Secondary battery and electronic device

Abstract

The invention discloses a secondary battery and an electronic device, the secondary battery comprises a packaging bag, an electrode assembly, an electric connecting piece, a first insulating piece and a second insulating piece, the electrode assembly is located in the packaging bag, the electrode assembly comprises a main body part and a tab assembly, the tab assembly comprises a plurality of tabs, and the electric connecting piece is located outside the packaging bag and is electrically connected with the tab assembly. The tab assembly comprises a first part and a second part, the first part extends out of the main body part and is connected with the second part, the second part is bent towards the main body part, the second part and the electric connecting piece form a welding mark, and the second part comprises a first surface and a second surface. The first insulating part covers the welding mark, the second insulating part is located on one side of the thickness direction of the tab and extends to the main body part from the first surface of the second part through the first part, the thickness of the first insulating part is T1, the thickness of the second insulating part is T2, T1 is larger than T2, T1 is larger than or equal to 25 microns and smaller than or equal to 60 microns, T2 is larger than or equal to 4 microns, and the safety performance and the falling performance of the secondary battery are both considered.

Description

Technical Field

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

[0002] As secondary batteries become increasingly popular in mobile device electronics and the electric vehicle market, in addition to the increasing demand for battery energy density, the safety performance of secondary batteries has also attracted much attention. Therefore, improving the safety performance of secondary batteries remains a problem that needs to be solved in the industry. Summary of the invention

[0003] In view of this, it is necessary to provide a secondary battery and an electronic device that take into account both the safety performance and the drop performance of the secondary battery.

[0004] The embodiment of the present application provides a secondary battery, including a packaging bag, an electrode assembly, an electrical connector, a first insulating member, and a second insulating member. The electrode assembly is located in the packaging bag, and the electrode assembly includes a main body and a tab assembly extending from the main body, and the tab assembly includes a plurality of tabs. One end of the electrical connector is located outside the packaging bag, and the other end is electrically connected to the tab assembly. The tab assembly includes a first part and a second part. The first part extends from the main body and connects to the second part, and the second part is bent toward the main body compared to the first part. The second part is welded with the electrical connector to form a weld mark, and the second part includes a first surface away from the main body and a second surface facing the main body. The first insulating member is provided on the first surface of the second part and covers the weld mark, the second insulating member is located on one side of the thickness direction of the tab, and the second insulating member extends from the first surface of the second part through the first part to the main body, the thickness of the first insulating member is T1, and the thickness of the second insulating member is T2, T1>T2, 25μm≤T1≤60μm, T2≥4μm. The weld mark is covered by the first insulating member to reduce the risk of the weld mark piercing the packaging bag and causing a short circuit. The first surface and the main body are connected by the second insulating member to fix the pole ear and the main body, thereby reducing the displacement of the position of the pole ear and the main body during transportation and use, and reducing the influence of the thickness of the second insulating member on the flatness of the secondary battery. The problem of overpressure at the second insulating member during the formation stage of the secondary battery is reduced, and the problem of purple spots caused by overpressure at the second insulating member and capacity loss after the secondary battery is cycled is improved.

[0005] In one or more of the above optional embodiments, the thickness of the electrode assembly is T, 2T2 / T×100%≤4.1%, which is beneficial to reducing the thickness of the second insulating member, reducing the influence of the thickness of the second insulating member on the flatness of the secondary battery, reducing the problem of overvoltage at the second insulating member during the formation stage of the secondary battery, and improving the problem of purple spots caused by overvoltage at the second insulating member and capacity loss after secondary battery cycling.

[0006] In one or more of the above optional embodiments, 2T2 / T×100%≤1.8%, which is further beneficial to reducing the thickness of the second insulating member, reducing the influence of the thickness of the second insulating member on the flatness of the secondary battery, reducing the problem of overvoltage at the second insulating member during the formation stage of the secondary battery, and improving the problem of purple spots caused by overvoltage at the second insulating member and capacity loss after secondary battery cycling.

[0007] In one or more optional embodiments above, 30 μm ≤ T1 ≤ 50 μm. In this way, the first insulating member can better reduce the risk of the welding mark piercing the packaging bag and causing a short circuit, reduce the space occupied by the first insulating member, and help reduce costs.

[0008] In one or more of the above optional embodiments, the first insulating member and the second insulating member at least partially overlap on the first surface, which helps to reduce the difficulty of assembly and facilitates the pasting of the first insulating member and the second insulating member.

[0009] In one or more optional embodiments above, the overlapping area of ​​the second insulating member with the first insulating member at least partially overlaps with the weld mark. The overlapping area is conducive to further reducing the risk of the weld mark piercing the packaging bag and causing a short circuit.

[0010] In one or more of the above optional embodiments, in the overlapping area of ​​the first insulating member and the second insulating member, the second part, the second insulating member and the first insulating member are stacked in sequence to prevent the edge of the second insulating member from warping, which is further beneficial to fix the tab and the main body and reduce the risk of the tab being broken or falling off due to stress during the transportation and use of the secondary battery.

[0011] In one or more optional embodiments above, along the direction in which the second insulating member and the first insulating member are stacked, the projection of the first insulating member is located inside the second insulating member. In this way, the risk of the welding mark piercing the packaging bag and causing a short circuit can be better reduced, which is conducive to fixing the tab and the main body, and reducing the risk of the tab being broken or falling off due to stress during the transportation and use of the secondary battery.

[0012] In one or more optional embodiments above, the area of ​​the first insulating member is A1, the overlapping area between the first insulating member and the second insulating member is A, and the secondary battery also satisfies: A ≥ 16.7% A1. In this way, the tolerance accuracy of the first insulating member and the second insulating member can be better reduced, the difficulty of assembly can be reduced, the first insulating member and the second insulating member can be easily pasted, which is conducive to assembly and reduces the risk of the edge of the second insulating member warping, causing the tab to break or fall off due to stress.

[0013] In one or more of the above optional embodiments, along the width direction of the main body of the electrode assembly, the width of the first insulating member is W1, and the width of the weld mark is W; along the extension direction of the pole ear, the length of the first insulating member is L1, and the length of the weld mark is L. The secondary battery also satisfies: 1.5W≤W1≤3W, 1.1L≤L1≤6.7L. This is beneficial for the first insulating member to cover the weld mark, reduce the risk of the weld mark piercing the packaging bag and causing a short circuit, and reduce the space occupied by the first insulating member in the packaging bag.

[0014] In one or more of the above optional embodiments, 1.8W≤W1≤2.7W, 1.5L≤L1≤5.4L. This is beneficial for the first insulating member to cover the weld mark, reduce the risk of the weld mark piercing the packaging bag and causing a short circuit, and further reduce the space occupied by the first insulating member in the packaging bag.

[0015] In one or more of the above optional embodiments, along the extension direction of the second insulating member, the overlapping length of the second insulating member and the main body is L5, and the overlapping length of the second insulating member, the pole ear and the electrical connector is L6, 3mm≤L5≤8mm and 3mm≤L6≤13mm, which is conducive to fixing the main body and the pole ear, reducing the risk of the pole ear moving or falling off during the movement or use of the secondary battery, reducing the space occupied by the second insulating member in the packaging bag, reducing the impact of the excessive length of the second insulating member on the heat-sealing adhesive layer, and helping to reduce costs.

[0016] In one or more of the above optional embodiments, the secondary battery also includes an electrolyte sealed in a packaging bag, and the peel strength between the first insulating member and the weld mark is greater than 0.26 N / mm, which is conducive to the adhesion of the first insulating member to the weld mark, so that the first insulating member covers the burrs on the weld mark, reducing the risk of the weld mark piercing the packaging bag and causing a short circuit.

[0017] In one or more of the above optional embodiments, the secondary battery also includes an electrolyte sealed in the packaging bag, and the peel strength between the second insulating member and the pole ear is greater than 0.08N / mm, which is conducive to fixing the pole ear and the main body and reducing the risk of movement or falling off of the pole ear during transportation and use.

[0018] In one or more of the above optional embodiments, the secondary battery further includes a third insulating member, which is located on the side of the pole ear away from the second insulating member, and the third insulating member extends from the electrical connector through the second surface of the second part and the first part to the main body in sequence, and the thickness of the third insulating member is T3, and the secondary battery also satisfies: T1>T3. The second surface and the main body are connected by the third insulating member, and the pole ear and the main body are further fixed, which reduces the displacement of the position of the pole ear and the main body during the transportation process and use. The thickness of the third insulating member is less than the thickness of the first insulating member, which reduces the influence of the thickness of the third insulating member on the flatness of the secondary battery, reduces the problem of easy overpressure at the position of the third insulating member in the formation stage of the secondary battery, and improves the problem of purple spots caused by overpressure at the position of the second insulating member and the loss of capacity of the secondary battery after cycling.

[0019] In one or more of the above optional embodiments, the thickness of the electrode assembly is T, and the secondary battery also satisfies: 2T3 / T×100%≤4.1%, which is beneficial to reducing the thickness of the third insulating member, reducing the influence of the thickness of the third insulating member on the flatness of the secondary battery, reducing the problem of easy overvoltage at the third insulating member position of the secondary battery during the formation stage, and improving the problem of purple spots caused by overvoltage at the second insulating member position and capacity loss of the secondary battery after cycling.

[0020] In one or more of the above optional embodiments, the secondary battery also satisfies: 2T3 / T×100%≤1.8%, which is further beneficial to reducing the thickness of the third insulating member, reducing the influence of the thickness of the third insulating member on the flatness of the secondary battery, reducing the problem of easy overvoltage at the third insulating member position of the secondary battery during the formation stage, and improving the problem of purple spots caused by overvoltage at the second insulating member position and capacity loss of the secondary battery after cycling.

[0021] In one or more optional embodiments above, along the extension direction of the third insulating member, the overlapping length of the third insulating member and the main body is L7, and the overlapping length of the third insulating member and the tab and the electrical connector is L8, 3mm≤L7≤8mm and 7mm≤L8≤13mm. This is conducive to fixing the main body and the tab, reducing the risk of the tab moving or falling off during the movement or use of the secondary battery, reducing the space occupied by the third insulating member in the packaging bag, reducing the influence of the excessive length of the third insulating member on the heat-sealing adhesive layer, and helping to reduce costs.

[0022] In one or more of the above optional embodiments, the secondary battery also includes an electrolyte sealed in the packaging bag, and the peel strength between the third insulating member and the pole ear is greater than 0.08N / mm, which is conducive to fixing the pole ear and the main body and reducing the risk of movement or falling off of the pole ear during transportation and use.

[0023] In one or more optional embodiments above, the first insulating member, the second insulating member and the third insulating member all include a base layer and an adhesive layer, and the adhesive layer connects the base layer. The base layer includes one or a combination of polyethylene terephthalate, polyimide, polyester film, polyethylene film, non-woven fabric and foam. The adhesive layer includes one or a combination of acrylic system, rubber system, styrene-isoprene-styrene, isooctyl acrylate, octyl methacrylate, isooctyl methacrylate, isoprene, styrene, butyl acrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, polymethyl methacrylate.

[0024] An embodiment of the present application provides an electronic device, comprising the secondary battery in any one of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a secondary battery in some embodiments of the present application is shown.

[0026] Figure 2 A partial structural schematic diagram of a secondary battery in some embodiments of the present application is shown.

[0027] Figure 3 A schematic cross-sectional view of a packaging bag in some embodiments of the present application is shown.

[0028] Figure 4 Partial structural schematic diagrams of secondary batteries in other embodiments of the present application are shown.

[0029] Figure 5 A partial structural schematic diagram of a secondary battery in some other embodiments of the present application is shown.

[0030] Figure 6 Shows this application Figure 4 A simplified structural diagram of the secondary battery observed along the second direction.

[0031] Figure 7 A schematic diagram of the structure of an electronic device in some embodiments of the present application is shown.

[0032] Description of main component symbols:

[0033] Secondary battery 100

[0034] Welding 101

[0035] Packaging bag 10

[0036] Protective layer 10a

[0037] Metal layer 10b

[0038] Adhesive layer 10c

[0039] Electrode assembly 20

[0040] Main body 21

[0041] Tab assembly 22

[0042] Connecting section 22a

[0043] Part 1221

[0044] Part 222

[0045] First surface 222a

[0046] Second surface 222b

[0047] Electrical connector 30

[0048] The first insulating member 40

[0049] The second insulating member 50

[0050] First section 51

[0051] Second section 52

[0052] The third insulating member 60

[0053] Third Segment 61

[0054] Section 4 62

[0055] Electronic device 200

[0056] First direction X

[0057] Second direction Y

[0058] The third direction Z

[0059] The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0060] The following specific embodiments are exemplary and non-limiting, and are intended to provide a basic understanding of the present application, and are not intended to identify the key or decisive elements of the present application or to limit the scope of protection. As long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way.

[0061] When a component is considered to be “provided on” another component, it can be directly provided on the other component or there may be a component in between. When a component is considered to be “connected to” another component, it can be directly connected to the other component or there may be a component in between.

[0062] It can be understood that the term "perpendicular" is used to describe an ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular or equal to each other 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.

[0063] The term "parallel" is used to describe an ideal state between two components. In actual production or use, two components may be approximately parallel or equal. For example, combined with numerical descriptions, parallel can refer to the angle between two straight lines being between 0°±10°, parallel can also refer to the dihedral angle between two planes being between 0°±10°, and parallel can also refer to the angle between a straight line and a plane being between 0°±10°. The two components described as "parallel" 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.

[0064] Some embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0065] See also Figure 1 and Figure 2 An embodiment of the present application provides a secondary battery 100, including a packaging bag 10 and an electrode assembly 20, wherein the electrode assembly 20 is located in the packaging bag 10. The electrode assembly 20 includes a main body 21 and a tab assembly 22 extending from the main body 21. The tab assembly 22 includes a plurality of tabs.

[0066] In some embodiments, the secondary battery 100 includes an electrical connector 30 , one end of the electrical connector 30 is located outside the packaging bag 10 , and the other end of the electrical connector 30 is electrically connected to the tab assembly 22 .

[0067] In some embodiments, the tab assembly 22 includes a connecting segment 22 a , and the connecting segment 22 a is formed by connecting a plurality of tabs in the tab assembly 22 .

[0068] In some embodiments, the connecting section 22 a includes a first portion 221 and a second portion 222 , wherein the first portion 221 extends from the main body 21 and is connected to the second portion 222 .

[0069] In some embodiments, the second portion 222 is bent toward the main body 21 compared to the first portion 221, and includes a first surface 222a away from the main body 21 and a second surface 222b facing the main body 21. The second portion 222 is welded to the electrical connector 30 to form a weld mark 101.

[0070] In some embodiments, the secondary battery 100 includes a first insulating member 40 . The first insulating member 40 is disposed on the first surface 222 a and covers the weld mark 101 .

[0071] In some embodiments, the secondary battery 100 includes a second insulating member 50 . The second insulating member 50 is located on one side of the tab assembly 22 in the thickness direction. The second insulating member 50 extends from the first surface 222 a through the first portion 221 to the main body 21 .

[0072] In some embodiments, the thickness of the first insulating member 40 is T1 , the thickness of the second insulating member 50 is T2 , and T1 > T2 .

[0073] In some embodiments, 25 μm≤T1≤60 μm, which is beneficial for the first insulating member 40 to reduce the risk of the welding mark 101 puncturing the packaging bag 10 and causing a short circuit, reduce the space occupied by the first insulating member 40, and help reduce costs.

[0074] Optionally, T1 can be any one of 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, 51μm, 52μm, 53μm, 54μm, 55μm, 56μm, 57μm, 58μm, 59μm, 60μm, or a range consisting of any two of them.

[0075] In some embodiments, T2 ≥ 4 μm, which helps to reduce the situation where the second insulating member 50 is too thin, causing tearing and failing to provide restraint.

[0076] In the present application, the thickness of the second insulating member 50 is less than that of the first insulating member 40. The first insulating member 40 covers the weld mark 101 to reduce the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit. The second insulating member 50 connects the first surface 222a and the main body 21 to fix the pole ear assembly 22 and the main body 21, thereby reducing the positional displacement of the pole ear assembly 22 and the main body 21 during transportation and use, and reducing the influence of the thickness of the second insulating member 50 on the flatness of the secondary battery 100, thereby reducing the problem of the second insulating member 50 being easily over-pressurized during the formation stage of the secondary battery 100, and improving the problem of purple spots caused by over-pressurization at the second insulating member 50 and the capacity loss of the secondary battery 100 after cycling.

[0077] In some embodiments, 30 μm≤T1≤50 μm. In this way, the first insulating member 40 can better reduce the risk of the welding mark 101 piercing the packaging bag 10 and causing a short circuit, reduce the space occupied by the first insulating member 40, and help reduce costs.

[0078] See also Figure 3 In some embodiments, the packaging bag 10 includes a protective layer 10a, a metal layer 10b and an adhesive layer 10c. The metal layer 10b is located between the protective layer 10a and the adhesive layer 10c. The protective layer 10a is located at the outermost side of the packaging bag 10, and the adhesive layer 10c is located at the innermost side of the packaging bag 10, and is used to seal the packaging bag 10. The second insulating member 50 covers the weld mark 101, thereby reducing the risk that the weld mark 101 pierces the adhesive layer 10c and contacts the metal layer 10b, causing the secondary battery 100 to short-circuit.

[0079] In some embodiments, the packaging bag 10 is a packaging bag packaged by a packaging film (such as an aluminum-plastic film), that is, the secondary battery 100 is a soft-pack battery.

[0080] In some embodiments, it includes a first pole piece and a second pole piece with different polarities and an isolation film disposed between the first pole piece and the second pole piece.

[0081] In some embodiments, the electrode assembly 20 is a wound structure.

[0082] In some embodiments, the electrode assembly 20 is a laminated structure. When the electrode assembly 20 is a laminated structure, the present application also improves the problem that the isolation film warps due to stress concentration at the edge of the isolation film during the lamination process due to uneven flatness of the secondary battery 100 of the laminated structure.

[0083] In some embodiments, the thickness direction of the electrode assembly 20 is defined as a first direction X. Along the first direction X, the thickness of the electrode assembly 20 is T, and 2T2 / T×100%≤4.1%, which is beneficial to reducing the thickness of the second insulating member 50, reducing the influence of the thickness of the second insulating member 50 on the flatness of the secondary battery 100, reducing the problem of easy overpressure at the position of the second insulating member 50 of the secondary battery 100 during the formation stage, and improving the problem of purple spots caused by overpressure at the position of the second insulating member 50 and capacity loss of the secondary battery 100 after cycling.

[0084] In some embodiments, 2T2 / T×100%≤1.8%, which is further beneficial to reduce the thickness of the second insulating member 50, reduce the influence of the thickness of the second insulating member 50 on the flatness of the secondary battery 100, reduce the problem of overpressure at the position of the second insulating member 50 during the formation stage of the secondary battery 100, and improve the problem of purple spots caused by overpressure at the position of the second insulating member 50 and capacity loss of the secondary battery 100 after cycling.

[0085] See also Figure 2 In some embodiments, the first insulating member 40 and the second insulating member 50 at least partially overlap on the first surface 222 a , which helps to reduce the difficulty of assembly and facilitates the pasting of the first insulating member 40 and the second insulating member 50 .

[0086] In some embodiments, along the stacking direction of the second insulating member 50 and the first insulating member 40, the second insulating member 50 is located on the side of the first insulating member 40 facing the tab assembly 22, which is beneficial to reduce the edge warping of the second insulating member 50 and reduce the risk of the tab assembly 22 being broken or falling off due to stress during the transportation and use of the secondary battery 100.

[0087] In some embodiments, the area of ​​the first insulating member 40 is A1, and the overlapping area between the first insulating member 40 and the second insulating member 50 is A, and A≥16.7%A1. In this way, the tolerance accuracy of the first insulating member 40 and the second insulating member 50 can be better reduced, the difficulty of assembly can be reduced, the first insulating member 40 and the second insulating member 50 can be easily pasted, and the assembly is facilitated, and the edge of the second insulating member 50 is lifted, which reduces the risk of the tab assembly 22 being broken or falling off due to force.

[0088] See also Figure 4 In some embodiments, the overlapping area between the second insulating member 50 and the first insulating member 40 at least partially overlaps with the weld mark 101 , and the overlapping area helps to further reduce the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit.

[0089] In some embodiments, in the overlapping area between the second insulating member 50 and the first insulating member 40, the second portion 222, the second insulating member 50 and the first insulating member 40 are stacked in sequence to prevent the edge of the second insulating member 50 from warping, which is further beneficial to fix the tab assembly 22 and the main body 21, and reduce the risk of the tab 33 being broken or falling off due to stress during the transportation and use of the secondary battery 100.

[0090] See also Figure 5 In some embodiments, along the direction in which the second insulating member 50 and the first insulating member 40 are stacked, the projection of the first insulating member 40 is located inside the second insulating member 50. In this way, the risk of the welding mark 101 piercing the packaging bag 10 and causing a short circuit can be better reduced, and the tab assembly 22 and the main body 21 can be fixed, reducing the risk of the tab assembly 22 being broken or falling off due to stress during the transportation and use of the secondary battery 100.

[0091] See also Figure 6 , define the length direction of the second part 222 as the second direction Y, define the width direction of the main body 21 as the third direction Z, and the first direction X, the second direction Y and the third direction Z are perpendicular to each other.

[0092] In some embodiments, along the third direction Z, the width of the first insulating member 40 is W1, the width of the weld mark 101 is W, and 1.5W≤W1≤3W. In this way, the first insulating member 40 is conducive to covering the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, and reducing the space in the packaging bag 10 occupied by the first insulating member 40. The width of the weld mark 101 refers to the maximum distance between the two outermost weld marks 101 in the third direction Z.

[0093] Optionally, W1 can be any one of 1.5 W, 1.6 W, 1.7 W, 1.8 W, 1.9 W, 2.0 W, 2.1 W, 2.2 W, 2.3 W, 2.4 W, 2.5 W, 2.6 W, 2.7 W, 2.8 W, 2.9 W, and 3.0 W, or a range consisting of any two of them.

[0094] In some embodiments, 1.8 W≤W1≤2.7 W. In this way, the first insulating member 40 can cover the weld mark 101 , reduce the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, and further reduce the space in the packaging bag 10 occupied by the first insulating member 40 .

[0095] In some embodiments, along the extension direction of the tab assembly 22, the length of the first insulating member 40 is L1, the length of the weld mark 101 is L, and 1.1L≤L1≤6.7L, so that the first insulating member 40 is conducive to covering the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, and reducing the space in the packaging bag 10 occupied by the first insulating member 40. Among them, the extension direction of the tab assembly 22 is substantially parallel to the first direction X, and the length of the weld mark 101 refers to the maximum distance between the two outermost weld marks 101 in the first direction X.

[0096] Optionally, L1 can be 1.5L, 1.6L, 1.7L, 1.8L, 1.9L, 2.0L, 2.1L, 2.2L, 2.3L, 2.4L, 2.5L, 2.6L, 2.7L, 2.8L, 2.9L, 3.0L, 3.1L, 3.2L, 3.3L, 3.4L, 3.5L, 3.6L, 3.7L, 3.8L, 3.9L, 4.0L, 4.1L, 4.4L The range consists of any one of or any two of the following: .2L, 4.3L, 4.4L, 4.5L, 4.6L, ​​4.7L, 4.8L, 4.9L, 5.0L, 5.1L, 5.2L, 5.3L, 5.4L, 5.5L, 5.6L, 5.7L, 5.8L, 5.9L, 6.0L, 6.1L, 6.2L, 6.3L, 6.4L, 6.5L, 6.6L, and 6.7L.

[0097] In some embodiments, 1.5L≤L1≤5.4L. In this way, the first insulating member 40 can cover the weld mark 101 , reduce the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, and further reduce the space occupied by the first insulating member 40 in the packaging bag 10 .

[0098] See also Figure 2 In some embodiments, along the extension direction of the second insulating member 50, the overlapping length of the second insulating member 50 and the main body 21 is L5, 3mm≤L5≤8mm. The overlapping length of the second insulating member 50, the tab assembly 22 and the electrical connector 30 is L6, 3mm≤L5≤8mm and 3mm≤L6≤13mm, which is conducive to fixing the main body 21 and the tab assembly 22, reducing the risk of the tab assembly 22 being broken or falling off when the secondary battery 100 is moved or used, reducing the space occupied by the second insulating member 50 in the packaging bag 10, reducing the influence of the excessive length of the second insulating member 50 on the heat-sealing adhesive layer 10c, and helping to reduce costs.

[0099] Among them, the overlapping length between the second insulating member 50 and the main body 21 refers to the bonding length of the second insulating member 50 and the main body 21, and the overlapping length between the second insulating member 50 and the tab assembly 22 and the electrical connector 30 refers to the bonding length of the second insulating member 50 and the tab assembly 22 and the electrical connector 30.

[0100] Optionally, L5 can be any one of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, or a range consisting of any two of them.

[0101] Optionally, L6 can be any one of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, or any two of them. In some embodiments, the length of the second insulating member 50 is the sum of the lengths of L5 and L6.

[0102] In some embodiments, the second insulating member 50 includes a first section 51, and the first section 51 is bonded to the main body 21. The length of the first section 51 is L5.

[0103] In some embodiments, the second insulating member 50 includes a second segment 52 connected to the first segment 51, and the second segment 52 is bonded to the tab assembly 22 and the electrical connector 30. The length of the second segment 52 is L6.

[0104] In some embodiments, the secondary battery 100 includes an electrolyte sealed in the packaging bag 10 , and the electrode assembly 20 and the first insulating member 40 are immersed in the electrolyte.

[0105] See also Figure 2 and Figure 4 In some embodiments, when the first insulating member 40 is not in contact with the electrolyte, the peel strength between the first insulating member 40 and the weld mark 101 is greater than 0.3 N / mm, which is conducive to the first insulating member 40 being bonded to the weld mark 101, so that the first insulating member 40 covers the burrs on the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit.

[0106] In some embodiments, after being immersed in the electrolyte, the peel strength between the first insulating member 40 and the weld mark 101 is greater than 0.26 N / mm, which is further conducive to the adhesion of the first insulating member 40 to the weld mark 101, so that the first insulating member 40 covers the burrs on the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit.

[0107] See also Figure 6 In some embodiments, when the first insulating member 40 and the second insulating member 50 are not in contact with the electrolyte, the peel strength between the first insulating member 40 and the second insulating member 50 is greater than 0.3 N / mm.

[0108] In some embodiments, after being immersed in electrolyte at 85° C. for 4 hours, the peel strength between the first insulating member 40 and the second insulating member 50 is greater than 0.26 N / mm.

[0109] In some embodiments, the second insulating member 50 is immersed in the electrolyte.

[0110] In some embodiments, when the second insulating member 50 is not in contact with the electrolyte, the peel strength between the second insulating member 50 and the tab assembly 22 is greater than 0.1 N / mm, which is beneficial for fixing the tab assembly 22 and the main body 21 and reducing the position displacement of the tab assembly 22 and the main body 21 during transportation and use.

[0111] In some embodiments, after being immersed in the electrolyte, the peel strength between the second insulating member 50 and the tab assembly 22 is greater than 0.08 N / mm, which is further beneficial to fix the tab assembly 22 and the main body 21 and reduce the position displacement of the tab assembly 22 and the main body 21 during transportation and use.

[0112] See also Figure 2 , Figure 4 and Figure 6 The secondary battery 100 includes a third insulating member 60, which is located on the side of the tab assembly 22 away from the second insulating member 50, and the third insulating member 60 extends from the electrical connector 30 through the second surface 222b of the second part 222 and the first part 221 to the main body 21, and the thickness of the third insulating member 60 is T3, T1>T3. The second surface 222b and the main body 21 are connected by the third insulating member 60, and the tab assembly 22 and the main body 21 are further fixed, so as to reduce the displacement of the tab assembly 22 and the main body 21 during the transportation process and the use process. The thickness of the third insulating member 60 is less than the thickness of the first insulating member 40, so as to reduce the influence of the thickness of the third insulating member 60 on the flatness of the secondary battery 100, reduce the problem of easy overpressure at the position of the third insulating member 60 of the secondary battery 100 in the formation stage, and improve the problem of purple spots caused by overpressure at the position of the third insulating member 60 and the capacity loss of the secondary battery 100 after cycling.

[0113] In some embodiments, T3 ≥ 4 μm, which helps to reduce the situation where the third insulating member 60 is too thin, causing tearing and failing to provide restraint.

[0114] In some embodiments, along the first direction X, the thickness of the electrode assembly 20 is T, 2T3 / T×100%≤4.1%, which is beneficial to reducing the thickness of the third insulating member 60, reducing the influence of the thickness of the third insulating member 60 on the flatness of the secondary battery 100, reducing the problem of easy overpressure at the position of the third insulating member 60 of the secondary battery 100 during the formation stage, and improving the problem of purple spots caused by overpressure at the position of the third insulating member 60 and capacity loss of the secondary battery 100 after cycling.

[0115] In some embodiments, 2T3 / T×100%≤1.8%, which is further beneficial to reduce the thickness of the third insulating member 60, reduce the influence of the thickness of the third insulating member 60 on the flatness of the secondary battery 100, reduce the problem of overvoltage at the position of the third insulating member 60 of the secondary battery 100 during the formation stage, and improve the problem of purple spots caused by overvoltage at the position of the third insulating member 60 and capacity loss of the secondary battery 100 after cycling.

[0116] See also Figure 2 Along the extension direction of the third insulating member 60, the overlapping length of the third insulating member 60 and the main body 21 is L7, and the overlapping length of the third insulating member 60, the tab assembly 22 and the electrical connector 30 is L8, 3mm≤L7≤8mm and 3mm≤L8≤13mm, which is conducive to fixing the main body 21 and the tab assembly 22, reducing the risk of the tab assembly 22 being broken or falling off due to force during the movement or use of the secondary battery 100, reducing the space occupied by the third insulating member 60 in the packaging bag 10, reducing the influence of the excessive length of the third insulating member 60 on the heat-sealing adhesive layer 10c, and helping to reduce costs.

[0117] Among them, the overlapping length between the third insulating member 60 and the main body 21 refers to the bonding length of the third insulating member 60 and the main body 21, and the overlapping length between the third insulating member 60 and the tab assembly 22 and the electrical connector 30 refers to the bonding length of the third insulating member 60 and the tab assembly 22 and the electrical connector 30.

[0118] Optionally, L7 can be any one of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, or a range consisting of any two of them.

[0119] Optionally, L8 can be any one of 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, and 13mm, or a range consisting of any two of them.

[0120] In some embodiments, the length of the third insulating member 60 is the sum of the lengths of L7 and L8 .

[0121] In some embodiments, the third insulating member 60 includes a third section 61, and the third section 61 is bonded to the main body 21. The length of the third section 61 is L7.

[0122] In some embodiments, the third insulating member 60 includes a fourth segment 62 connected to the third segment 61, and the fourth segment 62 is bonded to the tab assembly 22 and the electrical connector 30. The length of the fourth segment 62 is L8.

[0123] In some embodiments, the third insulating member 60 is immersed in the electrolyte.

[0124] In some embodiments, when the third insulating member 60 is not in contact with the electrolyte, the peel strength between the third insulating member 60 and the tab assembly 22 is greater than 0.1 N / mm, which is beneficial for fixing the tab assembly 22 and the main body 21 and reducing the position displacement of the tab assembly 22 and the main body 21 during transportation and use.

[0125] In some embodiments, after being immersed in the electrolyte, the peel strength between the third insulating member 60 and the tab assembly 22 is greater than 0.08 N / mm, which is further beneficial to fix the tab assembly 22 and the main body 21 and reduce the position displacement of the tab assembly 22 and the main body 21 during transportation and use.

[0126] In some embodiments, the first insulating member 40 includes a first base layer and a first adhesive layer connected to the first base layer.

[0127] In some embodiments, the material of the first base layer includes one or a combination of polyethylene terephthalate, polyimide, polyester film, polyethylene film, non-woven fabric and foam.

[0128] In some embodiments, the material of the first adhesive layer includes one or a combination of rubber system, styrene-isoprene-styrene, polypropylene, isoprene or styrene, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone.

[0129] In some embodiments, the second insulating member 50 includes a second base layer and a second adhesive layer connected to the second base layer.

[0130] In some embodiments, the material of the second base layer includes one or a combination of polyethylene terephthalate, polyimide, polyester film, polyethylene film, non-woven fabric and foam.

[0131] In some embodiments, the material of the second adhesive layer includes one or a combination of acrylic system, rubber system, styrene-isoprene-styrene, isooctyl acrylate, octyl methacrylate, isooctyl methacrylate, isoprene, styrene, butyl acrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, and polymethyl methacrylate.

[0132] In some embodiments, the third insulating member 60 includes a third base layer and a third adhesive layer connected to the third base layer.

[0133] In some embodiments, the material of the third base layer includes one or a combination of polyethylene terephthalate, polyimide, polyester film, polyethylene film, non-woven fabric and foam.

[0134] In some embodiments, the material of the third adhesive layer includes one or a combination of acrylic system, rubber system, styrene-isoprene-styrene, isooctyl acrylate, octyl methacrylate, isooctyl methacrylate, isoprene, styrene, butyl acrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, and polymethyl methacrylate.

[0135] In some embodiments, peel strength test: obtained by testing using a high-speed rail tensile machine according to GB / T2792-2014 "Test method for peel strength of adhesive tape". The test process is as follows: discharge the secondary battery to 0V, then disassemble the secondary battery, remove the first insulating part 40, the pole ear assembly 22 and the weld print 101 as a whole, and wipe the electrolyte on the surface with dust-free paper. Then cut into 5mm×10mm strip specimens. Along the length direction of the specimen, the surface of the electrical connector 30 in the specimen facing away from the first insulating part 40 is adhered to the steel plate with double-sided tape (Nitto 5000NS), and the adhesion length is not less than 3mm. Fix the steel plate at the corresponding position of the high-speed rail tensile testing machine, pull up the sample, put the first insulating part 40 into the chuck and clamp it, wherein the angle between the pulled up first insulating part 40 and the steel plate in space is 180°, and the chuck pulls the sample at a speed of 50mm / min5±0.2mm / s. Finally, the average tensile force in the stable area is measured and recorded as the peel strength of the first insulating part 40 and the weld mark 101, in N / mm.

[0136] It is understandable that when testing the peel strength between the second insulating member 50 and the tab assembly 22 , the second insulating member 50 is clamped in a chuck and tested according to the above test method.

[0137] It is understandable that when testing the peel strength between the third insulating member 60 and the tab assembly 22, the third insulating member 60 and the tab assembly 22 are removed as a whole, the third insulating member 60 is clamped in a chuck and tested according to the above test method.

[0138] The present application will be further described below through specific embodiments.

[0139] 1. Cycle test:

[0140] Cycle capacity retention rate: Place the lithium-ion battery in a 25°C environment and let it stand for 30 minutes, then charge and discharge it in the following steps: charge it to 4.25V at a constant current of 1.5C, then charge it to 4.5V at a constant current of 1.2C, then charge it to 4.53V at a constant current of 0.8C, then charge it to 0.14C at a constant voltage, let it stand for 5 minutes, discharge it to 3V at a constant current of 1C, let it stand for 5 minutes, this is one cycle, and record the initial discharge capacity C0 of the lithium-ion battery. Cycle 500 times according to the above cycle steps, and measure the discharge capacity C1 of the lithium-ion battery after 500 cycles. During the cycle test, observe whether the lithium-ion battery has smoke, fire, explosion, etc. Capacity retention rate = C1 / C0×100%.

[0141] Purple spot / lithium deposition area test: After 500 cycles, disassemble the lithium-ion battery and observe the purple spots and lithium deposition status near the negative electrode tape. The non-lithium deposition area on the negative electrode surface is golden yellow, the purple spot area is dark purple, and the lithium deposition area is grayish white. The percentage of the purple spot / lithium deposition area is calculated based on the total area of ​​the single-sided negative electrode material layer. The judgment criteria for the purple spot / lithium deposition status on the surface of the negative electrode are as follows: purple spot / lithium deposition area less than or equal to 1% means no purple spot or no lithium deposition, purple spot / lithium deposition area less than or equal to 3% means mild purple spot / lithium deposition, purple spot / lithium deposition area of ​​3% to 5% means moderate purple spot / lithium deposition, and purple spot / lithium deposition area greater than 5% means severe purple spot / lithium deposition.

[0142] 2. Drop test method: The lithium-ion battery is placed in a 25°C environment and allowed to stand for 30 minutes, and then charged in the following steps: charged to 4.53V at a constant current of 0.5C, and then charged to 0.05C at a constant voltage. After standing for 60 minutes, the voltage of the lithium-ion battery before the drop test is tested; the lithium-ion battery is placed in a fixture and is dropped freely from a position 1.5m above the ground using a drop device in the following order: head-tail-head right corner-tail right corner-head left corner-tail left corner (angle: 45±15°), and repeated 6 rounds. After the drop, stand at room temperature for 24 hours, measure and record the voltage of the lithium-ion battery, and check the appearance of the lithium-ion battery before and after the test and take pictures. The pass judgment standard for the drop test: voltage drop <30mV, disassemble the lithium-ion battery to observe whether the pole ear is damaged or torn, and the pole ear is considered to have passed if it is not damaged or torn, otherwise it is considered to have failed the drop test, (20 lithium-ion batteries were tested, the number of lithium-ion batteries that failed the test was X, and the test failure rate was X / 20.

[0143] In some embodiments, a secondary battery 100 with a 50% SOC initial thickness of 2.43 mm, a length of 110 mm, and a width of 47.6 mm is assembled as follows:

[0144] (1) Preparation of negative electrode sheet: Mix the negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) in a weight ratio of 96:1.5:2.5, add deionized water as a solvent, prepare a slurry with a weight percentage of 50wt%, and stir evenly. Pre-apply foam glue to a part of the surface of the negative electrode current collector copper foil with a thickness of 6μm, and then evenly coat the slurry on one surface of the copper foil, heat to make the foam glue fall off so that part of the surface of the copper foil is exposed, and then dry at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. When preparing a double-sided coated negative electrode sheet, repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Then, the coated sheet is cold pressed to a thickness of 105μm, and a negative electrode tab is die-cut out in the empty foil area at the edge of the negative electrode sheet to form a negative electrode tab assembly.

[0145] (2) Preparation of positive electrode sheet: The positive electrode active materials lithium cobalt oxide (LiCoO2), conductive 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%, and stirred evenly. The slurry is evenly coated on one surface of the aluminum foil, and then dried at 90°C to obtain a positive electrode sheet coated with positive electrode active materials on one side. When preparing a double-sided coated positive electrode sheet, repeat the above coating steps on the other surface of the aluminum foil. The coated electrode sheet is then cold pressed to a thickness of 95μm, and the positive electrode tab is die-cut out in the empty foil area at the edge of the positive electrode sheet to form a positive electrode tab assembly.

[0146] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were 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) was added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0147] (4) Preparation of isolation membrane: A 7 μm thick polyethylene porous polymer film was used as the isolation membrane.

[0148] (5) Preparation of electrode assembly 20: stacking the positive electrode sheet, the separator and the negative electrode sheet, gathering a plurality of tabs to form a tab assembly and welding them to the electrical connector, and pasting the second insulating member 50, the first insulating member 40 and the third insulating member 60.

[0149] (6) Assembly of the electrode assembly 20: Place the aluminum-plastic film with the holes punched and formed in an assembly fixture, with the holes facing upward, place the electrode assembly in the holes, and apply external force to press it. Then, cover the electrode assembly with another aluminum-plastic film with the holes punched and formed, with the holes facing downward, and heat-seal the four sides of the two aluminum-plastic films by hot pressing to obtain an assembled electrode assembly.

[0150] (7) Liquid injection packaging: The assembled electrode assembly is injected with electrolyte, and after vacuum packaging, static standing, hot pressing, shaping and other processes, a secondary battery is produced.

[0151] It should be noted that, except for the parameters in the table, the other parameters of Comparative Examples 1-1 to 1-12 are the same as those of Example 1-1.

[0152] Table 1 (Except for the parameters mentioned in Table 1, all other parameters of Examples 1-2 to 1-15 are the same as those of Example 1-1.)

[0153]

[0154] It can be seen from Examples 1-1 to 1-15 in Table 1 that when T1>T2, T2≥4μm, and 25μm≤T1≤60μm, it is beneficial to reduce the risk of the weld mark 101 puncturing the packaging bag 10, reduce the risk of the tab assembly 22 being broken or falling off due to stress during transportation and use, improve the problem of purple spots and capacity loss after cycling, and enhance the drop performance of the second battery 100.

[0155] From Examples 1-8 to 1-15 in Table 1, it can be seen that as the 2T2 / T value decreases, the thickness difference of the secondary battery 100 decreases, and the purple spot / lithium deposition area decreases. When the 2T2 / T value is less than 4.1%, slight purple spots / lithium deposition appear at the second insulating member 50, and when the 2T2 / T value is less than 1.8%, there is no purple spot / lithium deposition at the second insulating member 50.

[0156] Table 2 (Except for the parameters mentioned in Table 2, all other parameters of Examples 2-1 to 2-14 are the same as those of Example 1-1.)

[0157]

[0158] From Examples 1-1, 2-1 to Example 2-8 in Table 2, it can be seen that when L1>6.7L, there is no significant improvement in improving the capacity loss after cycling. When 1.1L≤L1≤6.7L, it is beneficial for the first insulating member 40 to cover the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, improving the problem of capacity loss after cycling, and saving costs.

[0159] From Examples 1-1, 2-3 to 2-6 in Table 2, it can be seen that when 1.5L≤L1≤5.4L, the problem of capacity loss after cycling is better improved.

[0160] From Example 2-9 to Example 2-14 in Table 2, it can be known that when W1>3W, there is no significant improvement in improving the capacity loss after cycling. When 1.5W≤W1≤3W, it is beneficial for the first insulating member 40 to cover the weld mark 101, reducing the risk of the weld mark 101 piercing the packaging bag 10 and causing a short circuit, improving the problem of capacity loss after cycling, and helping to save costs.

[0161] From Example 2-10 to Example 2-12 in Table 2, it can be seen that when 1.8W≤W1≤2.7W, the problem of capacity loss after cycling is significantly improved.

[0162] Table 3 (Except for the parameters mentioned in Table 3, all other parameters of Examples 3-1 to 3-14 are the same as those of Example 1-1.)

[0163]

[0164]

[0165] From Examples 1-1, 3-1 to 3-3 and 3-5 to 3-11 and 3-13 in Table 3, it can be known that when 3mm≤L5≤8mm and 3mm≤L6≤13mm, it is beneficial to fix the main body 21 and the tab assembly 22, reduce the risk of the tab assembly 22 being broken or falling off due to force during the movement or use of the secondary battery 100, and is beneficial to improving the drop performance of the secondary battery 100.

[0166] From Examples 3-4, 3-12 and 3-14 in Table 3, it can be seen that the portion of L5 greater than 8 mm is likely to take up space, resulting in energy density loss and cost loss. The portion of L6 greater than 13 mm is likely to take up space, resulting in cost loss, and occupies the space at the head of the packaging bag 10, which is likely to affect the sealing of the packaging bag 10.

[0167] See also Figure 7 The present application also provides an electronic device 200 using the secondary battery 100 .

[0168] In one embodiment, the electronic device 200 of the present application may be, but is not limited to, a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, and the like.

[0169] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application, and are not used as limitations on the present application. As long as they are within the spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, comprising a packaging bag, an electrode assembly and an electrical connector, wherein the electrode assembly is located in the packaging bag, the electrode assembly comprises a main body and a tab assembly extending from the main body, the tab assembly comprises a plurality of tabs, one end of the electrical connector is located outside the packaging bag, and the other end is electrically connected to the tab assembly, wherein: The tab assembly includes a first portion and a second portion, the first portion extends from the main body and is connected to the second portion, the second portion is bent toward the main body compared to the first portion, the second portion is welded with the electrical connector to form a weld mark, and the second portion includes a first surface away from the main body and a second surface facing the main body; The secondary battery also includes a first insulating member and a second insulating member, the first insulating member is arranged on the first surface of the second part and covers the weld mark, the second insulating member is located on one side of the thickness direction of the electrode ear, and the second insulating member extends from the first surface of the second part through the first part to the main body, the thickness of the first insulating member is T1, the thickness of the second insulating member is T2, T1>T2, 25μm≤T1≤60μm, T2≥4μm.

2. The secondary battery according to claim 1, wherein The thickness of the electrode assembly is T, and 2T2 / T×100%≤4.1%.

3. The secondary battery according to claim 2, wherein: 2T2 / T×100%≤1.8%.

4. The secondary battery according to claim 1, wherein 30μm≤T1≤50μm.

5. The secondary battery according to claim 1, wherein The first insulating member and the second insulating member at least partially overlap on the first surface.

6. The secondary battery according to claim 5, wherein: An overlapping area of ​​the second insulating member with the first insulating member at least partially overlaps with the weld mark.

7. The secondary battery according to claim 5, wherein: In an overlapping area between the first insulating member and the second insulating member, the second portion, the second insulating member and the first insulating member are stacked in sequence.

8. The secondary battery according to claim 7, wherein: Along the stacking direction of the second insulating member and the first insulating member, the projection of the first insulating member is located inside the second insulating member.

9. The secondary battery according to claim 7, wherein: The area of ​​the first insulating member is A1, the overlapping area between the first insulating member and the second insulating member is A, and A≥16.7%A1.

10. The secondary battery according to claim 1, wherein Along the width direction of the main body of the electrode assembly, the width of the first insulating member is W1, and the width of the weld mark is W; along the extension direction of the electrode ear, the length of the first insulating member is L1, and the length of the weld mark is L, 1.5W≤W1≤3W, 1.1L≤L1≤6.7L.

11. The secondary battery according to claim 10, wherein 1.8W≤W1≤2.7W, 1.5L≤L1≤5.4L.

12. The secondary battery according to claim 1, wherein Along the extension direction of the second insulating member, the overlapping length between the second insulating member and the main body is L5, and the overlapping length between the second insulating member, the tab and the electrical connector is L6, 3mm≤L5≤8mm and 3mm≤L6≤13mm.

13. The secondary battery according to claim 1, wherein The secondary battery further includes an electrolyte sealed in the packaging bag, and the peel strength between the first insulating member and the weld mark is greater than 0.26 N / mm.

14. The secondary battery according to claim 1, wherein The secondary battery further includes an electrolyte sealed in the packaging bag, and the peel strength between the second insulating member and the tab is greater than 0.08 N / mm.

15. The secondary battery according to any one of claims 1 to 14, wherein: The secondary battery also includes a third insulating member, which is located on the side of the tab away from the second insulating member, and extends from the electrical connector through the second surface of the second part and the first part to the main body. The thickness of the third insulating member is T3, and the secondary battery also satisfies: T1>T3.

16. The secondary battery according to claim 15, wherein The thickness of the electrode assembly is T2T3 / T×100%≤4.1%.

17. The secondary battery according to claim 16, wherein 2T3 / T×100%≤1.8%.

18. The secondary battery according to claim 15, wherein Along the extension direction of the third insulating member, the overlapping length between the third insulating member and the main body is L7, and the overlapping length between the third insulating member, the tab and the electrical connector is L8, 3mm≤L7≤8mm and 7mm≤L8≤13mm.

19. The secondary battery according to claim 15, wherein The secondary battery further includes an electrolyte sealed in the packaging bag, and the peel strength between the third insulating member and the tab is greater than 0.08 N / mm.

20. The secondary battery according to claim 15, wherein The first insulating member, the second insulating member and the third insulating member each include a base layer and an adhesive layer, and the adhesive layer is connected to the base layer; The base layer comprises one or a combination of polyethylene terephthalate, polyimide, polyester film, polyethylene film, non-woven fabric and foam; The adhesive layer includes one or a combination of acrylic system, rubber system, styrene-isoprene-styrene, isooctyl acrylate, octyl methacrylate, isooctyl methacrylate, isoprene, styrene, butyl acrylate, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl acetate, and polymethyl methacrylate.

21. An electronic device, wherein: Comprising the secondary battery according to any one of claims 1 to 20.

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