Secondary battery and electronic device

Abstract

The present application relates to a secondary battery and an electronic device. The secondary battery comprises an electrode assembly and a first conductive member; the electrode assembly comprises a first electrode sheet and a plurality of first tabs connected to the first electrode sheet; the plurality of first tabs are stacked and connected to the first conductive member; the first tabs include a first outer tab located at an outermost layer of the stack and a first inner tab located at an inner layer of the stack; the first outer tab comprises a first connecting portion, a first bent portion, and a first welding portion that are connected in sequence; the surface of the first connecting portion is provided with a first insulating coating, and the length of the first insulating coating in the extension direction of the first outer tab is L1; the surface of the first inner tab is provided with a second insulating coating, the second insulating coating comprises a second sub-insulating coating, the surface of the first inner tab adjacent to the first outer tab is provided with the second sub-insulating coating, the length of the second sub-insulating coating in the extension direction of the first inner tab is L2, and L1<L2. The secondary battery and the electronic device of the present application can mitigate the problem of tab fracture failure.

Description

Secondary batteries and electronic devices Technical Field

[0001] This application relates to the field of battery technology, and in particular to a secondary battery and electronic device. Background Technology

[0002] Secondary batteries, as the power source for electronic devices, are crucial for ensuring their normal operation. A secondary battery consists of a casing and electrode assemblies located within it. During a drop, the electrode assemblies are prone to shifting within the casing, and the tabs connecting them to the electrode plates are easily broken and fail. Summary of the Invention

[0003] The inventors of this application have discovered that secondary batteries typically include a casing and an electrode assembly located within the casing. The portion where the tabs connect to the electrode plates is usually coated with an insulating layer to reduce the possibility of electrical connection between the tabs and the casing, other tabs, and other electrode plates. During a drop, the electrode assembly is prone to shifting within the casing. Due to the high hardness of the insulating coating, there is a significant hardness difference between the insulating coating and the tabs. This hardness difference leads to stress concentration. The hardness difference is greatest at the interface between the insulating coating and the non-insulating coating on the tabs. Therefore, the stress concentration is most pronounced at this interface, where the maximum stress concentration point of the tab is located. The tab is prone to breakage and failure at this interface.

[0004] The purpose of this application is to provide a secondary battery and electronic device that aims to improve the problem of tab breakage failure.

[0005] According to a first aspect of the present application, there is provided a secondary battery comprising a case, an electrolyte, an electrode assembly and a first conductive member, wherein the electrolyte and the electrode assembly are accommodated in the case, and the electrode assembly comprises a first pole piece and a plurality of first tabs connected to the first pole piece. In the thickness direction of the electrode assembly, the plurality of first tabs are stacked and connected to the first conductive member, and the first conductive member protrudes out of the case. The first tabs comprise a first outer tab and first inner tabs, the first tab located at the outermost layer of the stack is the first outer tab, and the first tabs located at the inner layer of the stack are the first inner tabs. Along the extension direction of the first outer tab, the first outer tab comprises a first connecting portion, a first bent portion and a first welding portion connected in sequence, the first connecting portion is connected to the first pole piece, the first welding portion is welded to the first conductive member, and a surface of the first connecting portion in the thickness direction is provided with a first insulating coating. Along the extension direction of the first outer tab, the length of the first insulating coating is L1. A surface of the first inner tab in the thickness direction is provided with a second insulating coating, the second insulating coating comprises a second sub-insulating coating, a surface of the first inner tab adjacent to the first outer tab is provided with the second sub-insulating coating, along the extension direction of the first inner tab, the length of the second sub-insulating coating is L2, and L1<L2. Wherein, all the first tabs except the first outer tab are first inner tabs.

[0006] In the above technical solution, the electrode assembly includes a first electrode and multiple first tabs connected to the first electrode. The multiple first tabs are connected to a first conductive element, which extends out of the housing and can transfer energy from the first electrode to the outside of the housing. Stacking multiple first tabs can reduce the space occupied by the first tabs. By providing a first insulating coating on the surface of the first outer tab in the thickness direction, the possibility of electrical connection between the first outer tab and the housing, other tabs, and other electrodes can be reduced. By providing a second insulating coating on the surface of the first inner tab in the thickness direction, the possibility of electrical connection between the first inner tab and the housing, other tabs, and other electrodes can be reduced. During a drop, stress concentration easily occurs at the interface between the tabs with and without insulating coatings. The stress concentration is more pronounced at the interface of the first outer tab, located on the outermost layer of the stack. The first outer tab is prone to bending and compressing the first inner tab of the stack at this interface, making it prone to breakage. By setting the length L1 of the first insulating coating to be less than the length L2 of the second sub-insulating coating, compared to the junction of the first inner electrode adjacent to the first outer electrode where the second sub-insulating coating is provided and where it is not, the junction of the first outer electrode where the first insulating coating is provided and where it is not is closer to the first electrode plate. This allows the first inner electrode adjacent to the first outer electrode to be stressed before the first outer electrode, reducing the stress on the first outer electrode and decreasing stress concentration, thus improving the problem of breakage failure of the first outer electrode. While adhesive tape can also insulate the first outer electrode by bonding it to its surface in the thickness direction, the adhesive strength of the tape decreases when it is wetted by the electrolyte, potentially causing the tape to slide or even detach from the electrode, and the tape's support effect is poor. Furthermore, if the first insulating coating extends beyond the first connecting portion, the effect of the first inner electrode being stressed before the first outer electrode is smaller. Also, the first bending portion will bend during the insertion of the first electrode into the housing. If the first insulating coating extends beyond the first connecting portion, part of the first insulating coating will be located on the surface of the first bending portion. Since the first insulating coating is relatively hard, it is easy for the first insulating coating to break during the bending process of the first bending portion. The breakage of the first insulating coating can easily lead to the breakage of the first electrode. By setting the first insulating coating to be located on the surface of the first connecting portion in the thickness direction, that is, the first insulating coating does not extend beyond the first connecting portion, the possibility of the first insulating coating breaking can be reduced, thereby reducing the possibility of the first electrode breaking.

[0007] In some preferred embodiments, a first insulating coating is provided on the surface of the first outer tab facing the first inner tab. During a drop, the stress concentration on the surface of the first outer tab facing the first inner tab is more pronounced than on the surface of the first outer tab facing away from the first inner tab. By providing a first insulating coating on the surface of the first outer tab facing the first inner tab, the problem of breakage failure of the first outer tab can be improved.

[0008] In some preferred embodiments, a first insulating coating is provided on both opposite surfaces of the first outer electrode in the thickness direction, which can improve the problem of breakage failure of the first outer electrode and further enhance the insulation effect of the first insulating coating on the first outer electrode.

[0009] In some preferred embodiments, the lengths of the first insulating coatings on the two opposing surfaces of the first outer tab are different along the extension direction of the first outer tab and in the thickness direction. When the lengths of the two first insulating coatings are the same, the junction between the two opposing surfaces of the first outer tab where the first insulating coating is applied and where the first insulating coating is not applied will coincide in the thickness direction of the first outer tab, resulting in significant stress concentration at this junction. By setting the lengths of the two first insulating coatings to be different, the junction between the two opposing surfaces of the first outer tab where the first insulating coating is applied and where the first insulating coating is not applied will not coincide in the thickness direction of the first outer tab, thus dispersing the stress on the first outer tab, reducing stress concentration, and consequently reducing the possibility of the first outer tab breaking.

[0010] In some preferred embodiments, the characteristic is that L1≥0.5mm, which is beneficial to improving the insulation effect of the first insulating coating on the first outer electrode.

[0011] In some preferred embodiments, the first insulating coating includes ceramic insulating particles and an adhesive. The ceramic insulating particles have high strength, which can improve the support effect of the first insulating coating.

[0012] In some preferred embodiments, the ceramic insulating particles include boehmite and / or alumina, which can improve the strength of the ceramic insulating particles.

[0013] In some preferred embodiments, the first insulating coating includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, which can improve the insulating effect of the first insulating coating.

[0014] In some preferred embodiments, the thickness of the first insulating coating is between 5 μm and 45 μm. A thickness ≥ 5 μm of the first insulating coating is beneficial for improving the insulation effect of the first insulating coating on the first outer electrode. A thickness ≤ 45 μm of the first insulating coating is beneficial for reducing the possibility of the first insulating coating losing energy density of the secondary battery.

[0015] In some preferred embodiments, the first electrode is a positive electrode, and the first tab is a positive tab. Since the positive electrode is usually shorter than the negative electrode, the positive tab can easily come into contact with the negative electrode. By providing an insulating coating on the surface of the positive tab in the thickness direction, the possibility of electrical connection between the positive tab and the negative electrode can be reduced.

[0016] In some preferred embodiments, along the extending direction of the first inner electrode tab, the first inner electrode tab includes a second connecting portion, a second bending portion, and a second welding portion connected in sequence. The second connecting portion is connected to the first electrode plate, and the second welding portion is connected to the first conductive element, which can transfer the energy of the first electrode plate to the first conductive element. A second insulating coating is provided on the surface of the second connecting portion in the thickness direction. Along the extending direction of the first inner electrode tab, the second insulating coating extends beyond the second connecting portion, which helps to increase the possibility that the first inner electrode tab is subjected to force before the first outer electrode tab, thereby further reducing the force on the first outer electrode tab.

[0017] In some preferred embodiments, the second weld portion is welded to the first conductive element, forming a solder mark. Along the extension direction of the first inner tab, the distance between the second insulating coating and the solder mark is T1, where T1 ≥ 0.5 mm, which can reduce the possibility that the second insulating coating will affect the welding effect between the second weld portion and the first conductive element.

[0018] In some preferred embodiments, a second insulating coating is provided on both opposite surfaces of the first inner tab in the thickness direction, which can further reduce the possibility of the first inner tab becoming electrically connected to the housing, other tabs, and other electrode plates.

[0019] In some preferred embodiments, the second insulating coating includes ceramic insulating particles and an adhesive. The ceramic insulating particles have high strength, which can improve the support effect of the second insulating coating.

[0020] In some preferred embodiments, 0.5mm ≤ L2-L1 ≤ 3mm. The larger the value of L2-L1, the greater the degree to which the first inner tab is stressed before the first outer tab, resulting in a better reduction in stress concentration on the first outer tab. Setting L2-L1 ≥ 0.5mm helps to further improve the problem of first outer tab fracture failure. However, the larger the value of L2-L1, the smaller L1 becomes, leading to a poorer insulation effect of the first insulating coating on the first outer tab. Furthermore, the larger L2 becomes, the easier it is for the second insulating coating to approach the solder joint. Therefore, it is preferable that L2-L1 ≤ 3mm, which is beneficial for improving the insulation effect of the first insulating coating on the first outer tab and reducing the possibility of the second insulating coating affecting the welding effect between the second weld and the first conductive component.

[0021] In some preferred embodiments, all second insulating coatings have the same length, which helps improve production continuity. It should be noted that, due to dimensional tolerances, "all second insulating coatings have the same length" means that the length difference between all second insulating coatings is ≤0.2 mm.

[0022] Secondly, this application also proposes an electronic device including a secondary battery as described in any of the embodiments of the first aspect above.

[0023] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0024] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the dimensions in the drawings do not constitute a limitation on scale.

[0025] Figure 1 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application;

[0026] Figure 2 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application;

[0027] Figure 3 is a schematic diagram of the structure of an electrode assembly according to some embodiments of this application;

[0028] Figure 4 is a schematic diagram of the structure of an electrode assembly according to some embodiments of this application;

[0029] Figure 5 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0030] Figure 6 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0031] Figure 7 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0032] Figure 8 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0033] Figure 9 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0034] Figure 10 is a schematic diagram of the unfolded structure of the first inner electrode tab and the first conductive element according to some embodiments of this application;

[0035] Figure 11 is a schematic diagram of the structure of the first electrode, the first electrode tab, and the first conductive element in some embodiments of this application;

[0036] Figure 12 is a schematic diagram of the structure of a secondary battery according to some embodiments of this application.

[0037] Explanation of reference numerals in the attached drawings: 100, secondary battery; 10, casing; 20, electrode assembly; 21, first electrode; 211, first current collector; 212, first active layer; 22, second electrode; 221, second current collector; 222, second active layer; 23, separator; 24, first tab; 241, first outer tab; 2411, first connecting part; 2412, first bending part; 2413, first weld; 242, first inner tab; 2421, second connecting part; 2422, second bending part; 2423, second weld; 2424, solder mark; 25, second tab; 26, first insulating coating; 27, second insulating coating; 271, second sub-insulating coating; 30, first conductive element; 40, second conductive element. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0039] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0040] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0041] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0042] The term "perpendicular" is used to describe an ideal state between two components. In actual production or use, two components can exist in a state that is approximately perpendicular. For example, in numerical terms, perpendicularity can refer to the angle between two straight lines within the range of 90 ± 10°, the dihedral angle between two planes within the range of 90 ± 10°, or the angle between a straight line and a plane within the range of 90 ± 10°. The two components described as "perpendicular" do not have to be absolutely straight lines or planes; they can be approximately straight lines or planes. From a macroscopic perspective, if the overall direction of extension is straight or plane, the component can be considered a "straight line" or "plane".

[0043] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0044] In a first aspect, embodiments of this application provide a secondary battery 100. Referring to Figure 1, the secondary battery 100 includes a housing 10, an electrolyte, an electrode assembly 20, a first conductive element 30, and a second conductive element 40. The housing 10 can accommodate the electrode assembly 20 and the electrolyte (not shown in the figure), and the electrolyte wets the electrode assembly 20 within the housing 10. The first conductive element 30 and the second conductive element 40 are respectively connected to the electrode assembly 20, and both the first conductive element 30 and the second conductive element 40 extend out of the housing 10 to assist the electrode assembly 20 in energy transfer with external electronic devices.

[0045] Referring to Figure 2, which illustrates the stacked structure of the electrode assembly 20, the electrode assembly 20 includes a first electrode 21, a diaphragm 23, and a second electrode 22. The first electrode 21 and the second electrode 22 have opposite polarities. A diaphragm 23 is disposed between adjacent second electrode 22 and first electrode 21. The first electrode 21, diaphragm 23, and second electrode 22 are stacked. In the embodiments of this application, the electrode assembly 20 is described as a stacked structure. In other embodiments, the electrode assembly 20 may also be a wound structure. For example, the first electrode 21, diaphragm 23, and second electrode 22 are sequentially stacked and wound to form a wound electrode assembly 20.

[0046] In some embodiments, please refer to FIG3, the first electrode 21 includes a first current collector 211 and a first active layer 212, and the surface of the first current collector 211 is provided with the first active layer 212.

[0047] In some embodiments, the first current collector 211 may be an aluminum foil or a copper foil.

[0048] In some embodiments, the first active layer 212 is immersed in the electrolyte within the housing 10 to undergo an electrochemical reaction. The first active layer 212 includes a positive electrode active material, a conductive agent, a binder, etc., and the above materials are mixed and stirred evenly and coated onto the surface of the first current collector 211 to obtain the first active layer 212. The positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium manganese iron phosphate.

[0049] In some embodiments, referring to Figures 2, 3, and 4, the first current collector 211 is connected to a plurality of first tabs 24. In the thickness direction of the electrode assembly 20, the plurality of first tabs 24 are stacked and connected to the first conductive element 30, enabling the transfer of energy from the first electrode 21 to the first conductive element 30. The stacking of the plurality of first tabs 24 reduces the space occupied by the first tabs 24.

[0050] In some embodiments, the first current collector 211 and the first tab 24 are integrally disposed.

[0051] In some embodiments, the second electrode 22 includes a second current collector 221 and a second active layer 222, and the second active layer 222 is disposed on the surface of the second current collector 221. The second current collector 221 is connected to a second tab 25, and the second current collector 221 and the second tab 25 are integrally disposed.

[0052] In some embodiments, the second current collector 221 may be an aluminum foil or a copper foil.

[0053] In some embodiments, the second active layer 222 is immersed in the electrolyte within the housing 10 to undergo an electrochemical reaction. The second active layer 222 includes a negative electrode active material, a conductive agent, a binder, etc., and the above materials are mixed and stirred evenly and coated onto the surface of the second current collector 221 to obtain the second active layer 222. The negative electrode active material may include at least one of graphite, silicon, hard carbon, and carbon fiber.

[0054] In some embodiments, referring to FIG. 2 and FIG. 5, the first tab 24 includes a first outer tab 241 and a first inner tab 242. The first tab 24 located at the outermost layer of the stack is the first outer tab 241, and the first tab 24 located at the inner layer of the stack is the first inner tab 242. All the first tabs 24 except the first outer tab 241 are the first inner tabs 242. A first insulating coating 26 is provided on the surface of the first outer tab 241 in the thickness direction, which can reduce the possibility of electrical connection between the first outer tab 241 and the casing 10, other tabs and other pole pieces. A second insulating coating 27 is provided on the surface of the first inner tab 242 in the thickness direction, which can reduce the possibility of electrical connection between the first inner tab 242 and the casing 10, other tabs and other pole pieces. However, when the secondary battery 100 drops, the electrode assembly 20 is prone to shifting inside the casing 10. Since the first insulating coating 26 has high hardness, there is a large hardness difference between the insulating coating and the tab, and the hardness difference will lead to stress concentration. The hardness difference at the junction between the region where the insulating coating is provided and the region where the insulating coating is not provided on the tab is the largest. The stress concentration at the junction between the region where the first insulating coating 26 is provided and the region where the first insulating coating 26 is not provided on the first outer tab 241 located at the outermost layer of the stack is more obvious, and the first outer tab 241 is prone to bend at the junction and extrude the first inner tab 242 located at the inner layer of the stack, resulting in easy fracture and failure of the first outer tab 241.

[0055] To improve the above problem, referring to FIG. 6, in the embodiment of the present application, along the extension direction of the first outer tab 241, the length of the first insulating coating 26 is L1. The second insulating coating 27 includes a second sub-insulating coating 271, the surface of the first inner tab 242 adjacent to the first outer tab 241 is provided with the second sub-insulating coating 271, along the extension direction of the first inner tab 242, the length of the second sub-insulating coating 271 is L2, and L1<L2. By setting the length L1 of the first insulating coating 26 smaller than the length L2 of the second sub-insulating coating 271, the junction between the region where the first insulating coating 26 is provided and the region where the first insulating coating 26 is not provided on the first outer tab 241 is closer to the first pole piece 21 compared with the junction between the region where the second sub-insulating coating 271 is provided and the region where the second sub-insulating coating 271 is not provided on the first inner tab 242 adjacent to the first outer tab 241. The first inner tab 242 adjacent to the first outer tab 241 can receive force before the first outer tab 241, which can reduce the stress on the first outer tab 241, reduce the stress concentration of the first outer tab 241, and further improve the problem of fracture and failure of the first outer tab 241. Although insulating the first outer tab 241 by adhering an adhesive tape to the surface of the first outer tab 241 in the thickness direction can also achieve insulation, the adhesiveness of the adhesive tape will decrease after being infiltrated by electrolyte, relative sliding or even falling off may occur between the adhesive tape and the tab, and the supporting effect of the adhesive tape is poor.

[0056] In some embodiments, along the extending direction of the first outer electrode 241, the first outer electrode 241 includes a first connecting portion 2411, a first bending portion 2412, and a first welding portion 2413 connected in sequence. The first connecting portion 2411 is connected to the first electrode 21. The maximum curvature point of the first outer electrode 241 is located at the boundary edge between the first bending portion 2412 and the first connecting portion 2411. The first welding portion 2413 is welded to the first conductive member 30. A first insulating coating 26 is provided on the surface of the first connecting portion 2411 in the thickness direction. During the insertion of the first tab 24 into the housing 10, the first bending portion 2412 will bend. If the first insulating coating 26 extends beyond the first connecting portion 2411, part of the first insulating coating 26 will be located on the surface of the first bending portion 2412. Since the first insulating coating 26 is relatively hard, it is easy for the first insulating coating 26 to break during the bending process of the first bending portion 2412. The breakage of the first insulating coating 26 can easily lead to the breakage of the first tab 24. By setting the first insulating coating 26 to be located on the surface of the first connecting portion 2411 in the thickness direction, that is, the first insulating coating 26 does not extend beyond the first connecting portion 2411, the possibility of the first insulating coating 26 breaking can be reduced, thereby reducing the possibility of the first tab 24 breaking.

[0057] In some embodiments, referring to Figure 7, a first insulating coating 26 is provided on the surface of the first outer tab 241 facing the first inner tab 242. During a drop, the stress concentration on the surface of the first outer tab 241 facing the first inner tab 242 is more pronounced than on the surface of the first outer tab 241 facing away from the first inner tab 242. By providing the first insulating coating 26 on the surface of the first outer tab 241 facing the first inner tab 242, the problem of breakage failure of the first outer tab 241 can be improved.

[0058] In some embodiments, referring to Figure 8, a first insulating coating 26 is provided on both opposite surfaces of the first outer tab 241 in the thickness direction. This can improve the problem of breakage failure of the first outer tab 241 and further enhance the insulation effect of the first insulating coating 26 on the first outer tab 241. In some embodiments, the lengths of the first insulating coating 26 on both opposite surfaces of the first outer tab 241 in the thickness direction can be the same along the extension direction of the first outer tab 241. It should be noted that, due to dimensional errors, the same length of the first insulating coating 26 on both opposite surfaces of the first outer tab 241 in the thickness direction means that the length difference of the first insulating coating 26 on both opposite surfaces of the first outer tab 241 in the thickness direction is ≤0.2mm.

[0059] In some embodiments, the feature is that L1≥0.5mm, which is beneficial to improving the insulation effect of the first insulating coating 26 on the first outer tab 241.

[0060] In some embodiments, the first insulating coating 26 includes ceramic insulating particles and an adhesive. The ceramic insulating particles have high strength, which can improve the support effect of the first insulating coating 26.

[0061] In some embodiments, the ceramic insulating particles include boehmite and / or alumina, which can enhance the strength of the ceramic insulating particles.

[0062] In some embodiments, the first insulating coating 26 includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, which can improve the insulating effect of the first insulating coating 26.

[0063] In some embodiments, the thickness H1 of the first insulating coating 26 is 5 μm to 45 μm. A thickness ≥ 5 μm of the first insulating coating 26 is beneficial for improving the insulation effect of the first insulating coating 26 on the first outer tab 241. A thickness ≤ 45 μm of the first insulating coating 26 is beneficial for reducing the possibility of the first insulating coating 26 losing energy density of the secondary battery 100.

[0064] In some embodiments, the first electrode 21 is a positive electrode, and the first tab 24 is a positive tab. Since the positive electrode is usually shorter than the negative electrode, the positive tab can easily come into contact with the negative electrode. By providing an insulating coating on the surface of the positive tab in the thickness direction, the possibility of electrical connection between the positive tab and the negative electrode can be reduced.

[0065] In some embodiments, referring to Figures 9 and 10, along the extending direction of the first inner electrode tab 242, the first inner electrode tab 242 includes a second connecting portion 2421, a second bending portion 2422, and a second welding portion 2423 connected in sequence. The second connecting portion 2421 is connected to the first electrode 21, and the maximum curvature point of the first inner electrode tab 242 is located at the junction edge of the second bending portion 2422 and the second connecting portion 2421. The second welding portion 2423 is welded to the first conductive element 30, which can transfer the energy of the first electrode 21 to the first conductive element 30. A second insulating coating 27 is provided on the surface of the second connecting portion 2421 in the thickness direction. Along the extending direction of the first inner electrode tab 242, the second insulating coating 27 extends beyond the second connecting portion 2421, which helps to increase the possibility that the first inner electrode tab 242 is subjected to force before the first outer electrode tab 241, thereby further reducing the force on the first outer electrode tab 241.

[0066] In some embodiments, the second weld portion 2423 is welded to the first conductive element 30, forming a solder mark 2424. Along the extending direction of the first inner tab 242, the distance between the second insulating coating 27 and the solder mark 2424 is T1, where T1 ≥ 0.5 mm, which can reduce the possibility that the second insulating coating 27 will affect the welding effect between the second weld portion 2423 and the first conductive element 30.

[0067] In some embodiments, 0.5mm ≤ L2-L1 ≤ 3mm. The larger the value of L2-L1, the greater the degree to which the first inner tab 242 is subjected to force before the first outer tab 241, and the better the effect of reducing stress concentration on the first outer tab 241. Setting L2-L1 ≥ 0.5mm is beneficial to further improve the problem of fracture failure of the first outer tab 241. However, the larger the value of L2-L1, the smaller L1 will be, the worse the insulation effect of the first insulating coating 26 on the first outer tab 241 will be, and the larger L2 will be, the easier it will be for the second insulating coating 27 to approach the solder mark 2424. Therefore, it is preferable that L2-L1 ≤ 3mm, which is beneficial to improve the insulation effect of the first insulating coating 26 on the first outer tab 241, and to reduce the possibility that the second insulating coating 27 will affect the welding effect between the second welded part 2423 and the first conductive element 30.

[0068] In some embodiments, all second insulating coatings 27 have the same length, which is beneficial for improving production continuity. It should be noted that, due to dimensional errors, all second insulating coatings 27 having the same length means that the length difference of all second insulating coatings 27 is ≤0.2mm.

[0069] In some embodiments, referring to FIG11, a second insulating coating 27 is provided on both opposite surfaces of the first inner tab 242 in the thickness direction, which can further reduce the possibility of the first inner tab 242 being electrically connected to the housing 10, other tabs and other electrode sheets.

[0070] In some embodiments, along the extension direction of the first outer tab 241, the lengths of the first insulating coatings 26 on opposite surfaces of the first outer tab 241 in the thickness direction are different. When the lengths of the two layers of first insulating coatings 26 are the same, the junction between the opposite surfaces of the first outer tab 241 where the first insulating coating 26 is provided and where the first insulating coating 26 is not provided will coincide in the thickness direction of the first outer tab 241, resulting in significant stress concentration at this junction. By setting the lengths of the two layers of first insulating coatings 26 to be different, the junction between the opposite surfaces of the first outer tab 241 where the first insulating coating 26 is provided and where the first insulating coating 26 is not provided will not coincide in the thickness direction of the first outer tab 241, thus dispersing the stress of the first outer tab 241, thereby reducing stress concentration and reducing the possibility of the first outer tab 241 breaking and failing.

[0071] In some embodiments, along the extending direction of the first inner tab 242, the lengths of the second insulating coatings 27 on opposite surfaces in the thickness direction of the first inner tab 242 may be the same. It should be noted that, due to dimensional errors, the same lengths of the second insulating coatings 27 on opposite surfaces in the thickness direction of the first inner tab 242 means that the length difference of the second insulating coatings 27 on opposite surfaces in the thickness direction of the first inner tab 242 is ≤0.2mm.

[0072] In some embodiments, the second insulating coating 27 includes ceramic insulating particles and an adhesive. The ceramic insulating particles have high strength, which can improve the support effect of the second insulating coating 27.

[0073] In some embodiments, all first insulating coatings 26 have the same width and the same thickness, which can improve the uniformity of force on the first outer electrode tab 241. In other embodiments, the width and thickness of each first insulating coating 26 may be different.

[0074] In some embodiments, all second insulating coatings 27 have the same width and the same thickness, which can improve the uniformity of force on the first inner tab 242. In other embodiments, the width and thickness of each second insulating coating 27 may be different.

[0075] In some embodiments, the width of the first insulating coating 26 and the width of the second insulating coating 27 are the same, and the thickness of the first insulating coating 26 and the thickness of the second insulating coating 27 are the same, which can improve the uniformity of force on the first electrode tab 24. In other embodiments, the width of the first insulating coating 26 and the width of the second insulating coating 27 may be different, and the thickness of the first insulating coating 26 and the thickness of the second insulating coating 27 may be different.

[0076] In some embodiments, referring to Figures 4 and 12, the second current collector 221 is connected to a plurality of second tabs 25. The plurality of second tabs 25 are stacked and connected to the second conductive element 40, which can transfer the energy of the second electrode 22 to the second conductive element 40. The stacking of the second tabs 25 can reduce the space occupied by the second tabs 25.

[0077] A second aspect of this application also provides an electronic device including a secondary battery 100 as described in any embodiment of the first aspect above. The electronic device in this application is not particularly limited and 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, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0078] Test section:

[0079] 1. Drop test of secondary batteries:

[0080] In a test environment of 20±5℃, on a stainless steel or marble floor, the sample is dropped from a height of 1.8m along the head and tail sides once, and then dropped from the four corners once, for a total of 7 rounds of testing. The drop order is (head -> tail -> head right corner -> tail right corner -> head left corner -> tail left corner (angle: 45±15 degrees, 6 times per round)). The drop test pass standard is: after removing the battery cell from the casing, observe the surface of the tabs for cracks using SEM (scanning electron microscope). If there are cracks on the surface of the tabs, the drop test fails.

[0081] Example 1

[0082] <Preparation of the positive electrode>:

[0083] Lithium cobalt oxide (LiCoO2), carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly.

[0084] Aluminum foil is selected as the positive electrode current collector. The above-mentioned slurry is coated on one surface of the positive electrode current collector, leaving a blank positive electrode foil section. The slurry is dried to obtain a single-sided positive electrode sheet with a positive electrode active material layer coated on one side. The above steps are repeated on the other surface of the positive electrode current collector to obtain a double-sided positive electrode sheet with a positive electrode active material layer coated on both sides. The blank positive electrode foil section is die-cut to form the first electrode tab.

[0085] <Preparation of negative electrode sheet>:

[0086] The negative electrode active material graphite, the binder styrene-butadiene rubber (SBR) and the thickener sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 96:2:2, and deionized water was added as a solvent to prepare a slurry with a solid content of 70 wt%, which was then stirred evenly.

[0087] Copper foil is selected as the negative electrode current collector. The above-mentioned slurry is coated on one surface of the negative electrode current collector, leaving a blank negative electrode foil section. The slurry is dried to obtain a single-sided negative electrode sheet with a negative electrode active material layer coated on one side. The above steps are repeated on the other surface of the negative electrode current collector to obtain a double-sided negative electrode sheet with a negative electrode active material layer coated on both sides. The blank negative electrode foil section is die-cut to form a second electrode tab.

[0088] <Preparation of the diaphragm>:

[0089] A porous polyethylene membrane is used as the substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one side of the substrate layer as a separator (CCS), wherein the mass percentage of alumina ceramic in the ceramic layer is 95%.

[0090] <Electrolyte Preparation>:

[0091] 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. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the basic organic solvent, dissolved, and mixed evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0092] <Preparation of Secondary Batteries>:

[0093] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to act as a separator. The stacked electrodes form the electrode assembly.

[0094] Aluminum foil is selected as the first conductive element. First tabs are stacked and connected to the first conductive element. The first tabs include a first outer tab and a first inner tab. The first tab located on the outermost layer of the stack is the first outer tab, and the first tab located on the innermost layer is the first inner tab. All other first tabs besides the first outer tab are first inner tabs. Along the extension direction of the first outer tab, the first outer tab includes a first connecting portion, a first bending portion, and a first welding portion connected in sequence. The first connecting portion is connected to the first electrode sheet. The maximum curvature point of the first outer tab is located at the boundary edge between the first bending portion and the first connecting portion. The first welding portion is welded to the first conductive element. The first connecting portion includes an inner surface facing the first inner tab and an outer surface facing away from the first inner tab. Both the inner and outer surfaces of the first connecting portion are coated with alumina particles and adhesive slurry to form a 25μm thick first insulating coating. Along the extension direction of the first outer tab, the first insulating coating does not extend beyond the first connecting portion, and the length L1 of the first insulating coating is 1.5mm.

[0095] Along the extending direction of the first inner electrode tab, the first inner electrode tab includes a second connecting portion, a second bending portion, and a second welding portion connected in sequence. The second connecting portion is connected to the first electrode plate. The maximum curvature point of the first inner electrode tab is located at the boundary edge between the second bending portion and the second connecting portion. The second welding portion is welded to the first conductive element, forming a solder mark. Both opposing surfaces of the second connecting portion are coated with alumina particles and adhesive slurry to form a 25μm thick second insulating coating. Along the extending direction of the first inner electrode tab, the second insulating coating does not extend beyond the second connecting portion. The second insulating coating includes a second sub-insulating coating. The surface of the first inner electrode tab adjacent to the first outer electrode tab is provided with the second sub-insulating coating, and the length L2 of the second sub-insulating coating is 2mm. All second insulating coatings are 2mm long, and the distance T1 between the second insulating coating and the solder mark is 3mm.

[0096] The electrode assembly is hot-pressed, placed into the aluminum-plastic film of the housing, injected with electrolyte, and encapsulated to obtain a secondary battery. The first conductive element extends out of the housing, the length of the secondary battery is 60 mm, and the width of the secondary battery is 50 mm.

[0097] The relevant parameters in Comparative Examples 1 to 6 and Examples 1 to 13 are shown in Table 1 below.

[0098] In Comparative Examples 1 to 5 and Examples 1 to 12, all second insulating coatings have the same length. In Comparative Example 6, the surface of the innermost first inner electrode tab is provided with a second sub-insulating coating, the length L2 of which is 2 mm, and the lengths of the other second insulating coatings besides the second sub-insulating coating are 2.5 mm. In Example 13, the surface of the first inner electrode tab adjacent to the first outer electrode tab is provided with a second sub-insulating coating, the length L2 of which is 2 mm, and the lengths of the other second insulating coatings besides the second sub-insulating coating are 2.5 mm.

[0099] In Comparative Example 1 and Examples 1 to 5, the first and second insulating coatings are both two layers. In Comparative Example 1 and Examples 1 to 3, the second insulating coating does not extend beyond the second connecting portion, while in Examples 4 and 5, the second insulating coating extends beyond the second connecting portion.

[0100] In Comparative Examples 2 and 3, and Examples 6 to 9, the first and second insulating coatings are both one layer. In Comparative Example 2, and Examples 6 and 8, the first insulating coating is located on the surface (inner surface) of the first outer electrode ear facing the first inner electrode ear. In Comparative Example 3, and Examples 7 and 9, the first insulating coating is located on the surface (outer surface) of the first outer electrode ear away from the first inner electrode ear. In Examples 8 and 9, the second insulating coating extends beyond the second connecting portion.

[0101] In Comparative Example 4 and Examples 10 and 11, the first insulating coating is one layer, and the second insulating coating is two layers.

[0102] In Example 12, the lengths of the first insulating coatings on the two opposite surfaces of the first outer tab are different, and the length difference between the two layers of the first insulating coating is 0.5 mm.

[0103] Table 1

[0104] According to Table 1 above, and in conjunction with Comparative Examples 1 to 6 and Examples 1 to 13, it can be seen that by setting a second insulating coating including a second sub-insulating coating, the surface of the first inner electrode adjacent to the first outer electrode is provided with a second sub-insulating coating. The length L1 of the first insulating coating is less than the length L2 of the second sub-insulating coating. Compared with the junction of the first inner electrode where the second sub-insulating coating is provided and where the second sub-insulating coating is not provided, the junction of the first outer electrode where the first insulating coating is provided and where the first insulating coating is not provided is closer to the first electrode plate. The first inner electrode adjacent to the first outer electrode can be subjected to force before the first outer electrode, which can reduce the force on the first outer electrode, reduce the stress concentration of the first outer electrode, and thus improve the problem of the first outer electrode fracture failure. The drop test pass rate of the secondary battery will increase, and the safety performance of the secondary battery can be improved.

[0105] Based on Comparative Example 5 and Example 1, it can be seen that, compared to the first insulating coating having a length L1 greater than the second sub-insulating coating having a length L2, the first insulating coating having a length L1 less than the second sub-insulating coating having a length L2, the first inner electrode adjacent to the first outer electrode can be subjected to force before the first outer electrode, which can improve the problem of the first outer electrode breaking and failing. Therefore, the secondary battery has a better drop test pass rate and better safety performance.

[0106] Based on Comparative Example 6 and Example 13, it can be seen that, compared to the second sub-insulating coating not being located on the surface of the first inner electrode adjacent to the first outer electrode, the second sub-insulating coating being located on the surface of the first inner electrode adjacent to the first outer electrode results in a more significant degree of stress on the first inner electrode adjacent to the first outer electrode, which more significantly improves the problem of the first outer electrode breaking and failing. Therefore, the secondary battery has a better drop test pass rate and better safety performance.

[0107] As can be seen from Examples 1 to 3, the smaller L1 is, the closer the junction between the first outer electrode tab with the first insulating coating and the one without the first insulating coating will be to the first electrode plate. The first outer electrode tab will be subjected to force later than the first inner electrode tab, and the force on the first outer electrode tab will be smaller. The drop test pass rate of the secondary battery will be higher. However, if the length L1 of the first insulating coating is small, the insulation effect of the first insulating coating on the first outer electrode tab will be poor. Therefore, it is preferable that L1 ≥ 0.5 mm, which is beneficial to improving the insulation effect of the first insulating coating on the first outer electrode tab.

[0108] As shown in Examples 1, 4, and 5, the larger L2 is, the more force is applied to the first inner tab before the first outer tab, resulting in less force on the first outer tab and a higher drop test pass rate for the secondary battery. However, if the second insulating coating is too long, it is prone to approaching the solder mark, thus affecting the welding effect between the second weld and the first conductive component. By setting the distance T1 between the second insulating coating and the solder mark to ≥ 0.5 mm, the possibility of the second insulating coating affecting the welding effect between the second weld and the first conductive component can be reduced. Furthermore, as shown in Examples 6 to 11, compared to when the second insulating coating does not extend beyond the second connection portion, when the second insulating coating extends beyond the second connection portion, the drop test pass rate of the secondary battery is higher.

[0109] Based on Examples 1 to 3 and Examples 1, 4, and 5, when the length of L2 or L1 remains constant, the larger the value of L2-L1, the greater the degree to which the first inner tab is subjected to force before the first outer tab, resulting in a better reduction in stress concentration on the first outer tab and thus a higher drop test pass rate for the secondary battery. Setting L2-L1 ≥ 0.5 mm is beneficial for improving the drop test pass rate of the secondary battery. However, the larger the value of L2-L1, the smaller L1 becomes, leading to a poorer insulation effect of the first insulating coating on the first outer tab. Furthermore, a larger L2 makes it easier for the second insulating coating to approach the solder joint. Therefore, L2-L1 ≤ 3 mm is preferable, as it improves the insulation effect of the first insulating coating on the first outer tab and reduces the possibility of the second insulating coating affecting the welding effect between the second weld and the first conductive component.

[0110] As can be seen from Examples 1 and 10, and Examples 4 and 11, compared to having a first insulating coating on both opposite surfaces of the first outer tab, having a first insulating coating on only one surface of the first outer tab results in a higher drop test pass rate for the secondary battery. This is because the first insulating coating includes materials with high hardness such as aluminum oxide, making its hardness greater than that of the first tab. The significant hardness difference between the first insulating coating and the first tab leads to more pronounced surface stress concentration on the first outer tab compared to having a first insulating coating on only one surface. This results in a more significant risk of breakage and failure. However, considering short-circuit safety, having a first insulating coating on both opposite surfaces of the first outer tab better reduces the risk of short circuits. Therefore, if the breakage and failure rate of the first outer tab is not significantly reduced when having a first insulating coating on both opposite surfaces, then considering short-circuit safety further, having a first insulating coating on both opposite surfaces of the first outer tab is better than having it on only one surface.

[0111] As can be seen from Examples 6 and 7, and Examples 8 and 9, compared to the surface (outer surface) of the first outer electrode ear that is away from the first inner electrode ear, the surface (inner surface) of the first outer electrode ear that faces the first inner electrode ear is closer to the inner layer of the stack, and the stress concentration is more obvious. By setting the first insulating coating on the surface of the first outer electrode ear facing the first inner electrode ear, compared with setting the first insulating coating on the surface of the first outer electrode ear that is away from the first inner electrode ear, the drop test pass rate is higher, which can better improve the problem of the first outer electrode ear fracture failure.

[0112] As can be seen from Examples 6 and 10, as well as Examples 8 and 11, compared to providing a second insulating coating on one surface of the first inner electrode, providing a second insulating coating on the opposite two surfaces of the first inner electrode will make the surface stress concentration of the first inner electrode more obvious, which can reduce the stress on the first outer electrode, thereby reducing the possibility of the first outer electrode breaking and failing, and increasing the drop test pass rate of the secondary battery.

[0113] As can be seen from Examples 1 and 12, when both opposite surfaces of the first outer tab are provided with a first insulating coating, the drop test pass rate of the secondary battery increases when the lengths of the two first insulating coatings are different. The reason is that when the lengths of the two first insulating coatings are the same, the junction between the opposite surfaces of the first outer tab where the first insulating coating is provided and where the first insulating coating is not provided will coincide in the thickness direction of the first outer tab. Therefore, there will be a large stress concentration at this junction. By setting the lengths of the two first insulating coatings to be different, the junction between the opposite surfaces of the first outer tab where the first insulating coating is provided and where the first insulating coating is not provided will not coincide in the thickness direction of the first outer tab. This can disperse the stress of the first outer tab, thereby reducing stress concentration and reducing the possibility of the first outer tab breaking and failing. Therefore, the drop test pass rate of the secondary battery increases.

[0114] The relevant parameters for Examples 1 and 14 to 19 are shown in Table 2 below. The only difference between Examples 1 and 14 to 19 is the thickness of the first insulating coating.

[0115] Table 2

[0116] Based on Examples 1 and 14 to 19 in Table 2 above, it can be seen that when the thickness of the first insulating coating is 5 μm to 45 μm, the drop safety is good. Furthermore, when the thickness of the first insulating coating is 10 μm to 45 μm, the secondary battery exhibits a good drop test pass rate (number of passes / number of tests). Due to the significant difference in hardness between the first insulating coating and the first outer tab, stress concentration occurs at the interface between the first and non-first insulating coating areas on the first outer tab. The smaller the thickness of the first insulating coating, the smaller the impact of the hardness difference on the first outer tab, and the smaller the stress concentration at the interface between the first and non-first insulating coating areas on the first outer tab. This improves the effectiveness of preventing breakage of the first outer tab and results in a better drop test pass rate for the secondary battery. However, when the thickness of the first insulating coating is less than 5 μm, the insulation effect of the first insulating coating decreases. When the thickness of the first insulating coating is greater than 45 μm, stress concentration will be more pronounced at the interface between the first outer tab and the area without the first insulating coating, leading to a lower drop test pass rate for the secondary battery and a greater loss of energy density. Furthermore, a first insulating coating thickness of 10 μm to 30 μm provides better drop safety and insulation performance. Since the second insulating coating has similar properties to the first insulating coating, its preferred thickness is the same as the first insulating coating.

[0117] In Table 1, Comparative Examples 2 to 4 only have a first insulating coating on one surface of the first outer tab. Therefore, the insulation performance of the first insulating coating in Comparative Examples 2 to 4 for the first outer tab is insufficient. In Table 2, Examples 14 to 19 have a first insulating coating on both opposite surfaces of the first outer tab. Therefore, the insulation performance of the first insulating coating in Examples 14 to 19 for the first outer tab is better. Because the first insulating coating is relatively hard, if both opposite surfaces of the first outer tab have the first insulating coating, the first outer tab is prone to breakage. Therefore, the drop test pass rate of Examples 14 to 19 is lower than that of Comparative Examples 2 to 4. However, considering both insulation performance and drop test pass rate, Examples 14 to 19 are better than Comparative Examples 2 to 4.

[0118] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A secondary battery, comprising a casing, an electrolyte, an electrode assembly, and a first conductive element, wherein the electrolyte and the electrode assembly are housed within the casing, the electrode assembly comprising a first electrode plate and a plurality of first tabs connected to the first electrode plate; in the thickness direction of the electrode assembly, the plurality of first tabs are stacked and connected to the first conductive element, the first conductive element extending out of the casing; Its features are, The first electrode tab includes a first outer electrode tab and a first inner electrode tab. The first electrode tab located on the outermost layer of the stack is the first outer electrode tab, and the first electrode tab located on the innermost layer of the stack is the first inner electrode tab. Along the extending direction of the first outer electrode tab, the first outer electrode tab includes a first connecting portion, a first bending portion, and a first welding portion connected in sequence. The first connecting portion is connected to the first electrode sheet, and the first welding portion is welded to the first conductive element. A first insulating coating is disposed on the surface of the first connecting portion in the thickness direction. Along the extending direction of the first outer electrode tab, the length of the first insulating coating is L1. A second insulating coating is disposed on the surface of the first inner electrode tab in the thickness direction. The second insulating coating includes a second sub-insulating coating. The surface of the first inner electrode tab adjacent to the first outer electrode tab is disposed with the second sub-insulating coating. Along the extending direction of the first inner electrode tab, the length of the second sub-insulating coating is L2. <L2。 2. The secondary battery according to claim 1, characterized in that, The first outer electrode tab has the first insulating coating on its surface facing the first inner electrode tab.

3. The secondary battery according to any one of claims 1 or 2, characterized in that, The first insulating coating is provided on both opposite surfaces of the first outer tab in the thickness direction.

4. The secondary battery according to claim 3, characterized in that, Along the extension direction of the first outer tab, the lengths of the first insulating coatings on the two opposite surfaces of the first outer tab in the thickness direction are different.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, L1≥0.5mm.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The first insulating coating comprises ceramic insulating particles and an adhesive.

7. The secondary battery according to claim 6, characterized in that, The ceramic insulating particles include boehmite and / or alumina.

8. The secondary battery according to any one of claims 1 to 5, characterized in that, The first insulating coating comprises at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The thickness of the first insulating coating is 5 μm to 45 μm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, The first electrode is a positive electrode, and the first tab is a positive tab.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, Along the extending direction of the first inner electrode tab, the first inner electrode tab includes a second connecting portion, a second bending portion, and a second welding portion connected in sequence. The second connecting portion is connected to the first electrode plate, and the second welding portion is connected to the first conductive element. A second insulating coating is provided on the surface of the second connecting portion in the thickness direction. Along the extending direction of the first inner electrode tab, the second insulating coating extends beyond the second connecting portion.

12. The secondary battery according to claim 11, characterized in that, The second welding part is welded to the first conductive element and forms a solder mark; along the extension direction of the first inner electrode, the distance between the second insulating coating and the solder mark is T1, where T1 ≥ 0.5 mm.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, The second insulating coating is provided on both opposite surfaces of the first inner electrode in the thickness direction.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, The second insulating coating comprises ceramic insulating particles and an adhesive.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, 0.5mm≤L2-L1≤3mm.

16. The secondary battery according to any one of claims 1 to 15, characterized in that, All of the second insulating coatings have the same length.

17. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 16.

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