Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery comprises a shell, an electrode assembly and a bonding piece, the shell is provided with a containing cavity, and the electrode assembly is arranged in the containing cavity. The bonding piece is of a single-layer structure. In a first direction, the bonding member adheres the housing and the electrode assembly, and the first direction is a thickness direction of the electrode assembly. In the direction perpendicular to the first direction, the tearing strength of the electrode assembly is tau 1, the minimum value of the peel strength between the bonding piece and the shell and the peel strength between the bonding piece and the electrode assembly is tau 2, and 1 N / cm < 2 > < tau 2 < = tau 1. When the secondary battery falls or vibrates, the possibility that the electrode assembly impacts the shell is reduced. And when the falling strength or the vibration strength is relatively high, the risk that the electrode assembly is torn is reduced, so that the service life of the secondary battery is 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 easily torn under the action of the drop energy or vibration energy, 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 housing, an electrode assembly and an adhesive. The housing has a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The adhesive is a single-layer structure. Along a first direction, the adhesive adheres the housing and the electrode assembly, and the first direction is the thickness direction of the electrode assembly. Along a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ 1 The minimum peel strength between the adhesive and the housing and between the adhesive and the electrode assembly is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0006] The adhesive is a single-layer structure that can easily make 1N / cm 2 <τ 2 ≤τ 1 . Set 1N / cm 2 <τ 2 The electrode assembly and the housing can be bonded and fixed by an adhesive, which is helpful to reduce the possibility of the electrode assembly impacting the housing when the secondary battery falls or vibrates. In addition, τ 2 ≤τ 1When the drop intensity or vibration intensity is large, the adhesive can be peeled off from the outer shell or electrode assembly before the electrode assembly is torn, thereby reducing the risk of the drop energy or vibration energy being transmitted to the electrode assembly through the adhesive and causing the electrode assembly to be torn, which is beneficial to improving the service life of the secondary battery.

[0007] In one or more of the above embodiments, the bonding area between the adhesive and the electrode assembly is greater than or equal to the bonding area between the adhesive and the housing.

[0008] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode sheet of the electrode assembly. Along the first direction, the projection of the outermost electrode sheet covers the projection of the adhesive, and the projection area of ​​the outermost electrode sheet is S 1 , the projected area of ​​the bond is S 2 , 0.35≤S 2 / S 1 ≤1. Set 0.35≤S 2 / S 1 ≤1, which can ensure that the bonding area between the adhesive and the housing and the electrode assembly is not too small, which is beneficial to improve τ 2 value, thereby further reducing the possibility of the electrode assembly impacting the outer casing when the secondary battery is dropped or vibrated.

[0009] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode sheet of the electrode assembly. In a direction perpendicular to the first direction, the maximum distance between the edge of the adhesive and the edge of the outermost electrode sheet is d, 0mm≤d≤10mm. Setting 0mm≤d makes it easy to place the adhesive between the housing and the electrode assembly along the first direction through the gluing process, which is beneficial to improving the convenience of bonding the housing and the electrode assembly with the adhesive. Setting d≤10mm prevents the bonding area of ​​the adhesive from being too small, which is beneficial to further reduce the possibility of the electrode assembly impacting the housing.

[0010] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode sheet of the electrode assembly. Along the first direction, the center of the circumscribed circle of the adhesive projection coincides with the center of the circumscribed circle of the outermost electrode sheet projection. In this case, along different directions perpendicular to the first direction, the distance between the edge of the adhesive and the edge of the outermost electrode sheet and the outer shell is relatively uniform, which can improve the peel strength of the adhesive and the outermost electrode sheet and the outer shell along different directions perpendicular to the first direction, which is conducive to improving τ 2 value, thereby helping to further reduce the possibility of the electrode assembly impacting the casing.

[0011] In one or more of the above embodiments, the material of the adhesive includes polyacrylate and isocyanate, and based on the total mass of the adhesive, the mass percentage of the polyacrylate is 95% to 100%, and the mass percentage of the isocyanate is 0% to 5%. By making the material of the adhesive include the above materials, and adjusting the mass percentage of the above materials in the adhesive within the above range, the peel strength between the adhesive and the housing or the electrode assembly can be adjusted, so as to make it easier to make 1N / cm 2 <τ 2 ≤τ 1 .

[0012] In one or more of the above embodiments, along the first direction, the thickness of the adhesive is D, 5μm≤D≤15μm. Setting 5μm≤D is conducive to reducing the possibility of the adhesive being peeled off from the shell or electrode assembly in the first direction before being peeled off from the shell or electrode assembly in a direction perpendicular to the first direction, thereby helping to reduce the possibility of the electrode assembly impacting the shell. Setting D≤15μm can prevent the adhesive from being 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 direction perpendicular to the first direction, the peeling strength between the adhesive and the housing is less than the peeling strength between the adhesive and the electrode assembly. In this case, when the drop strength or vibration strength is large, the adhesive can be peeled off from the housing first, which is beneficial to reduce the wear of the adhesive on the electrode assembly after peeling, thereby further improving the service life of the secondary battery.

[0014] In one or more of the above embodiments, τ 1 -τ 2 ≤3N / cm 2 . Set τ 1 -τ 2 ≤3N / cm 2 , under the premise that the adhesive is torn before the electrode assembly and peeled off from the housing or electrode assembly, τ 2 It is not too small, which helps to reduce the possibility of the electrode assembly impacting the shell.

[0015] In one or more of the above embodiments, 4N / cm 2 <τ 2 When the secondary battery is dropped or vibrated, it is helpful to further reduce the possibility of the electrode assembly impacting the outer shell.

[0016] In one or more of the above embodiments, the electrode assembly includes a negative electrode sheet, a positive electrode sheet and a separator, and the separator separates the negative electrode sheet from the positive electrode sheet. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is arranged on two opposite sides of the negative electrode current collector along the thickness direction. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is arranged on two opposite sides of the positive electrode current collector along the thickness direction. The material of the negative electrode active material layer includes styrene-butadiene rubber and carboxymethyl cellulose, the mass percentage of styrene-butadiene rubber is 1% to 2%, and the mass percentage of carboxymethyl cellulose is 1% to 2%. And / or, the material of the positive electrode active material layer includes polyvinylidene fluoride, and the mass percentage of polyvinylidene fluoride is 1% to 2%.

[0017] By making the negative electrode active material layer include the above materials, and adjusting the mass percentage of the above materials in the negative electrode active material layer within the above range, the peel strength between the negative electrode active material layer and the separator and the negative electrode current collector can be adjusted, thereby making it easier to make τ 2 ≤τ 1 The material of the positive electrode active material layer includes the above materials, and the mass percentage of the above materials in the positive electrode active material layer is controlled within the above range, which can adjust the peel strength between the positive electrode active material layer and the separator and the positive electrode current collector, thereby making it easier to make τ 2 ≤τ 1 .

[0018] 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

[0019] Figure 1 A front view of a secondary battery provided in accordance with an embodiment of the present application.

[0020] Figure 2 A top view of a secondary battery provided in accordance with an embodiment of the present application.

[0021] Figure 3 For along Figure 1 Cross-section along the midline AA.

[0022] Figure 4 A diagram showing the positional relationship between an adhesive member and an outermost electrode provided in one embodiment of the present application.

[0023] Figure 5 For along Figure 2 Cross-section along section line BB.

[0024] Figure 6 For along Figure 2 Cross-section along the center line CC.

[0025] Figure 7 An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0026] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, outer shell; 101, receiving cavity; 11, first shell; 111, bottom wall; 112, side wall; 12, second shell; 20, electrode assembly; 21, negative electrode plate; 211, negative 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; 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

[0027] 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.

[0028] 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.

[0029] Unless otherwise specified, the term "plurality" as used herein means two or more than two.

[0030] 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.

[0031] 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.

[0032] The embodiment of the present application provides a secondary battery, including a housing, an electrode assembly and an adhesive. The housing has a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The adhesive is a single-layer structure. Along a first direction, the adhesive adheres the housing and the electrode assembly, and the first direction is the thickness direction of the electrode assembly. Along a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ 1The minimum peel strength between the adhesive and the housing and between the adhesive and the electrode assembly is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0033] The adhesive is a single-layer structure that can easily make 1N / cm 2 <τ 2 ≤τ 1 . Set 1N / cm 2 <τ 2 The electrode assembly and the housing can be bonded and fixed by an adhesive, which is helpful to reduce the possibility of the electrode assembly impacting the housing when the secondary battery falls or vibrates. In addition, τ 2 ≤τ 1 When the drop intensity or vibration intensity is large, the adhesive can be peeled off from the outer shell or electrode assembly before the electrode assembly is torn, thereby reducing the risk of the drop energy or vibration energy being transmitted to the electrode assembly through the adhesive and causing the electrode assembly to be torn, which is beneficial to improving the service life of the secondary battery.

[0034] 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.

[0035] 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 30, wherein the electrode assembly 20 is accommodated in the housing 10. The adhesive 30 is respectively bonded to the housing 10 and the electrode assembly 20, so that the electrode assembly 20 and the housing 10 are bonded and fixed by the adhesive 30.

[0036] 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.

[0037] In some embodiments, the material of the housing 10 includes but is not limited to aluminum-plastic film or steel.

[0038] In some embodiments, see Figure 1 The 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 .

[0039] 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.

[0040] In some embodiments, the first shell 11 and the second shell 12 are connected along a first direction X, and the first direction X is a thickness direction of the electrode assembly 20 .

[0041] 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.

[0042] 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.

[0043] In some embodiments, the negative electrode sheet 21 and the positive electrode sheet 22 are respectively bonded to the separator 23 .

[0044] In some embodiments, along the thickness direction of the electrode assembly 20 , the projection of the negative electrode sheet 21 covers the projection of the positive electrode sheet 22 , and the projection of the separator 23 covers the projection of the negative electrode sheet 21 .

[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 , along the first direction X, the adhesive 30 adheres the housing 10 and the electrode assembly 20, and the first direction X is the thickness direction of the electrode assembly 20. The adhesive 30 is a single-layer structure. The adhesive 30 can be an adhesive film or an adhesive coating, etc. In some embodiments, the adhesive 30 is bonded to the second housing 12 and the outermost electrode sheet of the electrode assembly 20. 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 several electrode sheets of the electrode assembly 20 along the thickness direction of the electrode assembly 20. When the electrode assembly 20 is a winding 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 side.

[0053] In the direction perpendicular to the first direction X, the tear strength of the electrode assembly 20 is τ 1 The minimum peel strength between the adhesive 30 and the housing 10 and between the adhesive 30 and the electrode assembly 20 is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 The 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 1It 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 positive electrode active material layer 222 and the separator 23, the peeling of the negative electrode active material layer 212 and the negative electrode current collector 211, the tearing of the negative electrode active material layer 212 or the negative electrode current collector 211 itself, the peeling of the positive electrode active material layer 222 and the positive electrode current collector 221, 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 completely separate the adhesive 30 from the housing 10 or 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 adhesive 30 is a single-layer structure that can easily make 1N / cm 2 <τ 2 ≤τ 1 . Set 1N / cm 2 <τ 2 The electrode assembly 20 and the housing 10 can be bonded and fixed by the adhesive 30, which is helpful to reduce the possibility of the electrode assembly 20 impacting the housing 10 when the secondary battery 100 falls or vibrates. 2 ≤τ 1 When the drop intensity or vibration intensity is large, the adhesive 30 can be separated from the housing 10 or the electrode assembly 20 before the electrode assembly 20 is torn, thereby reducing the risk of the electrode assembly 20 being torn due to the drop energy or vibration energy being transmitted to the electrode assembly 20 through the adhesive 30, thereby facilitating the improvement of 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 helpful to reduce the risk of the first housing 11 and the second housing 12 being separated, resulting in leakage failure of the secondary battery 100.

[0057] It should be understood that when the drop intensity or vibration intensity is relatively large, after the adhesive 30 is peeled off, the adhesive 30 can reduce the drop energy or vibration energy through adhesive friction.

[0058] In some embodiments, the bonding area between the adhesive 30 and the electrode assembly 20 is greater than the bonding area between the adhesive 30 and the housing 10 .

[0059] In some embodiments, the bonding area between the adhesive 30 and the electrode assembly 20 is equal to the bonding area between the adhesive 30 and the housing 10. Without affecting the purpose of the invention of the present application, taking into account the reasons such as the precision in production and processing, when there is a 5% error between the bonding area between the adhesive 30 and the electrode assembly 20 and the bonding area between the adhesive 30 and the housing 10, it can also be considered that the bonding area between the adhesive 30 and the electrode assembly 20 is equal to the bonding area between the adhesive 30 and the housing 10.

[0060] It should be understood that, considering the situation in actual application that the bonding interface of the adhesive 30 is not completely used for bonding, the bonding area of ​​the adhesive 30 here refers to the area of ​​the bonding interface of the adhesive 30 used for bonding with the outer shell 10 or the electrode assembly 20.

[0061] In some embodiments, 4N / cm 2 <τ 2 When the secondary battery 100 is dropped or vibrated, the possibility of the electrode assembly 20 impacting the outer shell 10 is further reduced.

[0062] In some embodiments, τ 1 -τ 2 ≤3N / cm 2 . Set τ 1 -τ 2 ≤3N / cm 2 , under the premise that the adhesive 30 is torn before the electrode assembly 20 and is peeled off from the housing 10 or the electrode assembly 20, τ 2 It is not too small, which is helpful to reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0063] In some embodiments, the peel strength between the adhesive 30 and the housing 10 is less than the peel strength between the adhesive 30 and the electrode assembly 20 along the direction perpendicular to the first direction X. In this case, when the drop strength or vibration strength is large, the adhesive 30 can be peeled off from the housing 10 first, which is beneficial to reduce the wear of the adhesive 30 on the electrode assembly 20 after peeling, thereby further improving the service life of the secondary battery 100.

[0064] In some embodiments, the secondary battery 100 includes a wrapping glue (not shown), which is arranged around the periphery of the electrode assembly 20, and the width direction of the wrapping glue is perpendicular to the first direction X, so as to bind the negative electrode sheet 21, the positive electrode sheet 22 and the separator 23 along the thickness direction of the electrode assembly 20. This is conducive to improving the tear strength of the electrode assembly 20 and reducing the risk of the electrode assembly 20 being torn. In some embodiments, the thickness of the wrapping glue does not exceed 10μm at most. For example, the thickness of the wrapping glue can be 5μm, 6μm, 8μm, 10μm or any value between the listed endpoint values. In some embodiments, the thickness of the adhesive 30 is D, 5μm≤D≤15μm. The thickness of the adhesive 30 is equal to or greater than the thickness of the glue. For example, the thickness of the adhesive 30 is 5μm, 7μm, 9μm, 12μm, 15μm or any value between the listed endpoint values. When 5μm≤D is set, when the outer periphery of the electrode assembly 20 is provided with glue, it is convenient to make the thickness of the adhesive 30 equal to or greater than the thickness of the glue, which can reduce the possibility of the glue being compressed and stretching the bonding interface between the adhesive 30 and the shell 10 or the electrode assembly 20, thereby helping to reduce the possibility of the adhesive 30 being peeled off from the shell 10 or the electrode assembly 20 in the direction perpendicular to the first direction X in advance, thereby helping to reduce the possibility of the electrode assembly 20 impacting the shell 10. Setting D≤15μm can prevent the adhesive 30 from being too thick, which is conducive to improving the energy density of the secondary battery 100.

[0065] In some embodiments, the material of the adhesive 30 includes polyacrylate and isocyanate. Based on the total mass of the adhesive 30, the mass percentage of the polyacrylate is 95% to 100%, and the mass percentage of the isocyanate is 0% to 5%. By making the material of the adhesive 30 include the above materials and adjusting the mass percentage of the above materials in the adhesive 30 within the above range, the peel strength between the adhesive 30 and the housing 10 or the electrode assembly 20 can be adjusted, so that it is easier to make 1N / cm 2 <τ 2 ≤τ 1 For example, the mass percentage of isocyanate in the adhesive 30 may be increased, thereby increasing the peel strength between the adhesive 30 and the housing 10 and the electrode assembly 20 .

[0066] In some embodiments, the material of the negative electrode active material layer 212 includes styrene-butadiene rubber and carboxymethyl cellulose, the mass percentage of styrene-butadiene rubber is 1% to 2%, and the mass percentage of carboxymethyl cellulose is 1% to 2%. The material of the negative electrode active material layer 212 includes the above materials, and the mass percentage of the above materials in the negative electrode active material layer 212 is controlled within the above range, so that the peel strength between the negative electrode active material layer 212 and the separator 23 and the negative electrode current collector 211 can be adjusted, so that τ2 ≤τ 1 .

[0067] In some embodiments, the material of the positive electrode active material layer 222 includes polyvinylidene fluoride, and the mass percentage of polyvinylidene fluoride is 1% to 2%. The material of the positive electrode active material layer 222 includes the above materials, and the mass percentage of the above materials in the positive electrode active material layer 222 is controlled within the above range, which can adjust the peel strength between the positive electrode active material layer 222 and the separator 23 and the positive electrode current collector 221, thereby making it easier to make τ 2 ≤τ 1 .

[0068] In some embodiments, along the first direction X, the projection of the outermost pole piece covers the projection of the adhesive 30, and the projection area of ​​the outermost pole piece is S. 1 , the projection area of ​​the adhesive 30 is S 2 , 0.35≤S 2 / S 1 ≤1. For example, S 2 / S 1 The value of can be 0.35, 0.5, 0.6, 0.75, 1, or any value between the listed endpoints. Set 0.35≤S 2 / S 1 ≤1, so that the bonding area between the adhesive 30 and the housing 10 and the electrode assembly 20 is not too small, which is beneficial to improve τ 2 value, so that when the secondary battery 100 is dropped or vibrated, the possibility of the electrode assembly 20 impacting the outer shell 10 is further reduced.

[0069] In some embodiments, see Figure 4 , along the direction perpendicular to the first direction X, the maximum distance between the edge of the adhesive 30 and the edge of the outermost electrode sheet of the electrode assembly 20 is d, 0mm≤d≤10mm. For example, the value of d can be 0mm, 2mm, 4mm, 6mm, 8mm, 10mm or any value between the listed endpoint values. Setting 0mm≤d can facilitate the adhesive 30 to be arranged between the housing 10 and the electrode assembly 20 along the first direction X through the gluing process, which is conducive to improving the convenience of the adhesive 30 bonding the housing 10 and the electrode assembly 20. Setting d≤10mm, the bonding area of ​​the adhesive 30 will not be too small, which is conducive to further reducing the possibility of the electrode assembly 20 impacting the housing 10.

[0070] It should be understood that along different directions perpendicular to the first direction X, the distances between the edge of the adhesive 30 and the edge of the outermost electrode sheet of the electrode assembly 20 may be equal or different.

[0071] In some embodiments, see Figure 4, along the first direction X, the center of the circumscribed circle of the projection of the adhesive 30 coincides with the center of the circumscribed circle of the projection of the outermost pole piece. The coincidence referred to here means that the distance between the center of the circumscribed circle of the projection of the adhesive 30 and the center of the circumscribed circle of the projection of the outermost pole piece is 0mm to 1mm. In this case, along different directions perpendicular to the first direction X, the distance between the edge of the adhesive 30 and the edges of the outermost pole piece and the housing 10 is relatively uniform, which can improve the peeling strength between the adhesive 30 and the outermost pole piece and the housing 10 along different directions perpendicular to the first direction X, which is conducive to improving τ 2 The value of is beneficial to further reduce the possibility of the electrode assembly 20 impacting the shell 10.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 50 and then insulated and connected to the housing 10.

[0079] In some embodiments, see Figure 6The 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 .

[0080] 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.

[0081] In some embodiments, the pole 80 is insulated and fixed to the first housing 11. Figure 7 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 .

[0082] 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.

[0083] To verify this application 1 and τ 2 In order to study the influence of the relationship between and on the secondary battery 100, the inventors of the present application conducted the following experiment, which includes 8 groups of comparative examples and 9 groups of exemplary embodiments, and each group of comparative examples and exemplary embodiments includes 20 secondary batteries 100. The material of the outer shell 10 of the secondary battery 100 used in the comparative examples and exemplary embodiments is steel, the first shell 11 and the second shell 12 are welded and connected, and the first shell 11 is the shell body of the outer shell 10, and the second shell 12 is the shell cover of the outer 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. The adhesive 30 in the secondary battery 100 is centered relative to the outermost electrode sheet of the electrode assembly 20, and the adhesive 30 is bonded to the second shell 12 and the outermost electrode sheet of the electrode assembly 20, and the projection area S of the adhesive 30 is 2.4mm. 2 The projected area S of the outermost pole piece 1 Equal (S 1 With S 2 A 10% error is allowed between the two).

[0084] In the present application, the mass percentage of each material in the adhesive 30 can be changed to obtain the τ required for the experiment. 2 The τ required for the experiment can be obtained by changing the mass percentage of each material in the negative electrode sheet 21, the positive electrode sheet 22 and the separator 23. 1 Among them, the determination of τ 1 and τ 2 The method is as follows: 1) Sample preparation: According to the τ to be measured 1 and τ 2 , take out the samples to be peeled off in which the adhesive 30 remains bonded to the second shell 12 and the outermost electrode sheet of the electrode assembly 20, and the samples to be torn off in which the diaphragm 23 remains 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 peeling test samples and tearing test samples with a test area of ​​1 cm×1 cm from the different samples taken out.

[0085] 2) Test: Fix the peel test specimen and the tear test specimen to the test fixture of the high-speed rail tensile testing machine in turn, so that the thickness direction of the peel test specimen and the tear test specimen is 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 set the shear speed to 25±2mm / min until the shear interface of the peel test specimen is completely peeled off or the shear interface of the tear test specimen is completely torn.

[0086] 3) Value: The ratio of the maximum tensile force to the test area when the shear interface of the peel test specimen is completely peeled off is τ 2 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 .

[0087] 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 2 The 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 drop, check the appearance of the secondary battery 100. If the secondary battery 100 in the current round leaks or catches fire, stop dropping immediately.

[0088] 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.

[0089] After the test, the experimental results are recorded in Table 1: Table 1 In Table 1, the drop pass rate and tearing rate of Comparative Examples 1 to 3 are all 0%, which is due to τ 2 <1N / cm 2 , τ 2 When the drop test is performed, the adhesive 30 is easily separated from the housing 10 or the electrode assembly 20, so that the electrode assembly 20 impacts the housing 10 and causes leakage. 2 ≤τ 1 Or τ 2 >τ 1 , the falling energy cannot be transferred to the electrode assembly 20 through the adhesive 30, so that the electrode assembly 20 is not torn.

[0090] In Table 1, the drop pass rates of Comparative Examples 4 to 6 are all close to 0%, which is due to τ 2 =1N / cm 2 When the drop test is performed, the adhesive 30 is still easy to peel off from the housing 10 or the electrode assembly 20, so that the electrode assembly 20 impacts the housing 10 and causes leakage. The tearing rate of comparative example 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 transferred to the electrode assembly 20 through the adhesive 30, so that the electrode assembly 20 is torn. The tearing incidence rates of Comparative Examples 5 and 6 are lower than that of Comparative Example 4 because τ 2 ≤τ 1 In the portion of the secondary batteries 100 that pass 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.

[0091] 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 2When the drop test is performed, the adhesive 30 is not easily peeled off from the housing 10 or the electrode assembly 20, 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.

[0092] In Table 1, the drop pass rates of Examples 1 to 9 are significantly greater than those of Comparative Examples 1 to 6, and the drop pass rates of Examples 7 to 9 are significantly greater than those of 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. Further, by setting τ 2 >4N / cm 2 , which can further reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10.

[0093] 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.

[0094] 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 / cm 2 , which helps to reduce the possibility of the electrode assembly 20 impacting the shell 10.

[0095] 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, wherein the adhesive member is a single-layer structure; The adhesive adheres the housing and the electrode assembly along a first direction, and the first direction is a thickness direction of the electrode assembly; In the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1, and the minimum peel strength between the adhesive and the housing and between the adhesive and the electrode assembly is τ2, 1N / cm 2 <τ2≤τ1.

2. The secondary battery according to claim 1, characterized in that: The bonding area between the adhesive and the electrode assembly is greater than or equal to the bonding area between the adhesive and the housing.

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

4. The secondary battery according to claim 2, characterized in that: The adhesive is bonded to the outermost electrode sheet of the electrode assembly; along a direction perpendicular to the first direction, the maximum distance between the edge of the adhesive and the edge of the outermost electrode sheet is d, 0mm≤d≤10mm.

5. The secondary battery according to claim 2, characterized in that: The adhesive is bonded to the outermost electrode sheet of the electrode assembly; along the first direction, the center of the circumscribed circle of the projection of the adhesive coincides with the center of the circumscribed circle of the projection of the outermost electrode sheet.

6. The secondary battery according to claim 2, characterized in that: The material of the adhesive comprises polyacrylate and isocyanate. Based on the total mass of the adhesive, the mass percentage of the polyacrylate is 95% to 100%, and the mass percentage of the isocyanate is 0% to 5%.

7. The secondary battery according to claim 2, characterized in that: Along the first direction, the thickness of the adhesive is D, 5 μm≤D≤15 μm.

8. The secondary battery according to claim 2, characterized in that: Along a direction perpendicular to the first direction, a peeling strength between the adhesive and the housing is smaller than a peeling strength between the adhesive and the electrode assembly.

9. The secondary battery according to claim 2, characterized in that: τ1-τ2≤3N / cm 2 。 10. The secondary battery according to claim 2, characterized in that: 4N / cm 2 <τ2。 11. The secondary battery according to any one of claims 1 to 10, characterized in that: The electrode assembly comprises a negative electrode sheet, a positive electrode sheet and a separator, wherein the separator separates the negative electrode sheet from the positive electrode sheet; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is arranged on two opposite sides of the negative electrode current collector along the thickness direction; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is arranged on two opposite sides of the positive electrode current collector along the thickness direction; Among them, the material of the negative electrode active material layer includes styrene butadiene rubber and carboxymethyl cellulose, the mass percentage of the styrene butadiene rubber is 1% to 2%, and the mass percentage of the carboxymethyl cellulose is 1% to 2%; and / or, the material of the positive electrode active material layer includes polyvinylidene fluoride, and the mass percentage of the polyvinylidene fluoride is 1% to 2%.

12. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 11.

Images