Secondary battery and electronic device

Abstract

The invention relates to a secondary battery and electronic equipment, the secondary battery comprises an electrode assembly, the electrode assembly comprises a negative plate, a positive plate and a diaphragm, the diaphragm is arranged between the adjacent negative plate and positive plate, and the electrode assembly is formed by laminating and winding the negative plate, the positive plate and the diaphragm. The positive plate comprises a positive current collector and a first positive active layer, the positive current collector is provided with a first surface and a second surface which are opposite, the first surface of the positive current collector comprises a first area and a second area, the first area is provided with the first positive active layer, the second area is not provided with the first positive active layer, and the second area is connected with the first area. The electrode assembly further comprises a first insulating layer, the first insulating layer comprises a first part and a second part which are connected with each other, the first part covers the first positive electrode active layer, the second part covers the second area, and the first part of the first insulating layer is provided with a first hole. According to the secondary battery and the electronic equipment, the lithium precipitation problem of the negative plate can be improved.

Description

Technical Field

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

[0002] As the power source of electronic devices, secondary batteries are the key to ensure the normal use of electronic devices. In order to reduce the problem of lithium deposition on the surface of the negative electrode sheet during charging, the prior art usually designs the negative electrode active material layer to exceed the positive electrode active layer in the length and / or width direction, so that the negative electrode active layer can absorb the lithium ions released by the positive electrode active material layer as much as possible, and the negative electrode active material layer that exceeds the positive electrode active layer in the length direction of the electrode sheet is easy to contact with the positive electrode current collector without the positive electrode active layer to cause a short circuit, so it is necessary to adhere adhesive tape at the end of the active position of the positive electrode sheet to cover the positive electrode current collector without the positive electrode active layer area, so as to isolate the negative electrode active material layer that exceeds the positive electrode active layer and the positive electrode current collector, and reduce the possibility of the negative electrode active material layer that exceeds the positive electrode active layer contacting with the positive electrode current collector without the positive electrode active layer and causing a short circuit. In order to ensure that the adhesive tape covers the positive electrode current collector without the positive electrode active layer area as much as possible, part of the adhesive tape is usually adhered to the positive electrode active material layer, thereby shielding part of the positive electrode active material layer.

[0003] However, the adhesive force of the adhesive tape will be reduced after being soaked in electrolyte. During the charging process, when the adhesive force of the adhesive tape is insufficient, the lithium ions of the positive electrode active layer blocked by the adhesive tape will escape and bypass the edge of the adhesive tape to be transmitted to the opposite negative electrode sheet, making the lithium ion concentration of the opposite negative electrode sheet in the area corresponding to the edge of the adhesive tape too high, which can easily lead to lithium deposition in the area corresponding to the edge of the adhesive tape. Therefore, it is necessary to improve the above problem. Summary of the invention

[0004] The purpose of the present application is to provide a secondary battery and an electronic device, aiming to improve the lithium plating problem of the negative electrode sheet.

[0005] According to the first aspect of the present application, a secondary battery is provided, comprising an electrode assembly, the electrode assembly comprising a negative electrode sheet, a positive electrode sheet and a separator, a separator is arranged between adjacent negative electrode sheets and positive electrode sheets, and the electrode assembly is formed by stacking and winding the negative electrode sheets, the positive electrode sheets and the separator. The positive electrode sheet comprises a positive electrode collector and a first positive electrode active layer, the positive electrode collector has a first surface and a second surface relative to each other, the first surface of the positive electrode collector comprises a first region and a second region, the first region is provided with a first positive electrode active layer, the second region is not provided with the first positive electrode active layer, and the second region is connected to the first region. The electrode assembly also comprises a first insulating layer, the first insulating layer comprises a first part and a second part connected to each other, the first part covers the first positive electrode active layer, the second part covers the second region, and the first part of the first insulating layer is provided with a first hole.

[0006] In the above technical solution, the first portion of the first insulating layer covers the first positive electrode active layer, and the second portion covers the second region of the positive electrode current collector, so that the first insulating layer covers the second region where the first positive electrode active layer is not set as much as possible, so as to isolate the negative electrode sheet and the second region of the positive electrode current collector, and reduce the possibility of the negative electrode sheet contacting with the second region where the first positive electrode active layer is not set and causing a short circuit. By setting a first hole in the first portion of the first insulating layer, the positive electrode active material covered by the first insulating layer can release lithium ions through the first hole, so as to reduce the possibility of lithium ions in the positive electrode active material covered by the first insulating layer bypassing the first insulating layer and diffusing to the opposite negative electrode sheet, thereby reducing the possibility of lithium precipitation due to excessive lithium ion concentration at a local position of the negative electrode sheet, and improving the utilization rate of the positive electrode active material of the positive electrode sheet, thereby improving the energy density.

[0007] In some preferred embodiments, the negative electrode sheet includes a negative electrode current collector and a first negative electrode active layer, the surface of the negative electrode current collector facing the first positive electrode active layer is provided with the first negative electrode active layer, and the projection of the first negative electrode active layer on the surface of the positive electrode sheet covers the first positive electrode active layer in a direction perpendicular to the surface of the positive electrode current collector. Along the length direction of the positive electrode current collector, the width of the second part is L1, and on the side of the first negative electrode active layer close to the first insulating layer, the length of the first negative electrode active layer exceeding the first positive electrode active layer is L2, and L1>L2. By defining L1>L2, the second part of the first insulating layer can completely block the part of the first negative electrode active layer exceeding the first positive electrode active layer, thereby reducing the risk of short circuit between the positive electrode current collector and the negative electrode active layer.

[0008] In some preferred embodiments, 1mm≤L1-L2≤10mm, so that the second portion of the first insulating layer can cover the portion of the first negative electrode active layer that exceeds the first positive electrode active layer, while the width of the second portion is not too large, thereby not excessively reducing the energy density of the secondary battery.

[0009] In some preferred embodiments, 3mm≤L1-L2≤7mm, so as to further satisfy that the second portion of the first insulating layer can shield the portion of the first negative electrode active layer that exceeds the first positive electrode active layer, while the width of the second portion will not be too large, thereby not excessively reducing the energy density of the secondary battery.

[0010] In some preferred embodiments, the first insulating layer satisfies at least one of the following characteristics: (1) The ratio of the area of ​​the first part to the area of ​​the second part is 0.05:1 to 0.5:1, so as to reduce the accumulation of excessive lithium ions in the local area of ​​the first negative electrode active layer and cause lithium precipitation. At the same time, the area of ​​the first part will not be too large to avoid the first part with a larger area affecting the adhesion of the second part to the positive electrode sheet, and the first part will not excessively reduce the energy density of the secondary battery. (2) The minimum diameter of the circumscribed circle of the contour of the first hole is 0.2mm to 1mm, so that the first positive electrode active layer covered by the first part can better release lithium ions through the first hole. (3) The first part is provided with a plurality of first holes, and the spacing between two adjacent first holes is 0.1mm to 1mm, so that the first positive electrode active layer covered by the first part can uniformly release lithium ions through the plurality of first holes. (4) Along the length direction of the positive electrode current collector, the distance between the first hole near the edge of the first part and the edge of the first part is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the first negative electrode active layer opposite to the edge of the first part along the length direction of the positive electrode current collector. (5) Along the width direction of the positive electrode current collector, the distance between the first hole near the edge of the first part and the edge of the first part is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the first negative electrode active layer opposite to the edge of the first part along the width direction of the positive electrode current collector. (6) Along the length direction of the positive electrode current collector, the side of the first positive electrode active layer near the second area includes a first edge, and the distance between the first hole near the first edge and the first edge is 0.1 mm to 0.5 mm, so as to meet the requirement that the positive electrode active material near the first edge can release lithium ions through the first hole, while reducing the possibility that the metal burrs in the second area of ​​the positive electrode current collector where the first positive electrode active layer is not provided pass through the first hole and contact with the first negative electrode active layer to cause a short circuit. (7) The shape of the first hole is at least one of a circle, an ellipse or a polygon. (8) The ratio of the pore area to the non-pore area of ​​the first part is 0.1:1 to 1:1, so that the lithium ions in the first positive electrode active layer blocked by the first part can escape from the first pores relatively smoothly, and at the same time, the pore area of ​​the first part is not too large, so as not to excessively reduce the adhesion of the first insulating layer.

[0011] In some preferred embodiments, the positive electrode sheet includes a second positive electrode active layer, the second surface of the positive electrode current collector includes a third region and a fourth region connected to each other, the third region is provided with a second positive electrode active layer, and the fourth region is not provided with a second positive electrode active layer. The electrode assembly includes a second insulating layer, the second insulating layer includes a third portion and a fourth portion connected to each other, the third portion covers the second positive electrode active layer, the fourth portion covers the fourth region, and the third portion of the second insulating layer is provided with a second hole. By covering the second positive electrode active layer with the third portion of the second insulating layer and the fourth portion covering the fourth region of the positive electrode current collector, the second insulating layer covers the fourth region where the second positive electrode active layer is not provided as much as possible, so as to isolate the negative electrode sheet and the fourth region of the positive electrode current collector, and reduce the possibility of the negative electrode sheet contacting with the fourth region where the second positive electrode active layer is not provided and causing a short circuit. By setting a second hole in the third part of the second insulating layer, the positive electrode active material covered by the second insulating layer can release lithium ions through the second hole, so as to reduce the possibility of lithium ions in the positive electrode active material covered by the second insulating layer bypassing the second insulating layer and diffusing to the opposite negative electrode sheet, thereby reducing the possibility of lithium ion concentration at a local position of the negative electrode sheet being too high and causing lithium precipitation, and improving the utilization rate of the positive electrode active material of the positive electrode sheet, thereby improving the energy density.

[0012] In some preferred embodiments, the negative electrode sheet includes a negative electrode current collector and a second negative electrode active layer, the surface of the negative electrode current collector facing away from the first positive electrode active layer is provided with the second negative electrode active layer, and the projection of the second negative electrode active layer on the surface of the positive electrode sheet covers the second positive electrode active layer in a direction perpendicular to the surface of the positive electrode current collector. Along the length direction of the positive electrode current collector, the width of the fourth portion is L3, and on the side of the second negative electrode active layer close to the second insulating layer, the length of the second negative electrode active layer exceeding the second positive electrode active layer is L4, 1mm≤L3-L4≤10mm. By limiting the width L3 of the fourth portion of the second insulating layer to be greater than the length L4 of the second negative electrode active layer exceeding the second positive electrode active layer, the fourth portion without a hole can block the portion of the second negative electrode active layer exceeding the second positive electrode active layer as much as possible, thereby reducing the possibility of the negative electrode sheet contacting the fourth region where the second positive electrode active layer is not provided and short-circuiting. By limiting the width L3 of the fourth portion to be greater than the length L4 of the second negative electrode active layer extending beyond the second positive electrode active layer, ranging from 1 millimeter (mm) to 10 millimeters, the fourth portion of the second insulating layer can cover the portion of the second negative electrode active layer extending beyond the second positive electrode active layer, while the width of the fourth portion will not be too large, thereby not excessively reducing the energy density of the secondary battery.

[0013] In some preferred embodiments, the first insulating layer satisfies at least one of the following characteristics: (9) The thickness of the first insulating layer is D1, 4 μm ≤ D1 ≤ 30 μm, so that the first insulating layer has good anti-puncture performance and the first insulating layer is not too thick to avoid excessive reduction of the energy density of the secondary battery. (10) The first insulating layer includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, so that the first insulating layer has good insulation performance.

[0014] In a second aspect, the present application further proposes an electronic device, comprising a secondary battery as in any embodiment of the first aspect above.

[0015] The inventor of the present application has found that by setting adhesive tape on the positive electrode sheet to cover the positive electrode current collector without the positive electrode active layer, the possibility of the negative electrode active layer exceeding the positive electrode active layer contacting the positive electrode current collector and causing a short circuit can be reduced. However, during the charging process, the lithium ions in the positive electrode active material covered by the adhesive tape will bypass the edge of the adhesive tape and be transmitted to the opposite negative electrode sheet, resulting in lithium deposition in a local area of ​​the negative electrode sheet. By opening holes in the adhesive tape of the positive electrode sheet, the positive electrode active material covered by the adhesive tape can release lithium ions through the holes, thereby reducing the problem of lithium deposition in a local area of ​​the negative electrode sheet.

[0016] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the subsequent description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily described by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the dimensions in the drawings do not constitute proportional limitations.

[0018] Figure 1 A schematic diagram of the structure of a secondary battery in some embodiments of the present application;

[0019] Figure 2 This is a schematic diagram of the structure of the electrode assembly of some embodiments of the present application;

[0020] Figure 3 for Figure 2 A partial enlarged view of the middle part;

[0021] Figure 4 A schematic diagram of the structure of the first insulating layer in some embodiments of the present application;

[0022] Figure 5 This is a schematic diagram of the structure of the electrode assembly of some embodiments of the present application;

[0023] Figure 6 for Figure 5 A partial enlarged view of point B in the middle;

[0024] Figure 7 This is a schematic structural diagram of the second insulating layer of some embodiments of the present application.

[0025] Description of reference numerals:

[0026] 100, secondary battery; X, first direction; Y, second direction;

[0027] 10. Shell;

[0028] 20. Electrode assembly;

[0029] 21, positive electrode sheet; 211, positive electrode current collector; 2111, first surface; 2113, first region; 2114, second region; 2112, second surface; 2115, third region; 2116, fourth region; 212, first positive electrode active layer; 2121, first edge; 213, second positive electrode active layer; 2131, second edge;

[0030] 22, negative electrode sheet; 221, negative electrode current collector; 222, first negative electrode active layer; 223, second negative electrode active layer;

[0031] 23. Diaphragm;

[0032] 24, first insulating layer; 241, first portion; 2411, first hole; 242, second portion;

[0033] 25, second insulating layer; 251, third part; 2511, second hole; 252, fourth part. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0035] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0036] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0037] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0038] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0039] In the first aspect, the embodiment of the present application provides a secondary battery 100, please refer to Figure 1 The secondary battery 100 includes a shell 10 and an electrode assembly 20 . The shell 10 can accommodate the electrode assembly 20 and an electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 20 in the shell 10 .

[0040] For the electrode assembly 20, please refer to Figure 2 , Figure 2 The winding structure of the electrode assembly 20 is shown. The electrode assembly 20 includes a positive electrode sheet 21, a separator 23 and a negative electrode sheet 22. A separator 23 is arranged between the adjacent negative electrode sheets 22 and the positive electrode sheets 21. The positive electrode sheets 21, the separator 23 and the negative electrode sheets 22 are stacked and wound. Exemplarily, along the thickness direction of the positive electrode sheet 21 and / or the negative electrode sheet 22, the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22 are stacked in sequence and then wound to form a wound electrode assembly 20. In the embodiment of the present application, the electrode assembly 20 is taken as an example for explanation as a winding structure. In some other embodiments, the electrode assembly 20 may also be a laminated structure. For example, along the thickness direction of the positive electrode sheet 21 and / or the negative electrode sheet 22, the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22 are stacked in sequence to form a laminated electrode assembly 20.

[0041] For the positive electrode sheet 21, please refer to Figure 3The positive electrode sheet 21 includes a positive electrode current collector 211 and a first positive electrode active layer 212. The positive electrode current collector 211 has a first surface 2111 and a second surface 2112 opposite to each other in the thickness direction. The first surface 2111 of the positive electrode current collector 211 includes a first region 2113 and a second region 2114. The first region 2113 is provided with the first positive electrode active layer 212, and the second region 2114 is not provided with the first positive electrode active layer 212, and the second region 2114 is connected to the first region 2113. In the present application, the second region 2114 may be an empty foil region of the positive electrode current collector 211, or may be a surface of the positive electrode current collector 211 coated with a non-positive electrode active layer. In the present application, the second region 2114 is located at the end position of the positive electrode sheet 21 of the electrode assembly 20 of the wound structure. In some other embodiments, the second region 2114 may be located at the start position of the positive electrode sheet 21 of the electrode assembly 20 of the wound structure.

[0042] For the positive electrode current collector 211, the positive electrode current collector 211 may be a composite current collector (a composite structure of metal-polymer-metal), for example, the positive electrode current collector 211 includes a polymer layer and a metal layer disposed on two opposite surfaces of the polymer layer, the polymer layer as the main mechanical support layer of the positive electrode current collector 211, may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), the metal layer may include at least one of aluminum, copper, nickel, titanium, and silver, the positive electrode current collector 211 uses the polymer layer as the main mechanical support layer, the metal layer may be thinned, thereby reducing the metal burrs caused by mechanical damage to the secondary battery 100, and reducing the mass of the positive electrode current collector 211, thereby improving the mass energy density of the secondary battery 100. In some other embodiments, the positive electrode current collector 211 may be a single-layer metal foil, and the single-layer metal foil may include at least one of aluminum, copper, nickel, titanium, and silver.

[0043] For the first positive electrode active layer 212, the first positive electrode active layer 212 is infiltrated by the electrolyte in the housing 10 to generate an electrochemical reaction. The first positive electrode active layer 212 includes a first positive electrode active material, a conductive agent, a binder, etc. The above materials are mixed and stirred evenly and coated on the first area 2113 of the first surface 2111 of the positive current collector 211, thereby obtaining the first positive electrode active layer 212. The first 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.

[0044] For the above-mentioned negative electrode sheet 22, the negative electrode sheet 22 includes a negative electrode collector 221 and a first negative electrode active layer 222. Along the thickness direction of the negative electrode collector 221, the surface of the negative electrode collector 221 facing the first positive electrode active layer 212 is provided with the first negative electrode active layer 222. Along the direction perpendicular to the surface of the positive electrode collector 211, the projection of the first negative electrode active layer 222 on the surface of the positive electrode sheet 21 covers the first positive electrode active layer 212. The first negative electrode active layer 222 exceeds the first positive electrode active layer 212 along the length direction (first direction X) of the positive electrode collector 211, so that the first negative electrode active layer 222 can absorb the lithium ions released by the first positive electrode active layer 212 as much as possible.

[0045] For the negative electrode current collector 221, the negative electrode current collector 221 may be a composite current collector (a composite structure of metal-polymer-metal), for example, the negative electrode current collector 221 includes a polymer layer and a metal layer disposed on two opposite surfaces of the polymer layer, the polymer layer as the main mechanical support layer of the negative electrode current collector 221, may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), the metal layer may include at least one of aluminum, copper, nickel, titanium, and silver, the negative electrode current collector 221 uses the polymer layer as the main mechanical support layer, the metal layer may be thinned, thereby reducing the metal burrs caused by mechanical damage to the secondary battery 100, and reducing the mass of the negative electrode current collector 221, thereby improving the mass energy density of the secondary battery 100. In some other embodiments, the negative electrode current collector 221 may be a single-layer metal foil, and the single-layer metal foil may include at least one of aluminum, copper, nickel, titanium, and silver.

[0046] For the first negative electrode active layer 222, the first negative electrode active layer 222 is infiltrated by the electrolyte in the housing 10 to generate an electrochemical reaction. The first negative electrode active layer 222 includes a first negative electrode active material, a conductive agent, an adhesive, etc. The above materials are mixed and stirred evenly and coated on the surface of the negative electrode current collector 221 facing the first positive electrode active layer 212, thereby obtaining the first negative electrode active layer 222. The first negative electrode active material may include at least one of graphite, silicon, hard carbon, and carbon fiber.

[0047] In some embodiments, please refer to Figure 3 and Figure 4The electrode assembly 20 further includes a first insulating layer 24, which includes a first portion 241 and a second portion 242 connected to each other, wherein the first portion 241 covers the first positive electrode active layer 212, and the second portion 242 covers the second region 2114, so that the first insulating layer 24 covers the second region 2114 where the first positive electrode active layer 212 is not provided as much as possible, so as to isolate the negative electrode sheet 22 and the second region 2114 of the positive electrode current collector 211, and reduce the possibility of the negative electrode sheet 22 contacting with the second region 2114 where the first positive electrode active layer 212 is not provided and causing a short circuit. However, during the charging process of the secondary battery 100, the lithium ions in the first positive electrode active layer 212 covered by the first insulating layer 24 will bypass the edge of the first insulating layer 24 and be transmitted to the first negative electrode active layer 222 of the opposite negative electrode sheet 22, resulting in an excessively high lithium ion concentration at a local position of the first negative electrode active layer 222, and excessive lithium ions will accumulate on the surface of the first negative electrode active layer 222, causing a lithium precipitation problem.

[0048] It should be noted that the first portion 241 in the present application covers the first positive electrode active layer 212, which means that the first portion 241 covers part of the first positive electrode active layer 212, not that the first portion 241 completely covers all of the first positive electrode active layer 212. The second portion 242 in the present application covers the second region 2114, which means that the second portion 242 covers part of the second region 2114, not that the second portion 242 completely covers all of the second region 2114.

[0049] To improve the above problem, in an embodiment of the present application, the first part 241 of the first insulating layer 24 is provided with a first hole 2411, so that the first positive electrode active layer 212 covered by the first insulating layer 24 can release lithium ions through the first hole 2411, so as to reduce the possibility of lithium ions in the first positive electrode active layer 212 covered by the first insulating layer 24 bypassing the first insulating layer 24 and diffusing to the first negative electrode active layer 222 of the opposite negative electrode sheet 22, thereby reducing the possibility of lithium ion concentration at a local position of the first negative electrode active layer 222 being too high and lithium precipitation, and improving the utilization rate of the positive electrode active material of the first negative electrode active layer 222, thereby improving the energy density.

[0050] In some embodiments, along the length direction of the positive electrode current collector 211, the width of the second portion 242 of the first insulating layer 24 is L1, and on the side of the first negative electrode active layer 222 close to the first insulating layer 24, the length of the first negative electrode active layer 222 exceeding the first positive electrode active layer 212 is L2, and L1>L2. By limiting the width L1 of the second portion 242 of the first insulating layer 24 to be greater than the length L2 of the portion of the first negative electrode active layer 222 exceeding the first positive electrode active layer 212, the second portion 242 without a hole can block the portion of the first negative electrode active layer 222 exceeding the first positive electrode active layer 212 as much as possible, thereby reducing the possibility of the negative electrode sheet 22 contacting with the second region 2114 without the first positive electrode active layer 212 and causing a short circuit.

[0051] In some embodiments, 1mm≤L1-L2≤10mm, so that the second portion 242 of the first insulating layer 24 can cover the portion of the first negative electrode active layer 222 that extends beyond the first positive electrode active layer 212, while the width of the second portion 242 is not too large, thereby not excessively reducing the energy density of the secondary battery 100.

[0052] In some embodiments, 3mm≤L1-L2≤7mm, so as to further satisfy that the second portion 242 of the first insulating layer 24 can cover the portion of the first negative electrode active layer 222 that exceeds the first positive electrode active layer 212, while the width of the second portion 242 is not too large, thereby not excessively reducing the energy density of the secondary battery 100.

[0053] In some embodiments, the first insulating layer 24 satisfies at least one of the following characteristics: (1) the ratio of the area of ​​the first portion 241 to the area of ​​the second portion 242 is 0.05:1 to 0.5:1, so as to reduce the accumulation of excessive lithium ions in the local area of ​​the first negative active layer 222 and cause lithium deposition, while the area of ​​the first portion 241 is not too large, so as to avoid the first portion 241 with a larger area affecting the adhesion of the second portion 242 to the positive electrode sheet 21, and so that the first portion 241 does not excessively reduce the energy density of the secondary battery 100. The shapes of the first portion 241 and the second portion 242 are preferably rectangular, and the lengths of the first portion 241 and the second portion 242 along the width direction (second direction Y) of the positive current collector 211 are the same, so the ratio of the areas of the first portion 241 and the second portion 242 is equal to the ratio of the widths of the first portion 241 and the second portion 242 along the length direction of the positive current collector 211. (2) The minimum diameter of the circumscribed circle of the contour of the first hole 2411 is 0.2 mm to 1 mm, so that the first positive electrode active layer 212 covered by the first part 241 can release lithium ions through the first holes 2411. (3) The first part 241 is provided with a plurality of first holes 2411, and the spacing between two adjacent first holes 2411 is 0.1 mm to 1 mm, so that the first positive electrode active layer 212 covered by the first part 241 can release lithium ions uniformly through the plurality of first holes 2411. Assuming that the spacing between two adjacent first holes 2411 is A1, the distance between the centers of the circumscribed circles of the contours of two adjacent first holes 2411 is B1, and the radius of the circumscribed circle of the contours of the first holes 2411 is R1, then A1 = B1-2*R1. (4) Along the length direction of the positive current collector 211, the distance between the first hole 2411 near the edge of the first portion 241 and the edge of the first portion 241 is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the first negative electrode active layer 222 opposite to the edge of the first portion 241 along the length direction of the positive current collector 211. Wherein, assuming that the distance between the first hole 2411 and the edge of the first portion 241 along the length direction of the positive current collector 211 is C1, the distance between the center of the circumscribed circle of the contour of the first hole 2411 and the edge of the first portion 241 along the length direction of the positive current collector 211 is D1, and C1=D1-R1. (5) Along the width direction of the positive current collector 211, the distance between the first hole 2411 near the edge of the first portion 241 and the edge of the first portion 241 is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the first negative electrode active layer 222 opposite to the edge of the first portion 241 along the width direction of the positive current collector 211.Assuming that the distance between the first hole 2411 and the edge of the first portion 241 along the width direction of the positive current collector 211 is E1, the distance between the center of the circumscribed circle of the contour of the first hole 2411 and the edge of the first portion 241 along the width direction of the positive current collector 211 is F1, and E1=F1-R1. (6) Along the length direction of the positive current collector 211, the side of the first positive active layer 212 close to the second region 2114 includes a first edge 2121, and the distance between the first hole 2411 close to the first edge 2121 and the first edge 2121 is 0.1 mm to 0.5 mm, so that the positive active material close to the first edge 2121 can release lithium ions through the first hole 2411, while reducing the possibility that the metal burrs of the second region 2114 of the positive current collector 211 where the first positive active layer 212 is not provided pass through the first hole 2411 and contact with the first negative active layer 222 to cause a short circuit. Assuming that the distance between the first hole 2411 and the first edge 2121 is G1, the distance between the center of the circumscribed circle of the outline of the first hole 2411 and the first edge 2121 is H1, G1 = H1-R1. (7) The shape of the first hole 2411 is at least one of a circle, an ellipse or a polygon. (8) The ratio of the pore area to the non-pore area in the first part 241 is 0.1:1 to 1:1, so that the lithium ions in the first positive electrode active layer 212 blocked by the first part 241 can be relatively smoothly escaped from the first hole 2411, and at the same time, the pore area in the first part 241 will not be too large, so as not to excessively reduce the adhesion of the first insulating layer 24.

[0054] In some embodiments, please refer to Figure 5 , Figure 6 and Figure 7The positive electrode sheet 21 includes a second positive electrode active layer 213, and the second surface 2112 of the positive electrode current collector 211 includes a third region 2115 and a fourth region 2116 connected to each other. The third region 2115 is provided with the second positive electrode active layer 213, and the fourth region 2116 is not provided with the second positive electrode active layer 213. The electrode assembly 20 includes a second insulating layer 25, and the second insulating layer 25 includes a third portion 251 and a fourth portion 252 connected to each other. The third portion 251 covers the second positive electrode active layer 213, and the fourth portion 252 covers the fourth region 2116. The third portion 251 of the second insulating layer 25 is provided with a second hole 2511. The third portion 251 of the second insulating layer 25 covers the second positive active layer 213, and the fourth portion 252 covers the fourth region 2116 of the positive current collector 211, so that the second insulating layer 25 covers the fourth region 2116 where the second positive active layer 213 is not provided as much as possible, so as to isolate the negative electrode sheet 22 and the fourth region 2116 of the positive current collector 211, and reduce the possibility of the negative electrode sheet 22 contacting with the fourth region 2116 where the second positive active layer 213 is not provided and causing a short circuit. The second hole 2511 is provided in the third portion 251 of the second insulating layer 25, so that the positive active material covered by the second insulating layer 25 can release lithium ions through the second hole 2511, so as to reduce the possibility of lithium ions in the positive active material covered by the second insulating layer 25 bypassing the second insulating layer 25 and diffusing to the opposite negative electrode sheet 22, thereby reducing the possibility of lithium precipitation due to excessive lithium ion concentration at a local position of the negative electrode sheet 22, and improving the utilization rate of the positive active material of the positive electrode sheet 21, thereby improving the energy density.

[0055] In some embodiments, the negative electrode sheet 22 includes a negative electrode current collector 221 and a second negative electrode active layer 223. The second negative electrode active layer 223 is disposed on the surface of the negative electrode current collector 221 away from the first positive electrode active layer 212. In a direction perpendicular to the surface of the positive electrode current collector 211, the projection of the second negative electrode active layer 223 on the surface of the positive electrode sheet 21 covers the second positive electrode active layer 213. The second negative electrode active layer 223 exceeds the second positive electrode active layer 213 along the length direction of the positive electrode current collector 211, so that the second negative electrode active layer 223 can absorb the lithium ions released by the second positive electrode active layer 213 as much as possible. Along the length direction of the positive electrode current collector 211, the width of the fourth portion 252 is L3, and on the side of the second negative electrode active layer 223 close to the second insulating layer 25, the length of the second negative electrode active layer 223 exceeding the second positive electrode active layer 213 is L4, and 1mm≤L3-L4≤10mm. By limiting the width L3 of the fourth portion 252 of the second insulating layer 25 to be greater than the length L4 of the portion of the second negative electrode active layer 223 that exceeds the second positive electrode active layer 213, the fourth portion 252 without a hole can cover the portion of the second negative electrode active layer 223 that exceeds the second positive electrode active layer 213 as much as possible, thereby reducing the possibility of the negative electrode sheet 22 contacting the fourth region 2116 without the second positive electrode active layer 213 and causing a short circuit. By limiting the width L3 of the fourth portion 252 to be greater than the length L4 of the portion of the second negative electrode active layer 223 that exceeds the second positive electrode active layer 213 to be in the range of 1 mm to 10 mm, the fourth portion 252 of the second insulating layer 25 can cover the portion of the second negative electrode active layer 223 that exceeds the second positive electrode active layer 213, while the width of the fourth portion 252 will not be too large, and the energy density of the secondary battery 100 will not be excessively reduced.

[0056] In some embodiments, the first insulating layer 24 satisfies at least one of the following characteristics: (9) The thickness of the first insulating layer 24 is D1, 4 μm ≤ D1 ≤ 30 μm, so that the first insulating layer 24 has good anti-puncture performance, and the first insulating layer 24 is not too thick to avoid excessively reducing the energy density of the secondary battery 100. (10) The first insulating layer 24 includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, so that the first insulating layer 24 has good insulation performance.

[0057] In some embodiments, the second insulating layer 25 satisfies at least one of the following characteristics: (11) The ratio of the area of ​​the third portion 251 to the area of ​​the fourth portion 252 is 0.05:1 to 0.5:1, so as to reduce the accumulation of excessive lithium ions in the local area of ​​the second negative electrode active layer 223 and cause lithium deposition, while the area of ​​the third portion 251 is not too large, so as to avoid the third portion 251 with a larger area affecting the adhesion of the fourth portion 252 to the positive electrode sheet 21, and so that the third portion 251 does not excessively reduce the energy density of the secondary battery 100. The shapes of the third portion 251 and the fourth portion 252 are preferably rectangular, and the lengths of the third portion 251 and the fourth portion 252 along the width direction of the positive electrode collector 211 are the same, so the ratio of the areas of the third portion 251 and the fourth portion 252 is equal to the ratio of the widths of the third portion 251 and the fourth portion 252 along the length direction of the positive electrode collector 211. (12) The minimum diameter of the circumscribed circle of the contour of the second hole 2511 is 0.2 mm to 1 mm, so that the second positive electrode active layer 213 covered by the third part 251 can release lithium ions through the second holes 2511. (13) The third part 251 is provided with a plurality of second holes 2511, and the spacing between two adjacent second holes 2511 is 0.1 mm to 1 mm, so that the second positive electrode active layer 213 covered by the third part 251 can release lithium ions uniformly through the plurality of second holes 2511. Assuming that the spacing between two adjacent second holes 2511 is A2, the distance between the centers of the circumscribed circles of the contours of two adjacent second holes 2511 is B2, and the radius of the circumscribed circle of the contours of the second holes 2511 is R2, then A2 = B2-2*R2. (14) Along the length direction of the positive electrode current collector 211, the distance between the second hole 2511 near the edge of the third portion 251 and the edge of the third portion 251 is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the second negative electrode active layer 223 opposite the edge of the third portion 251 along the length direction of the positive electrode current collector 211. Assuming that the distance between the second hole 2511 and the edge of the third portion 251 along the length direction of the positive electrode current collector 211 is C2, the distance between the center of the circumscribed circle of the contour of the second hole 2511 and the edge of the third portion 251 along the length direction of the positive electrode current collector 211 is D2, and C2 = D2-R2. (15) Along the width direction of the positive electrode current collector 211, the distance between the second hole 2511 close to the edge of the third portion 251 and the edge of the third portion 251 is 0.2 mm to 0.5 mm, so as to reduce the possibility of lithium deposition in the corresponding area of ​​the second negative electrode active layer 223 opposite to the edge of the third portion 251 along the width direction of the positive electrode current collector 211.Assuming that the distance between the second hole 2511 and the edge of the third portion 251 along the width direction of the positive current collector 211 is E2, the distance between the center of the circumscribed circle of the contour of the second hole 2511 and the edge of the third portion 251 along the width direction of the positive current collector 211 is F2, and E2=F2-R2. (16) Along the length direction of the positive current collector 211, the side of the second positive active layer 213 close to the fourth region 2116 includes a second edge 2131, and the distance between the second hole 2511 close to the second edge 2131 and the second edge 2131 is 0.1 mm to 0.5 mm, so that the positive active material close to the second edge 2131 can release lithium ions through the second hole 2511, while reducing the possibility that the metal burrs of the fourth region 2116 of the positive current collector 211 where the second positive active layer 213 is not provided pass through the second hole 2511 and contact with the second negative active layer 223 to cause a short circuit. Assuming that the distance between the second hole 2511 and the second edge 2131 is G2, the distance between the center of the circumscribed circle of the contour of the second hole 2511 and the second edge 2131 is H2, G2 = H2-R2. (17) The shape of the second hole 2511 is at least one of a circle, an ellipse or a polygon. (18) The ratio of the pore area to the non-pore area in the third part 251 is 0.1:1 to 1:1, so that the lithium ions in the second positive electrode active layer 213 blocked by the third part 251 can be relatively smoothly released from the second hole 2511, and at the same time, the pore area in the third part 251 will not be too large, so as not to excessively reduce the adhesion of the second insulating layer 25.

[0058] In some embodiments, the thickness of the second insulating layer 25 is D2, 4 μm ≤ D2 ≤ 30 μm, so that the second insulating layer 25 has good anti-puncture performance, while the second insulating layer 25 is not too thick to avoid excessively reducing the energy density of the secondary battery 100. The second insulating layer 25 includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide, so that the second insulating layer 25 has good insulation performance.

[0059] In the second aspect of the present application, an electronic device is also proposed, including a secondary battery 100 as in any embodiment of the first aspect described above. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices include but are not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys can include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, electric airplane toys, and the like, and spacecraft can include airplanes, rockets, space shuttles, spacecraft, and the like.

[0060] Test part:

[0061] 1. Lithium analysis test:

[0062] Cyclic test of lithium-ion battery at 45℃: At 45℃, let the lithium-ion battery stand for 5 minutes, charge to 4.25V at 1.5C constant current, then charge to 4.48V at 1.2C constant current, then charge to 0.02C at 4.48V constant voltage, and let stand for 5 minutes; then discharge to 3.4V at 1C constant current, then discharge to 3.0V at 0.2C constant current, and let stand for 5 minutes. Repeat the above steps 700 times, let stand for 5 minutes, then charge to 4.48V at 1C constant current, then charge to 0.02C at 4.48V constant voltage, and finally let stand for 5 minutes, disassemble and observe the degree of lithium precipitation at the edge of the first negative electrode insulation layer and the second negative electrode insulation layer.

[0063] Among them, for the calculation method of the degree of lithium deposition in the area corresponding to the negative electrode sheet and the perforated insulating layer, the lithium deposition area in the area corresponding to the negative electrode sheet and the non-perforated insulating layer is S11, the lithium deposition area in the area corresponding to the negative electrode sheet and the insulating layer of any embodiment or comparative example is S12, and the degree of lithium deposition in the area corresponding to the negative electrode sheet and the insulating layer of any embodiment or comparative example is V1, then V1=S12 / S11.

[0064] 2. Adhesion test:

[0065] The insulating layer of each embodiment and the insulating layer in the comparative example are respectively pasted on aluminum foil, and the aluminum foil with the insulating layer pasted is cut into strip samples of 20mm×60mm, and hot-pressed at a temperature of 85°C and a pressure of 1MPa for 40min. Then, after being immersed in an electrolyte at 85°C for 4h, the sample is pasted on a steel plate with a double-sided tape (Nitto 5000NS) (the adhesion length is not less than 40mm), and the steel plate is fixed to the corresponding position of a high-speed rail tensile testing machine. The other end of the sample that is not adhered to the steel plate is pulled up, and the sample is clamped in a chuck, wherein the pulled-up sample part has an angle of 180° with the steel plate in space, and the chuck is pulled at a speed of 50mm / min. Finally, the average tensile force in the stable area is measured and recorded as the bonding force after immersion in the electrolyte.

[0066] Among them, the organic solvents of the electrolyte are ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP), and the mass ratio is EC:PC:DEC:EP=3:1:3:3, the solute is lithium hexafluorophosphate (LiPF6), and the concentration of LiPF6 is 1 mol / L.

[0067] 3. Drop test:

[0068] In a 20±5 test environment, a metal drop floor was used to drop the battery once along the head and tail surfaces and once at the four corners from a height of 1.5 m. A total of five rounds of tests were conducted in the order of drop (head -> tail -> right corner of the head -> right corner of the tail -> left corner of the head -> left corner of the tail (angle: 45±15 degrees, 6 times per round)); judgment criteria: no fire, no explosion, no smoke, no leakage. Ten batteries were tested for each embodiment or comparative example.

[0069] Example 1

[0070] <Preparation of positive electrode sheet>:

[0071] The positive electrode active material lithium cobalt oxide (LiCoO2), the conductive agent conductive carbon black (Super P), and the binder polyvinylidene fluoride are mixed in a mass ratio of 97:1.4:1.6, N-methylpyrrolidone (NMP) is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 75wt%. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9μm, and the aluminum foil is dried at 85°C to obtain a positive electrode sheet with a coating thickness of 110μm and a single-sided coating of a positive electrode active material layer. The above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material on both sides. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 85°C for 8h to obtain a positive electrode sheet with a specification of 74mm×851mm.

[0072] <Preparation of negative electrode sheet>:

[0073] The negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose (CMC-Na), and the binder styrene butadiene rubber (SBR) are mixed in a mass ratio of 96.4:1.5:0.5:1.6, deionized water is added, and the mixture is stirred evenly under the action of a vacuum mixer to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 70wt%. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and the copper foil is dried at 110°C to obtain a negative electrode sheet with a coating thickness of 130μm and a single-sided coating of a negative electrode active material layer. The above steps are repeated on the other surface of the aluminum foil to obtain a negative electrode sheet with a double-sided coating of negative electrode active materials. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 120°C for 12h to obtain a negative electrode sheet with a specification of 76mm×867mm.

[0074] <Preparation of diaphragm>:

[0075] A polyethylene porous polymer film is used as the separator.

[0076] <Electrolyte Preparation>:

[0077] In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate (EC), propylene carbonate (PC) and ethyl propionate (EP) were uniformly mixed in a mass ratio of 1:1:1 to form a basic solvent, and finally LiPF6 was added to dissolve and stirred evenly to form an electrolyte. Based on the total mass of the electrolyte, the mass percentage of LiPF6 was 12.5%, and the remainder was the basic solvent.

[0078] <Preparation of insulating layer>:

[0079] The insulating layer includes a glue layer arranged on one surface of the base material layer, wherein the thickness of the insulating layer is 20 μm, the thickness of the glue layer is 10 μm, and the thickness of the base material layer is 10 μm.

[0080] Polypropylene, elastomer polyurethane, filler titanium dioxide, and antioxidant diphenylamine are mixed evenly in a mass ratio of 60:25:7.5:7.5, and then coated on a substrate layer and dried at 120° C. to obtain an insulating layer. The substrate layer is a polyethylene terephthalate film.

[0081] The insulating layer is divided into a first part and a second part in the width direction, the ratio of the area of ​​the first part to the area of ​​the second part is 0.2:1, the width L1 of the second part is 15mm, and circular holes are punched in the first part by laser punching with a hole spacing of 0.5mm and a hole diameter of 1mm. The ratio of the hole area to the non-hole area in the first part is 0.1:1, and an insulating layer is obtained.

[0082] <Preparation of lithium-ion batteries>:

[0083] The insulating layer is pasted on the surface of the positive electrode sheet and covers the area of ​​the positive electrode sheet where the positive active layer is not set (the second area or the fourth area). Then the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order. On the side of the negative active layer close to the insulating layer, the length L2 of the negative active layer beyond the positive active layer is 14.5mm, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is wound. The electrode assembly is placed in an aluminum-plastic film packaging bag, and the electrolyte is injected after drying. After vacuum packaging, standing, formation, capacity, degassing, trimming and other processes, a lithium-ion battery is obtained. Among them, the formation conditions are to charge to 3.3V at a constant current of 0.02C, then charge to 3.6V at a constant current of 0.1C, and finally charge to 4.45V at a constant current of 0.2C.

[0084] The relevant parameters in Comparative Example 1 and Examples 2 to 10 are shown in Table 1 below.

[0085] The insulating layer in comparative example 1 is not perforated. The insulating layers in embodiments 1 to 6 differ only in the ratio of the area of ​​the holes to the area of ​​the non-holes in the first part. The insulating layers in embodiments 7 to 10 differ only in the ratio of the area of ​​the first part to the area of ​​the second part.

[0086] Table 1

[0087]

[0088] According to the above Table 1, combined with Comparative Example 1 and Examples 1 to 10, it can be seen that the lithium ion battery in the embodiment of the present application can effectively improve the lithium plating problem of the lithium ion battery by punching holes in the insulating layer at the end of the positive electrode sheet.

[0089] In combination with Examples 1 to 6, it can be seen that when the ratio of the pore area to the non-porous area in the first part of the insulating layer in the embodiments of the present application is lower than 0.1:1, the degree of lithium precipitation in the area opposite to the negative electrode active layer and the insulating layer is more obvious, and when the ratio of the pore area to the non-porous area in the first part of the insulating layer is higher than 1:1, the adhesion force of the insulating layer after soaking in the electrolyte is low, so the ratio of the pore area to the non-porous area in the first part of the insulating layer is preferably 0.1:1 to 1:1.

[0090] In combination with Examples 7 to 10, it can be seen that when the ratio of the first part area to the second part area of ​​the insulating layer in the embodiments of the present application is lower than 0.05:1, the degree of lithium plating in the area opposite to the negative electrode active layer and the insulating layer is more obvious, and when the ratio of the first part area to the second part area of ​​the insulating layer is higher than 0.5:1, the adhesion force of the insulating layer after soaking in the electrolyte is lower, so the ratio of the first part area to the second part area of ​​the insulating layer is preferably 0.05:1 to 0.5:1.

[0091] The relevant parameters in Example 1 and Examples 11 to 16 are shown in Table 2 below, wherein in Example 11, along the width direction of the insulating layer, the width of the second portion of the insulating layer is L1, and on the side of the negative electrode active layer close to the insulating layer, the length of the negative electrode active layer exceeding the positive electrode active layer is L2, and L1-L2=0.5mm. In Examples 11 to 16, only the value of L1-L2 is adjusted by adjusting the length L2 of the negative electrode sheet exceeding the positive electrode active material layer, and the other features are the same as in Example 1.

[0092] Table 2

[0093]

[0094] According to Table 2 above, combined with Example 1 and Examples 11 to 16, it can be seen that in the embodiments of the present application, when the value of L1-L2 is less than 1mm, the drop test pass rate of the lithium-ion battery is low, that is, the positive and negative electrodes are prone to short circuits. At the same time, in practical applications, when the value of L1-L2 is higher than 10mm, the insulating layer will be too wide, thereby losing the energy density of the lithium battery. Therefore, the preferred value of L1-L2 is 1mm to 10mm. In order to obtain a lower short circuit risk and better energy density, the value of L1-L2 is further preferably 3mm to 7mm.

[0095] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly comprising a negative electrode sheet, a positive electrode sheet and a separator, the separator being disposed between adjacent negative electrode sheets and positive electrode sheets, the electrode assembly being formed by stacking and winding the negative electrode sheets, the positive electrode sheets and the separator; the positive electrode sheet comprising a positive electrode collector and a first positive electrode active layer, the positive electrode collector having a first surface and a second surface opposite to each other, the first surface of the positive electrode collector comprising a first region and a second region, the first region being provided with the first positive electrode active layer, the second region being not provided with the first positive electrode active layer, and the second region being connected to the first region; It is characterized in that The electrode assembly further includes a first insulating layer, the first insulating layer including a first portion and a second portion connected to each other, the first portion covers the first positive active layer, the second portion covers the second region, and the first portion of the first insulating layer is provided with a first hole.

2. The secondary battery according to claim 1, characterized in that: The negative electrode sheet includes a negative electrode collector and a first negative electrode active layer, the first negative electrode active layer is arranged on the surface of the negative electrode collector facing the first positive electrode active layer, and along the direction perpendicular to the surface of the positive electrode collector, the projection of the first negative electrode active layer on the surface of the positive electrode sheet covers the first positive electrode active layer; along the length direction of the positive electrode collector, the width of the second part is L1, and on the side of the first negative electrode active layer close to the first insulating layer, the length of the first negative electrode active layer exceeding the first positive electrode active layer is L2, and L1>L2.

3. The secondary battery according to claim 2, characterized in that: 1mm≤L1-L2≤10mm.

4. The secondary battery according to claim 3, characterized in that: 3mm≤L1-L2≤7mm.

5. The secondary battery according to claim 1, characterized in that: The first insulating layer satisfies at least one of the following characteristics: (1) The ratio of the area of ​​the first part to the area of ​​the second part is 0.05:1 to 0.5:1; (2) The ratio of the pore area to the non-pore area in the first part is 0.1:1 to 1:1; (3) The shape of the first hole is at least one of circular, elliptical or polygonal.

6. The secondary battery according to claim 1, characterized in that: The positive electrode sheet includes a second positive electrode active layer, the second surface of the positive electrode collector includes a third region and a fourth region connected to each other, the third region is provided with the second positive electrode active layer, and the fourth region is not provided with the second positive electrode active layer; the electrode assembly includes a second insulating layer, the second insulating layer includes a third part and a fourth part connected to each other, the third part covers the second positive electrode active layer, the fourth part covers the fourth region, and the third part of the second insulating layer is provided with a second hole.

7. The secondary battery according to claim 6, characterized in that: The negative electrode sheet includes a negative electrode collector and a second negative electrode active layer, the second negative electrode active layer is arranged on the surface of the negative electrode collector facing away from the first positive electrode active layer, and along the direction perpendicular to the surface of the positive electrode collector, the projection of the second negative electrode active layer on the surface of the positive electrode sheet covers the second positive electrode active layer; along the length direction of the positive electrode collector, the width of the fourth part is L3, and on the side of the second negative electrode active layer close to the second insulating layer, the length of the second negative electrode active layer exceeding the second positive electrode active layer is L4, and L3>L4.

8. The secondary battery according to any one of claims 1 to 7, characterized in that: The first insulating layer satisfies at least one of the following characteristics: (4) The thickness of the first insulating layer is D1, 4 μm≤D1≤30 μm; (5) The first insulating layer includes at least one of polypropylene, modified polypropylene, styrene-isoprene-styrene copolymer, polyolefin, polyethylene terephthalate, and polyimide.

9. An electronic device, characterized in that: Comprising the secondary battery as claimed in any one of claims 1 to 8.

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