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 an accommodating cavity, the electrode assembly is arranged in the accommodating cavity, the bonding piece is arranged between the shell and the electrode assembly along the thickness direction of the electrode assembly, and the bonding piece is bonded with the shell and the electrode assembly. In the direction perpendicular to the first direction, the tearing strength of the electrode assembly is tau 1, the tearing strength of the bonding piece is tau 2, and 1 N / cm < 2 > < tau 2 < = tau 1. By setting 1N / cm < 2 > < tau < 2 >, the bonding piece is not easy to tear, and when the secondary battery falls or vibrates, the possibility that the electrode assembly impacts the shell is reduced. By setting tau 2 to be smaller than or equal to tau 1, when the falling strength or the vibration strength is large, the bonding piece can be torn before the electrode assembly is torn, and therefore the risk that falling energy or vibration energy is transmitted to the electrode assembly, and consequently the electrode assembly is torn can be reduced. Therefore, 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, including a housing, an electrode assembly and an adhesive, wherein the housing has a receiving cavity, the electrode assembly is disposed in the receiving cavity, and the adhesive is disposed between the housing and the electrode assembly along a first direction, the first direction being the thickness direction of the electrode assembly, and the adhesive is bonded to the housing and the electrode assembly. In a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ 1 , the tear strength of the bond is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0006] By setting 1N / cm 2 <τ 2 , the tear strength of the adhesive is not too small, which can make the adhesive less likely to tear. When the secondary battery falls or vibrates, it is helpful to reduce the possibility of the electrode assembly impacting the shell. 2 ≤τ 1, the tear strength of the adhesive is not too large. When the drop strength or vibration strength is large, the adhesive can tear itself before the electrode assembly tears, thereby reducing the risk of the electrode assembly being torn due to the drop energy or vibration energy being transmitted to the electrode assembly through the adhesive. The adhesive tears the first part that remains bonded to the shell and the second part that remains bonded to the electrode assembly, and the torn interface is an uneven interface. The uneven interface between the first part and the second part can provide a friction buffering effect, which is also beneficial to reduce the possibility of the electrode assembly impacting the shell, thereby helping to increase the service life of the secondary battery.

[0007] In one or more of the above embodiments, the adhesive member is an adhesive film or adhesive tape. The adhesive film includes a single adhesive layer. The adhesive tape includes a single base layer and two adhesive layers adhered to two surfaces of the base layer along the thickness direction of the base layer, and the thickness direction of the base layer is parallel to the first direction.

[0008] In one or more of the above embodiments, the adhesive member is an adhesive film, and along the first direction, the surface where the maximum projection area of ​​the adhesive member is located includes the bonding surface between the adhesive member and the electrode assembly.

[0009] In one or more of the above embodiments, the adhesive member is adhesive tape, and along the first direction, the projected area of ​​the adhesive layer bonded to the electrode assembly is greater than or equal to the projected area of ​​the base layer and the projected area of ​​the adhesive layer bonded to the shell.

[0010] In one or more of the above embodiments, the minimum value of the peel strength between the adhesive and the housing and the peel strength between the adhesive and the electrode assembly is τ 3 , τ 2 <τ 3 By setting τ 2 <τ 3 When the drop intensity or vibration intensity is large, the possibility of the adhesive being peeled off from the shell or the electrode assembly before being torn can be reduced, ensuring that the adhesive can be torn into the first part and the second part to provide a friction buffering effect.

[0011] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode sheet of the electrode assembly, and the minimum distance between the edge of the outermost electrode sheet and the edge of the adhesive layer bonded to the outermost electrode sheet along the direction perpendicular to the first direction is d, 10mm≤d. By setting 10mm≤d, the edge of the adhesive can be made farther away from the edge of the outermost electrode sheet and the outer shell, so that when the drop intensity or vibration intensity is large, the possibility of the adhesive being peeled off from the outer shell or the electrode assembly before being torn can be reduced, ensuring that the adhesive can be torn into the first part and the second part to provide a friction buffering effect.

[0012] In one or more of the above embodiments, the adhesive is bonded to the outermost electrode sheet of the electrode assembly, and 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 glue layer bonded to the outermost electrode is S 2 , 0.5≤S 2 / S 1 ≤1. By setting 0.35≤S 2 / S 1 ≤1, which can ensure that the bonding area between the glue layer and the electrode assembly is not too small, which is beneficial to improve τ 2 value, thereby reducing the possibility of the electrode assembly impacting the outer casing when the secondary battery is dropped or vibrated.

[0013] In one or more of the above embodiments, along the first direction, the thickness of the adhesive film is D 1 , the thickness of the adhesive tape is D 2 , 5μm≤D 1 ≤25μm, 15μm≤D 2 ≤35μm. By setting 5μm≤D 1 and 15μm≤D 2 , which can make the film and tape not too thin, which is beneficial to improve τ 2 The value of D is helpful to reduce the possibility of the electrode assembly impacting the shell. 1 ≤25μm and D 2 ≤35μm, which can prevent the adhesive film and adhesive paper 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 material of the adhesive layer includes polyacrylate and curing agent. Based on the total mass of the adhesive layer, 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 base layer includes a matrix resin, a tackifying resin, a polyether polyol, and microcrystals. Based on the total mass of the base layer, the mass percentage of the matrix 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 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 base layer includes the above materials and the mass percentage of the above materials in the base layer is regulated within the above range, so that 1N / cm 2 <τ 2 ≤τ 1 .

[0015] 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 current collector and a negative active material layer, and the negative active material layer is arranged on two opposite sides of the negative current collector along the thickness direction. The positive electrode sheet includes a positive current collector and a positive active material layer, and the positive active material layer is arranged on two opposite sides of the positive current collector along the thickness direction. The material of the negative 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 active material layer includes polyvinylidene fluoride, and the mass percentage of polyvinylidene fluoride is 1% to 2%. The material of the negative active material layer includes the above-mentioned materials, and the mass percentage of the above-mentioned materials in the negative active material layer is controlled within the above-mentioned range, so that the peeling strength between the negative active material layer and the separator and the negative current collector can be adjusted, so that it is 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 .

[0016] In one or more of the above embodiments, a surface of the adhesive member parallel to the first direction is provided with a recessed portion, the recessed direction of the recessed portion is perpendicular to the first direction and faces the inside of the adhesive member. The recessed portion can facilitate the formation of a stress concentration area, and when the drop intensity or vibration intensity is large, the adhesive member can be more easily torn before the electrode assembly is torn.

[0017] In one or more of the above embodiments, τ 1 -τ 2 ≤3N / cm 2 By setting τ 1 -τ 2 ≤3N / cm 2 , under the premise that the adhesive is torn before the electrode assembly is torn, τ 2 It is not too small, which helps to reduce the possibility of the electrode assembly impacting the shell.

[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 the first embodiment of this application Figure 1 Cross-section along the midline AA.

[0022] Figure 4 The second embodiment of this application is Figure 1 Cross-section along the midline AA.

[0023] Figure 5 A schematic diagram of an adhesive component provided in an embodiment of the present application after cohesive failure occurs.

[0024] Figure 6 A schematic diagram of an adhesive member provided in an embodiment of the present application having a recess.

[0025] Figure 7 For along Figure 2 Cross-section along section line BB.

[0026] Figure 8 For along Figure 2 Cross-section along the center line CC.

[0027] Fig. 9 An overall schematic diagram of an electrical device provided in one embodiment of the present application.

[0028] Main component symbols 1000, electrical equipment; 100, secondary battery; 10, shell; 101, receiving cavity; 102, recess; 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; 301, first part; 302, second part; 31, glue layer; 32, base 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

[0029] 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] The embodiment of the present application provides a secondary battery, including a housing, an electrode assembly and an adhesive, wherein the housing has a receiving cavity, the electrode assembly is arranged in the receiving cavity, and the adhesive is arranged between the housing and the electrode assembly along a first direction, the first direction is the thickness direction of the electrode assembly, and the adhesive is bonded to the housing and the electrode assembly. In a direction perpendicular to the first direction, the tear strength of the electrode assembly is τ 1 , the tear strength of the bond is τ 2 , 1N / cm 2 <τ 2 ≤τ 1 .

[0035] In the secondary battery of the present application, by setting 1N / cm 2 <τ 2 , the tear strength of the adhesive is not too small, which can make the adhesive less likely to tear. When the secondary battery falls or vibrates, it is helpful to reduce the possibility of the electrode assembly impacting the shell. 2 ≤τ 1, the tear strength of the adhesive is not too large. When the drop strength or vibration strength is large, the adhesive can tear itself before the electrode assembly tears, thereby reducing the risk of the electrode assembly being torn due to the drop energy or vibration energy being transmitted to the electrode assembly through the adhesive. The adhesive tears the first part that remains bonded to the shell and the second part that remains bonded to the electrode assembly, and the torn interface is an uneven interface. The uneven interface between the first part and the second part can provide a friction buffering effect, which is also beneficial to reduce the possibility of the electrode assembly impacting the shell, 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 4 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.

[0038] See also Figure 3 and Figure 4 The housing 10 is provided with a receiving cavity 101, and the receiving cavity 101 is filled with an electrolyte, and the electrolyte includes an electrolyte 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 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 .

[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 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 .

[0043] 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 and Figure 4The 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.

[0044] See also Figure 3 and Figure 4 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.

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

[0046] 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 .

[0047] 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 .

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In some embodiments, the diaphragm 23 is made of insulating film materials such as polyethylene film, polypropylene film, polyester film or polyimide film.

[0053] See also Figure 3 and Figure 4 , along the first direction X, the adhesive 30 is disposed between the housing 10 and the electrode assembly 20. Along the direction perpendicular to the first direction X, the tear strength of the electrode assembly 20 is τ 1 , the tear strength of the adhesive 30 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 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 completely tear (or cohesively destroy) the adhesive 30 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 tear strength of the adhesive 30 is not too small, so that the adhesive 30 is not easy to tear. When the secondary battery 100 falls or vibrates, it is helpful to reduce the possibility of the electrode assembly 20 impacting the outer shell 10. By setting τ 2 ≤τ 1, the tear strength of the adhesive 30 is not too large. When the drop strength or vibration strength is large, the adhesive 30 can tear itself 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. The adhesive 30 is torn into the first part 301 that remains bonded to the housing 10 and the second part 302 that remains bonded to the electrode assembly 20 (see Figure 5 ), and the torn interface is an uneven interface. The uneven interface between the first part 301 and the second part 302 can provide a friction buffering effect, which is also beneficial to reduce the possibility of the electrode assembly 20 impacting the shell 10, thereby helping to increase the service life of the secondary battery 100.

[0057] 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 τ 2 ≤τ 1 .

[0058] 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 .

[0059] In some embodiments, τ 1 -τ 2 ≤3N / cm 2 By setting τ 1 -τ 2 ≤3N / cm 2 , under the premise that the adhesive 30 is torn before the electrode assembly 20 is torn, τ 2 It is not too small, which helps to reduce the possibility of the electrode assembly 20 impacting the housing 10.

[0060] In some embodiments, see Figure 6The surface of the adhesive 30 parallel to the first direction X is provided with a recess 102, and the recess 102 is perpendicular to the first direction X and faces the inside of the adhesive 30. The recess 102 can facilitate the formation of a stress concentration area, and when the drop intensity or vibration intensity is large, the adhesive 30 can be more easily torn before the electrode assembly 20 is torn. In some embodiments, along the recess direction of the recess 102, the recess 102 is tapered, which is conducive to more concentrated stress.

[0061] In some embodiments, see Figure 3 , the adhesive member 30 is an adhesive film, and the adhesive film includes a single adhesive layer 31. In this case, the situation where the adhesive member 30 is torn includes the situation where the adhesive layer 31 itself is torn.

[0062] In some embodiments, the adhesive member 30 is an adhesive film, and along the first direction X, the surface where the maximum projection area of ​​the adhesive member 30 is located includes the bonding surface between the adhesive member 30 and the electrode assembly 20 .

[0063] In some embodiments, see Figure 4 , the adhesive member 30 is adhesive tape, the adhesive tape includes a single base layer 32 and two adhesive layers 31, the two adhesive layers 31 are adhered to the two surfaces of the base layer 32 along the thickness direction of the base layer 32, and the thickness direction of the base layer 32 is parallel to the first direction X. In this case, the tearing of the adhesive member 30 includes the peeling of the adhesive layer 31 and the base layer 32, the tearing of the adhesive layer 31 itself, and the tearing of the base layer 32 itself.

[0064] In some embodiments, the adhesive member 30 is adhesive tape, and along the first direction X, the projected area of ​​the adhesive layer 31 bonded to the electrode assembly 20 is larger than the projected area of ​​the base layer 32 and the projected area of ​​the adhesive layer 31 bonded to the housing 10 .

[0065] In some embodiments, the adhesive member 30 is adhesive tape, and along the first direction X, the projected area of ​​the adhesive layer 31 bonded to the electrode assembly 20 is equal to the projected area of ​​the base layer 32 and the projected area of ​​the adhesive layer 31 bonded to the housing 10. Under the premise of the purpose of the invention of this application, taking into account the accuracy of production and processing, when there is a 5% error between the projected area of ​​the adhesive layer 31 bonded to the electrode assembly 20 and the projected area of ​​the base layer 32 and the projected area of ​​the adhesive layer 31 bonded to the housing 10, it can also be considered that the projected area of ​​the adhesive layer 31 bonded to the electrode assembly 20 is equal to the projected area of ​​the base layer 32 and the projected area of ​​the adhesive layer 31 bonded to the housing 10.

[0066] In some embodiments, along the first direction X, the thickness of the adhesive film is D 1 , the thickness of the adhesive tape is D 2 , 5μm≤D 1 ≤25μm, 15μm≤D2 ≤35μm. For example, D 1 5μm, 10μm, 15μm, 20μm, 25μm or any value between the listed endpoints, D 2 15μm, 20μm, 25μm, 30μm, 35μm or any value between the listed endpoints. By setting 5μm≤D 1 and 15μm≤D 2 , which can make the film and tape not too thin, which is beneficial to improve τ 2 The value of D is thus helpful to reduce the possibility of the electrode assembly 20 impacting the housing 10. 1 ≤25μm and D 2 ≤35 μm, so that the adhesive film and the adhesive paper are not too thick, which is beneficial to improving the energy density of the secondary battery 100.

[0067] In some embodiments, the material of the adhesive layer 31 includes polyacrylate and curing agent. Based on the total mass of the adhesive layer 31, 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 adhesive layer 31 includes the above materials and the mass percentage of the above materials in the adhesive layer 31 is controlled within the above range, which can facilitate 1N / cm 2 <τ 2 ≤τ 1 .

[0068] In some embodiments, the material of the base layer 32 includes a base resin, a tackifying resin, a polyether polyol, and microcrystals. Based on the total mass of the base layer 32, 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 base layer 32 includes the above materials and the mass percentage of the above materials in the base layer 32 is controlled within the above range, which can facilitate the 1N / cm 2 <τ 2 ≤τ 1 .

[0069] 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 base layer 32. For example, the block ratio of polystyrene can be increased, thereby improving the rigidity and mechanical strength of the base 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 base layer 32 and the adhesive layer 31. 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.

[0070] In some embodiments, the minimum value of the peel strength between the adhesive 30 and the housing 10 and the peel strength between the adhesive 30 and the electrode assembly 20 is τ 3 , τ 2 <τ 3 By setting τ 2 <τ 3 When the drop intensity or vibration intensity is large, the possibility of the adhesive 30 being peeled off from the housing 10 or the electrode assembly 20 before being torn can be reduced, ensuring that the adhesive 30 can be torn into the first part 301 and the second part 302 to provide a friction buffering effect.

[0071] The so-called τ 3 It refers to the shear stress required to completely separate the adhesive 30 from the housing 10 or the adhesive 30 from 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.

[0072] In some embodiments, the adhesive 30 is bonded to the outermost electrode sheet of the electrode assembly 20, and the minimum distance between the edge of the outermost electrode sheet and the edge of the adhesive layer 31 bonded to the outermost electrode sheet along the direction perpendicular to the first direction X is d, 10mm≤d. For example, the value of d is 10mm, 11mm, 13mm or 15mm. By setting 10mm≤d, the edge of the adhesive 30 can be farther away from the edge of the outermost electrode sheet and the outer shell 10, so that when the drop intensity or vibration intensity is large, the possibility of the adhesive 30 being peeled off from the outer shell 10 or the electrode assembly 20 before being torn can be reduced, ensuring that the adhesive 30 can be torn into the first part 301 and the second part 302 to provide a friction buffering effect.

[0073] It should be understood that the distances between the edge of the outermost electrode sheet and the edge of the adhesive layer 31 bonded to the outermost electrode sheet along different directions perpendicular to the first direction X may be equal or different, but all satisfy 10 mm ≤ d. In addition, since space for setting the adhesive 30 needs to be reserved, the value of d is not too large.

[0074] In some embodiments, the adhesive 30 is bonded to the outermost electrode sheet of the electrode assembly 20. Along the first direction X, the projection of the outermost electrode sheet covers the projection of the adhesive 30. The projection area of ​​the outermost electrode sheet is S. 1 The projected area of ​​the glue layer 31 bonded to the outermost electrode is S 2 , 0.5≤S 2 / S 1 ≤1. For example, S 2 / S 1 The value of S is 0.35, 0.5, 0.6, 0.75, 1, or any value between the listed endpoints. 2 / S 1 ≤1, which can ensure that the bonding area between the adhesive layer 31 and the electrode assembly 20 is not too small, which is beneficial to improve τ 2 value, thereby reducing the possibility of the electrode assembly 20 impacting the outer shell 10 when the secondary battery 100 is dropped or vibrated.

[0075] In some embodiments, see Figure 7 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.

[0076] 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.

[0077] In some embodiments, see Figure 7 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.

[0078] 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.

[0079] In some embodiments, see Figure 8 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.

[0080] 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.

[0081] In some embodiments, see Figure 8The 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.

[0082] In some embodiments, see Figure 8 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 .

[0083] 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.

[0084] In some embodiments, the pole 80 is insulated and fixed to the first housing 11. Figure 8 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 .

[0085] See also Fig. 9 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.

[0086] To verify this application 1 , τ 2 and τ 3 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 17 groups of exemplary embodiments, and each group of comparative examples and exemplary embodiments includes 20 secondary batteries 100. In the secondary battery 100 used in the comparative examples and exemplary embodiments, the outer shell 10 is made of 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. In the secondary battery 100, the electrode assembly 20 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 30 is an adhesive film, and the adhesive 30 is centered relative to the outermost electrode sheet of the electrode assembly 20. The adhesive 30 is bonded to the shell cover of the outer shell 10 (i.e., the second shell 12) and the outermost electrode sheet of the electrode assembly 20, along the thickness direction of the adhesive 30, and the projection area S of the adhesive 30 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).

[0087] 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 and τ 3 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 .

[0088] Determination of τ 1 and τ 2 The method is as follows: 1) Sample preparation: Take out the adhesive 30 from the finished secondary battery 100 as the first sample to be torn, and take out the separator 23, the negative electrode sheet 21 and the positive electrode sheet 22 that remain bonded in the electrode assembly 20 as the second sample to be torn, and use a blade to cut out the tear test sample 1 and the tear test sample 2 with a test area of ​​1 cm×1 cm from the different samples taken out.

[0089] 2) Test: Fix the tear test specimens 1 and 2 to the test fixture of the high-speed rail tensile machine in sequence, so that the thickness direction of the tear test specimens 1 and 2 is perpendicular to the force direction of the high-speed rail tensile 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 specimens 1 and 2 is completely torn.

[0090] 3) Value: The ratio of the maximum tensile force to the test area when the shear interface of the tear test sample is completely torn is τ 2 The ratio of the maximum tensile force to the test area when the shear interface of the tear test sample 2 is completely torn is taken as τ 1 The value of .

[0091] Determination of τ 3 The method is as follows: 1) Sample preparation: Take out a sample to be peeled off from the finished secondary battery 100, in which the adhesive 30 is bonded to the second shell 12 and the outermost electrode sheet of the electrode assembly 20, and use a blade to cut out a peeling test sample with a test area of ​​1 cm×1 cm from the sample to be peeled off.

[0092] 2) Test: Fix the peel test specimen to the test fixture of the high-speed rail tensile testing machine. When fixing, make the thickness direction of the peel 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 peel test specimen is completely peeled off.

[0093] 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 3 The value of .

[0094] 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 , τ 2 and τ 3 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 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.

[0095] 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.

[0096] After the test, the experimental results are recorded in Table 1 and Table 2: Table 1 Table 2 In Table 1 and Table 2, τ in Comparative Examples 1 to 8 and Examples 1 to 9 is 3 Both 6N / cm 2 , τ 1 and τ 2 Different. τ in Example 10 and Example 11 3 Compared with τ in Example 3 3 Different, τ in Example 12 and Example 13 3 Compared with τ in Example 5 3 Different, τ in Example 14 and Example 15 3 Compared with τ in Example 7 3 Different, τ in Example 16 and Example 17 3Compared with τ in Example 9 3 different.

[0097] 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 torn, 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.

[0098] 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 tear, 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.

[0099] 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 adhesive 30 is less likely to tear, which can reduce the possibility of leakage caused by the electrode assembly 20 impacting the housing 10. The tearing rate of the secondary battery 100 in 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] According to Table 1 and Table 2, the drop pass rate of Example 10 and Example 11 is significantly lower than that of Example 3, the drop pass rate of Example 12 and Example 13 is significantly lower than that of Example 5, the drop pass rate of Example 14 and Example 15 is significantly lower than that of Example 7, and the drop pass rate of Example 16 and Example 17 is significantly lower than that of Example 9. That is, the present application sets τ 2 <τ 3 , which can ensure that the adhesive 30 is torn into the first part 301 and the second part 302, thereby providing a friction buffering effect, which is beneficial to reducing the possibility of leakage caused by the electrode assembly 20 impacting the shell 10.

[0104] 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, arranged between the housing and the electrode assembly along a first direction, the first direction being a thickness direction of the electrode assembly; the adhesive member is bonded to the housing and the electrode assembly; In the direction perpendicular to the first direction, the tear strength of the electrode assembly is τ1, and the tear strength of the adhesive is τ2, 1N / cm 2 <τ2≤τ1.

2. The secondary battery according to claim 1, characterized in that: The adhesive member is an adhesive film or adhesive tape; the adhesive film includes a single adhesive layer; the adhesive tape includes a single base layer and two adhesive layers bonded to two surfaces of the base layer along the thickness direction of the base layer, and the thickness direction of the base layer is parallel to the first direction.

3. The secondary battery according to claim 2, characterized in that: The adhesive member is the adhesive film, and along the first direction, the surface where the maximum projection area of ​​the adhesive member is located includes the bonding surface between the adhesive member and the electrode assembly.

4. The secondary battery according to claim 2, characterized in that: The adhesive member is the adhesive tape, and along the first direction, the projected area of ​​the adhesive layer bonded to the electrode assembly is greater than or equal to the projected area of ​​the base layer and the projected area of ​​the adhesive layer bonded to the shell.

5. The secondary battery according to claim 3 or 4, characterized in that: The minimum value of the peeling strength between the adhesive and the housing and the peeling strength between the adhesive and the electrode assembly is τ3, and τ2<τ3.

6. The secondary battery according to claim 3 or 4, 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 minimum distance between the edge of the outermost electrode sheet and the edge of the adhesive layer bonded to the outermost electrode sheet is d, 10mm≤d.

7. The secondary battery according to claim 3 or 4, 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, and the projection area of ​​the glue layer bonded to the outermost electrode sheet is S2, 0.5≤S2 / S1≤1.

8. The secondary battery according to claim 2, characterized in that: Along the first direction, the thickness of the adhesive film is D1, the thickness of the adhesive tape is D2, 5 μm≤D1≤25 μm, 15 μm≤D2≤35 μm.

9. The secondary battery according to claim 2, characterized in that: The material of the adhesive layer includes polyacrylate and a curing agent. Based on the total mass of the adhesive layer, 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 base layer includes a matrix resin, a tackifying resin, a polyether polyol and microcrystals. Based on the total mass of the base layer, the mass percentage of the matrix 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%.

10. The secondary battery according to claim 1, 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%.

11. The secondary battery according to claim 1, characterized in that: A concave portion is provided on a surface of the adhesive member parallel to the first direction, and a concave direction of the concave portion is perpendicular to the first direction and faces the inside of the adhesive member.

12. The secondary battery according to claim 1, characterized in that: τ1-τ2≤3N / cm 2 。 13. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 12.

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