Secondary battery and electrical device

Abstract

Provided in the embodiments of the present application are a secondary battery (100) and an electrical device (100). The secondary battery (100) comprises a case (20), an electrode assembly (10) and a first bonding member (50). The first bonding member (50) comprises a base layer (51), a first adhesive layer (52), a second adhesive layer (53), and a third adhesive layer (54). The first adhesive layer (52) bonds the case (20) to the base layer (51), and both the second adhesive layer (53) and the third adhesive layer (54) bond the electrode assembly (10) to the base layer (51). The second adhesive layer (53), the first adhesive layer (52) and the third adhesive layer (54) are sequentially arranged in a first direction (X); the projection of the first adhesive layer (52) is separated from the projection of the second adhesive layer (53), and the projection of the first adhesive layer (52) is separated from the projection of the third adhesive layer (54); the dimension of the first adhesive layer (52) in a second direction (Y) is defined as L1, the dimension of the second adhesive layer (53) in the second direction (Y) is defined as L2, and the dimension of the third adhesive layer (54) in the second direction (Y) is defined as L3, where L1<L2, and L1<L3; and both ends of the second adhesive layer (53) in the second direction (Y) extend beyond the first adhesive layer (52), and both ends of the third adhesive layer (54) in the second direction (Y) extend beyond the first adhesive layer (52). When the secondary battery (100) drops, the stress is mainly concentrated at an edge of the first adhesive layer (52), helping to reduce the possibility of damage to the electrode assembly (10) after the secondary battery (100) drops.

Description

Secondary battery and electric device TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a secondary battery and an electric device. BACKGROUND

[0002] In the case of impact such as falling, the electrode assembly inside the secondary battery or the electric device provided with the secondary battery has the risk of movement, and the movement of the electrode assembly is likely to cause battery failure. In order to improve the problem of battery failure, a double-sided adhesive layer is usually arranged between the electrode assembly and the shell of the secondary battery, one side of which is bonded to the shell and the other side is bonded to the electrode assembly.

[0003] SUMMARY

[0004] The present application inventors have found that when the secondary battery is impacted, if the adhesion of the adhesive layer is too small, it is easy to separate from the electrode assembly or the shell, causing the electrode assembly to move relative to the shell, which may cause the battery cell to fail; if the adhesion of the adhesive layer is too large, the adhesive layer will transmit the impact force to the outer foil of the electrode assembly, which is likely to cause the outer foil of the electrode assembly to tear.

[0005] In view of the above situation, it is necessary to provide a secondary battery and an electric device to reduce the possibility of damage to the electrode assembly when the secondary battery falls.

[0006] A first aspect of an embodiment of the present application provides a secondary battery, comprising a shell, an electrode assembly and a first bonding member. The electrode assembly is accommodated in the shell. The first bonding member comprises a base layer, a first adhesive layer, a second adhesive layer and a third adhesive layer. The base layer comprises a first surface and a second surface oppositely arranged along the thickness direction of the first bonding member, the first adhesive layer is arranged on the first surface, the second adhesive layer and the third adhesive layer are arranged on the second surface, the first adhesive layer bonds the shell and the base layer, and the second adhesive layer and the third adhesive layer both bond the electrode assembly and the base layer. The second adhesive layer, the first adhesive layer and the third adhesive layer are sequentially arranged along a first direction, the first direction being perpendicular to the thickness direction of the first bonding member; along the thickness direction of the first bonding member, the projection of the first adhesive layer is separated from the projection of the second adhesive layer, and the projection of the first adhesive layer is separated from the projection of the third adhesive layer; the size of the first adhesive layer along a second direction is L1, the size of the second adhesive layer along the second direction is L2, and the size of the third adhesive layer along the second direction is L3, L1 < L2, and L1 < L3, both ends of the second adhesive layer along the second direction exceed the first adhesive layer, and both ends of the third adhesive layer along the second direction exceed the first adhesive layer; the second direction is perpendicular to the first direction and the thickness direction of the first bonding member.

[0007] In the secondary battery, the projection of the first adhesive layer along the thickness direction of the first adhesive member is separated from the projections of the second adhesive layer and the third adhesive layer along the thickness direction of the first adhesive member. When the secondary battery falls, the stress generated by the falling is mainly concentrated in the first adhesive layer due to the direct connection between the first adhesive layer and the shell. In the process of stress transmission from the first adhesive layer to the second adhesive layer and the third adhesive layer through the base layer, part of the stress is consumed by the deformation of the base layer. Thus, the stress borne by the second adhesive layer and the third adhesive layer can be reduced, and the possibility of damage to the electrode assembly caused by stress when the secondary battery falls can be reduced. Moreover, for the first adhesive layer, the stress is mainly concentrated in the edge of the first adhesive layer, and the size of the second adhesive layer and the third adhesive layer along the second direction is greater than the size of the first adhesive layer along the second direction, which is conducive to reducing the stress of the edge of the second adhesive layer and the third adhesive layer, thereby further reducing the possibility of damage to the electrode assembly.

[0008] In an optional embodiment of the present application, the size of the shell along the second direction is L, and 0.4L≤L2≤0.8L. L2≥0.4L is set to prevent the size of the second adhesive layer along the second direction from being too small, which is conducive to increasing the bonding area of the second adhesive layer with the base layer and the electrode assembly. On the one hand, the stability of the connection between the electrode assembly and the shell is improved to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls. On the other hand, it is conducive to reducing the moment of stress generated by the vibration of the electrode assembly and the outer edge of the second adhesive layer along the second direction when the secondary battery falls, thereby reducing the possibility of tearing of the electrode assembly. L2≤0.8L is set to prevent the size of the second adhesive layer along the second direction from being too large. On the one hand, it is conducive to saving materials. On the other hand, it is conducive to reducing the possibility of affecting the packaging of the shell due to the excessive length of the second adhesive layer.

[0009] In an optional embodiment of the present application, 0.4L≤L3≤0.8L. L3≥0.4L is set to prevent the size of the third adhesive layer 54 along the second direction from being too small, which is conducive to increasing the bonding area of the third adhesive layer with the base layer and the electrode assembly. On the one hand, the stability of the connection between the electrode assembly and the shell is improved to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls. On the other hand, it is conducive to reducing the moment of stress generated by the vibration of the electrode assembly and the outer edge of the third adhesive layer along the second direction when the secondary battery falls, thereby reducing the possibility of tearing of the electrode assembly. L3≤0.8L is set to prevent the size of the third adhesive layer along the second direction from being too large. On the one hand, it is conducive to saving materials. On the other hand, it is conducive to reducing the possibility of affecting the packaging of the shell due to the excessive length of the third adhesive layer.

[0010] In an optional embodiment of the present application, 0.95≤L2 / L3≤1.05. By setting 0.95≤L2 / L3≤1.05, the size difference between the second adhesive layer and the third adhesive layer in the second direction is not too large, which is conducive to improving the uniformity of the stress on the second adhesive layer and the third adhesive layer and reducing the possibility of damage to the electrode assembly due to the concentration of stress on one of the second adhesive layer and the third adhesive layer.

[0011] In an optional embodiment of the present application, the size of the shell in the first direction is W, the maximum distance between the second adhesive layer and the third adhesive layer in the first direction is w, and 0.4W≤w≤0.8W. By setting w≥0.4W, the bonding area of the second adhesive layer and the third adhesive layer is not too close to the middle of the electrode assembly, which is conducive to reducing the moment of force of the stress generated by the vibration of the electrode assembly and the outer side edges of the second adhesive layer and the third adhesive layer in the first direction when the secondary battery falls, thereby reducing the possibility of tearing of the electrode assembly; by setting w≤0.8W, the distance between the second adhesive layer and the third adhesive layer and the edge of the electrode assembly is not too close, which is conducive to reducing the possibility of affecting the packaging of the shell due to the close distance between the second adhesive layer and the third adhesive layer and the edge of the electrode assembly.

[0012] In an optional embodiment of the present application, the second adhesive layer has a first end and a second end oppositely arranged in the second direction; the distance from the first end to the first adhesive layer in the second direction is D1, and 0.05L2≤D1≤0.3L2. By setting D1≥0.05L2, the distance between the first end and the first adhesive layer is not too small, which is conducive to reducing the stress generated by the first adhesive layer pulling the edge of the second adhesive layer located at the first end through the base layer when the secondary battery falls, thereby reducing the possibility of damage to the electrode assembly; by setting D1≤0.3L2, the distance between the first end and the first adhesive layer is not too large to compress the setting space of the first adhesive layer, so that the length of the first adhesive layer in the second direction is not too short, which is conducive to improving the stability of the connection between the electrode assembly and the shell and reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, thereby reducing the possibility of damage to the electrode assembly 10.

[0013] In an optional embodiment of the present application, the second end is spaced apart from the first adhesive layer by a distance D2 in the second direction, and 0.05L2≤D2≤0.3L2. Setting D2≥0.05L2, the distance between the second end and the first adhesive layer is not too small, which is conducive to reducing the stress generated by the first adhesive layer pulling the edge of the second adhesive layer at the second end through the base layer when the secondary battery falls, thereby reducing the possibility of damage to the electrode assembly; setting D2≤0.3L2, the distance between the second end and the first adhesive layer is not too large, so as to reduce the compression of the setting space of the first adhesive layer, so that the length of the first adhesive layer in the second direction is not too short, which is conducive to improving the stability of the connection between the electrode assembly and the shell, reducing the vibration amplitude of the electrode assembly when the secondary battery falls, and further reducing the possibility of damage to the electrode assembly.

[0014] In an optional embodiment of the present application, 0.95≤D1 / D2≤1.05. In this way, the difference between D1 and D2 is not too large, and the first end and the second end of the second adhesive layer are arranged approximately symmetrically on both sides of the first adhesive layer in the second direction, which is conducive to improving the uniformity of the stress on the second adhesive layer and reducing the possibility of damage to the electrode assembly due to the stress generated when the secondary battery falls being concentrated at the first end or the second end.

[0015] In an optional embodiment of the present application, the third adhesive layer has a third end and a fourth end arranged opposite in the second direction; the third end is spaced apart from the first adhesive layer by a distance D3 in the second direction, and 0.05L3≤D3≤0.3L3. Setting D3≥0.05L3, the distance between the third end and the first adhesive layer is not too small, which is conducive to reducing the stress generated by the first adhesive layer pulling the edge of the third adhesive layer at the third end through the base layer when the secondary battery falls, thereby reducing the possibility of damage to the electrode assembly; setting D3≤0.3L3, the distance between the third end and the first adhesive layer is not too large, so as to reduce the compression of the setting space of the first adhesive layer, so that the length of the first adhesive layer in the second direction is not too short, which is conducive to improving the stability of the connection between the electrode assembly and the shell, reducing the vibration amplitude of the electrode assembly when the secondary battery falls, and further reducing the possibility of damage to the electrode assembly.

[0016] In an optional embodiment of the present application, the fourth end is at a distance D4 from the first adhesive layer in the second direction, and 0.05L3≤D4≤0.3L3. Setting D4≥0.05L3, the distance between the fourth end and the first adhesive layer is not too small, which is conducive to reducing the stress generated by the first adhesive layer pulling the edge of the third adhesive layer at the fourth end through the base layer when the secondary battery falls, thereby reducing the possibility of damage to the electrode assembly; setting D4≤0.3L3, the distance between the fourth end and the first adhesive layer is not too large, so as to reduce the compression of the setting space of the first adhesive layer, so that the length of the first adhesive layer in the second direction is not too short, which is conducive to improving the stability of the connection between the electrode assembly and the shell, reducing the vibration amplitude of the electrode assembly when the secondary battery falls, and thereby reducing the possibility of damage to the electrode assembly.

[0017] In an optional embodiment of the present application, 0.95≤D3 / D4≤1.05. In this way, the difference between D3 and D4 is not too large, and the third end and the fourth end of the third adhesive layer are arranged approximately symmetrically on both sides of the first adhesive layer in the second direction, which is conducive to improving the uniformity of the stress on the third adhesive layer and reducing the possibility of damage to the electrode assembly due to the stress generated when the secondary battery falls being concentrated at the third end or the fourth end.

[0018] In an optional embodiment of the present application, the first adhesive layer has a third face and a fourth face arranged opposite in the first direction, the third face faces the second adhesive layer, and the fourth face faces the third adhesive layer; the second adhesive layer has a fifth face, which is the surface of the second adhesive layer facing away from the first adhesive layer in the first direction, and the third adhesive layer has a sixth face, which is the surface of the third adhesive layer facing away from the first adhesive layer in the first direction. In the first direction, the distance between the fifth face and the sixth face is w, the distance between the third face and the fifth face is w1, and 0.1w≤w1≤0.3w. Setting w1≥0.1w, the distance between the third face and the fifth face is not too small, which is conducive to leaving space on the base layer for arranging the second adhesive layer, so that the width of the second adhesive layer in the first direction is not too small, which is conducive to increasing the stability of the adhesion between the second adhesive layer and the electrode assembly, so as to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls; setting w1≤0.3w, the distance between the third face and the fifth face is not too large, which is conducive to leaving space on the base layer for arranging the first adhesive layer, so that the width of the first adhesive layer in the first direction is not too small, which is conducive to increasing the stability of the adhesion between the first adhesive layer and the shell, so as to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls.

[0019] In an optional embodiment of the present application, the distance between the fourth face and the sixth face is w2, and 0.1w≤w2≤0.3w. Setting w2≥0.1w, the distance between the fourth face and the sixth face is not too small, which is conducive to leaving space for arranging the third adhesive layer on the base layer, so that the width of the third adhesive layer along the first direction is not too small, which is conducive to increasing the stability of the adhesion between the third adhesive layer and the electrode assembly, so as to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls; setting w2≤0.3w, the distance between the fourth face and the sixth face is not too large, which is conducive to leaving space for arranging the first adhesive layer on the base layer, so that the width of the first adhesive layer along the first direction is not too small, which is conducive to increasing the stability of the adhesion between the first adhesive layer and the shell, so as to reduce the possibility of the electrode assembly impacting the top sealing position of the shell when the secondary battery falls.

[0020] In an optional embodiment of the present application, 0.95≤w1 / w2≤1.05. In this way, the difference between w1 and w2 is not too large, which is conducive to improving the symmetry of the second adhesive layer and the third adhesive layer relative to the first adhesive layer, and is conducive to improving the uniformity of the stress suffered by the electrode assembly when the secondary battery falls, thereby reducing the possibility of damage to the electrode assembly.

[0021] In an optional embodiment of the present application, the first adhesive layer has a third face and a fourth face oppositely arranged along the first direction, the third face faces the second adhesive layer, and the fourth face faces the third adhesive layer; the second adhesive layer has a fifth face and a seventh face oppositely arranged along the first direction, the seventh face faces the third face; the third adhesive layer has an eighth face and a sixth face oppositely arranged along the first direction, the second face faces the eighth face. Along the first direction, the distance between the fifth face and the third face is w1, the distance between the third face and the seventh face is h1, and 0.2w1≤h1≤0.5w1. Setting h1≥0.2w1, the distance between the third face and the seventh face is not too small, which is conducive to reducing the stress transmitted by the first adhesive layer to the second adhesive layer and reducing the possibility of damage to the electrode assembly; setting h1≤0.5w1, the distance between the third face and the seventh face is not too large, which is conducive to leaving space for arranging the first adhesive layer, so that the size of the first adhesive layer along the first direction is not too small, so as to improve the stability of the connection between the electrode assembly and the shell.

[0022] In an optional embodiment of the present application, the distance between the fourth face and the sixth face is w2, the distance between the fourth face and the eighth face is h2, and 0.2w2≤h2≤0.5w2. Setting h2≥0.2w2, the distance between the third face and the seventh face is not too small, which is conducive to reducing the stress transmitted by the first adhesive layer to the second adhesive layer and reducing the possibility of damage to the electrode assembly; setting h2≤0.5w2, the distance between the third face and the seventh face is not too large, which is conducive to leaving space for arranging the first adhesive layer, so that the size of the first adhesive layer along the first direction is not too small, so as to improve the stability of the connection between the electrode assembly and the shell.

[0023] In one optional embodiment of the present application, 0.95≤w1 / w2≤1.05, 0.95≤h1 / h2≤1.05. In this way, the difference between w1 and w2 is not too large, and the difference between h1 and h2 is not too large, which is conducive to improving the uniformity of the distribution of the first adhesive layer, the second adhesive layer and the third adhesive layer along the first direction, thereby being conducive to improving the uniformity of the stress suffered by the electrode assembly when the secondary battery falls, reducing the possibility that the stress is too concentrated in any one of the first adhesive layer, the second adhesive layer and the third adhesive layer, thereby reducing the possibility of damage to the electrode assembly.

[0024] A second aspect of embodiments of the present application provides a power consuming device including the secondary battery as described in any one of the preceding embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a schematic structural diagram of a secondary battery in one embodiment of the present application.

[0026] FIG. 2 is a schematic structural exploded diagram of a secondary battery in one embodiment of the present application.

[0027] FIG. 3 is a schematic sectional structural diagram of a secondary battery in one embodiment of the present application.

[0028] FIG. 4 is a schematic sectional structural diagram of a first adhesive member in one embodiment of the present application.

[0029] FIG. 5 is a schematic structural diagram of a part of a secondary battery in one embodiment of the present application.

[0030] FIG. 6 is a schematic structural diagram of a power consuming device in one embodiment of the present application.

[0031] MAIN ELEMENT SYMBOL EXPLANATION

[0032] Secondary battery 100

[0033] Electrode assembly 10

[0034] Positive electrode sheet 11

[0035] Positive electrode current collector 111

[0036] Positive electrode active material layer 112

[0037] Negative electrode sheet 12

[0038] Negative current collector 121

[0039] Negative active material layer 122

[0040] Separator 13

[0041] Housing 20

[0042] Positive electrode tab 30

[0043] Negative electrode tab 40

[0044] First adhesive member 50

[0045] Base layer 51

[0046] First face 511

[0047] Second face 512

[0048] First adhesive layer 52

[0049] Third face 521

[0050] Fourth face 522

[0051] Second adhesive layer 53

[0052] First end 531

[0053] Second end 532

[0054] Fifth surface 533

[0055] Seventh surface 534

[0056] Third adhesive layer 54

[0057] Third end 541

[0058] Fourth end 542

[0059] Sixth surface 543

[0060] Eighth surface 544

[0061] Electric device 100

[0062] First direction X

[0063] Second direction Y

[0064] Third direction Z DETAILED DESCRIPTION

[0065] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments of the present application.

[0066] It should be noted that when an element is referred to as being "connected", "coupled", or "disposed" to another element, it can be directly connected, coupled, or disposed to the other element, or there can be intervening elements present. When an element is referred to as being "disposed" on another element, it can be directly disposed on the other element, or there can be intervening elements present.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0068] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0069] In the description of the embodiments of the present application, the term "vertical" is used to describe the ideal state between two components. In the actual production or use state, there can be an approximate vertical state between the two components. The two components described as "vertical" can not be an absolute straight line, plane, but can be approximately straight or planar, and the overall extension direction is straight or planar from a macroscopic point of view. The components can be considered as "straight line" or "plane".

[0070] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. Various embodiments of the application can be combined with each other, if not in conflict.

[0071] It should be noted that the thickness, length, width, and other dimensions of various components in the embodiments of the present application shown in the drawings, and the overall thickness, length, width, and other dimensions of the integrated device are only exemplary and should not constitute any limitation on the present application.

[0072] The embodiment of the present application provides a secondary battery, which comprises a shell, an electrode assembly and a first adhesive. The electrode assembly is accommodated in the shell. The first adhesive comprises a base layer, a first glue layer, a second glue layer and a third glue layer. The base layer comprises a first surface and a second surface which are oppositely arranged along the thickness direction of the first adhesive, the first glue layer is arranged on the first surface, the second glue layer and the third glue layer are arranged on the second surface, the first glue layer is bonded with the shell, and the second glue layer and the third glue layer are bonded with the electrode assembly. The second glue layer, the first glue layer and the third glue layer are sequentially arranged along a first direction, the first direction is perpendicular to the thickness direction of the first adhesive; along the thickness direction of the first adhesive, the projection of the first glue layer is separated from the projection of the second glue layer, and the projection of the first glue layer is separated from the projection of the third glue layer; the size of the first glue layer along a second direction is L1, the size of the second glue layer along the second direction is L2, the size of the third glue layer along the second direction is L3, L1 < L2, and L1 < L3, both ends of the second glue layer along the second direction exceed the first glue layer, and both ends of the third glue layer along the second direction exceed the first glue layer; the second direction is perpendicular to the first direction and the thickness direction of the first adhesive.

[0073] In the secondary battery, the projection of the first glue layer along the thickness direction of the first adhesive is separated from the projection of the second glue layer and the third glue layer along the thickness direction of the first adhesive, when the secondary battery falls, the stress generated by the falling is mainly concentrated on the first glue layer, and in the process of transmitting the stress from the first glue layer to the second glue layer and the third glue layer through the base layer, part of the stress is consumed by the deformation of the base layer, so that the stress borne by the second glue layer and the third glue layer can be reduced, and the possibility of damage to the electrode assembly caused by the stress when the secondary battery falls can be reduced; and for the first glue layer, the stress is mainly concentrated on the edge of the first glue layer, and the size of the second glue layer and the third glue layer along the second direction is greater than the size of the first glue layer along the second direction, which is conducive to reducing the stress of the edge of the second glue layer and the third glue layer, thereby further reducing the possibility of damage to the electrode assembly.

[0074] The embodiment of the present application is further described below with reference to the drawings.

[0075] As shown in FIG. 1 and FIG. 2, the first embodiment of the present application provides a secondary battery 100, which comprises a shell 20 and an electrode assembly 10, and the electrode assembly 10 is accommodated in the shell 20.

[0076] In some embodiments, the shell 20 is made of an aluminum plastic film.

[0077] In some embodiments, the shell 20 is made of steel.

[0078] In some embodiments, the secondary battery 100 further comprises a positive electrode tab 30 and a negative electrode tab 40, and the positive electrode tab 30 and the negative electrode tab 40 are both electrically connected with the electrode assembly 10 and both extend out of the shell 20.

[0079] In some embodiments, as shown in FIG. 3, the electrode assembly 10 includes a positive electrode tab 11, a negative electrode tab 12, and a separator 13. The positive electrode tab 11 is connected with a positive electrode lug 30, and the negative electrode tab 12 is connected with a negative electrode lug 40.

[0080] In some embodiments, a plurality of positive electrode tabs 11, a plurality of separators 13, and a plurality of negative electrode tabs 12 are stacked along the thickness direction of the positive electrode tab 11 to form a laminated structure, and a separator 13 is arranged between any adjacent positive electrode tab 11 and negative electrode tab 12.

[0081] In some embodiments, as shown in FIG. 3, the positive electrode tab 11, the separator 13, and the negative electrode tab 12 are stacked and wound to form a wound structure.

[0082] In some embodiments, as shown in FIG. 3, the positive electrode tab 11 includes a positive electrode current collector 111 and a positive electrode active material layer 112, the positive electrode current collector 111 has two surfaces oppositely arranged along the thickness direction of the positive electrode tab 11, and the positive electrode active material layer 112 is arranged on at least one of the two surfaces.

[0083] In some embodiments, as shown in FIG. 3, the negative electrode tab 12 includes a negative electrode current collector 121 and a negative electrode active material layer 122, the negative electrode current collector 121 has two surfaces oppositely arranged along the thickness direction of the negative electrode tab 12, and the negative electrode active material layer 122 is arranged on at least one of the two surfaces.

[0084] In some embodiments, the positive electrode current collector 111 and the negative electrode current collector 121 are both metal layers. As an exemplary example, the positive electrode current collector 111 can be a metal layer including at least one of aluminum, nickel, tantalum, and titanium, such as an aluminum foil. The negative electrode current collector 121 can be a metal layer including at least one of copper, nickel, tantalum, and titanium, such as a copper foil.

[0085] In some embodiments, the positive electrode current collector 111 and the negative electrode current collector 121 are composite current collectors.

[0086] In some embodiments, the positive electrode active material layer 112 includes a positive electrode active material, and the positive electrode active material includes at least one of lithium cobaltate, lithium nickel cobalt manganese acid, lithium nickel cobalt aluminum acid, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese acid.

[0087] In some embodiments, the negative electrode active material layer 122 includes a negative electrode active material, and the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, and silicon-carbon material.

[0088] In some embodiments, the separator 13 is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0089] In some embodiments, the secondary battery 100 further includes an electrolyte (not shown) which is accommodated in the case 2010.

[0090] In some embodiments, the electrolyte is in any one of a gel state, a solid state, and a liquid state.

[0091] In some embodiments, the electrolyte includes a lithium salt and a nonaqueous solvent.

[0092] In some embodiments, the lithium salt includes at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or LiPO2F2, etc.

[0093] In some embodiments, the nonaqueous solvent includes at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, or other organic solvent, etc. For example, the carbonate compound can include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, or trifluoromethyl ethylene carbonate, etc.

[0094] In some embodiments, as shown in FIG. 3, the secondary battery 100 further includes a first adhesive 50 which is accommodated in the case 20 and which adheres the case 20 and the electrode assembly 10.

[0095] In some embodiments, as shown in FIGS. 3 and 4, the first adhesive 50 includes a base layer 51, a first adhesive layer 52, a second adhesive layer 53, and a third adhesive layer 54. The base layer 51 includes a first surface 511 and a second surface 512 which are oppositely disposed along a thickness direction (indicated by a third direction Z in the drawings) of the first adhesive 50, the first adhesive layer 52 is provided on the first surface 511, the second adhesive layer 53 and the third adhesive layer 54 are provided on the second surface 512, the first adhesive layer 52 adheres the case 20 and the base layer 51, and the second adhesive layer 53 and the third adhesive layer 54 each adhere the electrode assembly 10 and the base layer 51.

[0096] In some embodiments, as shown in FIG. 4 and FIG. 5, the second adhesive layer 53, the first adhesive layer 52 and the third adhesive layer 54 are sequentially arranged along the first direction X, and the first direction X is perpendicular to the thickness direction of the first adhesive member 50. The projection of the first adhesive layer 52 along the thickness direction of the first adhesive member 50 is separated from the projection of the second adhesive layer 53, and the projection of the first adhesive layer 52 is separated from the projection of the third adhesive layer 54. The size of the first adhesive layer 52 along the second direction Y is L1, the size of the second adhesive layer 53 along the second direction Y is L2, the size of the third adhesive layer 54 along the second direction Y is L3, L1 < L2, and L1 < L3, both ends of the second adhesive layer 53 along the second direction Y exceed the first adhesive layer 52, and both ends of the third adhesive layer 54 along the second direction Y exceed the first adhesive layer 52. The second direction Y is perpendicular to the first direction X and the third direction Z.

[0097] In the secondary battery 100, the projection of the first adhesive layer 52 along the thickness direction of the first adhesive member 50 is separated from the projection of the second adhesive layer 53 and the third adhesive layer 54 along the thickness direction of the first adhesive member 50. When the secondary battery 100 falls, since the first adhesive layer 52 is directly connected to the shell 20, the stress generated by the falling is mainly concentrated on the first adhesive layer 52, and in the process of the stress being transmitted from the first adhesive layer 52 to the second adhesive layer 53 and the third adhesive layer 54 through the base layer 51, part of the stress is consumed by the deformation of the base layer 51, thereby reducing the stress borne by the second adhesive layer 53 and the third adhesive layer 54, and further reducing the possibility of damage to the electrode assembly 10 caused by the stress when the secondary battery 100 falls; and for the first adhesive layer 52, the stress is mainly concentrated on the edge of the first adhesive layer 52, and the size of the second adhesive layer 53 and the third adhesive layer 54 along the second direction Y is greater than the size of the first adhesive layer 52 along the second direction Y, which is conducive to reducing the stress on the edge of the second adhesive layer 53 and the third adhesive layer 54, thereby further reducing the possibility of damage to the electrode assembly 10.

[0098] In the embodiments of the present application, the shapes of the base layer 51, the first adhesive layer 52, the second adhesive layer 53 and the third adhesive layer 54 are not specifically limited. As an exemplary example, the shape of the base layer 51 can be one of a rectangle, an ellipse, a hexagon and a trapezoid; the shapes of the first adhesive layer 52, the second adhesive layer 53 and the third adhesive layer 54 can be one of a rectangle, an ellipse and a trapezoid. Among them, the shapes of the base layer 51, the first adhesive layer 52, the second adhesive layer 53 and the third adhesive layer 54 refer to the shapes of the projections of the base layer 51, the first adhesive layer 52, the second adhesive layer 53 and the third adhesive layer 54 along the third direction Z.

[0099] In some embodiments, the shapes of the base layer 51, the first adhesive layer 52, the second adhesive layer 53 and the third adhesive layer 54 are all rectangles.

[0100] In some embodiments, as shown in FIG. 2, the shell 20 is made of an aluminum plastic film, and the second direction Y is the direction in which the positive and negative tabs 30 and 40 extend out of the shell 20. In this way, the first, second and third adhesive layers 52, 53 and 54 extend in the direction in which the positive and negative tabs 30 and 40 extend out of the shell 20, which is conducive to reducing the possibility that the electrode assembly 10 will impact the top edge position of the shell 20 when the secondary battery 100 falls.

[0101] In some embodiments, the first adhesive 50 is a hot-melt pressure-sensitive adhesive, wherein the first adhesive layer 52 is a hot-melt adhesive layer, and the second adhesive layer 53 is a pressure-sensitive adhesive layer. The first adhesive layer 52 is activated in a hot-pressing process of the secondary battery 100 after the electrode assembly 10 is packaged in the shell 20. In this way, the electrode assembly 10 and the shell 20 are not bonded by the first adhesive layer 52 when the shell 20 is packaged, which is conducive to reducing the difficulty of adjusting the position of the electrode assembly 10 when the electrode assembly 10 is installed in the shell 20.

[0102] In some embodiments, the first adhesive layer 52 comprises a styrene-isoprene-styrene block copolymer.

[0103] In some embodiments, the base layer 51 comprises at least one of polyethylene terephthalate, polyimide or polypropylene.

[0104] In some embodiments, the material of the second and third adhesive layers 53 and 54 comprises at least one of polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE) or polyamide.

[0105] In some embodiments, as shown in FIG. 5, the dimension of the shell 20 along the second direction Y is L, and 0.4L≤L2≤0.8L. Setting L2≥0.4L, the dimension of the second adhesive layer 53 along the second direction Y is not too small, which is conducive to increasing the bonding area of the second adhesive layer 53 with the base layer 51 and the electrode assembly 10, on the one hand, to improve the stability of the connection between the electrode assembly 10 and the shell 20, to reduce the possibility that the electrode assembly 10 will impact the top edge position of the shell 20 when the secondary battery 100 falls, and on the other hand, to reduce the moment of stress generated by the vibration of the electrode assembly 10 and the outer edge of the second adhesive layer 53 along the second direction Y when the secondary battery 100 falls, thereby reducing the possibility of tearing of the electrode assembly 10. Setting L2≤0.8L, the dimension of the second adhesive layer 53 along the second direction Y is not too large, on the one hand, which is conducive to saving materials, and on the other hand, which is conducive to reducing the possibility that the second adhesive layer 53 will affect the packaging of the shell 20.

[0106] In some embodiments, the value of L2 is any one of 0.45L, 0.5L, 0.55L, 0.6L, 0.65L, 0.7L or 0.75L.

[0107] In some embodiments, as shown in FIG. 5, 0.4L≤L3≤0.8L. Setting L3≥0.4L, the size of the third adhesive layer 54 along the second direction Y is not too small, which is conducive to increasing the bonding area of the third adhesive layer 54 with the base layer 51 and the electrode assembly 10, on the one hand, improving the stability of the connection between the electrode assembly 10 and the shell 20 to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls, on the other hand, it is conducive to reducing the moment of stress generated by the vibration of the electrode assembly 10 and the outer side edge of the third adhesive layer 54 along the second direction Y, thereby reducing the possibility of tearing of the electrode assembly 10 when the secondary battery 100 falls; setting L3≤0.8L, the size of the third adhesive layer 54 along the second direction Y is not too large, on the one hand, it is conducive to saving materials, on the other hand, it is conducive to reducing the possibility of affecting the packaging of the shell 20 due to the excessive length of the third adhesive layer 54.

[0108] In some embodiments, the value of L3 is any one of 0.45L, 0.5L, 0.55L, 0.6L, 0.65L, 0.7L, 0.75L.

[0109] In some embodiments, 0.95≤L2 / L3≤1.05. Setting 0.95≤L2 / L3≤1.05, the size difference between the second adhesive layer 53 and the third adhesive layer 54 along the second direction Y is not too large, which is conducive to improving the uniformity of the stress on the second adhesive layer 53 and the third adhesive layer 54, and reducing the possibility of damage to the electrode assembly 10 due to the stress being concentrated on one of the second adhesive layer 53 and the third adhesive layer 54.

[0110] In some embodiments, as shown in FIG. 5, the size of the shell 20 along the first direction X is W, the maximum distance of the second adhesive layer 53 and the third adhesive layer 54 along the first direction X is w, and 0.4W≤w≤0.8W. Setting w≥0.4W, the bonding area of the second adhesive layer 53 and the third adhesive layer 54 is not too close to the middle of the electrode assembly 10, which is conducive to reducing the moment of stress generated by the vibration of the electrode assembly 10 and the outer side edge of the second adhesive layer 53 and the third adhesive layer 54 along the first direction X, thereby reducing the possibility of tearing of the electrode assembly 10 when the secondary battery 100 falls; setting w≤0.8W, the distance between the second adhesive layer 53 and the third adhesive layer 54 and the edge of the electrode assembly 10 is not too close, which is conducive to reducing the possibility of affecting the packaging of the shell 20 due to the second adhesive layer 53 and the third adhesive layer 54 being too close to the edge of the electrode assembly 10.

[0111] It should be noted that the maximum distance of the second adhesive layer 53 and the third adhesive layer 54 along the first direction X refers to the distance between the outermost edges of the second adhesive layer 53 and the third adhesive layer 54 along the first direction X. w can be characterized by the distance between the fifth surface 533 and the sixth surface 543 mentioned below. Wherein, "outer side" is relative to the geometric center of the electrode assembly 10.

[0112] In some embodiments, the value of w is any one of 0.45W, 0.5W, 0.55W, 0.6W, 0.65W, 0.7W, 0.75W.

[0113] In some embodiments, as shown in FIG. 5, the second adhesive layer 53 has a first end 531 and a second end 532 oppositely arranged along the second direction Y; the distance of the first end 531 to the first adhesive layer 52 along the second direction Y is D1, and 0.05L2≤D1≤0.3L2. D1≥0.05L2 is set, the distance of the first end 531 to the first adhesive layer 52 is not too small, which is conducive to reducing the stress generated when the secondary battery 100 falls when the first adhesive layer 52 pulls the edge of the second adhesive layer 53 at the first end 531 through the base layer 51, thereby reducing the possibility of damage to the electrode assembly 10; D1≤0.3L2 is set, the distance of the first end 531 to the first adhesive layer 52 is not too large, so as to reduce the compression of the setting space of the first adhesive layer 52, so that the length of the first adhesive layer 52 along the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, and further reducing the possibility of damage to the electrode assembly 10.

[0114] In some embodiments, the value of D1 is any one of 0.1L2, 0.15L2, 0.2L2, 0.25L2.

[0115] In some embodiments, as shown in FIG. 5, the distance of the second end 532 to the first adhesive layer 52 along the second direction Y is D2, and 0.05L2≤D2≤0.3L2. D2≥0.05L2 is set, the distance of the second end 532 to the first adhesive layer 52 is not too small, which is conducive to reducing the stress generated when the secondary battery 100 falls when the first adhesive layer 52 pulls the edge of the second adhesive layer 53 at the second end 532 through the base layer 51, thereby reducing the possibility of damage to the electrode assembly 10; D2≤0.3L2 is set, the distance of the second end 532 to the first adhesive layer 52 is not too large, so as to reduce the compression of the setting space of the first adhesive layer 52, so that the length of the first adhesive layer 52 along the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, and further reducing the possibility of damage to the electrode assembly 10.

[0116] In some embodiments, the value of D2 is any one of 0.1L2, 0.15L2, 0.2L2, 0.25L2.

[0117] In some embodiments, 0.95≤D1 / D2≤1.05. In this way, the difference between D1 and D2 is not too large, and the first end 531 and the second end 532 of the second adhesive layer 53 are symmetrically arranged on both sides of the first adhesive layer 52 along the second direction Y, which is conducive to improving the uniformity of the stress on the second adhesive layer 53 and reducing the possibility of damage to the electrode assembly 10 due to the stress on the first end 531 or the second end 532 when the secondary battery 100 falls.

[0118] In some embodiments, as shown in FIG. 5, the third adhesive layer 54 has a third end 541 and a fourth end 542 arranged opposite along the second direction Y. The distance between the third end 541 and the first adhesive layer 52 along the second direction Y is D3, and 0.05L3≤D3≤0.3L3. By setting D3≥0.05L3, the distance between the third end 541 and the first adhesive layer 52 is not too small, which is conducive to reducing the stress on the edge of the third adhesive layer 54 at the third end 541 caused by the first adhesive layer 52 pulling the third adhesive layer 54 when the secondary battery 100 falls, thereby reducing the possibility of damage to the electrode assembly 10. By setting D3≤0.3L3, the distance between the third end 541 and the first adhesive layer 52 is not too large, so as to reduce the compression of the space for arranging the first adhesive layer 52, so that the length of the first adhesive layer 52 along the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, and further reducing the possibility of damage to the electrode assembly 10.

[0119] In some embodiments, the value of D3 is any one of 0.1L3, 0.15L3, 0.2L3, 0.25L3.

[0120] In some embodiments, as shown in FIG. 5, the fourth end 542 is spaced apart from the first adhesive layer 52 by a distance D4 along the second direction Y, and 0.05L3≤D4≤0.3L3. The distance D4 is set to be greater than or equal to 0.05L3 so that the fourth end 542 is not too close to the first adhesive layer 52, which is conducive to reducing the stress on the third adhesive layer 54 caused by the first adhesive layer 52 pulling the edge of the third adhesive layer 54 at the fourth end 542 when the secondary battery 100 falls, thereby reducing the likelihood of damage to the electrode assembly 10. The distance D4 is set to be less than or equal to 0.3L3 so as to reduce the compression of the space available for the first adhesive layer 52, so that the length of the first adhesive layer 52 along the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the housing 20, reducing the amplitude of the vibration of the electrode assembly 10 when the secondary battery 100 falls, and thereby reducing the likelihood of damage to the electrode assembly 10.

[0121] In some embodiments, the value of D4 is any one of 0.1L3, 0.15L3, 0.2L3, or 0.25L3.

[0122] In some embodiments, 0.95≤D3 / D4≤1.05. In this way, the difference between D3 and D4 is not too large, and the third end 541 and the fourth end 542 of the third adhesive layer 54 are disposed substantially symmetrically on both sides of the first adhesive layer 52 along the second direction Y, which is conducive to improving the uniformity of the stress on the third adhesive layer 54 and reducing the likelihood of damage to the electrode assembly 10 caused by the stress generated when the secondary battery 100 falls being concentrated at the third end 541 or the fourth end 542.

[0123] In some embodiments, as shown in FIG. 4, the first adhesive layer 52 has a third surface 521 and a fourth surface 522 disposed opposite each other along the first direction X, the third surface 521 faces the second adhesive layer 53, and the fourth surface 522 faces the third adhesive layer 54; the second adhesive layer 53 has a fifth surface 533, which is a surface of the second adhesive layer 53 facing away from the first adhesive layer 52 along the first direction X; and the third adhesive layer 54 has a sixth surface 543, which is a surface of the third adhesive layer 54 facing away from the first adhesive layer 52 along the first direction X.

[0124] In some embodiments, as shown in FIG. 4, the fifth face 533 is spaced apart from the sixth face 543 by a distance w, and the third face 521 is spaced apart from the fifth face 533 by a distance w1, 0.1w≤w1≤0.3w. Setting w1≥0.1w, the distance between the third face 521 and the fifth face 533 is not too small, which is conducive to leaving a space on the base layer 51 for arranging the second adhesive layer 53, so that the width of the second adhesive layer 53 along the first direction X is not too small, which is conducive to increasing the stability of the adhesion between the second adhesive layer 53 and the electrode assembly 10, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls; setting w1≤0.3w, the distance between the third face 521 and the fifth face 533 is not too large, which is conducive to leaving a space on the base layer 51 for arranging the first adhesive layer 52, so that the width of the first adhesive layer 52 along the first direction X is not too small, which is conducive to increasing the stability of the adhesion between the first adhesive layer 52 and the shell 20, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls.

[0125] In some embodiments, the value of w1 is any one of 0.15w, 0.2w, 0.25w.

[0126] In some embodiments, as shown in FIG. 4, along the first direction X, the fourth face 522 is spaced apart from the sixth face 543 by a distance w2, 0.1w≤w2≤0.3w. Setting w2≥0.1w, the distance between the fourth face 522 and the sixth face 543 is not too small, which is conducive to leaving a space on the base layer 51 for arranging the third adhesive layer 54, so that the width of the third adhesive layer 54 along the first direction X is not too small, which is conducive to increasing the stability of the adhesion between the third adhesive layer 54 and the electrode assembly 10, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls; setting w2≤0.3w, the distance between the fourth face 522 and the sixth face 543 is not too large, which is conducive to leaving a space on the base layer 51 for arranging the first adhesive layer 52, so that the width of the first adhesive layer 52 along the first direction X is not too small, which is conducive to increasing the stability of the adhesion between the first adhesive layer 52 and the shell 20, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls.

[0127] In some embodiments, the value of w2 is any one of 0.15w, 0.2w, 0.25w.

[0128] In some embodiments, 0.95≤w1 / w2≤1.05. In this way, the difference between w1 and w2 is not too large, which is conducive to improving the symmetry of the second adhesive layer 53 and the third adhesive layer 54 relative to the first adhesive layer 52, and is conducive to improving the uniformity of the stress suffered by the electrode assembly 10 when the secondary battery 100 falls, thereby reducing the possibility of damage to the electrode assembly 10.

[0129] In some embodiments, as shown in FIG. 4, the second adhesive layer 53 has a seventh surface 534 opposite to the fifth surface 533 along the first direction X, and the seventh surface 534 faces the third surface 521. The third adhesive layer 54 has an eighth surface 544 opposite to the sixth surface 543 along the first direction X, and the fourth surface 522 faces the eighth surface 544.

[0130] In some embodiments, as shown in FIG. 4, the distance between the third surface 521 and the seventh surface 534 along the first direction X is h1, and 0.2w1≤h1≤0.5w1. The distance between the third surface 521 and the seventh surface 534 is not too small by setting h1≥0.2w1, which is conducive to reducing the stress generated by the first adhesive layer 52 pulling the second adhesive layer 53 through the base layer 51, and reducing the possibility of damage to the electrode assembly 10. The distance between the third surface 521 and the seventh surface 534 is not too large by setting h1≤0.5w1, which is conducive to leaving space for arranging the first adhesive layer 52, so that the size of the first adhesive layer 52 along the first direction X is not too small, thereby improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, and further reducing the possibility of damage to the electrode assembly 10.

[0131] In some embodiments, the value of h1 is any one of 0.25w1, 0.3w1, 0.35w1, 0.4w1, 0.45w1.

[0132] In some embodiments, as shown in FIG. 4, the distance between the fourth surface 522 and the eighth surface 544 along the first direction X is h2, and 0.2w2≤h2≤0.5w2. The distance between the third surface 521 and the seventh surface 534 is not too small by setting h2≥0.2w2, which is conducive to reducing the stress generated by the first adhesive layer 52 pulling the second adhesive layer 53 through the base layer 51, and reducing the possibility of damage to the electrode assembly 10. The distance between the third surface 521 and the seventh surface 534 is not too large by setting h2≤0.5w2, which is conducive to leaving space for arranging the first adhesive layer 52, so that the size of the first adhesive layer 52 along the first direction X is not too small, thereby improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 falls, and further reducing the possibility of damage to the electrode assembly 10.

[0133] In some embodiments, the value of h2 is any one of 0.25w2, 0.3w2, 0.35w2, 0.4w2, 0.45w2.

[0134] In some embodiments, 0.95≤w1 / w2≤1.05, and 0.95≤h1 / h2≤1.05. In this way, the difference between w1 and w2 is not too large, and the difference between h1 and h2 is not too large, which is conducive to improving the uniformity of the distribution of the first adhesive layer 52, the second adhesive layer 53, and the third adhesive layer 54 along the first direction X, thereby being conducive to improving the uniformity of the stress suffered by the electrode assembly 10 when the secondary battery 100 falls, reducing the possibility that the stress is too concentrated in any one of the first adhesive layer 52, the second adhesive layer 53, and the third adhesive layer 54, thereby reducing the possibility of damage to the electrode assembly 10.

[0135] It should be noted that in the embodiments of the present application, the values of L, L1, L2, L3, W, w, w1, w2, D1, D2, D3, D4, h1, and h2 can be measured by using a vernier caliper. For the dimensions related to the first adhesive 50, the first adhesive 50 can be separated from the case 20 and the electrode assembly 10 for measurement.

[0136] The embodiments of the present application also provide a use electric device 100, which comprises the secondary battery 100 related to any of the foregoing embodiments.

[0137] In some embodiments, the use electric device 100 includes but is not limited to a mobile phone, a notebook computer, an electric toy, and an electric tool.

[0138] To verify the effect of the scheme in the embodiments of the present application on improving the damage to the electrode assembly when the secondary battery falls, the inventors conducted the following experiment, which included 3 control groups and 25 experimental groups, each of which included 50 secondary batteries 100. Each of the secondary batteries 100 was tested after being prepared and falling, and after the test, the secondary battery was disassembled, and the damage to the electrode assembly 10 was observed. Specifically, the tearing of the outermost circle of the electrode assembly 10 (in this experiment, the outermost circle of the secondary battery 100 was the positive electrode sheet 11) was observed, and if there was no tearing, it was recorded as a test pass.

[0139] The preparation process of the secondary battery 100 in Embodiment 1 is as follows:

[0140] (1) Preparation of the positive electrode sheet 11: An active material, lithium cobaltate (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotube), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a positive electrode active material having a solid content of 75 wt%, which was then stirred uniformly. An aluminum foil having a thickness of 10 μm was used as the positive electrode current collector 111. The above active material was uniformly coated on one surface of the positive electrode current collector 111 in the thickness direction using a slot coater, and then dried at 90°C to obtain a positive electrode sheet 11 having the positive electrode active material coated on one surface. At this time, the thickness of the positive electrode active material layer 112 in the thickness direction of the positive electrode current collector 111 was 50 μm. The above coating step was repeated on the other surface of the positive electrode current collector 111 in the thickness direction to obtain a positive electrode sheet 11 having the positive electrode active material layer 112 coated on both surfaces. The coated positive electrode sheet 11 was then cold-pressed, and the thickness of the positive electrode active material layer 112 after cold-pressing was 35 μm. Thereafter, the positive electrode tab 30 was welded to the portion of the positive electrode current collector 111 not covered by the positive electrode active material layer 112.

[0141] (2) Preparation of the negative electrode sheet 12: An active material, artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) were mixed in a weight ratio of 97:0.5:1.3:1.2, and deionized water was added as a solvent to prepare a negative electrode active material having a weight percentage of 50 wt%, which was then stirred uniformly. A copper foil having a thickness of 10 μm was used as the negative electrode current collector 121. The above negative electrode active material was uniformly coated on one surface of the negative electrode current collector 121 in the thickness direction using a slot coater, and then dried at 110°C to obtain a negative electrode sheet 12 having a negative electrode active material layer 122 coated on one surface. At this time, the thickness of the negative electrode active material layer 122 in the thickness direction of the negative electrode current collector 121 was 55 μm. The above step was repeated on the other surface of the negative electrode current collector 121 in the thickness direction to obtain a negative electrode sheet 12 having the negative electrode active material layer 122 coated on both surfaces. The coated negative electrode sheet 12 was cold-pressed, and the thickness of the negative electrode active material layer 122 after cold-pressing was 45 μm. Thereafter, the negative electrode tab 40 was welded to the portion of the negative electrode current collector 121 not covered by the negative electrode active material layer 122.

[0142] (3) Preparation of the electrolyte: In a dry argon atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC: EMC: DEC = 30:50:20 to form a base organic solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) was added to the base organic solvent to be dissolved and mixed uniformly to obtain an electrolyte having a lithium salt concentration of 1.15 mol / L.

[0143] (4) Preparation of the separator: A 7-μm-thick polyethylene porous polymer film was used as the separator.

[0144] (5) Preparation of the electrode assembly 10: The positive electrode sheet 11, the separator 13, and the negative electrode sheet 12 were stacked along the thickness direction of the negative electrode sheet 12 and wound to obtain the electrode assembly 10.

[0145] (6) Assembly of the secondary battery 100: The aluminum plastic film punched into a shape was placed in an assembly jig with the bottom of the pit facing upward, the second adhesive layer 53 and the third adhesive layer 54 of the first adhesive member 50 were adhered to the electrode assembly 10, the electrode assembly 10 was placed in the pit with the first adhesive layer 52 of the first adhesive member 50 facing the bottom of the pit, and an external force was applied to press it. Then, another aluminum plastic film punched into a shape was placed on the electrode assembly 10 with the bottom of the pit facing downward, and the three edges of the two aluminum plastic films were heat-sealed by hot pressing, and the edge that was not heat-sealed was the side where the negative electrode tab 40 and the positive electrode tab 30 protruded out of the case 20. Then, the electrolyte was injected through the edge that was not heat-sealed, and the secondary battery 100 was obtained after the processes of vacuum packaging, standing, hot pressing, and shaping.

[0146] The preparation process of the secondary battery 100 in Comparative Example 1 was basically the same as that of the secondary battery 100 in Example 1, and the difference was that the structure of the adhesive member used to adhere the electrode assembly 10 and the case 20 in Comparative Example 1 was different. For the sake of distinction, the adhesive member used in the secondary battery 100 in Comparative Example 1 was a second adhesive member, which included a second base layer, a fourth adhesive layer, and a fifth adhesive layer. The fourth adhesive layer was a pressure-sensitive adhesive layer, and the fifth adhesive layer was a hot melt adhesive layer. The fourth adhesive layer adhered the electrode assembly and the second base layer, and the fifth adhesive layer adhered the case and the second base layer. The fourth adhesive layer and the fifth adhesive layer were symmetrically arranged on the two surfaces of the second base layer along the thickness direction thereof.

[0147] The preparation methods of the secondary battery 100 in Comparative Examples 2 and 3 were basically the same as that of the secondary battery 100 in Example 1, and the difference was that the length of the first adhesive layer 52 along the second direction in the secondary battery in Comparative Example 2 was greater than the lengths of the second adhesive layer 53 and the third adhesive layer 54 along the second direction. The two ends of the first adhesive layer 52 along the second direction Y both exceeded the second adhesive layer 53 and the third adhesive layer 54, and the length of the excess was 5 mm. In Comparative Example 3, the length of the first adhesive layer along the second direction was equal to the lengths of the second adhesive layer and the third adhesive layer along the second direction.

[0148] The preparation methods of the secondary battery 100 in Examples 2-25 were basically the same as that of the secondary battery 100 in Example 1, and the difference was that the parameters recorded in Table 1 of the secondary battery 100 in Examples 1-25 were different between different groups.

[0149] In Examples 1-25, w1 = w2, L2 = L3, D1 = D3, D2 = D4 for the first adhesive 50, the length L of the case 20 in the second direction Y = 60 mm, and the width W of the case 20 in the first direction X = 50 mm.

[0150] The procedure for the drop test is as follows:

[0151] The secondary battery 100 was fixed in the drop test fixture using double-sided tape, and the six faces of the fixture were numbered A1, A2, A3, A4, A5, and A6 in order, and the four corners of the fixture were numbered C1, C2, C3, and C4 in order.

[0152] The fixture was placed on a test stand 1.8 m high at 25°C, and the lithium ion secondary battery 100 was dropped in order according to the numbers A1-A6, and then the secondary battery 100 was dropped in order according to the numbers C1-C4, and then:

[0153] (1) Whether the case 20 of the lithium ion secondary battery was damaged or the top seal was burst open was observed.

[0154] (2) The electrode assembly 10 was disassembled to observe whether it was damaged.

[0155] If the case 20 of the secondary battery 100 was not damaged, the top seal was not burst open, and the electrode assembly 10 was not damaged, it was considered to have passed the drop test.

[0156] After the test was completed, the experimental results were recorded in Table 1:

[0157] Table 1 Note: In Table 1, " / " indicates that there is no data; the units of L2, w, w1, D1, D2, and h1 are all millimeters (mm).

[0158] As can be seen from Table 1, in Examples 1-25, the length of the first adhesive layer in the second direction Y is less than the length of the second adhesive layer and the third adhesive layer in the second direction Y, and the projection of the first adhesive layer 52 in the third direction Z is separated from the projection of the second adhesive layer 53 and the third adhesive layer 54 in the third direction Z, and the pass rate of the secondary battery 100 in the drop test in Examples 1-25 is higher than that in Comparative Examples 1-3. It can be seen that in the examples of the present application, the projection of the first adhesive layer 52 in the thickness direction of the first adhesive 50 is separated from the projection of the second adhesive layer 53 and the third adhesive layer 54 in the thickness direction of the first adhesive 50, and when the secondary battery 100 falls, the stress generated by the fall is mainly concentrated in the first adhesive layer 52, and in the process of the stress being transmitted from the first adhesive layer 52 to the second adhesive layer 53 and the third adhesive layer 54 through the base layer 51, part of the stress is consumed by the deformation of the base layer 51, thereby reducing the stress borne by the second adhesive layer 53 and the third adhesive layer 54, and further reducing the possibility of damage to the electrode assembly 10 caused by stress when the secondary battery 100 falls; and for the first adhesive layer 52, the stress is mainly concentrated in the edge of the first adhesive layer 52, and the size of the second adhesive layer 53 and the third adhesive layer 54 in the second direction Y is greater than that of the first adhesive layer 52 in the second direction Y, which is conducive to reducing the stress of the edge of the second adhesive layer 53 and the third adhesive layer 54, thereby further reducing the possibility of damage to the electrode assembly 10.

[0159] In Examples 2-4, the value of w1 satisfies 0.1w≤w1≤0.3w, and the value of w2 satisfies 0.1w≤w2≤0.3w, and the pass rate of the secondary battery 100 in the drop test in Examples 2-4 is higher than that in Example 1 and Example 5. It can be seen that setting w1≥0.1w is conducive to leaving a space for setting the second adhesive layer 53 on the base layer 51, increasing the stability of the adhesion between the second adhesive layer 53 and the electrode assembly 10, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls; setting w1≤0.3w is conducive to leaving a space for setting the first adhesive layer 52 on the base layer 51, increasing the stability of the adhesion between the first adhesive layer 52 and the shell 20, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls. Setting w2≥0.1w is conducive to leaving a space for setting the third adhesive layer 54 on the base layer 51, increasing the stability of the adhesion between the third adhesive layer 54 and the electrode assembly 10, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls; setting w2≤0.3w is conducive to leaving a space for setting the first adhesive layer 52 on the base layer 51, increasing the stability of the adhesion between the first adhesive layer 52 and the shell 20, so as to reduce the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 falls.

[0160] In Embodiment 3 and Embodiments 7-8, the value of D1 satisfies 0.05L2≤D1≤0.3L2, and the value of D3 satisfies 0.05L3≤D3≤0.3L3. The secondary battery 100 in Embodiment 3 and Embodiments 7-8 has a higher pass rate in the drop test than Embodiment 6 and Embodiment 9. It can be seen that, by setting D1≥0.05L2, the stress generated by the first adhesive layer 52 pulling the edge of the second adhesive layer 53 at the first end 531 through the base layer 51 when the secondary battery 100 drops is reduced, thereby reducing the possibility of damage to the electrode assembly 10. By setting D1≤0.3L2, the length of the first adhesive layer 52 in the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10. By setting D3≥0.05L3, the stress generated by the first adhesive layer 52 pulling the edge of the third adhesive layer 54 at the third end 541 through the base layer 51 when the secondary battery 100 drops is reduced, thereby reducing the possibility of damage to the electrode assembly 10. By setting D3≤0.3L3, the length of the first adhesive layer 52 in the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10.

[0161] In Embodiment 3 and Embodiments 11-12, the value of D2 satisfies 0.05L2≤D2≤0.3L2, and the value of D4 satisfies 0.05L3≤D4≤0.3L3. The secondary battery 100 in Embodiment 3 and Embodiments 11-12 has a higher pass rate in the drop test than Embodiment 10 and Embodiment 13. It can be seen that, by setting D2≥0.05L2, the stress generated by the first adhesive layer 52 pulling the edge of the second adhesive layer 53 at the second end 532 through the base layer 51 when the secondary battery 100 drops is reduced, thereby reducing the possibility of damage to the electrode assembly 10. By setting D2≤0.3L2, the length of the first adhesive layer 52 in the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10. By setting D4≥0.05L3, the distance between the fourth end 542 and the first adhesive layer 52 is not too small, which is conducive to reducing the stress generated by the first adhesive layer 52 pulling the edge of the third adhesive layer 54 at the fourth end 542 through the base layer 51 when the secondary battery 100 drops, thereby reducing the possibility of damage to the electrode assembly 10. By setting D4≤0.3L3, the length of the first adhesive layer 52 in the second direction Y is not too short, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10.

[0162] In Embodiment 3 and Embodiments 15-16, h1 satisfies 0.2w1≤h1≤0.5w1, h2 satisfies 0.2w2≤h2≤0.5w2, and the passing rate of the secondary battery 100 in the drop test in Embodiment 3 and Embodiments 15-16 is higher than that in Embodiment 14 and Embodiment 17. It can be seen that, by setting h1≥0.2w1, the stress generated by the first adhesive layer 52 pulling the second adhesive layer 53 through the base layer 51 is reduced, and the possibility of damage to the electrode assembly 10 is reduced; by setting h1≤0.5w1, the size of the first adhesive layer 52 in the first direction X is not too small, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10. By setting h2≥0.2w2, the stress generated by the first adhesive layer 52 pulling the second adhesive layer 53 through the base layer 51 is reduced, and the possibility of damage to the electrode assembly 10 is reduced; by setting h2≤0.5w2, the size of the first adhesive layer 52 in the first direction X is not too small, which is conducive to improving the stability of the connection between the electrode assembly 10 and the shell 20, reducing the vibration amplitude of the electrode assembly 10 when the secondary battery 100 drops, and further reducing the possibility of damage to the electrode assembly 10.

[0163] In Embodiments 3 and Embodiments 19-20, L2 satisfies 0.4L≤L2≤0.8L, and L3 satisfies 0.4L≤L3≤0.8L. The passing rate of the secondary battery 100 in the drop test in Embodiments 3 and Embodiments 19-20 is not significantly different from that in Embodiment 18, and is significantly higher than that in Embodiment 21. It can be seen that, by setting L2≥0.4L, the bonding area of the second adhesive layer 53 and the base layer 51 and the electrode assembly 10 is increased, which on the one hand reduces the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 drops, and on the other hand reduces the possibility of the electrode assembly 10 being torn; by setting L2≤0.8L, the passing rate of the secondary battery 100 in the drop test and the material cost are considered. By setting L3≥0.4L, the bonding area of the third adhesive layer 54 and the base layer 51 and the electrode assembly 10 is increased, which on the one hand reduces the possibility of the electrode assembly 10 impacting the top sealing position of the shell 20 when the secondary battery 100 drops, and on the other hand reduces the possibility of the electrode assembly 10 being torn; by setting L3≤0.8L, the passing rate of the secondary battery 100 in the drop test and the material cost are considered.

[0164] In Embodiments 3 and 23-24, w satisfies 0.4W≤w≤0.8W, the pass rate of the secondary battery 100 in the drop test in Embodiments 3 and 23-24 is obviously different from that in Embodiment 22, and is obviously higher than that in Embodiment 25. It can be seen that, by setting w≥0.4W, the stress generated by the vibration of the electrode assembly 10 when the secondary battery 100 drops and the moment of force of the second adhesive layer 53 and the third adhesive layer 54 along the outer side edge in the first direction X are reduced, thereby reducing the possibility of tearing of the electrode assembly 10; by setting w≤0.8W, the pass rate of the secondary battery 100 in the drop test and the packaging success rate of the shell 20 are taken into account.

[0165] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as a limitation to the present application, and as long as the above embodiments are within the spirit and scope of the present application, any suitable changes and variations made to the above embodiments are within the disclosure range of the present application.

Claims

1. A secondary battery (100) characterized by comprising: The application relates to a shell (20), an electrode assembly (10) accommodated in the shell (20), a first adhesive member (50) comprising a base layer (51), a first adhesive layer (52), a second adhesive layer (53) and a third adhesive layer (54), the base layer (51) comprising a first surface (511) and a second surface (512) oppositely arranged along the thickness direction of the first adhesive member (50), the first adhesive layer (52) being arranged on the first surface (511), the second adhesive layer (53) and the third adhesive layer (54) being arranged on the second surface (512), the first adhesive layer (52) bonding the shell (20) and the base layer (51), the second adhesive layer (53) and the third adhesive layer (54) both bonding the electrode assembly (10) and the base layer (51), the second adhesive layer (53), the first adhesive layer (52) and the third adhesive layer (54) being sequentially arranged along a first direction (X) perpendicular to the thickness direction of the first adhesive member (50), the projection of the first adhesive layer (52) being separated from the projection of the second adhesive layer (53) and the projection of the third adhesive layer (54) along the thickness direction of the first adhesive member (50), the size of the first adhesive layer (52) along a second direction (Y) being L1, the size of the second adhesive layer (53) along the second direction (Y) being L2, the size of the third adhesive layer (54) along the second direction (Y) being L3, L1 < L2 and L1 < L3, both ends of the second adhesive layer (53) along the second direction (Y) exceeding the first adhesive layer (52), and both ends of the third adhesive layer (54) along the second direction (Y) exceeding the first adhesive layer (52), the second direction (Y) being perpendicular to the first direction (X) and the thickness direction of the first adhesive member (50). The size of the shell (20) along the second direction (Y) is L, 0.4L <= L2 <= 0.8L, and / or 0.4L <= L3 <= 0.8L. 0.95 <= L2 / L3 <= 1.

05. The size of the shell (20) along the first direction (X) is W, the maximum distance of the second adhesive layer (53) and the third adhesive layer (54) along the first direction (X) is w, 0.4W <= w <= 0.8W. The second adhesive layer (53) has a first end (531) and a second end (532) oppositely arranged along the second direction (Y), the distance of the first end (531) to the first adhesive layer (52) along the second direction (Y) is D1, the distance of the second end (532) to the first adhesive layer (52) along the second direction (Y) is D2, D1 and D2 satisfying at least one of the following conditions a, b and c:

2. The secondary battery (100) according to claim 1, characterized by a, 0.05L2 <= D1 <= 0.3L2; 3. The secondary battery (100) according to claim 1 or 2, characterized by b, 0.05L2 <= D2 <= 0.3L2; 4. The secondary battery (100) according to any one of claims 1 to 3, characterized by c, 0.95 <= D1 / D2 <= 1.

05.

5. The secondary battery (100) according to any one of claims 1 to 4, characterized by ​ ​ ​ ​ 6. The secondary battery (100) according to any one of claims 1 to 5, characterized by The third adhesive layer (54) has a third end (541) and a fourth end (542) oppositely arranged along the second direction (Y); the distance from the third end (541) to the first adhesive layer (52) along the second direction (Y) is D3, and the distance from the fourth end (542) to the first adhesive layer (52) along the second direction (Y) is D4, D3 and D4 satisfy at least one of conditions d, e, f: d, 0.05L3≤D3≤0.3L3; e, 0.05L3≤D4≤0.3L3; f, 0.95≤D3 / D4≤1.

05.

7. The secondary battery (100) according to any one of claims 1 to 6, characterized by The first adhesive layer (52) has a third face (521) and a fourth face (522) oppositely arranged along the first direction (X), the third face (521) faces the second adhesive layer (53), and the fourth face (522) faces the third adhesive layer (54); the second adhesive layer (53) has a fifth face (533), which is the surface of the second adhesive layer (53) facing away from the first adhesive layer (52) along the first direction (X), and the third adhesive layer (54) has a sixth face (543), which is the surface of the third adhesive layer (54) facing away from the first adhesive layer (52) along the first direction (X); Along the first direction (X), the distance between the fifth face (533) and the sixth face (543) is w, the distance between the third face (521) and the fifth face (533) is w1, and the distance between the fourth face (522) and the sixth face (543) is w2, w, w1 and w2 satisfy at least one of conditions g, h, i: g, 0.1w≤w1≤0.3w, h, 0.1w≤w2≤0.3w, i, 0.95≤w1 / w2≤1.

05.

8. The secondary battery (100) according to any one of claims 1-7, characterized in that, The first adhesive layer (52) has a third face (521) and a fourth face (522) oppositely arranged along the first direction (X), the third face (521) faces the second adhesive layer (53), and the fourth face (522) faces the third adhesive layer (54); the second adhesive layer (53) has a fifth face (533) and a seventh face (534) oppositely arranged along the first direction (X), the seventh face (534) faces the third face (521); the third adhesive layer (54) has an eighth face (544) and a sixth face (543) oppositely arranged along the first direction (X), the second face (512) faces the eighth face (544); Along the first direction (X), the distance between the fifth face (533) and the third face (521) is w1, the distance between the third face (521) and the seventh face (534) is h1, the distance between the fourth face (522) and the sixth face (543) is w2, and the distance between the fourth face (522) and the eighth face (544) is h2; w1, w2, h1, h2 satisfy one of conditions j, k: j, 0.2w1≤h1≤0.5w1; k, 0.2w2≤h2≤0.5w2.

9. The secondary battery (100) according to claim 8, characterized in that 0.95≤w1 / w2≤1.05, 0.95≤h1 / h2≤1.

05.

10. An electrical consumer (100), characterized in that A secondary battery (100) as claimed in any one of claims 1 to 9.

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