Secondary battery, battery pack, and electronic device

Abstract

The embodiment of the utility model provides a secondary battery, a battery pack and an electronic device, the secondary battery comprises an electrode assembly, the electrode assembly comprises a negative pole piece, a positive pole piece and a diaphragm arranged between the negative pole piece and the positive pole piece, the negative electrode uncoated area of the negative electrode plate comprises a negative electrode lug and a negative electrode connecting area connected between the negative electrode lug and the negative electrode coated area, the negative electrode lug comprises a negative electrode lug body and a negative electrode lug transition part connected between the negative electrode connecting area and the negative electrode lug body, and the negative electrode lug transition part comprises a first negative electrode lug transition end point; the first negative electrode tab transition end point is a position where the tangent line of the negative electrode tab transition part intersects with the extension direction of the negative electrode connection area, and the distance between the first negative electrode tab transition end point and the first diaphragm end of the diaphragm in the first direction in the first direction ranges from 0.5 mm to 2 mm. According to the technical scheme, the diaphragm can be at least prevented from being damaged in the manufacturing process.

Description

Technical Field

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

[0002] In the field of new energy power batteries, the application of rechargeable batteries is becoming increasingly widespread. These batteries (such as lithium-ion batteries) can be used in vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, e-cigarettes, digital products, power tools, power units, and other electronic devices. One type of rechargeable battery is the cylindrical battery, which includes a casing and an electrode assembly. The electrode assembly consists of a positive electrode, a first separator, a negative electrode, and a second separator, which are stacked sequentially and wound to form the electrode assembly, which is then encapsulated within the casing. However, existing rechargeable batteries still require further improvement in certain aspects. Utility Model Content

[0003] In view of the problems existing in the related technologies, the purpose of this utility model is to provide a secondary battery, battery pack and electronic device that can at least avoid damage to the separator during the manufacturing process.

[0004] To achieve the above objectives, embodiments of this application provide a secondary battery, comprising: an electrode assembly including a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. The negative electrode includes a negative current collector and a negative active material layer. The negative current collector includes a negative electrode coated area covered by the negative active material layer and a negative electrode uncoated area not covered by the negative active material layer. The direction from the negative electrode coated area to the negative electrode uncoated area is a first direction. The separator includes a first separator end in the first direction. Along the first direction, the negative electrode uncoated area... The device includes a negative electrode tab and a negative electrode connection region connecting the negative electrode tab and the negative electrode coating region. The negative electrode tab includes a negative electrode tab body and a negative electrode tab transition portion connecting the negative electrode connection region and the negative electrode tab body. The negative electrode tab transition portion includes a first negative electrode tab transition endpoint connected to the negative electrode connection region. The first negative electrode tab transition endpoint is the position where the tangent of the negative electrode tab transition portion intersects the extension direction of the negative electrode connection region. The distance by which the first negative electrode tab transition endpoint extends beyond the first diaphragm end in the first direction ranges from 0.5 mm to 2 mm.

[0005] In some embodiments, the negative electrode active material layer includes a first negative electrode in a first direction, wherein the distance by which the first negative electrode tab transition end extends beyond the first negative electrode in the first direction ranges from 1.5 mm to 3 mm.

[0006] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer, the positive active material layer including a first positive terminal in a first direction, wherein the first negative terminal extends beyond the first positive terminal by a distance of 1.0 mm to 1.5 mm in the first direction.

[0007] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer. The positive current collector includes a positive electrode coated area covered by the positive active material layer and a positive electrode uncoated area not covered by the positive active material layer. The direction from the positive electrode coated area to the positive electrode uncoated area is a second direction, which is the opposite of the first direction. Along the second direction, the positive electrode uncoated area includes a positive electrode tab and a positive electrode connection area connecting the positive electrode tab and the positive electrode coated area. The positive electrode tab includes a positive electrode tab body and a positive electrode tab transition portion connecting the positive electrode connection area and the positive electrode tab body. The positive electrode tab transition portion includes a first positive electrode tab transition endpoint connected to the positive electrode connection area. The first positive electrode tab transition endpoint is the position where the tangent of the positive electrode tab transition portion intersects the extension direction of the positive electrode connection area. The electrode assembly also includes an insulating layer that covers the positive electrode connection area. The width of the insulating layer in the second direction is 0.5 mm to 2.5 mm.

[0008] In some embodiments, the negative electrode active material layer includes a second negative electrode end in the second direction, and the insulating layer includes a first insulating layer end in the first direction, wherein the distance by which the second negative electrode end extends beyond the first insulating layer end in the second direction ranges from 0.5 mm to 1 mm.

[0009] In some embodiments, the insulating layer includes a second insulating layer end in the second direction, wherein the distance by which the second insulating layer end extends beyond the second negative terminal in the second direction ranges from 0.5 mm to 1 mm.

[0010] In some embodiments, the negative electrode active material layer includes a first negative electrode in a first direction, wherein the distance by which the first diaphragm end extends beyond the first negative electrode in the first direction ranges from 0.5 mm to 1.5 mm.

[0011] In some embodiments, the secondary battery further includes: a housing for accommodating an electrode assembly, the housing including a peripheral sidewall and an end wall connected to one end of the peripheral sidewall, the other end of the peripheral sidewall having an opening, and an inwardly protruding crimping portion provided on the peripheral sidewall adjacent to the opening, the electrode assembly being located between the end wall and the crimping portion, wherein a negative electrode tab faces the opening and is connected to the housing via a negative electrode current collector, and the welding position of the negative electrode current collector to the peripheral sidewall is located on the side of the crimping portion facing the electrode assembly.

[0012] The beneficial technical effects of this utility model are as follows:

[0013] The technical solution of this application, by configuring the transition end of the first negative electrode tab of the negative electrode sheet to extend beyond the first negative electrode tip by 0.5mm-2mm, can avoid damage to the diaphragm during manufacturing, avoid excessive space waste, and ensure that the negative electrode current collector does not undergo undesirable deformation. For example, since the negative electrode tab body of the negative electrode current collector is welded to the negative electrode current collector disk, the risk of burning the diaphragm during welding is high. The technical solution of this application can avoid burning the diaphragm during welding, avoid excessive space waste, and ensure that the negative electrode current collector does not undergo undesirable deformation. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.

[0016] Figure 2 A perspective view of a secondary battery according to an embodiment of this application is shown.

[0017] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of this application is shown.

[0018] Figure 4 A cross-sectional view of an electrode assembly according to some embodiments is shown.

[0019] Figure 5A The negative electrode plate is shown in Figure 4 A schematic diagram of the cross-section at region A1.

[0020] Figure 5B The negative electrode plate is shown in Figure 4 A schematic diagram of the cross-section at region A1.

[0021] Figure 6A A cross-sectional schematic diagram showing the relevant dimensions of the negative electrode in an electrode assembly according to some embodiments is shown.

[0022] Figure 6B A cross-sectional schematic diagram showing the relevant dimensions of the negative electrode in an electrode assembly according to some embodiments is shown.

[0023] Figure 6C A schematic diagram illustrating the relationship between the positive and negative electrodes in an electrode assembly according to some embodiments is shown. Detailed Implementation

[0024] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0025] Embodiments of this 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 reference to the accompanying drawings are illustrative and diagrammatic in nature and are intended to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application.

[0026] As used herein, the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, the terms may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately.

[0027] 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 (e.g., “horizontally,” “downward,” “upward,” etc.) should be interpreted as referring to the directions described in the discussion or in the accompanying drawings. These relative terms are used for descriptive convenience only and do not require that this application be constructed or operated in a particular orientation.

[0028] For ease of description, the terms "first," "second," "third," etc., are used herein to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe corresponding components. Furthermore, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] This application provides an electronic device 1000. For ease of explanation, the following embodiments use a vehicle as an example to illustrate the electronic device 1000. See also... Figure 1The vehicle has a battery pack 1002 installed inside, which can be located at the bottom, front, or rear of the vehicle body 1001. The battery pack 1002 can be used to power the vehicle; for example, it can serve as the vehicle's operating power source. The working part of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical power. The vehicle can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part is the vehicle body, and the battery pack 1002 is located at the bottom of the vehicle body, providing electrical power for the vehicle's movement or the operation of its internal electrical components. However, in some other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part can obtain electrical energy from the battery pack 1002 and perform corresponding functions, such as a fan blade rotation unit or a vacuum cleaner's suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1000.

[0030] Battery pack 1002 may include multiple secondary batteries (such as...) Figure 2 The secondary battery 100 and the casing that houses multiple secondary batteries are described below. In the following description, a cylindrical battery is used as an example for illustration. Figure 2 A perspective view of a secondary battery 100 according to an embodiment of this application is shown. Figure 3 A cross-sectional view of a secondary battery 100 according to an embodiment of this application is shown.

[0031] See also Figure 2 and Figure 3The secondary battery 100 is a cylindrical battery. The secondary battery 100 may include an electrode assembly 120, an electrolyte, a housing 200, and a cover plate 202. The housing 200 includes a peripheral sidewall 109 and an end wall 111 connected to one end of the peripheral sidewall 109. An opening 205 is provided at the other end of the peripheral sidewall 109 opposite to the end wall 111, and the cover plate 202 covers the opening 205. The cover plate 202 can be used to encapsulate the electrode assembly 120 and the electrolyte together with the housing 200. The housing 200 can be made of any of a variety of available materials, such as copper, iron, aluminum, steel, or aluminum alloy. The housing 200 may be cylindrical and define a receiving cavity in which the electrode assembly 120 is disposed. The outer diameter of the housing 200 can be determined according to the specific diameter of the electrode assembly 120; for example, the outer diameter of the housing 200 may be 18mm, 21mm, or 46mm. In some embodiments, the secondary battery 100 may be a 4680 cylindrical battery (outer diameter 46mm, height 80mm), or a 4695 cylindrical battery (outer diameter 46mm, height 95mm), or a 46120 cylindrical battery (outer diameter 46mm, height 120mm).

[0032] The electrode assembly 120 can be formed primarily by sequentially stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator located between the positive and negative electrode sheets (described in detail below). The wound electrode assembly 120 can have a winding center hole 120c. In some embodiments, the positive electrode sheet may include a positive current collector and a positive active material layer, the positive active material layer being coated on a portion of the surface of the positive current collector. The uncoated positive electrode area 28b of the positive current collector, which is not covered by the positive electrode coating area, can be used to form a positive electrode tab. The negative electrode sheet may include a negative current collector and a negative active material layer, the negative active material layer being coated on a portion of the surface of the negative current collector. The uncoated negative electrode area 18b of the negative current collector, which is not covered by the negative electrode coating area, can be used to form a negative electrode tab.

[0033] An inwardly protruding crimping portion 113 (also referred to as a groove) is formed on the peripheral sidewall of the housing 200 adjacent to the opening 205. An electrode assembly 120 is disposed between the end wall 111 and the crimping portion 113, and the crimping portion 113 restricts the movement of the electrode assembly 120 in the height direction and the opposite direction between the end wall 111 and the crimping portion 113. The end of the peripheral sidewall 109 of the housing 200 on the opening 205 side can be configured as a rolled edge portion 32, which extends radially inward along the housing 200. The rolled edge portion 32 and the crimping portion 113 are spaced apart along the height direction, and the crimping portion 113 and the rolled edge portion 32 can jointly clamp the cover plate 220. The cover plate 220 is electrically insulated from the housing 200.

[0034] The uncoated negative electrode area 18b of the electrode assembly 120 faces the opening 205 and can be electrically connected to the housing 200 via a negative electrode current collector 201 located between the cover plate 220 and the electrode assembly 120, thereby making the housing 200 negatively charged. The negative electrode current collector 201 can be welded to the housing 200 by laser welding. Specifically, the welding position between the negative electrode current collector 201 and the peripheral sidewall 109 of the housing 200 is located on the side of the crimp portion 113 facing the electrode assembly 120.

[0035] The secondary battery 100 may further include a terminal post 160 that passes through and is insulated from the end wall 111. The terminal post 160 can be electrically connected to the uncoated positive electrode region 28b of the positive electrode plate via a positive current collector 202 located between it and the electrode assembly 120, thereby making the terminal post 160 positively charged. In some embodiments, the terminal post 160 can be welded to the positive current collector 202 by laser penetration welding.

[0036] In one example of the cylindrical battery of this application, the method for manufacturing the secondary battery 100 of this application includes the following steps:

[0037] Winding: A winding structure is formed by stacking and winding the negative electrode sheet, the separator, and the positive electrode sheet. The uncoated negative electrode area 18b of the negative electrode sheet and the uncoated positive electrode area 28b of the positive electrode sheet are used as the positive electrode tab and the negative electrode tab, and the uncoated positive electrode area 28b and the uncoated negative electrode area 18b are bent along the radial direction of the electrode assembly 120.

[0038] Welding of current collectors to electrode assemblies: The positive current collector 202 and the negative current collector 201 are welded to the surface areas of the bent positive uncoated area 28b and negative uncoated area 18b, respectively.

[0039] Installation into the housing: The electrode assembly 120, which has been welded to the negative current collector 201 and the positive current collector 202, is installed into the housing 200 through the opening 205. The method of installing the electrode assembly 120 in this step is not limited. For example, it can be installed manually or by a robot.

[0040] Install pole 160.

[0041] Electrolyte injection: The method of electrolyte injection is not limited, and injection can be carried out through opening 205. In this embodiment, electrolyte is injected through opening 205, which reduces the step of opening an injection hole in the end wall 111. The existing opening 205 can be used directly for injection, simplifying the process and reducing costs.

[0042] Sealing: The cover plate 220 is sealed and installed on the opening 205. There are various sealing methods, and this is not limited to one. In some embodiments, a pressing portion 113 recessed towards the center of the housing 200 is first formed by rolling the outer periphery of the housing 200 to restrict the movement of the electrode assembly 120 in the height direction. Then, a mechanical sealing process is used to press and seal the cover plate 220 to form a rolled edge portion 32, thereby sealing and installing the cover plate 220 on the opening 205 of the housing 200. This step is a mature process, low in cost, and highly efficient.

[0043] Figure 4 A cross-sectional view of an electrode assembly 120 according to some embodiments is shown. See also Figure 4 As shown, the electrode assembly 120 is mainly formed by winding a negative electrode 10 and a positive electrode 20, and a separator 122 is provided between the negative electrode 10 and the positive electrode 20. Electrolyte can be filled between the negative electrode 10, the positive electrode 20 and the separator 122.

[0044] The negative electrode 10 may include a negative electrode current collector 18 and a negative electrode active material layer 16. A portion of the opposing surfaces of the negative electrode current collector 18 along its thickness direction is covered by the negative electrode active material layer 16. Therefore, the negative electrode current collector 18 includes a negative electrode coated region 18a covered by the negative electrode active material layer 16 and a negative electrode uncoated region 18b not covered by the negative electrode active material layer 16. The positive electrode 20 includes a positive electrode current collector 28 and a positive electrode active material layer 26. At least a portion of the opposing surfaces of the positive electrode current collector 28 along its thickness direction is covered by the positive electrode active material layer 26. Therefore, the positive electrode current collector 28 includes a positive electrode coated region 28a covered by the positive electrode active material layer 26 and a positive electrode uncoated region 28b not covered by the positive electrode active material layer 26. The direction from the negative electrode coated region 18a to the negative electrode uncoated region 18b is a first direction D1. The opposite direction of the first direction D1 is a second direction D2. The uncoated negative electrode region 18b of the negative electrode current collector 18 can be used to form a negative electrode tab. The uncoated positive electrode region 28b of the positive electrode current collector 28 can be used to form a positive electrode tab.

[0045] Taking a lithium-ion battery as an example, the material of the negative electrode current collector 18 can be, for example, copper, and the negative electrode current collector 18 can be copper foil. The negative electrode active material of the negative electrode active material layer 16 can be carbon or silicon, etc. The material of the positive electrode current collector 28 can be, for example, aluminum, and the positive electrode active material of the positive electrode active material layer 26 can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The material of the separator 122 can be PP (polypropylene) or PE (polyethylene), etc.

[0046] Figure 5A The negative electrode 10 is shown in Figure 4 A cross-sectional schematic diagram of region A1. (Reference) Figure 5AAs shown, the uncoated negative electrode region 18b includes a negative electrode tab 18b2 and a negative electrode connection region 18b1 connecting the negative electrode tab 18b2 and the coated negative electrode region 18a. The negative electrode tab 18b2 includes a negative electrode tab body 18b22 and a negative electrode tab transition portion 18b21 connecting the negative electrode connection region 18b1 and the negative electrode tab body 18b22. Figure 5A In the cross-sectional view, the negative electrode tab transition portion 18b21 has a curved extension path, and the negative electrode tab body 18b22 has a straight extension path. The extension path of the negative electrode connection region 18b1 is a straight line along the first direction D1.

[0047] The negative electrode tab transition portion 18b21 includes a first negative electrode tab transition endpoint E11 connected to the negative electrode connection region 18b1. The first negative electrode tab transition endpoint E11 is the position where the tangent of the negative electrode tab transition portion 18b21 intersects the extending direction of the negative electrode connection region 18b1. The negative electrode tab transition portion 18b21 also includes a second negative electrode tab transition endpoint E12, the position where the tangent of the negative electrode tab transition portion 18b21 intersects the extending direction of the negative electrode tab body 18b22.

[0048] Figure 5B The positive electrode 20 is shown in Figure 4 A schematic cross-sectional view of region A2 in the diagram. (Reference) Figure 5B As shown, the uncoated positive electrode region 28b includes a positive electrode tab 28b2 and a positive electrode connection region 28b1 connecting the positive electrode tab 28b2 and the coated positive electrode region 28a. The positive electrode tab 28b2 includes a positive electrode tab body 28b22 and a positive electrode tab transition portion 28b21 connecting the positive electrode connection region 28b1 and the positive electrode tab body 28b22. Figure 5B In the cross-sectional view, the positive electrode tab transition portion 28b21 has a curved extension path, and the positive electrode tab body 28b22 has a straight extension path. The extension path of the positive electrode connection region 28b1 is a straight line along the second direction D2.

[0049] The positive electrode tab transition portion 28b21 includes a first positive electrode tab transition endpoint E21 connected to the positive electrode connection region 28b1. The first positive electrode tab transition endpoint E21 is the position where the tangent of the positive electrode tab transition portion 28b21 intersects the extending direction of the positive electrode connection region 28b1. The positive electrode tab transition portion 28b21 also includes a second positive electrode tab transition endpoint E22, the position where the tangent of the positive electrode tab transition portion 28b21 intersects the extending direction of the positive electrode tab body 28b22. An insulating layer 40 covers the positive electrode connection region 28b1. Providing an insulating layer 40 minimizes the possibility of contact between the negative electrode plate 10 and the positive electrode plate 20. The insulating layer 40 can be provided on both sides of the uncoated positive electrode region 28b. The insulating layer 40 can effectively prevent electrical contact between the negative electrode plate 10 and the positive electrode plate 20.

[0050] In some embodiments, the insulating layer 40 is mainly composed of boehmite and PVDF (polyvinylidene difluoride). Boehmite accounts for 80% and PVDF accounts for 20%. In some embodiments, the insulating layer is a ceramic material layer. The thickness of the insulating layer 40 can be 1.5mm-2.5mm, for example, 1.5mm, 1.7mm, 2mm, 2.1mm, 2.3mm, or 2.5mm. By setting the thickness range of the insulating layer 40, it avoids the situation where the coating thickness of the insulating layer 40 is too thin, making it difficult to obtain the required electrical insulation and support strength; at the same time, it avoids the situation where the thickness of the insulating layer 40 is too thick, which could lead to a longer curing time for the coating layer and an increase in the overall structural thickness.

[0051] In some embodiments, the insulating layer 40 includes a color developer to distinguish whether the side coated with the insulating layer 40 is the front or back side of the positive electrode 20 through the color development effect of the color developer, including but not limited to distinguishing the areal density of the front and back sides of the positive electrode 20. The main component of the color developer may be bismuth vanadate, which is yellow in color.

[0052] Figure 6A A cross-sectional schematic diagram showing the relevant dimensions of the negative electrode sheet in an electrode assembly according to some embodiments is shown. Figure 6A The diagram shows the upper end of the diaphragm 122 in the first direction D1, referred to as the first diaphragm end 122u, and the lower end of the diaphragm 122 in the second direction D2, referred to as the second diaphragm end 122l. Furthermore, the height of the diaphragm 122 in the cross-section is H. 122 .

[0053] In some embodiments, the distance H3 between the first negative electrode tab transition end E11 and the first diaphragm end 122u of the diaphragm 122 in the first direction D1 ranges from 0.5mm to 2mm. The extreme case of the relative positional relationship between the first negative electrode tab transition end E11 and the first diaphragm end 122u of the diaphragm 122 is 0 (i.e., H3 is 0). However, since the negative electrode tab body 18b22 is welded to the negative electrode current collector, the risk of burning the diaphragm 122 during welding is high. If the distance H3 is too large, there will be significant space wastage, and the negative electrode current collector may collapse due to insufficient support. The technical solution of this application, by configuring the distance H3 to be in the range of 0.5mm-2mm, can avoid burning the diaphragm 122 during welding, without excessive space wastage, and can ensure that the negative electrode current collector does not undergo undesirable deformation.

[0054] Furthermore, the negative electrode active material layer 16 has an upper end in the first direction D1, referred to as the first negative terminal 16u, and a lower end in the second direction D2, referred to as the second negative terminal 16l. In some embodiments, the distance H6 beyond the first negative terminal 16u in the first direction D1 is H6, and the range of distance H6 can be 1.5mm-3mm. This range of distance H6 can prevent the heat generated during the welding of the negative electrode tab body 18b22 and the negative electrode current collector from affecting the negative electrode active material layer 16, and will not waste too much space.

[0055] Figure 6B A cross-sectional schematic diagram showing the relevant dimensions of the negative electrode 20 in an electrode assembly according to some embodiments is shown. (In conjunction with...) Figures 4 to 6B As shown, in some embodiments, the insulating layer 40 has a width H8 in the second direction D2, and the width H8 can range from 0.5mm to 2.5mm. Insulating layer 40 within this range can provide good support and good electrical isolation. If the width H8 is greater than 2.5mm, too much internal battery space will be wasted. In a preferred embodiment, the width H8 of the insulating layer 40 is 2mm-2.5mm. In some embodiments, the insulating layer 40 can be adjacent to the transition end point E21 of the first positive electrode tab, that is, the positive electrode tab 28b2 begins to bend at the lower end of the insulating layer 40.

[0056] In some embodiments, the insulating layer 40 may not be provided on the uncoated positive electrode region 28b. In such embodiments, the distance between the first positive electrode tab transition end E21 and the second diaphragm end 122l of the diaphragm 122 can be 0.5mm-2mm (similar to the case on the negative electrode side).

[0057] Figure 6C A schematic diagram illustrating the relationship between the positive and negative electrode plates in an electrode assembly according to some embodiments is shown. (Reference) Figure 6C As shown, in some embodiments, in the first direction D1, the distance H4 between the first separator end 122u (upper end) of the separator 122 and the first negative electrode end 16u (upper end) of the negative electrode active material layer 16. In some embodiments, the distance H4 ranges from 0.5mm to 1.5mm. Preferably, the distance H4 is approximately 1mm. The upper end of the separator extending beyond the negative electrode active material layer can prevent negative electrode misalignment under vibration conditions, thereby improving battery safety.

[0058] The positive electrode active material layer 26 has an upper end in the first direction D1, referred to as the first positive terminal 26u, and the negative electrode active material layer 16 has a lower end in the second direction D2, referred to as the second positive terminal 26l. In the first direction D1, the distance H2 between the first negative terminal 16u (upper end) of the negative electrode active material layer 16 and the first positive terminal 26u (upper end) of the positive electrode active material layer 26 of the positive electrode plate 20 is 1.0mm-1.5mm. This can avoid lithium plating and not occupy too much internal space of the battery.

[0059] The insulating layer 40 has an upper end in the first direction D1, referred to as the first insulating layer end 40u, and a lower end in the second direction D2, referred to as the second insulating layer end 40l. In some embodiments, in the second direction D2, the distance H7 by which the second insulating layer end 40l (lower end) of the insulating layer 40 extends beyond the second negative electrode end 16l (lower end) of the negative electrode active material layer 16 is 0.5mm-1mm, so as to ensure electrical isolation and not occupy too much internal space of the battery.

[0060] In some embodiments, in the second direction D2, the distance by which the second negative electrode 16l (lower end) of the negative electrode active material layer 16 extends beyond the first insulating layer end 40u (upper end) of the insulating layer 40 is H1, and the distance H1 ranges from 0.5mm to 1mm. This ensures that the insulating layer 40 isolates the lower end of the negative electrode active material layer 16 from the positive electrode, ensuring safety, and without occupying too much internal space of the battery.

[0061] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A secondary battery, characterized in that, include: An electrode assembly includes a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. The negative electrode includes a negative current collector and a negative active material layer. The negative current collector includes a negative electrode coated area covered by the negative active material layer and a negative electrode uncoated area not covered by the negative active material layer. The direction from the negative electrode coated area to the negative electrode uncoated area is a first direction. The separator includes a first separator end in the first direction. Along the first direction, the uncoated negative electrode area includes a negative electrode tab and a negative electrode connection area connecting the negative electrode tab and the coated negative electrode area. The negative electrode tab includes a negative electrode tab body and a negative electrode tab transition portion connecting the negative electrode connection area and the negative electrode tab body. The negative electrode tab transition portion includes a first negative electrode tab transition endpoint connected to the negative electrode connection area. The first negative electrode tab transition endpoint is the position where the tangent of the negative electrode tab transition portion intersects the extending direction of the negative electrode connection area. Wherein, the distance by which the first negative electrode tab transition end extends beyond the first diaphragm end in the first direction is in the range of 0.5mm-2mm.

2. The secondary battery according to claim 1, characterized in that, The negative electrode active material layer includes a first negative electrode in the first direction, wherein the distance by which the first negative electrode tab transition end extends beyond the first negative electrode in the first direction is in the range of 1.5mm-3mm.

3. The secondary battery according to claim 1, characterized in that, The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer includes a first positive terminal in the first direction. The first negative terminal of the negative active material layer extends beyond the first positive terminal in the first direction by a distance of 1.0 mm to 1.5 mm.

4. The secondary battery according to claim 1, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer. The positive current collector includes a positive electrode coated area covered by the positive active material layer and a positive electrode uncoated area not covered by the positive active material layer. The direction from the positive electrode coated area to the positive electrode uncoated area is a second direction, which is the opposite direction of the first direction. Along the second direction, the uncoated positive electrode area includes a positive electrode tab and a positive electrode connection area connecting the positive electrode tab and the coated positive electrode area. The positive electrode tab includes a positive electrode tab body and a positive electrode tab transition portion connecting the positive electrode connection area and the positive electrode tab body. The positive electrode tab transition portion includes a first positive electrode tab transition endpoint connected to the positive electrode connection area. The first positive electrode tab transition endpoint is the position where the tangent of the positive electrode tab transition portion intersects the extension direction of the positive electrode connection area. The electrode assembly further includes an insulating layer that covers the positive electrode connection area, and the width of the insulating layer in the second direction is 0.5mm-2.5mm.

5. The secondary battery according to claim 4, characterized in that, The negative electrode active material layer includes a second negative electrode in the second direction, and the insulating layer includes a first insulating layer end in the first direction, wherein the distance by which the second negative electrode extends beyond the first insulating layer end in the second direction is in the range of 0.5mm-1mm.

6. The secondary battery according to claim 5, characterized in that, The insulating layer includes a second insulating layer end in the second direction, wherein the distance by which the second insulating layer end extends beyond the second negative terminal in the second direction is in the range of 0.5mm-1mm.

7. The secondary battery according to claim 1, characterized in that, The negative electrode active material layer includes a first negative electrode in the first direction, wherein the distance by which the first diaphragm end extends beyond the first negative electrode in the first direction is in the range of 0.5mm-1.5mm.

8. The secondary battery according to claim 4, characterized in that, Also includes: A housing for accommodating the electrode assembly, the housing including a peripheral sidewall and an end wall connected to one end of the peripheral sidewall, the other end of the peripheral sidewall having an opening, and an inwardly protruding crimping portion provided on the peripheral sidewall adjacent to the opening, the electrode assembly being located between the end wall and the crimping portion. The negative electrode tab faces the opening and is connected to the housing via a negative electrode current collector. The welding position of the negative electrode current collector to the peripheral sidewall is located on the side of the crimping portion facing the electrode assembly.

9. A battery pack, characterized in that, Includes the secondary battery as described in any one of claims 1-8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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