat area of ​​the electrode sheet of the outermost winding located between the bending areas and close to the adhesive 30.

[0066] In some embodiments, the peel strength between the adhesive layer 32 and the electrode assembly 20 along the direction perpendicular to the first direction X is τ 3 , τ 3 ≥τ 2 The so-called τ 3 It refers to the shear stress required to completely separate the adhesive layer 32 from the electrode assembly 20 under the action of a load perpendicular to the first direction X. 3 <τ 2 , set τ 3 ≥τ 2 The possibility of the adhesive layer 32 being separated from the electrode assembly 20 in advance can be reduced, which is beneficial for the friction layer 33 to maintain a friction buffering effect with the shell 10.

[0067] In some embodiments, τ 3 -τ 2 ≤10N / cm 2 . When satisfying τ 3 ≥τ 2 Under the premise of 3 It is not too large, which is conducive to improving the convenience of preparing the adhesive layer 32. In some embodiments, along the first direction X, the bonding area of ​​the adhesive layer 32 is larger than the friction area of ​​the friction layer 33, which can facilitate τ 3 ≥τ 2 .

[0068] In some embodiments, along a direction perpendicular to the first direction X, the peel strength between the adhesive layer 32 and the base layer 31 and between the friction layer 33 and the base layer 31 is greater than the anti-slip strength between the friction layer 33 and the housing 10 .

[0069] In some embodiments, see Figure 4The base layer 31 is provided with a through hole 311 penetrating along the first direction X, and the adhesive layer 32 and the friction layer 33 are connected through the through hole 311 and are integrally arranged. The possibility of separation of the adhesive layer 32 or the friction layer 33 from the base layer 31 can be reduced, which is beneficial to improving the overall structural stability of the adhesive member 30, so that the friction layer 33 maintains a friction buffering effect with the housing 10.

[0070] In some embodiments, there are multiple through holes 311 , such as 2, 3, 4, 5 or more, and the multiple through holes 311 are distributed at intervals.

[0071] In some embodiments, see Figure 4 , along the first direction X, the thickness of the adhesive 30 is D, 9μm≤D≤65μm. For example, the thickness of the adhesive 30 is 9μm, 15μm, 25μm, 40μm, 65μm or any value between the listed endpoint values. By setting 9μm≤D, the adhesive 30 can be made not too thin, which is conducive to reducing the possibility of fatigue damage of the adhesive 30 under continuous friction, thereby facilitating the friction layer 33 to maintain the friction buffering effect. By setting D≤65μm, the adhesive 30 is not too thick, which is conducive to improving the energy density of the secondary battery 100.

[0072] In some embodiments, along the first direction X, the thickness of the base layer 31 is d 1 , the thickness of the adhesive layer 32 is d 2 , the thickness of the friction layer 33 is d 3 , 3μm≤d 1 ≤15μm,3μm≤d 2 ≤25μm,3μm≤d 3 ≤25μm. For example, d 1 3μm, 5μm, 7μm, 10μm, 15μm or any value between the listed endpoints, d 2 3μm, 5μm, 10μm, 15μm, 25μm or any value between the listed endpoints, d 3 3μm, 5μm, 10μm, 15μm, 25μm or any value between the listed endpoints. By setting 3μm≤d 1 、3μm≤d 2 and 3μm≤d 3 , so that the base layer 31, the adhesive layer 32 and the friction layer 33 are not too thin, which is beneficial to reduce the possibility of fatigue damage of the adhesive 30 under continuous friction, thereby helping the friction layer 33 to maintain the friction buffering effect. 1 ≤15μm, d 2 ≤25μm and d 3≤25 μm, so that the base layer 31 , the adhesive layer 32 and the friction layer 33 are not too thick, which is beneficial to improving the energy density of the secondary battery 100 .

[0073] In some embodiments, the shear modulus of the adhesive 30 is G, 50MPa≤G≤1000MPa. For example, the value of G is 50MPa, 100MPa, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa, 400MPa, 450MPa, 500MPa, 550MPa, 600MPa, 650MPa, 700MPa, 750MPa, 800MPa, 850MPa, 900MPa, 950MPa, 1000MPa or any value between the listed endpoint values. By setting 50MPa≤G, the rigidity of the adhesive 30 can be prevented from being too weak, which is conducive to reducing the possibility of fatigue damage of the adhesive 30 under continuous friction, thereby helping to keep the friction layer 33 to produce a friction buffering effect. By setting G≤1000 MPa, the rigidity of the adhesive 30 can be made not too strong, and the adhesive 30 can be easily elastically deformed, which is beneficial to reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0074] In some embodiments, the material of the adhesive layer 32 includes a base resin, a tackifying resin, a polyether polyol, and microcrystals, wherein the mass percentage of the base resin is 30% to 40%, the mass percentage of the tackifying resin is 54% to 69%, the mass percentage of the polyether polyol is 0% to 5%, and the mass percentage of the microcrystals is 1% to 2%. The material of the adhesive layer 32 includes the above materials and the mass percentage of the above materials in the adhesive layer 32 is controlled within the above range, so that 1N / cm 2 <τ 2 ≤τ 1 .

[0075] In some embodiments, the base resin includes 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 required rigidity and mechanical strength of the adhesive layer 32. For example, the block ratio of polystyrene can be increased, thereby improving the rigidity and mechanical strength of the adhesive layer 32. The tackifying resin includes hydrogenated resins, which can increase the mass percentage of the tackifying resin, thereby improving the peel strength between the adhesive layer 32 and the housing 10 or the adhesive layer 32 and the electrode assembly 20. The polyether polyol is prepared by a polyaddition reaction of an initiator (i.e., a compound containing an active hydrogen group) with ethylene oxide, propylene oxide, butylene oxide, etc. under catalysis.

[0076] In some embodiments, the material of the friction layer 33 includes polyacrylate and curing agent, the mass percentage of the polyacrylate is 95% to 99%, and the mass percentage of the curing agent is 1% to 4%. The curing agent includes but is not limited to epoxy resin and polyamide. The material of the friction layer 33 includes the above materials and the mass percentage of the above materials in the friction layer 33 is controlled within the above range, which can facilitate 1N / cm 2 <τ 2 ≤τ 1 .

[0077] In some embodiments, see Figure 5 The secondary battery 100 includes a negative electrode tab 40 , which is connected to the negative electrode current collector 211 and extends out of the negative electrode current collector 211 along the third direction Z.

[0078] In some embodiments, the negative electrode tab 40 is integrally formed with the negative electrode current collector 211. In some embodiments, the negative electrode tab 40 is connected to the negative electrode current collector 211 by welding.

[0079] In some embodiments, see Figure 5 The plurality of negative electrode tabs 40 are stacked in sequence along the first direction X and welded to form a negative electrode tab bundle 50. The negative electrode tab bundle 50 is bent in a direction opposite to the stacking direction of the plurality of negative electrode tabs 40 and then electrically connected to the housing 10.

[0080] 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 shell 11.

[0081] In some embodiments, see Figure 6 The secondary battery 100 includes a positive electrode tab 60 , which is connected to the positive electrode collector 221 and extends out of the positive electrode collector 221 along the third direction Z.

[0082] In some embodiments, the positive electrode tab 60 is integrally formed with the positive electrode current collector 221. In some embodiments, the positive electrode tab 60 is connected to the positive electrode current collector 221 by welding.

[0083] In some embodiments, see Figure 6 The plurality of positive electrode tabs 60 are stacked in sequence along the first direction X and welded to form a positive electrode tab bundle 70. The positive electrode tab bundle 70 is bent in a direction opposite to the stacking direction of the plurality of positive electrode tabs 60 and then insulated and connected to the housing 10.

[0084] In some embodiments, see Figure 6 The secondary battery 100 includes a pole 80 , which is insulated and fixed to the housing 10 , and the positive electrode tab bundle 70 is electrically connected to the pole 80 .

[0085] In some embodiments, the positive electrode tab bundle 70 is connected to the pole 80 through an adapter (not shown), and the material of the adapter is one or more conductive materials such as copper, aluminum, nickel, and nickel alloy.

[0086] In some embodiments, the pole 80 is insulated and fixed to the first housing 11. Figure 6 The secondary battery 100 includes an insulating member 90 , which is disposed on the first housing 11 . Along the first direction X and the third direction Z, the pole 80 is spaced apart from the first housing 11 by at least a portion of the insulating member 90 .

[0087] See also Figure 7 One embodiment of the present application provides an electric device 1000, comprising the secondary battery 100 as described above. The secondary battery 100 has a relatively high service life, which is beneficial to prolonging the service life of the electric device 1000. The electric device 1000 includes but is not limited to electronic devices such as mobile phones, tablet computers, and laptop computers.

[0088] In order to verify the effect of the solution provided in the present application on the secondary battery 100, the inventor of the present application conducted the following experiment, which includes 8 groups of comparative examples and 20 groups of embodiments, each of which includes 20 secondary batteries 100. The material of the shell 10 in the secondary battery 100 used in the comparative examples and embodiments is steel, the first shell 11 and the second shell 12 are welded, and the first shell 11 is the shell body of the shell 10, and the second shell 12 is the shell cover of the shell 10. The electrode assembly 20 in the secondary battery 100 is a stacked structure, and the outermost electrode sheet of the electrode assembly 20 is a single-sided negative electrode sheet 21. In the secondary battery 100, the adhesive member 30 is arranged centrally relative to the outermost electrode sheet of the electrode assembly 20, the adhesive layer 32 is bonded to the outermost electrode sheet of the electrode assembly 20, the friction layer 33 and the shell cover (i.e., the second shell 12) of the shell 10 can move relative to each other, and along the thickness direction of the adhesive member 30, the projections of the base layer 31, the adhesive layer 32, and the friction layer 33 are all overlapped, and the friction area S of the friction layer 33 is 2 The projected area S of the outermost pole piece 1 Equal (S 1 and S 2 A 10% error is allowed between the two).

[0089] In the present application, the mass percentage of each material in the negative electrode sheet 21, the positive electrode sheet 22 and the separator 23 can be changed to obtain the τ required for the experiment. 1 Among them, the determination of τ 1 The method is as follows: 1) Sample preparation: Take out a sample to be torn in which the separator 23 is bonded to the negative electrode sheet 21 and the positive electrode sheet 22 from the finished secondary battery 100, and use a blade to cut out a tear test sample with a test area of ​​1 cm×1 cm from the taken out sample to be torn.

[0090] 2) Test: Fix the tear test specimen to the test fixture of the high-speed rail tensile testing machine. When fixing, make the thickness direction of the tear test specimen perpendicular to the force direction of the high-speed rail tensile testing machine. Select the shear mode, set the shear angle to 0 degrees, and the shear speed to 25±2mm / min. Start the test until the shear interface of the tear test specimen is completely torn.

[0091] 3) Value: The ratio of the maximum tensile force to the test area when the shear interface of the tear test specimen is completely torn is taken as τ 1 The value of .

[0092] In the present application, the mass percentage of each material in the friction layer 33 can be changed to obtain the τ required for the experiment. 2 Among them, the determination of τ 2 The method is as follows: 1) placing the finished secondary battery 100 in an environment of 25±1°C; 2) charging with a constant current of 3C and discharging with a constant current of 1C so that the secondary battery 100 is cycled for 800 times, and then the expansion force generated by the secondary battery 100 is measured by an expansion force tester; 3) Take out the shell cover of the housing 10 from the secondary battery 100 as the sliding sample, and take out the adhesive member 30 and the outermost electrode sheet that remain bonded as the sliding sample, and use a blade to cut out a sliding test sample with a test area of ​​3 cm×3 cm from the taken out sliding sample; 4) Fix the sliding test sample to the test slider of the friction coefficient tester, wherein the outermost pole piece is located between the adhesive 30 and the test slider, and the friction layer 33 is located at the outermost side away from the test slider. Fix the sliding sample on the horizontal test bench to ensure that the sliding test sample is parallel to the sliding sample on the horizontal test bench. Set the slider speed to 60±2mm / min. Start the test so that the sliding test sample starts to move on the sliding sample. After stopping, the reading of the friction coefficient tester is the friction coefficient between the test samples. 5) Repeat step 4 for 5 times and take the average value; 6) Calculate the product of the expansion force generated by the secondary battery 100 and the friction coefficient, and divide it by the friction area S of the friction layer 33 2 , the resulting ratio is τ 2 The value of .

[0093] In the present application, the drop pass rate of the secondary battery 100 and the tearing rate of the electrode assembly 20 can be used to reflect the τ 1 and τ 2The relationship between the drop test and the electrode assembly 20 has an impact on the secondary battery 100. The drop pass rate refers to the proportion of secondary batteries 100 that have no leakage or fire after the drop test, and the tearing rate refers to the proportion of secondary batteries 100 that have tearing in the electrode assembly 20 after the drop test. The drop test method is as follows: 1) 20 secondary batteries 100 of each comparative example and embodiment are grouped as one, and the 20 secondary batteries 100 are sequentially placed in a special fixture and freely dropped from a height of 1.5 meters onto a marble surface; each secondary battery 100 is dropped three times in total, and the position sequence of the secondary battery 100 facing the marble surface during each drop is: upper shell cover - lower bottom wall - upper right corner - lower right corner - upper left corner - lower left corner; 2) After each round of dropping, check the appearance of the secondary battery 100. If the secondary battery 100 in the round leaks or catches fire, stop dropping immediately.

[0094] 3) After all 20 secondary batteries 100 in each group have been dropped, the secondary batteries 100 are disassembled, and the number of secondary batteries 100 that have not leaked or caught fire is counted as N, and the number of secondary batteries 100 whose electrode assemblies 20 have been torn is counted as F. The drop pass rate of the secondary batteries 100 in this group is N / 20, and the tearing rate of the electrode assemblies 20 is F / 20.

[0095] After the test, the experimental results are recorded in Tables 1 to 3: Table 1 Table 2 Table 3 In Tables 1 to 3, the shear modulus G of Comparative Examples 1 to 8, Examples 1 to 9, and Examples 16 to 20 are all 1100 MPa, τ 1 and τ 2 Different. τ in Examples 10 to 15 1 and τ 2 Compared with τ in Example 2 1 and τ 2 The same, the shear modulus G in Examples 10 to 15 is different from the shear modulus G in Example 2. Compared with Comparative Examples 1 to 8 and Examples 1 to 15, Examples 16 to 20 are first cycled 800 times before the drop test.

[0096] In Table 1, the drop pass rates of Comparative Examples 1 to 6 are all close to 0%, which is due to τ 2 ≤1N / cm 2When the drop test is performed, the friction layer 33 is prone to relative slippage with the housing 10, so that the electrode assembly 20 impacts the housing 10 and causes leakage. The tearing rate of Comparative Examples 1 and 4 is equivalent to the drop pass rate. This is because τ 2 >τ 1 In the portion of the secondary battery 100 that passed the drop test, the drop energy is transmitted to the electrode assembly 20 through the adhesive 30, so that the electrode assembly 20 is torn. The tearing incidence rates of Comparative Examples 2 and 3 are lower than that of Comparative Example 1, and the tearing incidence rates of Comparative Examples 5 and 6 are lower than that of Comparative Example 4. This is because τ 2 ≤τ 1 In the portion of the secondary batteries 100 that passed the drop test, the possibility that the drop energy is transmitted to the electrode assembly 20 through the adhesive 30 is low, and thus the possibility that the electrode assembly 20 is torn is low.

[0097] In Table 1, the drop pass rates of Comparative Examples 7 and 8 are significantly greater than those of Comparative Examples 1 to 6. This is because τ 2 >1N / cm 2 When the drop test is performed, the friction layer 33 and the housing 10 are not prone to relative slippage, which can reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10. The tearing rate of Comparative Examples 7 and 8 is equivalent to the drop pass rate. This is because τ 2 >τ 1 In the portion of the secondary batteries 100 that pass the drop test, the drop energy is transferred to the electrode assembly 20 through the adhesive 30 , so that the electrode assembly 20 is torn.

[0098] In Table 1, the drop pass rates of Examples 1 to 9 are significantly greater than the drop pass rates of Comparative Examples 1 to 6. That is, the present application sets τ 2 >1N / cm 2 , which can reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0099] In Table 1, the tearing incidence rates of Example 3 and Example 4 are significantly lower than that of Comparative Example 7, and the tearing incidence rates of Example 7 and Example 8 are significantly lower than that of Comparative Example 8. That is, the present application sets τ 2 ≤τ 1 , which helps to reduce the risk of the electrode assembly 20 being torn.

[0100] In Table 1, the drop pass rates of Example 4, Example 6, Example 8 and Example 9 are all significantly greater than the drop pass rate of Example 2, that is, the present application achieves a higher drop pass rate by setting τ 1 -τ 2 ≤3N / cm2 , which helps to reduce the possibility of the electrode assembly 20 impacting the shell 10.

[0101] In Table 2, the drop pass rates of Example 10 and Example 11 are equivalent, but the shear modulus of Example 11 is greater than that of Example 10. According to Example 11 to Example 15 and Example 2, the drop pass rates of Example 15 and Example 2 are equivalent, but the shear modulus of Example 2 is greater than that of Example 15; when G≤1000MPa, as the shear modulus G gradually decreases, the drop pass rate of the secondary battery 100 gradually increases. That is to say, the present application is conducive to reducing the possibility of fatigue damage of the adhesive 30 under continuous friction by setting 50MPa≤G, so as to enable the friction layer 33 to maintain the friction buffering effect. By setting G≤1000MPa, it is conducive to reducing the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0102] In Table 3, the tearing rate of the secondary battery in Example 16 after 100 cycles and 800 times is significantly greater than the tearing rate of the secondary battery in Examples 17 to 20 after 100 cycles and 800 times, and the tearing rate of the secondary battery in Example 19 after 100 cycles and 800 times is equivalent to the tearing rate of the secondary battery in Example 20 after 100 cycles and 800 times, that is, the present application sets 1N / cm 2 ≤τ 1 -τ 2 ≤3N / cm 2 This helps to reduce the risk of the electrode assembly 20 being torn when the secondary battery 100 is dropped or vibrated after cycling.

[0103] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not intended to limit the present application. As long as they are within the essential scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery, characterized in that: include: A housing having a receiving cavity; An electrode assembly, wherein the electrode assembly is disposed in the receiving cavity; An adhesive member, the adhesive member comprising a base layer, an adhesive layer and a friction layer, wherein along a first direction, the adhesive layer and the friction layer are respectively arranged on two opposite sides of the base layer, and the adhesive layer is bonded to one of the housing and the electrode assembly; The friction layer and the other of the housing and the electrode assembly can move relative to each other in a direction perpendicular to the first direction, and can generate friction during the relative movement; the first direction is the thickness direction of the base layer; 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 friction layer and the shell or between the friction layer and the electrode assembly is τ2, 1N / 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, characterized in that: The friction coefficient between the friction layer and the shell or the electrode assembly is f, 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 claim 1, characterized in that: The base layer is provided with a through hole penetrating along the first direction, and the adhesive layer and the friction layer are connected through the through hole and are integrally arranged.

6. The secondary battery according to claim 1, characterized in that: The shear modulus of the adhesive is G, 50MPa≤G≤1000MPa.

7. The secondary battery according to claim 1, characterized in that: Along the first direction, the thickness of the adhesive is D, 9 μm≤D≤65 μm.

8. The secondary battery according to claim 7, characterized in that: Along the first direction, the thickness of the base layer is d1, the thickness of the adhesive layer is d2, and the thickness of the friction layer is d3, 3μm≤d1≤15μm, 3μm≤d2≤25μm, 3μm≤d3≤25μm.

9. The secondary battery according to claim 1, characterized in that: The bonding layer is bonded to one of the housing and the electrode assembly, and the friction layer is in contact with the other of the housing and the electrode assembly.

10. The secondary battery according to claim 1, characterized in that: The bonding layer is bonded to the electrode assembly; and the friction layer and the shell can move relative to each other along a direction perpendicular to the first direction.

11. The secondary battery according to claim 10, characterized in that: Along the first direction, the bonding area of ​​the bonding layer is greater than or equal to the friction area of ​​the friction layer.

12. The secondary battery according to claim 11, characterized in that: The bonding layer is bonded to the outermost pole piece of the electrode assembly; along the first direction, the projection area of ​​the outermost pole piece is S1, and the friction area of ​​the friction layer is S2; 0.5≤S2 / S1≤1.

13. The secondary battery according to claim 11, characterized in that: Along a direction perpendicular to the first direction, the peeling strength between the adhesive layer and the electrode assembly is τ3, and τ3≥τ2.

14. The secondary battery according to claim 13, characterized in that: τ3-τ2≤10N / cm 2 。 15. The secondary battery according to any one of claims 1 to 14, characterized in that: The material of the bonding layer includes a base resin, a tackifying resin, a polyether polyol and microcrystals, the mass percentage of the base resin is 30% to 40%, the mass percentage of the tackifying resin is 54% to 69%, the mass percentage of the polyether polyol is 0% to 5%, and the mass percentage of the microcrystals is 1% to 2%; the material of the friction layer includes polyacrylate and a curing agent, the mass percentage of the polyacrylate is 95% to 99%, and the mass percentage of the curing agent is 1% to 4%.

16. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 15.

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