Secondary battery and electronic device

Abstract

The invention relates to a secondary battery and electronic equipment, the secondary battery comprises a shell and an electrode assembly arranged in the shell, the shell comprises a first wall, a second wall and a third wall which are connected in sequence, and the first wall and the third wall are oppositely arranged along the thickness direction of the electrode assembly. A first bonding piece is arranged between the electrode assembly and the shell, the first bonding piece comprises a first part, a second part and a third part which are connected in sequence, the first part is bonded to the first wall, the second part is located between the second wall and the electrode assembly, the third part is bonded to the third wall, and the bonding strength between the first part and the first wall is 100 N / m or above; the adhesive strength between the third portion and the third wall is 100 N / m or more, and the adhesive strength between the first adhesive and the electrode assembly is 14 N / m or less. According to the secondary battery and the electronic equipment, the problem that the shell is damaged in the falling or vibration process of the secondary battery can be solved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] As the power source of electronic devices, secondary batteries are the key to ensuring the normal use of electronic devices. In actual application, there is inevitably the possibility of falling or repeated vibration. During this process, the electrode assembly and the shell of the secondary battery will produce relative movement, and the electrode assembly will impact the shell, causing the shell to be damaged and the secondary battery to leak and fail. Summary of the invention

[0003] The inventor of the present application has found that when a secondary battery is dropped or vibrated, the electrode assembly is likely to impact the shell, causing the shell to break and the secondary battery to leak and fail. Although the problem of shell rupture can be improved by thickening the shell to improve the shell's anti-deformation ability, this method will increase the volume of the secondary battery, thereby losing energy density.

[0004] The purpose of the present application is to provide a secondary battery and an electronic device, aiming to improve the problem of shell damage of the secondary battery during falling or vibration.

[0005] According to the first aspect of the present application, a secondary battery is provided, comprising a shell and an electrode assembly arranged in the shell, the shell comprising a first wall, a second wall and a third wall connected in sequence, and the first wall and the third wall are arranged oppositely along the thickness direction of the electrode assembly. A first adhesive is arranged between the electrode assembly and the shell, the first adhesive comprises a first part, a second part and a third part connected in sequence, the first part is bonded to the first wall, the second part is located between the second wall and the electrode assembly, the third part is bonded to the third wall, the bonding strength between the first part and the first wall is 100N / m or more, the bonding strength between the third part and the third wall is 100N / m or more, and the bonding strength between the first adhesive and the electrode assembly is 14N / m or less. Wherein, the bonding strength of 100N / m or more means that the bonding strength is greater than or equal to 100N / m, and the bonding strength of 14N / m or less means that the bonding strength is less than or equal to 14N / m.

[0006] In the above technical solution, a first adhesive is arranged between the electrode assembly and the shell, and the bonding strength between the first part and the first wall is greater than 100 N / m, and the bonding strength between the third part and the third wall is greater than 100 N / m. When the secondary battery falls or vibrates, the electrode assembly will first impact the first adhesive. The strength of the first adhesive itself and the bonding shear strength formed with the shell can absorb the impact energy of the first adhesive to buffer the impact of the electrode assembly and produce the effect of restraining the electrode assembly, thereby reducing the possibility of the electrode assembly impacting the shell and causing damage to the shell. If the first adhesive has a strong bonding strength with the electrode assembly at the same time, the impact of the electrode assembly will be directly transmitted back to the electrode assembly through the first adhesive. The electrode assembly has insufficient anti-adhesive shear strength, the electrode sheet of the electrode assembly will be deformed, and the metal foil of the electrode sheet current collector will be torn, thereby piercing the diaphragm, forming a short circuit, and causing the voltage drop failure to deteriorate significantly. Therefore, the bonding strength between the first adhesive and the electrode assembly is limited to less than 14 N / m, so that the first adhesive and the electrode assembly can be easily debonded during the falling process, thereby reducing the possibility of the first adhesive transmitting the impact back to the electrode assembly.

[0007] In some preferred embodiments, along the thickness direction of the electrode assembly, the outer surface of the electrode assembly has a first angle and a second angle relative to each other, the projection of the first part on the outer surface of the electrode assembly covers the first angle, and the projection of the third part on the outer surface of the electrode assembly covers the second angle. In this way, when the secondary battery is dropped or vibrated, the first angle and the second angle of the electrode assembly will first impact the first adhesive member to reduce the possibility of the first angle and the second angle impacting the shell.

[0008] In some preferred embodiments, along the length and / or width direction of the electrode assembly, the projection of the first adhesive on the outer surface of the electrode assembly covers the first angle position to reduce the possibility of the first angle position impacting the shell. And / or, along the length and / or width direction of the electrode assembly, the projection of the first adhesive on the outer surface of the electrode assembly covers the second angle position to reduce the possibility of the second angle position impacting the shell.

[0009] In some preferred embodiments, the tensile strength of the first adhesive is T1, 80Mpa≤T1≤300Mpa. If the tensile strength of the first adhesive is less than 80Mpa, the first adhesive is easy to break, and it is difficult to reduce the possibility of shell damage. If the tensile strength of the first adhesive is greater than 300Mpa, the first adhesive is a rigid body, it is difficult to absorb the impulse of the electrode assembly, and it will rebound to the electrode assembly, the electrode assembly is deformed by force, resulting in a short circuit point inside, resulting in a significant deterioration of the voltage drop failure.

[0010] In some preferred embodiments, 100Mpa≤T1≤200Mpa, which can further balance the fracture resistance and rigidity of the first adhesive component, so as to further balance the problem of shell breakage when the secondary battery is dropped and the problem of failure due to drop voltage drop.

[0011] In some preferred embodiments, the bonding strength between the first part and the electrode assembly is 0N / m to reduce the possibility that the first part transmits the impact back to the electrode assembly. And / or, the bonding strength between the second part and the electrode assembly is 0N / m to reduce the possibility that the second part transmits the impact back to the electrode assembly. And / or, the bonding strength between the third part and the electrode assembly is 0N / m to reduce the possibility that the third part transmits the impact back to the electrode assembly. It should be noted that the bonding strength of 0N / m is a measured value under ideal conditions. There may be errors in actual conditions, and the bonding strength between the two objects may be a non-zero value close to 0N / m.

[0012] In some preferred embodiments, the bonding strength between the second part and the second wall is 0 N / m. If the second part is bonded to the second wall, the first adhesive and the shell are likely to form an integrated structure, reducing the buffering effect of the first adhesive on the electrode assembly and increasing the possibility of shell damage. Limiting the bonding strength between the second part and the second wall to 0 N / m can enhance the buffering effect of the first adhesive on the electrode assembly and reduce the possibility of shell damage.

[0013] In some preferred embodiments, along the width direction of the electrode assembly, the width of the electrode assembly is W1, the length of the first adhesive is L1, and 1 / 3≤L1 / W1≤1. Increasing the length of the first adhesive can increase the force-bearing area of ​​the first adhesive and improve its ability to resist impact damage to the electrode assembly. If L1 / W1<1 / 3, the first adhesive is easy to break and lose the effect of binding the electrode assembly.

[0014] In some preferred embodiments, along the length direction of the electrode assembly, the width of the first part is W2, 5mm≤W2≤20mm. Increasing the width of the first part can increase the bonding area between the first adhesive and the shell, increase the adhesive shear force, and enhance the binding effect on the electrode assembly. If W2<5mm, the first part and the shell are easily debonded under the impact of the electrode assembly, and the binding effect is lost. If W2>20mm, the first adhesive has a more serious loss on the energy density of the secondary battery.

[0015] In some preferred embodiments, along the length direction of the electrode assembly, the width of the third part is W3, 5mm≤W3≤20mm. Increasing the width of the third part can increase the bonding area between the first adhesive and the shell, increase the adhesive shear force, and enhance the binding effect on the electrode assembly. If W3<5mm, under the impact of the electrode assembly, the third part and the shell are easily debonded and lose the binding effect. If W3>20mm, the first adhesive has a more serious loss on the energy density of the secondary battery.

[0016] In some preferred embodiments, the secondary battery includes a tab connected to the electrode assembly, and the tab extends out of the shell along the length direction of the electrode assembly. Since the electrode assembly is more likely to damage the shell when the tab extends out of the shell, the first adhesive is limited to be arranged along the direction in which the tab extends out of the shell, which can reduce the possibility of the electrode assembly impacting the shell in the direction in which the tab extends out of the shell, causing damage to the shell.

[0017] In some preferred embodiments, the first adhesive member includes a first adhesive layer, a first substrate layer, and a second adhesive layer stacked in sequence.

[0018] In some preferred embodiments, the thickness of the first adhesive is H1, 10 μm ≤ H1 ≤ 30 μm. If H1 ≥ 10 μm, the first adhesive has good tensile strength and wear resistance. If H1 > 30 μm, the first adhesive causes a serious loss in the energy density of the secondary battery.

[0019] In some preferred embodiments, the secondary battery further comprises an electrolyte disposed in the housing, and the first adhesive is separated from the electrode assembly after being soaked in the electrolyte.

[0020] In some preferred embodiments, a second adhesive is provided between the electrode assembly and the shell, and the second adhesive includes a fourth part, a fifth part, and a sixth part connected in sequence, the fourth part is bonded to the first wall, the fifth part is located between the second wall and the electrode assembly, and the sixth part is bonded to the third wall. Along the thickness direction of the electrode assembly, the outer surface of the electrode assembly has a relative third angle and a fourth angle, the projection of the fourth part on the outer surface of the electrode assembly covers the third angle, and the projection of the sixth part on the outer surface of the electrode assembly covers the fourth angle. The second adhesive can enhance the binding effect on the electrode assembly.

[0021] In some preferred embodiments, the housing further comprises a fourth wall, the two sides of the fourth wall are respectively connected to the first wall and the third wall, the fourth wall and the second wall are arranged opposite to each other along the length direction of the electrode assembly, a third adhesive is arranged between the electrode assembly and the housing, the third adhesive comprises a seventh part, an eighth part and a ninth part connected in sequence, the seventh part is bonded to the first wall, the eighth part is located between the fourth wall and the electrode assembly, and the ninth part is bonded to the third wall. In combination with the first adhesive and the third adhesive, the binding effect on the electrode assembly can be improved in the length direction of the electrode assembly.

[0022] In some preferred embodiments, the housing further comprises a fifth wall, which is respectively connected to the first wall, the second wall and the third wall. A fourth adhesive is provided between the electrode assembly and the housing, and the fourth adhesive comprises a tenth part, an eleventh part and a twelfth part connected in sequence, the tenth part is bonded to the first wall, the eleventh part is located between the fifth wall and the electrode assembly, and the twelfth part is bonded to the third wall. The fourth adhesive can enhance the binding effect on the electrode assembly in the width direction of the electrode assembly.

[0023] In a second aspect, the present application further proposes an electronic device, comprising a secondary battery as in any embodiment of the first aspect above.

[0024] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the subsequent description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] One or more embodiments are exemplarily described by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the dimensions in the drawings do not constitute proportional limitations.

[0026] Figure 1 A schematic diagram of the structure of a secondary battery in some embodiments of the present application;

[0027] Figure 2 This is a schematic diagram of the structure of the electrode assembly of some embodiments of the present application;

[0028] Figure 3 A schematic diagram of the structure of a secondary battery in some embodiments of the present application in the width direction of an electrode assembly;

[0029] Figure 4 A schematic diagram of the structure of a secondary battery in the thickness direction of an electrode assembly according to some embodiments of the present application;

[0030] Figure 5 A schematic diagram of the structure of a secondary battery in the thickness direction of an electrode assembly according to some embodiments of the present application;

[0031] Figure 6 A schematic structural diagram of a first adhesive member in some embodiments of the present application;

[0032] Figure 7 A schematic diagram of the structure of a secondary battery in some embodiments of the present application in the width direction of an electrode assembly;

[0033] Figure 8 A schematic diagram of the structure of a secondary battery in the thickness direction of an electrode assembly according to some embodiments of the present application;

[0034] Fig. 9 A schematic diagram of the structure of a secondary battery in the thickness direction of an electrode assembly according to some embodiments of the present application;

[0035] Fig.10 A schematic diagram of the structure of a secondary battery in some embodiments of the present application in the width direction of an electrode assembly;

[0036] Fig.11 A schematic diagram of the structure of a secondary battery in the thickness direction of an electrode assembly according to some embodiments of the present application;

[0037] Fig.12 A schematic diagram of the structure of a secondary battery in the length direction of an electrode assembly according to some embodiments of the present application;

[0038] Fig.13 This is a schematic diagram of the structure of a secondary battery in the thickness direction of the electrode assembly of some embodiments of the present application.

[0039] Description of reference numerals:

[0040] 100. Secondary battery;

[0041] 10. Shell; 11. First wall; 12. Second wall; 13. Third wall; 14. Fourth wall; 15. Fifth wall;

[0042] 20, electrode assembly; 20a, pole ear; 21, positive electrode sheet; 22, negative electrode sheet; 23, separator; 24, first angle position; 25, second angle position; 26, third angle position; 27, fourth angle position;

[0043] 30. first adhesive member; 31. first portion; 32. second portion; 33. third portion; 34. first substrate layer; 35. first adhesive layer; 36. second adhesive layer;

[0044] 40. second adhesive member; 41. fourth portion; 42. fifth portion; 43. sixth portion;

[0045] 50. third adhesive member; 51. seventh portion; 52. eighth portion; 53. ninth portion;

[0046] 60. fourth adhesive member; 61. tenth portion; 62. eleventh portion; 63. twelfth portion;

[0047] X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly 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, not all of the embodiments.

[0049] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0050] In the description of the embodiments of the present application, the technical terms "first", "second", etc. 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 indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0051] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0052] The term "perpendicular" is used to describe the ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular between the two components. For example, in combination with numerical descriptions, perpendicularity can refer to the angle between two straight lines being between 90±10°, perpendicularity can also refer to the dihedral angle between two planes being between 90±10°, and perpendicularity can also refer to the angle between a straight line and a plane being between 90±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if the overall extension direction is a straight line or a plane.

[0053] The first direction X, the second direction Y and the third direction Z of the present application are bidirectional directions, that is, the first direction X includes the direction indicated by the arrow in the drawing and the opposite direction thereof, the second direction Y includes the direction indicated by the arrow in the drawing and the opposite direction thereof, and the third direction Z includes the direction indicated by the arrow in the drawing and the opposite direction thereof.

[0054] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0055] In the first aspect, the embodiment of the present application provides a secondary battery 100, please refer to Figure 1 The secondary battery 100 includes a housing 10, an electrode assembly 20 and a tab 20a. The housing 10 can accommodate the electrode assembly 20 and an electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 20 in the housing 10. The tab 20a is connected to the electrode assembly 20. The tab 20a extends out of the housing 10 in the length direction (second direction Y) of the electrode assembly 20 to assist the electrode assembly 20 in energy transmission with an external electronic device.

[0056] For the electrode assembly 20, please refer to Figure 2 , Figure 2 The lamination structure of the electrode assembly 20 is shown. The electrode assembly 20 includes a negative electrode sheet 22, a positive electrode sheet 21 and a separator 23. The positive electrode sheet 21 and the negative electrode sheet 22 are alternately stacked. A separator 23 is provided between adjacent positive electrode sheets 21 and negative electrode sheets 22. The separator 23 is used to insulate and separate the positive electrode sheet 21 and the negative electrode sheet 22. In the embodiment of the present application, the electrode assembly 20 is described as a lamination structure as an example. In some other embodiments, the electrode assembly 20 may also be a winding structure. For example, the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22 are sequentially stacked and then wound to form a wound electrode assembly 20.

[0057] When the secondary battery 100 is dropped or vibrated, the electrode assembly 20 is likely to impact the housing 10, causing the housing 10 to break and the secondary battery 100 to leak and fail. Although the problem of housing 10 rupture can be improved by thickening the housing 10 to improve its anti-deformation ability, this method will increase the volume of the secondary battery 100, thereby losing energy density.

[0058] To improve the above problems, in the embodiments of this application, please refer to Figure 3The housing 10 includes a first wall 11, a second wall 12 and a third wall 13 connected in sequence, and the first wall 11 and the third wall 13 are arranged opposite to each other along the thickness direction (first direction X) of the electrode assembly 20. A first adhesive member 30 is arranged between the electrode assembly 20 and the housing 10, and the first adhesive member 30 includes a first portion 31, a second portion 32 and a third portion 33 connected in sequence, the first portion 31 is bonded to the first wall 11, the second portion 32 is located between the second wall 12 and the electrode assembly 20, and the third portion 33 is bonded to the third wall 13, the bonding strength between the first portion 31 and the first wall 11 is greater than 100 N / m, the bonding strength between the third portion 33 and the third wall 13 is greater than 100 N / m, and the bonding strength between the first adhesive member 30 and the electrode assembly 20 is less than 14 N / m.

[0059] By setting the first adhesive 30 between the electrode assembly 20 and the shell 10, the bonding strength between the first part 31 and the first wall 11 is greater than 100 N / m, and the bonding strength between the third part 33 and the third wall 13 is greater than 100 N / m. When the secondary battery 100 falls or vibrates, the electrode assembly 20 will first impact the first adhesive 30. The strength of the first adhesive 30 itself and the bonding shear strength formed with the shell 10 can absorb the impact energy of the first adhesive 30 to buffer the impact of the electrode assembly 20, produce the effect of restraining the electrode assembly 20, and thereby reduce the possibility of the electrode assembly 20 impacting the shell 10 and causing damage to the shell 10. If the first adhesive 30 and the electrode assembly 20 have strong bonding strength at the same time, the impact of the electrode assembly 20 will be directly transmitted back to the electrode assembly 20 through the first adhesive 30, the electrode assembly 20 has insufficient anti-adhesive shear strength, the electrode sheet of the electrode assembly 20 will be deformed, the collector metal foil of the electrode sheet will be torn, and then pierce the diaphragm 23, forming a short circuit, resulting in a significant deterioration of the voltage drop failure. Therefore, the bonding strength between the first adhesive 30 and the electrode assembly 20 is limited to 14N / m or less, so that the first adhesive 30 and the electrode assembly 20 can be easily debonded during the drop process, reducing the possibility of the first adhesive 30 transmitting the impact back to the electrode assembly 20. Among them, the bonding strength refers to the stress required to cause the adhesive in the adhesive to be damaged at the interface or its vicinity with the bonded material under the action of external force, which is used to characterize the bonding effect of the interface between the adhesive and the bonded material.

[0060] In some embodiments, the bonding strength between the first portion 31 and the first wall 11 may be 100 N / m, 102 N / m, 150 N / m, 200 N / m, 250 N / m, 300 N / m, 330 N / m, 400 N / m, 480 N / m, 500 N / m, 1000 N / m, or a range consisting of any two of these values, and the bonding strength between the first portion 31 and the first wall 11 may also be greater than 1000 N / m. The bonding strength between the third portion 33 and the third wall 13 may be 100 N / m, 102 N / m, 150 N / m, 200 N / m, 250 N / m, 300 N / m, 330 N / m, 400 N / m, 480 N / m, 500 N / m, 1000 N / m, or a range consisting of any two of these values. The bonding strength between the first adhesive 30 and the electrode assembly 20 may be 14 N / m, 13 N / m, 12 N / m, 11 N / m, 10 N / m, 5 N / m, 0 N / m, or a range consisting of any two of these values.

[0061] In some embodiments, please refer to Figures 3 to 5 , along the thickness direction of the electrode assembly 20, the outer surface of the electrode assembly 20 has a first angle 24 and a second angle 25 relative to each other, the projection of the first portion 31 on the outer surface of the electrode assembly 20 covers the first angle 24, and the projection of the third portion 33 on the outer surface of the electrode assembly 20 covers the second angle 25. In this way, when the secondary battery 100 is dropped or vibrated, the first angle 24 and the second angle 25 of the electrode assembly 20 will impact the first adhesive 30 first, so as to reduce the possibility that the first angle 24 and the second angle 25 impact the housing 10.

[0062] In the embodiment of the present application, the corner position of the outer surface of the electrode assembly 20 refers to the area near the intersection of each adjacent side of the outer surface of the electrode assembly 20. Since an angle is formed between two adjacent sides, the area near the intersection is called the corner position. Taking the rectangular parallelepiped electrode assembly 20 as an example, the outer surface of the electrode assembly 20 is a rectangle, then it has 4 corner positions, and the 4 corner positions are respectively located near the intersection of each two adjacent sides of the rectangle. The rectangular parallelepiped electrode assembly 20 has a total of 8 corner positions.

[0063] In some embodiments, the number of the first adhesive members 30 may be more than two, for example, the number of the first adhesive members 30 may be the same as the number of the corners of the electrode assembly 20, and one first adhesive member 30 covers one corner of the electrode assembly 20. For another example, more than two first adhesive members 30 may be spaced and / or arranged relative to each other in the length and / or width direction of the electrode assembly 20.

[0064] In some embodiments, the tensile strength of the first adhesive 30 is T1, 80Mpa≤T1≤300Mpa. If the tensile strength of the first adhesive 30 is less than 80Mpa, the first adhesive 30 is easy to break, and it is difficult to reduce the possibility of damage to the shell 10. If the tensile strength of the first adhesive 30 is greater than 300Mpa, the first adhesive 30 is a rigid body, it is difficult to absorb the impulse of the electrode assembly 20, and it will rebound to the electrode assembly 20, the electrode assembly 20 is deformed by force, resulting in a short circuit point inside, resulting in a significant deterioration of the voltage drop failure. Among them, the tensile strength refers to the maximum bearing capacity of the material under static tensile conditions, which is used to characterize the tensile effect of the material.

[0065] In some embodiments, 100 MPa≤T1≤200 MPa, which can further balance the fracture resistance and rigidity of the first adhesive 30 , so as to further balance the breakage problem of the secondary battery 100 falling off the housing 10 and the failure problem of falling voltage drop.

[0066] In some embodiments, the tensile strength T1 of the first adhesive 30 may be 80 MPa, 90 MPa, 100 MPa, 113 MPa, 150 MPa, 200 MPa, 223 MPa, 250 MPa, 300 MPa or a range consisting of any two of these values.

[0067] In some embodiments, the bonding strength between the first portion 31 and the electrode assembly 20 is 0 N / m to reduce the possibility that the first portion 31 transmits impact back to the electrode assembly 20 .

[0068] In some embodiments, the bonding strength between the third portion 33 and the electrode assembly 20 is 0 N / m to reduce the possibility that the third portion 33 transmits impact back to the electrode assembly 20 .

[0069] In some embodiments, the bonding strength between the second portion 32 and the second wall 12 is 0 N / m. If the second portion 32 is bonded to the second wall 12, the first adhesive 30 and the housing 10 are easily integrated, which reduces the buffering effect of the first adhesive 30 on the electrode assembly 20 and increases the possibility of damage to the housing 10. Limiting the bonding strength between the second portion 32 and the second wall 12 to 0 N / m can enhance the buffering effect of the first adhesive 30 on the electrode assembly 20 and reduce the possibility of damage to the housing 10.

[0070] In some embodiments, please refer to Figure 4, along the width direction of the electrode assembly 20 (third direction Z), the width of the electrode assembly 20 is W1, the length of the first adhesive 30 is L1, and 1 / 3≤L1 / W1≤1. Increasing the length of the first adhesive 30 can increase the force-bearing area of ​​the first adhesive 30 and improve its ability to resist impact damage to the electrode assembly 20. If L1 / W1<1 / 3, the first adhesive 30 is easy to break and loses the effect of binding the electrode assembly 20.

[0071] In some embodiments, along the length direction of the electrode assembly 20, the width of the first portion 31 is W2, 5mm≤W2≤20mm. Increasing the width of the first portion 31 can increase the bonding area between the first adhesive 30 and the shell 10, increase the adhesive shear force, and enhance the binding effect on the electrode assembly 20. If W2<5mm, under the impact of the electrode assembly 20, the first portion 31 and the shell 10 are easily debonded and lose the binding effect. If W2>20mm, the first adhesive 30 causes a more serious loss of energy density of the secondary battery 100.

[0072] In some embodiments, please refer to Figure 5 , along the length direction of the electrode assembly 20, the width of the third part 33 is W3, 5mm≤W3≤20mm. Increasing the width of the third part 33 can increase the bonding area between the first adhesive 30 and the shell 10, increase the adhesive shear force, and enhance the binding effect on the electrode assembly 20. If W3<5mm, under the impact of the electrode assembly 20, the third part 33 and the shell 10 are easily debonded and lose the binding effect. If W3>20mm, the first adhesive 30 causes a serious loss in the energy density of the secondary battery 100.

[0073] In some embodiments, please refer to Figure 6 The first adhesive member 30 includes a first adhesive layer 35, a first base material layer 34, and a second adhesive layer 36 stacked in sequence. The first base material layer 34 includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, the first adhesive layer 35 includes at least one of polypropylene, elastomeric polyurethane, filler titanium dioxide, and antioxidant diphenylamine, and the second adhesive layer 36 includes at least one of polypropylene, elastomeric polyurethane, filler titanium dioxide, and antioxidant diphenylamine.

[0074] In some embodiments, the thickness of the first adhesive 30 is H1, 10 μm ≤ H1 ≤ 30 μm. If H1 ≥ 10 μm, the first adhesive 30 has good tensile strength and wear resistance. If H1 > 30 μm, the first adhesive 30 causes a serious loss in the energy density of the secondary battery 100.

[0075] In some embodiments, the thickness H1 of the first adhesive member 30 is 20 μm, the thickness of the first substrate layer 34 is 12 μm, the thickness of the first adhesive layer 35 is 4 μm, and the thickness of the second adhesive layer 36 is 4 μm.

[0076] In some embodiments, the secondary battery 100 further includes an electrolyte disposed in the housing 10 , and the first adhesive 30 is separated from the electrode assembly 20 after being soaked in the electrolyte.

[0077] In some embodiments, please refer to Figures 7 to 9 A second adhesive member 40 is provided between the electrode assembly 20 and the shell 10. The second adhesive member 40 includes a fourth portion 41, a fifth portion 42, and a sixth portion 43 connected in sequence. The fourth portion 41 is bonded to the first wall 11, the fifth portion 42 is located between the second wall 12 and the electrode assembly 20, and the sixth portion 43 is bonded to the third wall 13. Along the thickness direction of the electrode assembly 20, the outer surface of the electrode assembly 20 has a third angle 26 and a fourth angle 27 relative to each other. The projection of the fourth portion 41 on the outer surface of the electrode assembly 20 covers the third angle 26, and the projection of the sixth portion 43 on the outer surface of the electrode assembly 20 covers the fourth angle 27. The second adhesive member 40 can enhance the binding effect on the electrode assembly 20.

[0078] In some embodiments, the bonding strength between the fourth part 41 and the first wall 11 is greater than 100 N / m, the bonding strength between the sixth part 43 and the third wall 13 is greater than 100 N / m, and the bonding strength between the second adhesive 40 and the electrode assembly 20 is less than 14 N / m.

[0079] In some embodiments, please refer to Figure 10 to Figure 11 The housing 10 further includes a fourth wall 14, the two sides of which are connected to the first wall 11 and the third wall 13 respectively, the fourth wall 14 and the second wall 12 are arranged opposite to each other along the length direction of the electrode assembly 20, a third adhesive 50 is arranged between the electrode assembly 20 and the housing 10, and the third adhesive 50 includes a seventh portion 51, an eighth portion 52 and a ninth portion 53 connected in sequence, the seventh portion 51 is bonded to the first wall 11, the eighth portion 52 is located between the fourth wall 14 and the electrode assembly 20, and the ninth portion 53 is bonded to the third wall 13. In combination with the first adhesive 30 and the third adhesive 50, the binding effect on the electrode assembly 20 can be improved in the length direction of the electrode assembly 20.

[0080] In some embodiments, the bonding strength between the seventh part 51 and the first wall 11 is greater than 100 N / m, the bonding strength between the ninth part 53 and the third wall 13 is greater than 100 N / m, and the bonding strength between the third adhesive 50 and the electrode assembly 20 is less than 14 N / m.

[0081] In some embodiments, please refer to Figure 12 to Figure 13 The housing 10 further includes a fifth wall 15, which is respectively connected to the first wall 11, the second wall 12 and the third wall 13. A fourth adhesive 60 is provided between the electrode assembly 20 and the housing 10, and the fourth adhesive 60 includes a tenth portion 61, an eleventh portion 62 and a twelfth portion 63 which are sequentially connected, the tenth portion 61 is bonded to the first wall 11, the eleventh portion 62 is located between the fifth wall 15 and the electrode assembly 20, and the twelfth portion 63 is bonded to the third wall 13. The fourth adhesive 60 can enhance the binding effect on the electrode assembly 20 in the width direction of the electrode assembly 20.

[0082] In some embodiments, the bonding strength between the tenth part 61 and the first wall 11 is greater than 100 N / m, the bonding strength between the twelfth part 63 and the third wall 13 is greater than 100 N / m, and the bonding strength between the fourth adhesive 60 and the electrode assembly 20 is less than 14 N / m.

[0083] In some embodiments, the number of the second adhesive 40, the third adhesive 50 and the fourth adhesive 60 may be more than two, and the more than two second adhesives 40, the third adhesive 50 and the fourth adhesive 60 may be spaced and / or relatively arranged in the length and / or width direction of the electrode assembly 20.

[0084] In some embodiments, the material, structure and size of the first adhesive 30 , the second adhesive 40 , the third adhesive 50 and the fourth adhesive 60 may be the same.

[0085] In some embodiments, the tensile strengths of the first adhesive 30 , the second adhesive 40 , the third adhesive 50 , and the fourth adhesive 60 may be the same.

[0086] In some embodiments, the first adhesive 30 , the second adhesive 40 , the third adhesive 50 , and the fourth adhesive 60 may have the same bonding strength with the first wall 11 and the third wall 13 .

[0087] In some embodiments, the first adhesive member 30 , the second adhesive member 40 , the third adhesive member 50 , and the fourth adhesive member 60 may have the same bonding strength to the electrode assembly 20 .

[0088] In some embodiments, the second adhesive 40 , the third adhesive 50 , and the fourth adhesive 60 are separated from the electrode assembly 20 after being soaked in the electrolyte.

[0089] In the second aspect of the present application, an electronic device is also proposed, including a secondary battery 100 as in any embodiment of the first aspect described above. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices include but are not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys can include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, electric airplane toys, and the like, and spacecraft can include airplanes, rockets, space shuttles, spacecraft, and the like.

[0090] Test part:

[0091] 1. Bonding strength test of adhesive parts:

[0092] 1) Sample preparation: Take out the bonded adhesive part and shell or adhesive part and electrode assembly from the lithium-ion battery, and cut them into test samples with a width of 20 mm and a length of 100 mm using a cutter.

[0093] 2) Test: Fix the test sample to the test fixture of the high-speed rail tensile machine, select the peel strength mode, the peel angle is 180 degrees, the tensile speed is 5±0.2mm / min, and the gauge length is 50mm.

[0094] 3) Value selection: Select the two ends of the peeling curve, perform average processing, and take the average value as the material interface bonding strength.

[0095] 2. Bonding parts tensile strength test:

[0096] 1) Sample preparation: Use a cutter to cut the adhesive into test specimens with a width of 15 mm and a length of 80 mm;

[0097] 2) Test: Fix the test sample to the test fixture of the high-speed rail tensile machine, select the stretching mode, the stretching speed is 25mm / min, the distance between the markings is set to 30mm, and stretch until the sample breaks.

[0098] 3) Value selection: The maximum force when the sample is stretched is taken as the tensile strength of the material.

[0099] 3. Lithium-ion battery drop test:

[0100] 1) Place the lithium-ion battery in a special fixture and let it fall freely from a height of 1.5 meters onto the marble surface;

[0101] 2) Drop sequence: lithium-ion battery up-down-upper right-lower right-upper left-lower left, one round, a total of 5 rounds;

[0102] 3) After the drop, check the appearance of the lithium-ion battery and record the leakage probability (determine whether the lithium-ion battery is leaking by smelling the leakage). After standing for 24 hours, check the voltage drop. If the voltage drop is greater than 30mV, it is judged as failure.

[0103] Example 1

[0104] <Preparation of positive electrode sheet>:

[0105] The positive electrode active materials lithium cobalt oxide (LiCoO2), carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, which is then stirred evenly.

[0106] Aluminum foil is selected as the positive electrode current collector, and the above slurry is coated on one surface of the positive electrode current collector and a positive electrode empty foil section is reserved. The slurry is dried to obtain a single-sided positive electrode sheet coated with a positive electrode active material layer on one side. On the other surface of the positive electrode current collector, the above steps are repeated to obtain a double-sided positive electrode sheet coated with a positive electrode active material layer on both sides.

[0107] <Preparation of negative electrode sheet>:

[0108] Using graphite as the negative electrode active material, the negative electrode active material graphite, the binder styrene butadiene rubber (SBR) and the thickener sodium carboxymethyl cellulose (CMC) are mixed in a weight ratio of 96:2:2, deionized water is added as a solvent, a slurry with a solid content of 70wt% is prepared, and the slurry is stirred evenly.

[0109] Copper foil is selected as the negative electrode current collector, and the above slurry is coated on one surface of the negative electrode current collector and a negative electrode empty foil section is reserved. The slurry is dried to obtain a single-sided negative electrode sheet coated with a negative electrode active material layer on one side. On the other surface of the negative electrode current collector, the above steps are repeated to obtain a double-sided negative electrode sheet coated with a negative electrode active material layer on both sides.

[0110] <Preparation of diaphragm>:

[0111] A polyethylene porous membrane is used as a substrate layer, and a ceramic layer containing alumina ceramics and a PVDF binder is coated on one surface of the substrate layer as a diaphragm (CCS), wherein the mass percentage of the alumina ceramics in the ceramic layer is 95%.

[0112] <Preparation of electrode assembly>:

[0113] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is obtained by winding or stacking.

[0114] <Preparation of bonding parts>:

[0115] The adhesive member includes a substrate layer and adhesive layers arranged on two opposite surfaces of the substrate layer, wherein the thickness of the adhesive member is 20 μm, the thickness of the substrate layer is 12 μm, and the thickness of any adhesive layer is 4 μm.

[0116] Polypropylene, elastomer polyurethane, filler titanium dioxide, and antioxidant diphenylamine are mixed evenly in a mass ratio of 60:25:7.5:7.5, and then coated on both surfaces of the substrate layer and dried at 120° C. to obtain a bonding member. The substrate layer is a polyethylene terephthalate film.

[0117] <Electrolyte Preparation>:

[0118] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a basic organic solvent, and then lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0119] <Preparation of lithium-ion batteries>:

[0120] Adhesives are bonded to the sides (head and tail sides) of the electrode assembly in the length direction near the corners. In the width direction of the electrode assembly, the width of the electrode assembly is W1, and the cumulative length of the adhesives on any side of the electrode assembly in the length direction is 2 / 3W1. The electrode assembly bonded with adhesives is placed in the shell, so that any adhesive is bonded to the upper surface (first wall) and the lower surface (third wall) of the shell. In the length direction of the electrode assembly, the width W2 of the part (first part) bonded to the first wall of the shell by any adhesive is 10mm, and the width W2 of the part (third part) bonded to the third wall of the shell by any adhesive is 10mm. After the electrode ear welding, shell cover welding, coding, vacuum drying, electrolyte injection, high temperature standing, formation and capacity, and sealing nail welding, the finished lithium-ion battery can be obtained. The bonding strength between any adhesive and the first and third walls of the shell is 480 N / m, the bonding strength between the adhesive and the electrode assembly after being soaked in electrolyte is 0 N / m, and the bonding strength between the adhesive and the side surface (second wall) of the shell after being soaked in electrolyte is 0 N / m. The tensile strength of any adhesive is 113 Mpa.

[0121] The relevant parameters in Comparative Examples 1 to 3 and Examples 1 to 18 are shown in Table 1 below.

[0122] Among them, in comparative example 1, the bonding strength between the adhesive and the first wall and the third wall of the shell is 0 N / m, and the bonding strength between the adhesive and the electrode assembly is 330 N / m.

[0123] In Comparative Example 2, Example 1, Example 3 and Example 4, only the bonding strength between the adhesive member and the first wall and the third wall of the shell is different.

[0124] In Comparative Example 3, Example 1 and Example 2, only the bonding strength between the adhesive and the electrode assembly is different.

[0125] Compared with Example 1, Example 5 is different only in the bonding strength between the adhesive and the second wall of the shell.

[0126] In Example 1 and Examples 6 to 12, only the tensile strength of the adhesive member is different.

[0127] In Example 1 and Examples 13 to 15, only the length of the accumulated adhesive on any side of the electrode assembly is different.

[0128] In Embodiment 1 and Embodiments 16 to 18, only the width of the portion where the adhesive member is bonded to the first wall and the third wall of the housing is different.

[0129] Table 1

[0130]

[0131]

[0132] According to Table 1 above, combined with Comparative Examples 1 to 3, Examples 1 to 2 and Example 5, it can be seen that the conventional method is to bond the adhesive to the electrode assembly, and the adhesive and the electrode assembly of the lithium-ion battery impact the shell together, which easily causes the shell to be damaged by force. By arranging an adhesive between the shell and the electrode assembly, and making the bonding strength between the adhesive and the first wall and the third wall of the shell greater than 100 N / m, and the bonding strength between the adhesive and the electrode assembly less than 14 N / m, the binding effect of the adhesive on the electrode assembly can be improved, thereby reducing the possibility of damage to the shell when the lithium-ion battery falls, and reducing the possibility of failure of the lithium-ion battery due to voltage drop when it falls.

[0133] Combining Comparative Example 2, Example 1, Example 3 and Example 4, it can be seen that when the bonding strength between the adhesive and the first and third walls of the shell is 100 N / m or more, the probability of the shell of the lithium-ion battery falling and being damaged is low. During the falling process of the lithium-ion battery, the electrode assembly impacts the adhesive, and the adhesive's own strength and the bonding shear strength formed with the shell absorb the impact energy of the adhesive. When the bonding strength between the adhesive and the first and third walls of the shell is less than 100 N / m, the adhesive is easily debonded from the first and third walls of the shell, and the adhesive loses the effect of restraining the electrode assembly. Therefore, the bonding strength between the adhesive and the first and third walls of the shell is preferably 100 N / m or more.

[0134] Combining Comparative Example 3, Example 1 and Example 2, it can be seen that when the bonding strength between the adhesive and the electrode assembly is below 14 N / m, the probability of the lithium-ion battery failing due to voltage drop is low. When the adhesive is bonded to both the housing and the electrode assembly, the force during the fall will be directly transmitted back to the electrode assembly through the adhesive, the electrode assembly will have insufficient anti-adhesive shear strength, the electrode sheet of the electrode assembly will be deformed, the collector metal foil of the electrode sheet will be torn, and then the diaphragm will be pierced, forming a short circuit, resulting in a significant deterioration of the voltage drop failure.

[0135] Combining Example 1 and Example 5, it can be seen that by improving the bonding strength between the adhesive and the second wall of the shell, the adhesive and the shell are easy to form an integrated structure, thereby reducing the buffering effect of the adhesive on the electrode assembly, and the probability of the lithium-ion battery falling and damaging the shell will increase. Therefore, the bonding strength between the adhesive and the second wall of the shell is preferably 0N / m.

[0136] In combination with Example 1 and Examples 6 to 12, it can be seen that when the tensile strength of the adhesive is 80Mpa to 300Mpa, the probability of damage to the lithium-ion battery shell when it falls is low, and the probability of failure of the lithium-ion battery drop voltage drop is low. In practical applications, if the tensile strength of the adhesive is less than 80Mpa, the adhesive is easy to break. If the tensile strength of the adhesive is greater than 80Mpa, the problem of the shell weld being opened during the fall process can be improved. However, if the tensile strength of the adhesive is greater than 300Mpa, the adhesive is a rigid body and cannot absorb the impulse of the electrode assembly, and rebounds to the electrode assembly, the electrode assembly is deformed by force, resulting in a short circuit point inside, and then the proportion of failure due to drop voltage drop is significantly increased. When the tensile strength of the adhesive is 100Mpa to 200Mpa, the problem of damage to the lithium-ion battery shell when it falls and the problem of failure due to drop voltage drop of the lithium-ion battery can be further balanced.

[0137] Combining Example 1 and Examples 13 to 15, it can be seen that increasing the length of the cumulative adhesive on any side of the electrode assembly can increase the force-bearing area of ​​the adhesive, improve the ability to resist impact damage to the electrode assembly, and significantly improve the damage to the shell when it falls. When the ratio of the cumulative adhesive length to the width of the electrode assembly is less than 1 / 3, the adhesive is easy to break, lose the effect of restraining the electrode assembly, and the shell is easy to break due to impact.

[0138] In combination with Example 1 and Examples 16 to 18, it can be known that when the width of the portion where the adhesive is bonded to the first and third walls of the shell is less than 5 mm, the bonding area between the adhesive and the shell is reduced, the adhesive shear force is reduced, and the adhesive surface is debonded by the electrode assembly during the drop process, and then the electrode assembly impacts the shell, the shell ruptures, and the lithium-ion battery leaks and fails. When the width of the portion where the adhesive is bonded to the first and third walls of the shell is greater than 20 mm, the possibility of the adhesive being debonded during the drop process is low, and the probability of the lithium-ion battery falling shell being damaged is low. Continuing to increase the width of the portion where the adhesive is bonded to the first and third walls of the shell will deplete the energy density of the lithium-ion battery. Therefore, the width of the portion where the adhesive is bonded to the first and third walls of the shell is preferably 5 mm to 20 mm.

[0139] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A secondary battery, comprising a shell and an electrode assembly disposed in the shell, wherein the shell comprises a first wall, a second wall and a third wall connected in sequence, and the first wall and the third wall are disposed opposite to each other along a thickness direction of the electrode assembly; It is characterized in that A first adhesive is arranged between the electrode assembly and the shell, and the first adhesive includes a first part, a second part and a third part connected in sequence, the first part is bonded to the first wall, the second part is located between the second wall and the electrode assembly, and the third part is bonded to the third wall. The bonding strength between the first part and the first wall is greater than 100 N / m, the bonding strength between the third part and the third wall is greater than 100 N / m, and the bonding strength between the first adhesive and the electrode assembly is less than 14 N / m.

2. The secondary battery according to claim 1, characterized in that: Along the thickness direction of the electrode assembly, the outer surface of the electrode assembly has a relative first angle position and a second angle position, the projection of the first part on the outer surface of the electrode assembly covers the first angle position, and the projection of the third part on the outer surface of the electrode assembly covers the second angle position.

3. The secondary battery according to claim 2, characterized in that: Along the length and / or width direction of the electrode assembly, the projection of the first adhesive on the outer surface of the electrode assembly covers the first angle; And / or, along the length and / or width direction of the electrode assembly, the projection of the first adhesive on the outer surface of the electrode assembly covers the second angle.

4. The secondary battery according to claim 1, characterized in that: The tensile strength of the first adhesive member is T1, 80Mpa≤T1≤300Mpa.

5. The secondary battery according to claim 4, characterized in that: 100Mpa≤T1≤200Mpa.

6. The secondary battery according to claim 1, characterized in that: The bonding strength between the first part and the electrode assembly is 0 N / m; and / or the bonding strength between the second part and the electrode assembly is 0 N / m; And / or, the bonding strength between the third part and the electrode assembly is 0 N / m.

7. The secondary battery according to claim 1, characterized in that: The bonding strength between the second portion and the second wall is 0 N / m.

8. The secondary battery according to claim 1, characterized in that: Along the width direction of the electrode assembly, the width of the electrode assembly is W1, the length of the first adhesive is L1, and 1 / 3≤L1 / W1≤1.

9. The secondary battery according to claim 1, characterized in that: Along the length direction of the electrode assembly, the width of the first portion is W2, 5mm≤W2≤20mm.

10. The secondary battery according to claim 1, characterized in that: Along the length direction of the electrode assembly, the width of the third portion is W3, 5mm≤W3≤20mm.

11. The secondary battery according to claim 9 or 10, characterized in that: The secondary battery includes a tab connected to the electrode assembly, and the tab extends out of the housing along a length direction of the electrode assembly.

12. The secondary battery according to claim 1, characterized in that: The first adhesive member includes a first adhesive layer, a first base material layer and a second adhesive layer stacked in sequence.

13. The secondary battery according to claim 1, characterized in that: A second adhesive member is disposed between the electrode assembly and the shell, the second adhesive member comprising a fourth portion, a fifth portion and a sixth portion connected in sequence, the fourth portion being bonded to the first wall, the fifth portion being located between the second wall and the electrode assembly, and the sixth portion being bonded to the third wall; Along the thickness direction of the electrode assembly, the outer surface of the electrode assembly has relative third and fourth angles, the projection of the fourth part on the outer surface of the electrode assembly covers the third angle, and the projection of the sixth part on the outer surface of the electrode assembly covers the fourth angle.

14. The secondary battery according to claim 1, characterized in that: The shell also includes a fourth wall, and the two sides of the fourth wall are respectively connected to the first wall and the third wall, the fourth wall and the second wall are arranged opposite to each other along the length direction of the electrode assembly, and a third adhesive is arranged between the electrode assembly and the shell, and the third adhesive includes a seventh part, an eighth part and a ninth part connected in sequence, the seventh part is adhered to the first wall, the eighth part is located between the fourth wall and the electrode assembly, and the ninth part is adhered to the third wall.

15. The secondary battery according to claim 1, characterized in that: The shell also includes a fifth wall, which is respectively connected to the first wall, the second wall and the third wall; a fourth adhesive is arranged between the electrode assembly and the shell, and the fourth adhesive includes a tenth part, an eleventh part and a twelfth part connected in sequence, the tenth part is bonded to the first wall, the eleventh part is located between the fifth wall and the electrode assembly, and the twelfth part is bonded to the third wall.

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

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