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; a negative current collector of the negative pole piece sequentially comprises a first negative uncoated area, a second negative uncoated area and a third negative uncoated area along the winding direction; the second negative electrode uncoated area comprises a plurality of negative electrode tabs along the first direction and a negative electrode connecting area connected between the plurality of negative electrode tabs and the negative electrode coated area, the first negative electrode uncoated area and the third negative electrode uncoated area do not comprise negative electrode tabs, and the width of the negative electrode connecting area along the first direction is larger than 0mm and smaller than or equal to 2mm. According to the technical scheme, the pressure influence or heat influence on the electrode assembly can be reduced at least.

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. For example, rechargeable batteries (such as lithium-ion batteries) can be used in electronic devices such as vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, digital products, power tools, power units, and energy storage devices. One type of rechargeable battery is the cylindrical battery, which includes a casing and an electrode assembly. The electrode assembly includes a positive electrode, a first separator, a negative electrode, and a second separator, which are stacked sequentially and wound to form the electrode assembly, and then encapsulated in the casing. However, existing rechargeable batteries still require further improvement in some aspects. Utility Model Content

[0003] In view of the problems existing in related technologies, the purpose of this utility model is to provide a secondary battery, a battery pack and an electronic device.

[0004] According to one aspect of an embodiment of this application, a secondary battery is provided, comprising an electrode assembly. The electrode assembly includes a negative electrode sheet, a positive electrode sheet, and a separator disposed between the negative electrode sheet and the positive electrode sheet. The negative electrode sheet includes a negative current collector and a negative active material layer. Along the height direction of the electrode assembly, 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. Along the winding direction of the electrode assembly, the negative electrode uncoated area sequentially includes a first negative electrode uncoated area, a second negative electrode uncoated area, and a third negative electrode uncoated area. Along the first direction, the second negative electrode uncoated area includes a plurality of negative electrode tabs and a negative electrode connection area connecting the plurality of negative electrode tabs and the negative electrode coated area. Neither the first nor the third negative electrode uncoated area includes negative electrode tabs. The width of the negative electrode connection area along the first direction is greater than 0 mm and less than or equal to 2 mm.

[0005] In some embodiments, a plurality of negative electrode tabs are bent toward the winding center hole of the electrode assembly, and the bent plurality of negative electrode tabs are stacked to form a negative electrode tab surface area.

[0006] In some embodiments, the secondary battery further includes: a negative electrode current collector, which is welded to the surface area of ​​the negative electrode tab.

[0007] 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 the surface area of ​​the negative electrode tab faces the opening and is connected to the housing through 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.

[0008] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer. Along the height direction of the electrode assembly, 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. Along the winding direction of the electrode assembly, the positive electrode uncoated area sequentially includes a first positive electrode uncoated area, a second positive electrode uncoated area, and a third positive electrode uncoated area. Along the second direction, the second positive electrode uncoated area includes a positive electrode tab and a positive electrode connection area connected between the positive electrode tab and the positive electrode coated area. Neither the first nor the third positive electrode uncoated area includes a positive electrode tab. The first, third, and positive electrode uncoated areas and the positive electrode connection area are covered by an insulating layer.

[0009] In some embodiments, the width of the negative electrode connection area ranges from 0.5 to 1.5 mm.

[0010] In some embodiments, the widths of the first uncoated negative electrode region and the third uncoated negative electrode region along the first direction are the same as the width of the negative electrode connection region.

[0011] In some embodiments, the negative current collector is copper foil.

[0012] Embodiments of this application also provide a battery pack, which includes any of the above-described secondary batteries.

[0013] Embodiments of this application also provide an electronic device that includes the battery pack described above.

[0014] The beneficial technical effects of this utility model are as follows:

[0015] By setting a negative electrode connection region with a non-zero width between each negative electrode tab and the negative electrode active material layer, the distance between the negative electrode current collector and the diaphragm can be increased, providing a suitable process window for welding, reducing the heat impact caused by welding, and without excessively increasing the height of the electrode assembly. Furthermore, during welding with the negative electrode current collector, pressure is applied to the negative electrode current collector and negative electrode tab using a pressurizing device; by setting a negative electrode connection region of a certain width, it can also serve as a buffer area to prevent pressure from affecting the electrode assembly. Attached Figure Description

[0016] 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.

[0017] Figure 1 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle.

[0018] Figure 2 A perspective view of a secondary battery according to an embodiment of this application is shown.

[0019] Figure 3 A cross-sectional view of a secondary battery according to an embodiment of this application is shown.

[0020] Figure 4 A cross-sectional view of an electrode assembly according to an embodiment of this application is shown.

[0021] Figure 5 A perspective view of an electrode assembly according to an embodiment of this application is shown.

[0022] Figure 6 A planar schematic diagram of the negative electrode sheet in its unfolded state according to an embodiment of this application is shown.

[0023] Figure 7 A planar schematic diagram of the positive electrode sheet in its unfolded state according to an embodiment of this application 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 indicated 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 depicted 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 1 The 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 cylindrical batteries). In the following description, cylindrical batteries are used as an example of secondary batteries. Figure 2 A perspective view of a cylindrical battery 100 according to an embodiment of this application is shown. Figure 3 A cross-sectional view of a cylindrical battery 100 according to an embodiment of this application is shown.

[0031] Combination Figures 2 to 3 As shown, the cylindrical battery 100 includes a housing 200, which 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 a cover plate 220 covers the opening 205 of the housing 200. The cover plate 220 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 can 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 can be, for example, 18 mm, 21 mm, or 46 mm. In some embodiments, the cylindrical 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] Electrode assembly 120 can be mainly formed by sequentially stacking and winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate (see below). Figure 4 (Detailed description). The wound electrode assembly 120 has a wound center hole 120c.

[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 Hd 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 in the height direction Hd, 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 negative electrode tab of the electrode assembly 120 faces the opening 205 and can be electrically connected to the housing 200 via the 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 of the negative electrode current collector 201 to the housing 200 can be located on the side of the crimp portion 113 facing the electrode assembly 120.

[0035] The cylindrical 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 positive electrode tab of the electrode assembly 120 via a negative current collector 202 located between the end wall 111 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] 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.

[0037] The negative electrode 10 may include a negative electrode current collector 18 and a negative electrode active material layer 16, wherein 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. In the height direction Hd, 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, wherein 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. In the height direction Hd, 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 uncoated negative electrode region 18b of the negative current collector 18 and the uncoated positive electrode region 28b of the positive current collector 28 are located at opposite ends in the height direction Hd of the electrode assembly 120. The uncoated negative electrode region 18b of the negative current collector 18 can be used to form a negative electrode tab. The uncoated positive electrode region 28b of the positive current collector 28 can be used to form a positive electrode tab. The direction from the coated negative electrode region 18a to the uncoated negative electrode region 18b is the first direction D1.

[0038] Figure 5 This is a perspective view of an electrode assembly according to an embodiment of this application. (Reference) Figure 4 and Figure 5As shown, the uncoated negative electrode region 18b and the uncoated positive electrode region 28b can be bent toward the winding center hole 120c of the electrode assembly 120. The bent uncoated negative electrode region 18b and the uncoated positive electrode region 28b can be stacked on top of each other. The stacked uncoated negative electrode region 18b can be welded to the negative electrode current collector 201 and further electrically connected to the housing 200 (see Figure 120). Figure 3 The stacked uncoated positive electrode regions 28b can be welded to the positive electrode current collector 202 and further electrically connected to the terminal post 160 (see...). Figure 3 Bending the uncoated negative electrode region 18b and the uncoated positive electrode region 28b can reduce the space occupied by the uncoated negative electrode region 18b and the uncoated positive electrode region 28b, thereby increasing the battery energy density.

[0039] 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.

[0040] To minimize the possibility of contact between the negative electrode 10 and the positive electrode 20, the electrode assembly 120 may further include an insulating layer 40, which covers at least a portion of the uncoated area 28a of the positive current collector 28. The insulating layer 40 may be provided on both sides of the positive current collector 28. The insulating layer 40 effectively prevents electrical contact between the negative electrode 10 and the positive electrode 20.

[0041] In some embodiments, the insulating layer 40 is mainly composed of boehmite and PVDF (polyvinylidene fluoride). Boehmite accounts for 80% of the composition, and PVDF accounts for 20%. In some embodiments, the insulating layer is a ceramic material layer. The thickness of the insulating layer 40 is 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 is avoided that 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 is avoided that the thickness of the insulating layer 40 is too thick, which may lead to a longer curing time for the coating layer and an increase in the overall structural thickness.

[0042] 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.

[0043] The uncoated negative electrode regions 18b and 28a of the negative electrode current collector 18 and the positive electrode current collector 28 can be bent toward the winding center hole 120c of the electrode assembly 120, respectively. In some embodiments, the diameter of the winding center hole 120c can be in the range of 4 mm to 7 mm.

[0044] In one example of the cylindrical battery 100 of the present invention, the method for manufacturing the cylindrical battery 100 of the present invention includes the following steps:

[0045] Winding: The negative electrode 10, the separator 122, and the positive electrode 20 are stacked and wound together to form a winding structure. The uncoated portion 18b of the negative electrode current collector 18 of the negative electrode 10 and the uncoated portion 28b of the positive electrode current collector 28 of the positive electrode 20 are bent radially along the electrode assembly 120.

[0046] Welding of current collectors to electrode assemblies: The negative current collector 201 and the positive current collector 202 are welded to the surface areas of the bent uncoated negative electrode portion 18b and the uncoated positive electrode portion 28b, respectively.

[0047] 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.

[0048] Install pole 160.

[0049] 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.

[0050] 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 Hd. 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.

[0051] Figure 6 This is a planar schematic diagram of the negative electrode sheet 10 in its unfolded state according to an embodiment of this application. (See reference) Figures 4 to 6 As shown, a portion of the uncoated negative electrode region 18b forms multiple negative electrode tabs 18b21, which are segments divided from the portion of the uncoated negative electrode region 18b. The end of each negative electrode tab 18b21 furthest from the negative electrode active material layer 16 is bent toward the winding center hole 120c of the electrode assembly 120. The bent negative electrode tabs 18b21 are stacked to form the negative electrode tab surface region 188 (see...). Figure 5 Furthermore, the negative electrode current collector 201 is welded to the negative electrode tab surface area 188.

[0052] For details, please refer to Figure 6 As shown, along the winding direction Dj, the negative electrode sheet 10 is wound from the beginning of the roll 10b and terminates at the end of the roll 10e. Along the winding direction Dj, the uncoated negative electrode area 18b sequentially includes a first uncoated negative electrode area 18b1, a second uncoated negative electrode area 18b2, and a third uncoated negative electrode area 18b3. Along the second direction D2, the second uncoated negative electrode area 18b2 includes multiple negative electrode tabs 18b21 and a negative electrode connection area 18b22 connecting the negative electrode tabs 18b21 and the coated negative electrode area 18a. Neither the first uncoated negative electrode area 18b1 nor the third uncoated negative electrode area 18b3 includes negative electrode tabs 18b21. The first uncoated negative electrode area 18b1 is connected to the beginning of the roll 10b of the negative electrode sheet 10. The third uncoated negative electrode area 18b3 is connected to the end of the roll 10e of the negative electrode sheet 10.

[0053] Multiple negative electrode tabs 18b21 are arranged along the winding direction Dj. Multiple negative electrode tabs 18b21 can be formed by cutting a portion of the uncoated negative electrode area 18b. The negative electrode connection area 18b22 is the uncut portion of the uncoated negative electrode area 18b. The width of the negative electrode connection area 18b22 along the first direction D1 is W1. In some embodiments, the width W1 of the negative electrode connection area 18b22 is greater than 0 mm and less than or equal to 2 mm (0 < W1 ≤ 2 mm).

[0054] Since the multiple negative electrode tabs 18b21, after being bent, will be welded to the negative electrode current collector 201, the heat generated during the welding process may damage the diaphragm 122 (e.g., burn the diaphragm, deform the diaphragm). The technical solution of this application, by providing a negative electrode connection region 18b22 with a non-zero width W1 between each negative electrode tab 18b21 and the negative electrode active material layer 16, can increase the distance between the negative electrode current collector 201 and the diaphragm 122, providing a suitable process window for welding, reducing the heat impact caused by welding, and without excessively increasing the height of the electrode assembly. Furthermore, during welding with the negative electrode current collector 201, pressure is applied to the negative electrode current collector 201 and the negative electrode tabs 18b21 using a pressurizing device. By providing a negative electrode connection region 18b22 of a certain width, it can also serve as a buffer area to prevent pressure from affecting the electrode assembly.

[0055] In some embodiments, the negative current collector 18 is a copper foil. In such embodiments, based on experimental verification and the support properties of the copper foil, a maximum width W1 of 2 mm is preferred for the negative electrode connection area 18b22. This is because if the width W1 is greater than 2 mm, the supporting surface of the copper foil may collapse after bending and flattening multiple negative electrode tabs 18b21.

[0056] In some embodiments, the width W1 of the negative electrode connection region 18b22 ranges from 0.5 mm to 1.5 mm. This range provides an appropriate process window for welding while minimizing the increase in height of the electrode assembly, and also ensures that the negative electrode current collector 18 does not collapse after bending multiple negative electrode tabs 18b21.

[0057] In some embodiments, the first uncoated negative electrode region 18b1 has a width W2 along the first direction D1, and the third uncoated negative electrode region 18b3 has a width W3 along the first direction D1. Widths W2 and W3 can be consistent with the width W1 of the negative electrode connection region 18b22 (considering manufacturing process variations). Thus, the first uncoated negative electrode region 18b1 and the third uncoated negative electrode region 18b3 can further be used to increase the distance between the negative electrode current collector 201 and the diaphragm 122 and serve as a buffer area to reduce the heat impact caused by welding and to prevent pressure from affecting the electrode assembly.

[0058] Each negative electrode tab 18b21 may include a first side Ea and a second side Eb opposite each other in the winding direction Dj, and a third side Ec connecting the ends of the first side Ea and the second side Eb away from the negative electrode connection area 18b22. The first side Ea and the second side Eb may be parallel to each other. The second side Eb is closer to the winding end 10e than the first side Ea, and the first side Ea and the second side Eb are inclined toward the winding end 10e, so the angle between the second side Eb and the third side Ec is an acute angle. During the winding of the negative electrode sheet 10, since the first side Ea and the second side Eb of each negative electrode tab 18b21 are inclined toward the winding end 10e, it is convenient to bend and smooth the negative electrode tab 18b21 toward the winding center hole 120c when winding the negative electrode sheet 10. This can effectively reduce the force required to bend the negative electrode tab 18b21, thereby avoiding electrode deformation, reducing the material shedding of the negative electrode active material layer 16 of the negative electrode sheet 10, and improving the yield of the electrode assembly 120.

[0059] Figure 7 This is a planar schematic diagram of the positive electrode 20 in its unfolded state according to an embodiment of this application. (In conjunction with...) Figure 4 and Figure 7 As shown, a portion of the uncoated positive electrode region 28b forms a plurality of positive electrode tabs 28b21. The plurality of positive electrode tabs 28b21 are multiple segments divided from a portion of the uncoated positive electrode region 28b. The end of each positive electrode tab 28b21 that is away from the positive electrode active material layer 26 is bent toward the winding center hole 120c of the electrode assembly 120.

[0060] For details, see Figure 7 Along the winding direction Dj, the positive electrode 20 begins winding from its winding start end 20b and terminates at its winding end end 20e. Along the winding direction Dj, the uncoated positive electrode region 28b sequentially includes a first uncoated positive electrode region 28b1, a second uncoated positive electrode region 28b2, and a third uncoated positive electrode region 28b3. Along the first direction D1, the second uncoated positive electrode region 28b2 includes multiple positive electrode tabs 28b21 and a positive electrode connection region 28b22 connecting the positive electrode tabs 28b21 and the coated positive electrode region 28a. Neither the first uncoated positive electrode region 28b1 nor the third uncoated positive electrode region 28b3 includes positive electrode tabs 28b21. The first uncoated positive electrode region 28b1 is connected to the winding start end 20b of the positive electrode 20. The third uncoated positive electrode region 28b3 is connected to the winding end 20e of the positive electrode 20.

[0061] In some embodiments, the first uncoated positive electrode region 28b1, the positive electrode connection region 28b22, and the third uncoated positive electrode region 28b3 are all covered by the insulating layer 40. Covering the first uncoated positive electrode region 28b1, the positive electrode connection region 28b22, and the third uncoated positive electrode region 28b3 with the insulating layer 40 for electrical isolation increases the distance between the positive electrode current collector 202 and the diaphragm 122, providing a suitable process window for welding the positive electrode current collector, reducing the heat impact caused by welding, and without excessively increasing the height of the electrode assembly. Furthermore, during welding with the positive electrode current collector 202, pressure is applied using a pressurizing device; the insulating layer 40 also provides support, preventing pressure from affecting the electrode assembly.

[0062] 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, The electrode assembly includes a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. Along the height direction of the electrode assembly, the negative electrode current collector includes a negative electrode coated area covered by the negative electrode active material layer and a negative electrode uncoated area not covered by the negative electrode active material layer. The direction from the negative electrode coated area to the negative electrode uncoated area is a first direction. Along the winding direction of the electrode assembly, the uncoated negative electrode area sequentially includes a first uncoated negative electrode area, a second uncoated negative electrode area, and a third uncoated negative electrode area. Along the first direction, the second uncoated negative electrode region includes a plurality of negative electrode tabs and a negative electrode connection region connecting the plurality of negative electrode tabs and the negative electrode coated region. Neither the first nor the third uncoated negative electrode region includes the negative electrode tabs. The width of the negative electrode connection area along the first direction is greater than 0 mm and less than or equal to 2 mm.

2. The secondary battery according to claim 1, characterized in that, The plurality of negative electrode tabs are bent toward the winding center hole of the electrode assembly, and the bent plurality of negative electrode tabs are stacked to form a negative electrode tab surface area.

3. The secondary battery according to claim 2, characterized in that, Also includes: The negative electrode current collector is welded to the surface area of ​​the negative electrode tab.

4. The secondary battery according to claim 3, 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 surface area faces the opening and is connected to the housing through the 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 part facing the electrode assembly.

5. The secondary battery according to claim 1, characterized in that, The positive electrode includes a positive current collector and a positive active material layer. Along the height direction of the electrode assembly, 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. Along the winding direction of the electrode assembly, the uncoated positive electrode area sequentially includes a first uncoated positive electrode area, a second uncoated positive electrode area, and a third uncoated positive electrode area. Along the second direction, the second uncoated positive electrode region includes a positive electrode tab and a positive electrode connection region connecting the positive electrode tab and the coated positive electrode region. Neither the first nor the third uncoated positive electrode region includes the positive electrode tab. The first uncoated positive electrode area, the third uncoated positive electrode area, and the positive electrode connection area are covered by an insulating layer.

6. The secondary battery according to claim 1, characterized in that, The width of the negative electrode connection area ranges from 0.5 to 1.5 mm.

7. The secondary battery according to claim 1, characterized in that, The widths of the first uncoated negative electrode area and the third uncoated negative electrode area along the first direction are the same as the width of the negative electrode connection area.

8. The secondary battery according to claim 1, characterized in that, The negative electrode current collector is copper foil.

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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