Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device, and the secondary battery comprises an electrode assembly which comprises a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece. The first pole piece comprises a first current collector, the first current collector is provided with a first surface and a second surface which are opposite to each other along the thickness direction of the first current collector, part of the first surface and the second surface of the first current collector is covered by a first active material layer, and the first current collector comprises an uncoated area which is not covered by the first active material layer; the insulating layer covers at least part of the uncoated area and comprises a first insulating layer located on the first surface and a second insulating layer located on the second surface; wherein the uncoated region of the first current collector is bent towards one side of the first surface, the direction of the first active material layer towards the insulating layer is a first direction, and the second upper end surface of the second insulating layer exceeds the first upper end surface of the first insulating layer along the first direction. According to the technical scheme, at least the safety of the secondary battery can be improved.

Description

Technical Field

[0001] The utility model relates to a secondary battery, a battery pack and an electronic device. Background Art

[0002] In the field of new energy power batteries, secondary batteries refer to rechargeable batteries, also known as renewable batteries or storage batteries. Unlike primary batteries, secondary batteries can be reverse charged and discharged for multiple cycles so that they can be reused. Secondary batteries generally include electrode assemblies, casings, cover plates, etc. Cylindrical batteries refer to batteries containing cylindrical wound cores, which include casings and electrode assemblies. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. These positive electrode sheets, negative electrode sheets, and separators are stacked on each other and wound into an electrode assembly, which is then encapsulated in a casing. Utility Model Content

[0003] In view of the problems existing in the related art, the purpose of the present invention is to provide a secondary battery, a battery pack and an electronic device, so as to at least improve the safety of the secondary battery.

[0004] To achieve the above-mentioned objectives, the present invention provides a secondary battery, comprising an electrode assembly, the electrode assembly comprising a first electrode piece, a second electrode piece and a diaphragm arranged between the first electrode piece and the second electrode piece, wherein the first electrode piece comprises: a first current collector, having a first surface and a second surface relative to each other along its thickness direction, part of the first surface and the second surface of the first current collector being covered by a first active material layer, the first current collector comprising an uncoated area not covered by the first active material layer; an insulating layer covering at least part of the uncoated area, the insulating layer comprising a first insulating layer located on the first surface and a second insulating layer located on the second surface; wherein the uncoated area of ​​the first current collector is bent toward one side of the first surface, the direction of the first active material layer toward the insulating layer is a first direction, and along the first direction, the second upper end surface of the second insulating layer exceeds the first upper end surface of the first insulating layer.

[0005] In the above technical solution, by configuring the first insulating layer on the bent side of the uncoated region of the first current collector to be lower than the second insulating layer on the other side, the pressure on the first insulating layer caused by the bending of the uncoated region can be reduced, preventing the first insulating layer from falling off on the bent side. This avoids the problem of foreign matter generated by the falling insulating layer causing battery failure, thereby improving the safety of the secondary battery. Furthermore, because the height of the first insulating layer on the bent side is lower, the uncoated region can be bent and pressed down more easily and smoothly.

[0006] In some embodiments, along the first direction, the second upper end surface exceeds the first upper end surface by 0.01 mm to 8 mm, or the second upper end surface exceeds the first upper end surface by 0.01 mm to 2 mm.

[0007] In some embodiments, the electrode assembly has a winding center hole, the first surface is a surface of the first current collector close to the winding center hole, and the second surface is a surface of the first current collector away from the winding center hole.

[0008] In some embodiments, the first current collector includes a bend, and an orthographic projection of a starting end of the bend along a thickness direction of the first current collector does not overlap with the second insulating layer.

[0009] In some embodiments, in the winding direction of the electrode assembly, the uncoated region of the first current collector includes a plurality of bends.

[0010] In some embodiments, the second pole piece includes: a second current collector; a second active material layer covering at least a portion of the surface of the second current collector on both sides of the thickness direction of the second current collector; wherein, along the first direction, the upper end of the second active material layer exceeds the upper end of the first active material layer by a distance of 0.5mm-1.5mm; along the direction away from the first direction, the lower end of the second active material layer exceeds the lower end of the first active material layer by a distance of 1mm-2mm; and along the first direction, the first upper end surface of the first insulating layer exceeds the upper end surface of the second active material layer.

[0011] In some embodiments, the first upper end surface of the first insulating layer extends beyond the upper end surface of the second active material layer by 0.5 mm to 2 mm; and along the direction away from the first direction, one end of the diaphragm extends beyond the lower end of the second active material layer by 0.5 mm to 1.5 mm.

[0012] In some embodiments, the first electrode is a positive electrode; the first insulating layer and the second insulating layer are different in color; the uncoated area of ​​the first current collector is a tab; and the secondary battery is a cylindrical battery.

[0013] An embodiment of the present application further provides a battery pack comprising any one of the above-mentioned secondary batteries.

[0014] An embodiment of the present application further provides an electronic device including the above-mentioned battery pack.

[0015] The beneficial technical effects of the utility model include:

[0016] By configuring the insulating layer on one side of the first current collector to have a lower height than the insulating layer on the other side, the pressure on the insulating layer on this side due to bending is reduced, preventing the insulating layer from falling off. This prevents foreign matter from falling off and causing battery failure, thereby improving the safety of the secondary battery. Furthermore, because the insulating layer on the inwardly bent side is lower, the first current collector is easier and smoother to bend and press down. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 A schematic diagram showing an electronic device according to an embodiment of the present application is a vehicle.

[0019] Figure 2 A perspective view of a secondary battery according to an embodiment of the present application is shown.

[0020] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of the present application is shown.

[0021] Figure 4 A cross-sectional view of a conventional electrode assembly is shown.

[0022] Figure 5 Shows the bend Figure 4 Schematic cross-sectional view of the first current collecting process.

[0023] Figure 6A A cross-sectional view of an electrode assembly according to an embodiment of the present application is shown.

[0024] Figure 6B yes Figure 6A Schematic cross-sectional view of the uncoated area of ​​the first current collector.

[0025] Figure 7A A schematic diagram of forming a first pole piece using a coating device is shown.

[0026] Figure 7B Schematic top view of the first current collector after coating the first active material layer and the insulating layer.

[0027] Figure 7C yes Figure 7B A partial enlarged schematic diagram of area B after the first pole piece is cut. DETAILED DESCRIPTION

[0028] In order to better understand the spirit of the embodiments of the present application, some preferred embodiments of the present application are further described below.

[0029] The embodiments of the present application will be described in detail below. Throughout this specification, identical or similar components and components having identical or similar functions are represented by similar reference numerals. The embodiments described herein with respect to the accompanying drawings are illustrative and diagrammatic and are intended to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

[0030] As used herein, the terms "substantially," "substantially," and "approximately" are used to describe and illustrate small variations. When used in conjunction with an event or circumstance, the terms may refer to instances where the event or circumstance occurred precisely as well as instances where the event or circumstance occurred very approximately.

[0031] In this specification, unless otherwise specified or limited, relative terms such as "central", "longitudinal", "lateral", "front", "rear", "right", "left", "inner", "outer", "lower", "higher", "horizontal", "vertical", "above", "below", "above", "below", "top", "bottom" and their derivatives (such as "horizontally", "downwardly", "upwardly", etc.) should be interpreted as referring to the directions described in the discussion or depicted in the drawings. These relative terms are only used for convenience of description and do not require that the present application be constructed or operated in a specific orientation.

[0032] For ease of description, “first,” “second,” “third,” etc. may be used herein to distinguish different components in a figure or a series of figures. “First,” “second,” “third,” etc. are not intended to describe the corresponding components.

[0033] The present application provides an electronic device 1000. For the convenience of description, the following embodiments are described by taking the electronic device 1000 as a vehicle as an example. Figure 1The vehicle is equipped with a battery pack 1002 inside. Battery pack 1002 can be located at the bottom, front, or rear of the vehicle body 1001. Battery pack 1002 can be used to power the vehicle, for example, as the vehicle's operating power source. The working portion of the electronic device 1000 is electrically connected to battery pack 1002 to obtain electrical energy. The vehicle can be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle, among others, but is not limited thereto. The working portion is the vehicle body, with battery pack 1002 located at the bottom of the vehicle body and providing electrical energy for the vehicle's operation and for the operation of its electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or electric tool, among others. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, among others. The working portion can draw electrical energy from battery pack 1002 and perform corresponding operations, such as the blade rotation unit of a fan or the dust collection unit of a vacuum cleaner. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment of the present application does not impose any particular limitation on the electronic device 1000.

[0034] Figure 2 A perspective view of a secondary battery 100 according to an embodiment of the present application is shown. Figure 3 1 shows a cross-sectional view of a secondary battery 100 according to an embodiment of the present application. Figure 2 and Figure 3 As shown, in an embodiment where the secondary battery 100 is a cylindrical battery, the secondary battery 100 includes a housing 200 and an electrode assembly 120 sealed and installed in the housing 200. Figure 3 As shown, along the height direction h of the secondary battery 100, the electrode assembly 120 is disposed between the end wall 111 of the housing 200 and the rolling groove 113. The rolling groove 113 can limit the axial movement of the electrode assembly 120 between the end wall 111 and the rolling groove 113. The electrode assembly 120 has a winding center hole 120c at its radial center.

[0035] Figure 4 FIG. 1 shows a cross-sectional view of a conventional electrode assembly 120 ′. Figure 4 As shown, the conventional electrode assembly 120' is mainly formed by winding a first electrode sheet 10 and a second electrode sheet 20, and a separator 122 is provided between the first electrode sheet 10 and the second electrode sheet 20. The electrolyte can be filled between the first electrode sheet 10, the second electrode sheet 20 and the separator 122.

[0036] The first electrode sheet 10 may include a first current collector 18 and a first active material layer 16. Portions of opposing surfaces of the first current collector 18 along its thickness direction are covered by the first active material layer 16. The first current collector 18 includes an uncoated region 18a not covered by the first active material layer 16. The first current collector 18 includes a second current collector 28 and a second active material layer 26. At least portions of both sides of the second current collector 28 along its thickness direction are covered by the second active material layer 26. The second current collector 28 includes an uncoated region 28a not covered by the second active material layer 26.

[0037] To minimize the possibility of contact between the first electrode sheet 10 and the second electrode sheet 20, the electrode assembly 120 may further include an insulating layer 40 that covers at least a portion of the uncoated region 18a of the first current collector 18. The insulating layer 40 may be provided on both sides of the first current collector 18. The insulating layer 40 can effectively prevent electrical contact between the first electrode sheet 10 and the second electrode sheet 20.

[0038] The uncoated areas 18a and 28a of the first current collector 18 and the second current collector 28 may face the winding center hole 120c of the electrode assembly 120, respectively. The bent uncoated areas 18a and 28a are stacked on each other. Figure 3 ) can be connected to (for example, connected by welding) the uncoated areas 18a stacked on each other, and further electrically connected to the pole 80 (see Figure 3 Another transfer sheet 50 (not shown) may be connected to the uncoated regions 28a stacked on each other and further electrically connected to the housing 200 (see FIG. Figure 3 After the adapter is welded, a flattening process may be performed to further bend the uncoated regions 18a, 28a of the first and second current collectors 18, 28. Bending the uncoated regions 18a, 28a of the first and second current collectors 18, 28 can reduce the space occupied by the uncoated regions 18a, 28a, thereby increasing the battery energy density.

[0039] Figure 5 Shows the bend Figure 4 Schematic diagram of the cross section of the first current collector 18 process. Figure 5As shown, because the peeling force of the insulating layer 40 may be limited, at least a portion of the insulating layer 40 may fall off during the bending of the first current collector 18 in the direction of arrow A1. For example, portion 40T of the insulating layer 40 adjacent to the bend may fall off. In addition, there is also a risk of at least a portion of the insulating layer 40 falling off during the flattening process after the adapter is welded. In particular, on the side of the bend of the first current collector 18, due to the large curvature of the bend portion of the first current collector 18, the risk of portion 40T of the insulating layer 40 falling off is even greater. This can lead to the introduction of foreign matter into the electrode assembly, causing battery failure, or even a short circuit and fire.

[0040] Figure 6A A cross-sectional view of an electrode assembly 120 according to an embodiment of the present application is shown. In the electrode assembly 120 according to an embodiment of the present application, the electrode assembly 120 is formed by winding a first electrode sheet 10 and a second electrode sheet 20, and a separator 122 is provided between the first electrode sheet 10 and the second electrode sheet 20. In the first direction from the first active material layer 16 to the insulating layer 40 (i.e., the height direction h of the electrode assembly 120), one end of the first current collector 18 includes an uncoated area 18a that is not coated with the first active material layer 16. The uncoated area 18a can be used as a first pole tab. In a direction opposite to the height direction h, one end of the second current collector 28 includes an uncoated area 28a that is not coated with the second active material layer 26. The uncoated area 28a can be used as a second pole tab.

[0041] In this application, the first electrode sheet 10 is used as a positive electrode sheet, and the second electrode sheet 20 is used as a negative electrode sheet as an example to illustrate the embodiments of the present application. In such an embodiment, the uncoated area 18a is a positive electrode tab, and the uncoated area 28a is a negative electrode tab. At least part of the surface of the second current collector 28 along both sides of the thickness direction is covered by the second active material layer 26.

[0042] Taking a lithium-ion battery as an example, the first current collector 18 is the positive electrode current collector, which can be made of aluminum. The first active material layer 16 is the positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The second current collector 28 is the negative electrode current collector, which can be made of copper. The second active material layer 26 is the negative electrode active material, which can be carbon or silicon. The separator can be made of materials such as PP (polypropylene) or PE (polyethylene).

[0043] According to an embodiment of the present application, the insulating layers 40 on opposite surfaces of the first current collector 18 may have a height difference. Specifically, Figure 6B yes Figure 6A Schematic cross-sectional view of the uncoated area 18a of the first current collector 18. Figure 6BAs shown, the first current collector 18 has a first surface 181 and a second surface 182 that are opposite to each other along its thickness direction. The insulating layer 40 covers a portion of the first surface 181 and the second surface 182 of the uncoated region 18a of the first current collector 18. Specifically, the insulating layer 40 may include a first insulating layer 40a formed on the first surface 181 and a second insulating layer 40b formed on the second surface 182. The insulating layer 40 is located between the bent portion 18B and the first active material layer 16.

[0044] The uncoated area 18a of the first current collector 18 is bent toward the first surface 181 and extends along the first direction from the first active material layer 16 to the insulating layer 40, that is, along the first direction from the first active material layer 16 to the insulating layer 40. Figure 6A and Figure 6B In the height direction h shown in FIG, the second upper end surface 402 of the second insulating layer 40b on the second surface 182 extends beyond the first insulating layer 40a on the first surface 181, that is, extends beyond the first upper end surface 401 of the first insulating layer 40a. In other words, the second upper end surface 402 of the second insulating layer 40b along the height direction h is higher than the first upper end surface 401 of the first insulating layer 40a. Therefore, there is a height difference d1 between the first insulating layer 40a and the second insulating layer 40b on the first surface 181 and the second surface 182, and the distance between the second upper end surface 402 and the first upper end surface 401 along the height direction h is the height difference d1.

[0045] By configuring the first insulating layer 40a on one side of the bend to have a lower height than the second insulating layer 40b on the other side, the pressure on the first insulating layer 40a on the first surface 181 caused by the bending of the uncoated area 18a can be reduced, thereby preventing the first insulating layer 40a on the first surface 181 from falling off. This prevents foreign matter from falling off the insulating layer 40a and causing battery failure, thereby improving the safety of the secondary battery. Furthermore, because the top height of the first insulating layer 40a on the first surface 181 on the bend side is lower, the uncoated area 18a is bent and pressed down more easily and smoothly.

[0046] In some embodiments, the height difference d1 between the second upper end surface 402 of the second insulating layer 40b and the first upper end surface 401 of the first insulating layer 40a ranges from 0.01 mm to 8 mm, i.e., 8 mm ≥ d1 ≥ 0.01 mm. In some embodiments, the height d2 of the first insulating layer 40a along the height direction h can be approximately 2 mm. It should be understood that this value includes process errors during the production process. Taking into account engineering fluctuations such as coating errors of the insulating layer, setting the height difference d1 to a range of 0.01 mm to 8 mm can ensure that the height of the first insulating layer 40a on the first surface 181 does not exceed that of the second insulating layer 40b on the first surface 182. In some embodiments, the height difference d1 between the second upper end surface 402 and the first upper end surface 401 ranges from 0.01 mm to 2 mm. The first insulating layer 40a has a first lower end surface 403 opposite to its first upper end surface 401, and the second insulating layer 40b has a second lower end surface 404 opposite to its second upper end surface 402. The first lower end surface 403 and the second lower end surface 404 can be basically flush along the thickness direction of the first current collector 18 (taking into account engineering fluctuations such as coating errors of the insulating layer).

[0047] The first insulating layer 40a and the second insulating layer 40b with a height difference provided in the present application can be applied to a variety of secondary batteries. In the embodiment where the secondary battery is a cylindrical battery, the bending direction of the uncoated area 18a is toward the winding center hole 120c of the electrode assembly 120, that is, the first surface 181 is the surface of the first current collector 18 close to the winding center hole 120c, and the second surface 182 is the surface of the first current collector 18 away from the winding center hole 120c. The bent uncoated areas 18a can be stacked on each other, and the adapter sheet 50 (see Figure 3 ) can be connected to the stacked uncoated areas 18a. In the application of cylindrical batteries, the technical solution of the present application can prevent the first insulating layer 40a on the first surface 181 on the bent side from falling off, thereby avoiding the problem of foreign matter generated by the shedding of the insulating layer causing battery failure, thereby improving the safety of cylindrical batteries.

[0048] The first current collector 18 includes a bend 18B. In the height direction h, the starting end P1 of the bend 18B extends beyond the second upper end surface 402 of the second insulating layer 40b. In other words, the orthographic projection of the starting end P1 of the bend 18B along the thickness direction of the first current collector 18 does not overlap with the second insulating layer 40b. The starting end P1 of the bend 18B refers to the position where the first current collector 18 first bends in the height direction h. In this way, the bending of the first current collector 18 does not cause the first insulating layer 40a and the second insulating layer 40b to bend, thereby preventing the insulating layers from falling off, improving the safety of the secondary battery, and making it easier and smoother to bend and press down the uncoated area 18a.

[0049] In some embodiments, the materials of the first insulating layer 40a and the second insulating layer 40b on the first surface 181 and the second surface 182 may be substantially the same. In some embodiments, the first insulating layer 40a and the second insulating layer 40b on the first surface 181 and the second surface 182 may both contain ceramic materials (also referred to as ceramic fillers). While ensuring insulation, the ceramic material also has a high hardness and can provide a more stable supporting force. Especially in cylindrical batteries using full-ear technology, from the safety perspective of cylindrical batteries, a ceramic material layer is usually used as an insulating layer. However, the peeling force of such a ceramic material layer is limited and it is more likely to fall off. Therefore, when the insulating layer is a ceramic material layer, the first insulating layer 40a and the second insulating layer 40b with a height difference are used to effectively prevent the ceramic material layer from falling off, avoid battery failure, and improve the safety of the cylindrical battery.

[0050] Combine Figure 6A and Figure 6B As shown, in some embodiments, both ends of the second active material layer 26 extend beyond the first active material layer 16 along the height direction h and the direction opposite to the height direction h. In some embodiments, along the height direction h, the upper end of the second active material layer 26 extends beyond the upper end of the first active material layer 16 by 0.5 mm to 1.5 mm. In a direction away from the height direction h, the lower end of the second active material layer 26 extends beyond the lower end of the first active material layer 16 by 1 mm to 2 mm. The above-mentioned distance range in which the upper and lower ends of the second active material layer 26 of the second electrode sheet 20 (negative electrode sheet) extend beyond the first active material layer 16 of the first electrode sheet 10 (positive electrode sheet) can optimize the energy density of the battery.

[0051] In some embodiments, in the height direction h, the first upper end surface 401 of the first insulating layer 40a on the first surface 181 extends beyond the upper end surface of the second active material layer 26 of the second electrode sheet 20. The distance that the first upper end surface 401 of the first insulating layer 40a extends beyond the upper end surface of the second active material layer 26 can be 0.5 mm to 2 mm. In other words, while the first insulating layer 40a and the second insulating layer 40b on the first surface 181 and the second surface 182 have a height difference to prevent the insulating layer from falling off, the first upper end surface 401 of the lower first insulating layer 40a is still higher than the second active material layer 26 of the second electrode sheet 20, which can prevent the negative electrode active material layer 26 from contacting the uncoated area 18a (positive electrode tab) of the first current collector 18, thereby providing good insulation.

[0052] In addition, in some embodiments, one end ( Figure 6AThe lower end of the separator 122 extends beyond the lower end of the second active material layer 26 by 0.5 mm to 1.5 mm. The separator 122 extends beyond the negative electrode active material layer 26 to provide good insulation and enhance battery safety.

[0053] Figure 7A Schematic diagram of forming the first pole piece 10 using a coating device is shown. Figure 7A In some embodiments, the insulating layer 40 and the first active material layer 16 can be formed simultaneously on the same side surface. The first discharge port 1091 of the coating device 109 can be used to apply the first active material layer 16, and the two second discharge ports 1092 of the coating device 109 on both sides of the first discharge port 1091 are used to apply the insulating layer 40.

[0054] Figure 7B FIG. 1 is a schematic top view of the first current collector 18 after the first active material layer 16 and the insulating layer 40 are coated. Figure 7A The cross-sectional view of the first pole piece 10 in FIG. Figure 7B After the first active material layer 16 and the first insulating layer 40a and the second insulating layer 40b are coated on the first surface 181 and the second surface 182 of the first current collector 18, the top view structures of the first surface 181 and the second surface 182 of the first current collector 18 can be as shown. Figure 7B As shown, the difference is that the widths of the first insulating layer 40 a and the second insulating layer 40 b along the direction D on the first surface 181 and the second surface 182 may be different.

[0055] Combine Figure 7A and Figure 7B As shown, the first current collector 18 coated with the first active material layer 16 and the insulating layer 40 can be cut along the center line Lc to obtain a single first electrode piece 10. In a single first electrode piece 10, the first active material layer 16 can include a flat region 14 and a thinned region 12 located at one end of the flat region 14 along a direction D. The insulating layer 40 can cover at least a portion of the thinned region 12. The direction D can correspond to Figure 6A and Figure 6B The height direction h in .

[0056] By combining the above-mentioned production process of the electrode, the width difference of the first insulating layer 40a and the second insulating layer 40b coated on the first surface 181 and the second surface 182 along the direction D can be achieved (the width difference is Figure 6B The height difference d1 along the height direction h is used to solve the problem of the insulating layer 40 falling off during the battery production process and reduce the risk of foreign matter.

[0057] In some embodiments, the first insulating layer 40a on the first surface 181 and the second insulating layer 40b on the second surface 182 can have different colors. Specifically, compared to the first insulating layer 40a, the second insulating layer 40b can be added with a coloring material, so that the color of the first insulating layer 40a on the first surface 181 is easier to detect by a CCD (charge coupled device) camera than the second insulating layer 40b on the second surface 182. For example, the first insulating layer 40a on the first surface 181 can be a coloring ceramic material layer (such as a yellow ceramic material layer, which can be achieved by adding a coloring material), and the second insulating layer 40b on the second surface 182 can be a conventional white ceramic material layer to distinguish the first surface 181 from the second surface 182. In cylindrical batteries, the surface density of the active material layer 16 on the first surface 181 and the second surface 182 of the first electrode sheet 10 is generally different, and the positive electrode capacity is also different, so it is necessary to distinguish the first surface 181 from the second surface 182. For example, after winding, the first insulating layer 40a on the first surface 181 of the first electrode sheet 10, which has a more obvious color, faces the winding center hole of the electrode assembly. With the above configuration, a CCD camera can be used to identify the colors of the first insulating layer 40a and the second insulating layer 40b to determine whether the first surface 181 and the second surface 182 of the first electrode sheet 10 are correct.

[0058] refer to Figure 7B For cylindrical batteries, after coating the first active material layer 16 and the insulating layer 40, the portion of the first current collector 18 of the first electrode sheet 10 not coated with the first active material layer 16 and the insulating layer 40 can be trimmed. During this trimming process, the insulating layer 40 can be used to reduce the generation of burrs.

[0059] Figure 7C yes Figure 7B A partial enlarged schematic diagram of the area B after the first pole piece 10 is cut. Figure 7C As shown, in the embodiment of the cylindrical battery, direction D may correspond to Figure 6A and Figure 6B The height direction h of the first current collector 18 is perpendicular to the direction D, and the direction perpendicular to the direction D may correspond to the winding direction of the electrode assembly. In the direction perpendicular to the direction D, the portion of the first current collector 18 not covered by any insulating layer 40 may be cut into a plurality of spaced-apart segments 18F. Figure 7C Only one segment 18F is shown in the partial enlarged view as an example. In the cylindrical battery, each segment 18F has the above Figure 6A and Figure 6B In such an embodiment, in the winding direction of the electrode assembly, the above Figure 6A and Figure 6BThe depicted uncoated region 18 a of the first current collector 18 may include a plurality of bends 18B.

[0060] In some embodiments, the dimension d2' of the first insulating layer 40a along the direction D may be approximately 2 mm, which includes the process error during the production process. Figure 6B The height d2 of the first insulating layer 40a in the section 18F is shown in FIG. In some embodiments, the length d3 of the section 18F along the direction D can range from 4 mm to 8 mm. In some embodiments, the width of the section 18F gradually decreases along the direction D. In a direction perpendicular to the direction D, the maximum width d4 of the section 18F can be approximately 4 mm, which includes process errors during the production process.

[0061] It should be understood that although the above example shows that the insulating layer 40 is disposed only on the first current collector 18 of the first pole piece 10, in some other embodiments, the insulating layer 40 described above may be disposed only on the second current collector 28 of the second pole piece 20. Alternatively, the insulating layer 40 described above may be disposed on both the first current collector 18 of the first pole piece 10 and the second current collector 28 of the second pole piece 20.

[0062] The embodiment of the present application also provides a battery pack 1002 (see Figure 1 ), including the secondary battery 100 of any one of the above items, and the battery pack 1002 can have the beneficial effects described above with respect to the secondary battery 100.

[0063] The embodiment of the present application also provides an electronic device 1000 (see Figure 1 ), including the above-mentioned battery pack 1002, and the electronic device 1000 can have the beneficial effects described above with respect to the secondary battery 100 and / or the battery pack 1002.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A secondary battery, characterized in that: The invention comprises an electrode assembly, wherein the electrode assembly comprises a first electrode piece, a second electrode piece, and a diaphragm disposed between the first electrode piece and the second electrode piece, wherein the first electrode piece comprises: a first current collector having a first surface and a second surface opposite to each other along a thickness direction thereof, wherein portions of the first surface and the second surface of the first current collector are covered by a first active material layer, and the first current collector includes an uncoated area not covered by the first active material layer; an insulating layer covering at least a portion of the uncoated area, the insulating layer comprising a first insulating layer located on the first surface and a second insulating layer located on the second surface; The uncoated area of ​​the first current collector is bent toward the first surface, the direction of the first active material layer toward the insulating layer is a first direction, and along the first direction, the second upper end surface of the second insulating layer exceeds the first upper end surface of the first insulating layer.

2. The secondary battery according to claim 1, wherein Along the first direction, The second upper end surface exceeds the first upper end surface by 0.01 mm to 8 mm, or The second upper end surface exceeds the first upper end surface by 0.01 mm to 2 mm.

3. The secondary battery according to claim 1, wherein The electrode assembly has a winding center hole, and the first surface is a surface of the first current collector close to the winding center hole; The second surface is a surface of the first current collector facing away from the winding center hole.

4. The secondary battery according to claim 1, wherein The first current collector includes a bend, the insulating layer is located between the bend and the first active material layer, and the orthographic projection of the starting end of the bend of the first current collector along the thickness direction of the first current collector does not overlap with the second insulating layer.

5. The secondary battery according to claim 4, wherein In the winding direction of the electrode assembly, the uncoated region of the first current collector includes a plurality of the bent portions.

6. The secondary battery according to claim 1, wherein The second pole piece includes: Second collector; a second active material layer covering at least a portion of the surface of the second current collector on both sides along the thickness direction of the second current collector; Wherein, along the first direction, the distance that the upper end of the second active material layer exceeds the upper end of the first active material layer is 0.5 mm-1.5 mm; In a direction away from the first direction, the lower end of the second active material layer extends beyond the lower end of the first active material layer by 1 mm to 2 mm; Furthermore, along the first direction, the first upper end surface of the first insulating layer exceeds an upper end surface of the second active material layer.

7. The secondary battery according to claim 6, characterized in that The distance between the first upper end surface of the first insulating layer and the upper end surface of the second active material layer is 0.5 mm to 2 mm; In a direction away from the first direction, one end of the separator extends beyond the lower end of the second active material layer by a distance of 0.5 mm to 1.5 mm.

8. The secondary battery according to claim 1, wherein The first pole piece is a positive pole piece; The first insulating layer and the second insulating layer have different colors; The uncoated area of ​​the first current collector is a tab, and the secondary battery is a cylindrical battery.

9. A battery pack, characterized in that: The secondary battery comprises the secondary battery according to any one of claims 1 to 8.

10. An electronic device, characterized in that: Comprising the battery pack as claimed in claim 9.

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