Secondary battery, battery pack, and electronic device

Abstract

The embodiment of the invention provides a secondary battery, a battery pack and an electronic device, the secondary battery comprises an electrode assembly, a negative electrode piece in the electrode assembly comprises a negative electrode current collector, a negative electrode active material layer and a reinforcing layer, the negative electrode current collector comprises an active material layer uncoated area, the reinforcing layer covers a part of the active material layer uncoated area, and the reinforcing layer covers a part of the active material layer uncoated area. The negative pole piece is provided with a pole piece main body and a pole lug extending from a first edge of the pole piece main body along a first direction, the active material layer uncoated area comprises the pole lug, and the pole lug side edge of the pole lug and the first edge are in transition through a fillet area; the active material layer uncoated area is provided with an edge exposed foil area which is not covered by the reinforcing layer and is located between at least one part of the fillet area and the reinforcing layer, and the value range of the maximum exposed width d [mu] m of the edge exposed foil area in the radial direction of the fillet area is 1 [mu] m-700 [mu] m. According to the technical scheme, at least the wrinkling of the current collector can be reduced, and the problems that the negative electrode lug is torn and the bottom is scratched are solved.

Description

Technical Field

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

[0002] In the field of new energy power batteries, secondary batteries are increasingly being used in a wide range of applications. For example, secondary batteries (such as lithium-ion batteries) can be applied to electronic devices such as cars, energy storage, mobile phones, tablets, wearable devices, mobile power supplies, e-cigarettes, digital products, power tools, power devices, and energy storage devices. One type of secondary battery is a prismatic battery, which includes a housing and an electrode assembly. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive and negative electrode sheets. These are stacked in sequence and wound into a flat rectangular electrode assembly, which is then encapsulated in a housing.

[0003] The negative current collector of existing negative electrode sheets only has a negative active material layer, which directly adjoins the uncoated area. With future demands for higher battery energy density and faster charging, current collectors will become increasingly thinner, and the wrinkling problem of ultra-thin current collectors urgently needs to be addressed. Summary of the Invention

[0004] In response to the problems existing in the related art, the purpose of this application is to provide a secondary battery, a battery pack and an electronic device that can at least reduce the wrinkling of the current collector and reduce the problems of tearing of the negative electrode tab and scratching of the bottom.

[0005] To achieve the above-mentioned purpose, an embodiment of the present application provides a secondary battery, which includes an electrode assembly, the electrode assembly includes a negative electrode sheet, a positive electrode sheet and a separator arranged between the negative electrode sheet and the positive electrode sheet, the negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer and a reinforcement layer, the negative electrode current collector includes an active material layer coating area covered by the negative electrode active material layer and an active material layer uncoated area not covered by the negative electrode active material layer, and the reinforcement layer covers a portion of the active material layer uncoated area, wherein the negative electrode sheet has a sheet body and a tab, and the tab extends from the sheet body along the first direction. The first edge of the active material layer extends out, the uncoated area of the active material layer includes a pole ear, the pole ear has a pole ear top edge away from the pole piece body, and a pole ear side edge connected between the pole ear top edge and the pole ear body, the pole ear side edge and the first edge are transitioned by a fillet area, the reinforcement layer is adjacent to at least a part of the fillet area along the second direction, and the second direction is perpendicular to the first direction; wherein, the uncoated area of the active material layer has an edge foil leakage area that is not covered by the reinforcement layer and is located between at least a part of the fillet area and the reinforcement layer, the maximum exposed width of the edge foil exposure area along the radial direction of the fillet area is dμm, and the value range of d is 1-700.

[0006] In some embodiments, the side edge of the pole tab includes a first side edge of the pole tab, the angle between the first side edge of the pole tab and the adjacent first edge is α1°, 90°≤α1°≤95°, the rounded corner area includes a first rounded corner area located between the first side edge of the pole tab and the first edge, the edge exposed foil area includes a first edge exposed foil area located between the first rounded corner area and the reinforcement layer, the maximum exposed width of the first edge exposed foil area is d1μm, and the value range of d1 is 1-400.

[0007] In some embodiments, the side edge of the pole tab includes a second side edge of the pole tab, the angle between the second side edge of the pole tab and the adjacent first edge is α2°, 95°<α2°<170°, the rounded corner area includes a second rounded corner area located between the second side edge of the pole tab and the first edge, the edge exposed foil area includes a second edge exposed foil area located between the second rounded corner area and the reinforcement layer, the maximum exposed width of the second edge exposed foil area is d2μm, the value range of d2 is 100-700, and d2>d1.

[0008] In some embodiments, a portion of the active material layer is disposed on a portion of the surface of the tab along the first direction.

[0009] In some embodiments, a transition region is provided between the tab and the active material layer coating region, and the reinforcement layer is located on a portion of the transition region and a portion of the surface of the tab.

[0010] In some embodiments, the maximum width of the reinforcement layer in the first direction is W mm, wherein the ratio of W mm to d μm ranges from 15 to 60.

[0011] In some embodiments, a reinforcing rib is provided on the tab, and the maximum width of the overlapping portion of the reinforcing rib and the reinforcing layer in the first direction is D mm, wherein the ratio of D mm to W mm is in the range of 0.1-1.

[0012] In some embodiments, the secondary battery further includes: a shell, the shell including a circumferential side wall and an end wall connected to one end of the circumferential side wall, the circumferential side wall being provided with an opening at the other end opposite to the end wall; a cover plate assembly covering the opening to define a accommodating cavity together with the shell, the electrode assembly being located in the accommodating cavity, the cover plate assembly being provided with a pole, and the pole tab being connected to the pole post; and an insulating tape, the insulating tape including a first adhesive area, a second adhesive area and a non-adhesive area, the first adhesive area covering a portion of the outer circumferential surface of the electrode assembly, the second adhesive area covering a weld mark on the pole tab for connection to the pole post, wherein the non-adhesive area covers the reinforcing layer.

[0013] An embodiment of the present application further provides a battery pack, which includes the above-mentioned secondary battery.

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

[0015] The beneficial technical effects of this application are:

[0016] The technical solution of this application effectively reduces current collector wrinkling by providing a reinforcement layer at the tab. Furthermore, by rationally configuring the maximum exposed width dμm of the edge foil area to be between 1μm and 700μm, it can reduce the problems of negative tab tearing and bottom scratching, thereby improving battery performance. 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 perspective view of a secondary battery according to an embodiment of the present application is shown.

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

[0020] Figure 3 yes Figure 2 Schematic cross-sectional view of an electrode assembly of a secondary battery.

[0021] Figures 4A to 4D Schematic diagram showing different manufacturing stages of a negative electrode sheet according to an embodiment of the present application.

[0022] Figure 4E According to the embodiment of this application Figure 4D Schematic cross-section of .

[0023] Figure 5 According to some embodiments Figure 4D A partially enlarged schematic diagram of area A1 in FIG.

[0024] Figure 6 According to other embodiments, Figure 4D A partially enlarged schematic diagram of area A1 in FIG.

[0025] Figure 7A Schematic diagram of a negative electrode sheet after the negative electrode tab is cut according to some other embodiments.

[0026] Figure 7B According to other embodiments, Figure 7A A partially enlarged schematic diagram of area A2 in FIG.

[0027] Figure 8A and Figure 8BSchematic diagrams of parts of the negative electrode sheet according to different embodiments.

[0028] Figure 9A This is a schematic diagram of the electrode tabs, adapter plates, and electrode posts of two electrode assemblies after welding according to some embodiments.

[0029] Figure 9B According to some embodiments Figure 9A Schematic diagram of the structure after bonding the insulating tape.

[0030] Figure 10 A schematic diagram showing an electronic device according to an embodiment of the present application is a vehicle. DETAILED DESCRIPTION

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 corresponding components. In addition, the embodiments and features in the embodiments of this application may be combined with each other unless there is a conflict.

[0036] The negative current collector of existing negative electrode sheets consists solely of a negative active material layer, which directly adjoins uncoated areas. With future demands for higher battery energy density and faster charging, current collectors will become increasingly thinner, leading to the problem of wrinkling.

[0037] On the one hand, in order to match the large-capacity battery cell, more layers of tabs are required. When the multi-layer tabs are laser welded to the adapter, the outer tabs need to be bent due to the multi-layer tabs, so the required tab path is longer, which results in the tabs (i.e., the uncoated area of the active material layer of the current collector) needing to be higher. For example, the conventional height of the tabs is usually 30mm-32mm, but now it needs to be 35mm-38mm. The high height of the uncoated area of the active material layer makes the current collector easy to wrinkle. On the other hand, in order to increase the energy density, the thickness of the current collector needs to be thinner. Therefore, due to the requirements of battery energy density and fast charging, the current collector needs to be thinner and thinner, but thin current collectors are easy to wrinkle.

[0038] Figure 1 A schematic perspective view of a secondary battery according to an embodiment of the present application is shown. Figure 2 A schematic cross-sectional view of a secondary battery according to an embodiment of the present application is shown. Figure 3 yes Figure 2 Schematic cross-sectional view of an electrode assembly of a secondary battery.

[0039] Combine Figures 1 to 2 As shown, the secondary battery 100 may include a housing 200, which includes a peripheral sidewall 109 and an end wall 111 connected to one end of the peripheral sidewall 109. The other end of the peripheral sidewall 109 opposite the end wall 111 is provided with an opening 205. The cover plate assembly 221 covers the opening 205 of the housing 200 to define a receiving cavity together with the housing 200. The electrode assembly 120 is located in the receiving cavity.

[0040] The direction from the end wall 111 to the cover plate assembly 221 is the height direction Z of the secondary battery 100. The height direction Z may correspond to the direction D1 described below. In this embodiment, two electrode assemblies 120 are stacked and arranged in the housing 200 along the thickness direction of the electrode assemblies 120. In other embodiments, more than two electrode assemblies 120 may be arranged in the housing 200.

[0041] In some embodiments, see Figure 3As shown, the electrode assembly 120 is a wound body formed by winding the positive electrode sheet 102, the negative electrode sheet 101, and the separator 204 positioned between the positive electrode sheet 102 and the negative electrode sheet 101. In other embodiments, the electrode assembly 120 may also be a laminated body formed by sequentially stacking the positive electrode sheet 102, the negative electrode sheet 101, and the separator 204 between the positive electrode sheet 102 and the negative electrode sheet 101. The positive electrode sheet 102, the negative electrode sheet 101, and the separator 204 are wound or stacked to form the electrode assembly 120, which is then enclosed in the casing 200 to form a secondary battery. The electrode assembly 120 can be flat. Accordingly, the casing 200 can be flat and have a rectangular parallelepiped shape. The multiple positive electrode tabs 151 of the positive electrode sheet 102 and the multiple negative electrode tabs 150 of the negative electrode sheet 101 can be stacked in the thickness direction of the electrode assembly 120.

[0042] The positive electrode plate may include a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer is coated on a portion of the surface of the positive electrode current collector. The negative electrode plate may include a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer is coated on a portion of the surface of the negative electrode current collector. In some embodiments, for example, in a lithium-ion battery, the material of the positive electrode current collector may be aluminum. The positive electrode active material layer may include a positive electrode active material, and the positive electrode active material may be lithium cobalt oxide, lithium iron phosphate, ternary lithium or lithium manganese oxide, etc. For a high-nickel ternary lithium battery, the positive electrode active material may be a ternary material composed of three elements: nickel, cobalt, and manganese (or aluminum). The material of the negative electrode current collector may be copper. The negative electrode active material layer may include a negative electrode active material, and the negative electrode active material may be carbon or silicon, etc. The material of the diaphragm may be, for example, PP (polypropylene) or PE (polyethylene, polyethylene), etc.

[0043] Combine Figures 1 to 3 As shown, the negative electrode post 223 and the positive electrode post 224 are arranged on the cover plate assembly 221. The negative electrode post 223 and the positive electrode post 224 can pass through the cover plate assembly 221 and can be insulated from the cover plate assembly 221. The electrode assembly 120 is provided with a tab at one end facing the cover plate assembly 221. In this embodiment, the negative electrode tab 150 and the positive electrode tab 151 at one end of the electrode assembly 120 are respectively connected to the corresponding negative electrode post 223 and positive electrode post 224. In some embodiments, the positive electrode tab 151 and the positive electrode post 224, and the negative electrode tab 150 and the negative electrode post 223 can be connected through corresponding adapter plates 226. The adapter plates 226 can be welded to the bent positive electrode tab 151 and the negative electrode tab 150.

[0044] It should be understood that Figures 1 to 3The secondary battery is a square-shell battery as an example for description. The secondary battery of the present application may also be any other appropriate type of secondary battery, such as a soft-pack battery, a cylindrical battery, etc.

[0045] Figures 4A to 4E Schematic diagram showing different manufacturing stages of a negative electrode sheet according to an embodiment of the present application. Figure 4A As shown, a negative electrode active material layer 130 is applied to opposite sides of the negative electrode current collector 110 along its thickness direction. In some embodiments, the negative electrode active material layer 130 may be applied to one of the two side surfaces of the negative electrode current collector 110. The negative electrode active material layer 130 may be applied to the negative electrode current collector 110 by a coating device. The negative electrode current collector 110 includes an active material layer-coated area 110f covered by the negative electrode active material layer 130, and an active material layer-uncoated area 110e not covered by the negative electrode active material layer 130. The edge portion of the negative electrode current collector 110 in the width direction is not coated with the negative electrode active material layer 130, forming the active material layer-uncoated area 110e. In some embodiments, the material of the negative electrode current collector 110 may be, for example, copper.

[0046] See also Figure 4B As shown, a reinforcement layer 190 is applied, and the reinforcement layer 190 covers a portion of the active material layer uncoated area 110e. In some embodiments, the negative active material layer 130 and the reinforcement layer 190 may be applied simultaneously.

[0047] In some embodiments, the material of reinforcement layer 190 may include a water-based binder, a color developer, and a ceramic. In some embodiments, the ceramic particles include, for example, at least one of boehmite, aluminum oxide, titanium dioxide, zirconium dioxide, zinc oxide, barium sulfate, boron nitride, aluminum nitride, or magnesium nitride. In some embodiments, the water-based binder includes, for example, at least one of polyacrylic acid (PAA), styrene butadiene rubber (SBR), or sodium carboxymethylcellulose (CMC-Na). In some embodiments, the color developer includes, for example, at least one of carbon black, chromium oxide green, cobalt green, cobalt blue, iron blue, cadmium red, carbon black, or iron oxide red.

[0048] If the reinforcing layer 190 does not contain a color developer, the reinforcing layer 190 will be white. This makes the color difference between the negative electrode current collector 110 (for example, copper) and the white reinforcing layer 190 small, and image recognition equipment (such as CCD (Charge-Coupled Device)) can be easily recognized. Devices (charge-coupled device cameras) can be difficult to identify, leading to image recognition issues. In embodiments where the reinforcing layer 190 includes a color developer (e.g., carbon black), the color of the reinforcing layer 190 can be essentially black, for example, to address the issue of difficulty with image recognition devices. Furthermore, compared to a white reinforcing layer 190, by selecting a reinforcing layer 190 containing a color developer, the reinforcing layer 190 can absorb more energy, thereby reducing the power of the laser used in the tab cutting process. This also reduces the power of the laser used in the tab cutting process using a variable-power laser. By selecting a water-based binder for the reinforcing layer 190, compared to using an oil-based binder, the production line for the negative electrode sheet can eliminate the need for organic gas recovery equipment when preparing the reinforcing layer 190. Ceramic particles can provide both support and performance for the reinforcing layer 190, thereby improving the design of the width of the uncoated area of the active material layer, enabling a larger width of the uncoated area of the active material layer while also enhancing the insulation properties of the reinforcing layer 190.

[0049] After coating the negative electrode active material layer 130 and the reinforcement layer 190, the negative electrode current collector 110 and the negative electrode active material layer 130 may be cut along the dotted line L1 to obtain Figure 4C A single negative electrode sheet 101 for forming a single electrode assembly is shown in FIG. Subsequently, one side of the active material layer-uncoated region 110e of the negative electrode current collector 110 of the negative electrode sheet 101 may be trimmed, a process referred to as tab trimming. In some embodiments, the tab trimming process may be performed using a laser.

[0050] After cutting, see Figure 4D and Figure 4E As shown, Figure 4E yes Figure 4D , a cross-sectional schematic diagram is shown, forming a plurality of negative electrode tabs 150 spaced apart along the length direction (direction D2) of the negative electrode sheet 101. The uncut portion of the negative electrode current collector 110 and the negative electrode active material layer 130 may be referred to as the sheet body 160. The negative electrode tab 150 extends from the first edge 160e of the sheet body 160 along the direction D1 (which may be referred to as the first direction). The active material layer uncoated area 110e includes the negative electrode tab 150. Direction D1 may correspond to the above-mentioned height direction Z of the secondary battery 100. Reference Figure 4EThe electrode body 160 may include a negative electrode current collector 110 and a negative electrode active material layer 130, wherein the negative electrode active material layer 130 at least partially covers two opposing surfaces of the negative electrode current collector 110 along its thickness direction. Furthermore, a thinned region 130e is formed at the edge of the negative electrode active material layer 130 along direction D1. The thinned region 130e is connected to the uniformly coated flat region 130b of the negative electrode active material layer 130. The thickness of the thinned region 130e gradually decreases along direction D1.

[0051] This application uses the example of forming a pole ear after the current collector is coated with active material and cut. The pole ear involved in this application can also be connected to the pole piece body 160 by other methods such as welding.

[0052] The problem of current collector wrinkling can be effectively reduced by providing a reinforcement layer 190 at the negative electrode tab 150. In addition, providing a reinforcement layer 190 at the negative electrode tab 150 can avoid undesirable electrical short circuits, making the battery safer.

[0053] Refer again Figure 4D As shown, the negative electrode tab 150 is connected to a first edge 160e of the electrode body 160. The first edge 160e extends in a direction D2 (which may be referred to as a second direction) perpendicular to direction D1. Direction D2 may be the width direction of the negative electrode tab 150. The width of each negative electrode tab 150 may decrease as the distance from the electrode body 160 increases. The negative electrode tab 150 has a tab top edge 150a away from the electrode body 160, and a first tab side edge 150b1 and a second tab side edge 150b2 connected between the tab top edge 150a and the tab body 160.

[0054] Figure 5 According to some embodiments Figure 4D A partial enlarged schematic diagram of area A1 in FIG. Figure 5 As shown, the first tab side 150b1 transitions to the first edge 160e via a first rounded corner region 150c1, and the second tab side 150b2 transitions to the first edge 160e via a second rounded corner region 150c2. The first rounded corner region 150c1 and the second rounded corner region 150c2 may be formed during the tab cutting process.

[0055] Reinforcement layer 190 is adjacent to at least a portion of first and second fillet regions 150c1, 150c2 along direction D2. Active material layer uncoated region 110e includes a first edge exposed foil region 110a1 and a second edge exposed foil region 110a2, which are not covered by reinforcement layer 190. First edge exposed foil region 110a1 is located between at least a portion of first fillet region 150c1 and reinforcement layer 190, while second edge exposed foil region 110a2 is located between at least a portion of second fillet region 150c2 and reinforcement layer 190. The maximum exposed width of first and second edge exposed foil regions 110a1, 110a2, along the radial direction of the corresponding first and second fillet regions 150c1, 150c2 is d μm. The value of d ranges from 1 to 700. The exposed width of the first edge exposed foil area 110a1 at the first fillet area 150c1 refers to the distance S1 from the edge of the first fillet area 150c1 to the adjacent edge of the reinforcing layer 190 along the radial direction F1 of the first fillet area 150c1. The exposed width of the second edge exposed foil area 110a2 at the second fillet area 150c2 refers to the distance S2 from the edge of the second fillet area 150c2 to the adjacent edge of the reinforcing layer 190 along the radial direction F2 of the second fillet area 150c2. In other words, the maximum exposed widths of the first edge exposed foil area 110a1 at the first fillet area 150c1 and the second edge exposed foil area 110a2 at the second fillet area 150c2 are 1 μm to 700 μm, respectively.

[0056] The first edge exposed foil area 110a1 and the second edge exposed foil area 110a2 may be formed due to the cutting of the tab, for example, due to the heat ablation of the laser used for cutting. The active material layer uncoated area 110e of the negative electrode current collector 110 may have burrs at the first fillet area 150c1 and the second fillet area 150c2. If the width of the first edge exposed foil area 110a1 and the second edge exposed foil area 110a2 is too large, the negative electrode tab may be torn along the burrs. In addition, the negative electrode tabs of the electrode assembly 120 of the wound body or laminated body need to be aligned with each other for welding. When the negative electrode tabs are aligned, the first edge exposed foil area 110a1 and the second edge exposed foil area 110a will cause scratches on the bottom of the corresponding tab. By rationally configuring the maximum exposed width dμm of the first edge exposed foil area 110a1 and the second edge exposed foil area 110a2, where the value of d ranges from 1 to 700, the problems of negative electrode tab tearing and bottom scratching can be reduced, thereby improving battery performance.

[0057] In this embodiment, only the area covered by the reinforcement layer 190 is cut during the tab cutting process, so that the reinforcement layer 190 is located in the active material layer uncoated area 110e in the electrode body 160 and also on the active material layer uncoated area 110e in the negative electrode tab 150. A transition region 153 is provided between the negative electrode tab 150 and the active material layer coated area 130f, and the reinforcement layer 190 is located on a portion of the transition region 153 and a portion of the surface of the negative electrode tab 150.

[0058] The reinforcement layer 190 on the negative electrode tab 150 provides support for the negative electrode tab 150. The reinforcement layer 190 on the electrode body 160 also extends between the first edge 160e of the electrode body 160 and the negative electrode active material layer 130. The first edge exposed foil area 110a1 extends along at least a portion of the first fillet area 150c1 (at least adjacent to a portion of the negative electrode active material layer 130) and the first edge 160e. The second edge exposed foil area 110a2 extends along at least a portion of the second fillet area 150c2 (at least adjacent to a portion of the negative electrode active material layer 130) and the first edge 160e.

[0059] In the negative electrode sheet 101 of this structure, since only the area covered by the reinforcing layer 190 is cut, the laser energy used for cutting can be reduced, thereby reducing energy consumption. In other words, compared with cutting the area covered by the active material layer (as described below), Figure 7A and Figure 7B As described above, the laser energy is lower. Due to the reduced laser power and energy, the widths of the first edge exposed foil area 110a1 and the second edge exposed foil area 110a2 can be reduced. Furthermore, in embodiments where the reinforcing layer 190 includes a color developer (e.g., carbon black), the laser power used in the tab cutting process can be significantly reduced by selecting a reinforcing layer 190 containing a color developer, compared to a white reinforcing layer.

[0060] In some embodiments, the maximum width of the reinforcing layer 190 in the direction D1 is W mm. The ratio of W mm to the width dμm of each first edge exposed foil area 110a1 and second edge exposed foil area 110a2 is W / d. In some embodiments, the value range of W / d is 15-60. In some embodiments, the maximum width of the reinforcing layer 190 is 4 mm-6 mm, for example, 6 mm. When the maximum width W mm of the reinforcing layer 190 is constant, the value of dμm can be reasonably optimized by taking the value range of this ratio into account to ensure support. On the other hand, it can also prevent the width of the coated reinforcing layer 190 from being too wide, thereby preventing the first edge exposed foil area 110a1 and the second edge exposed foil area 110a2 from being too large and affecting safety.

[0061] The angle between the first tab side 150b1 and the adjacent first edge 160e is α1°, and the angle between the second tab side 150b2 and the adjacent first edge 160e is α2°. In this embodiment, α1° and α2° can be equal. In some embodiments, 90°≤α1°≤170°, and 90°≤α2°≤170°.

[0062] In direction D1, a gap G is defined between the reinforcement layer 190 and the negative electrode active material layer 130. Since both the reinforcement layer 190 and the negative electrode active material layer 130 can be aqueous, in some embodiments, the reinforcement layer 190 is a water-based binder, and the peel force between the reinforcement layer 190 and the negative electrode current collector 110 is greater than 300 N / m. If there is no gap between the reinforcement layer 190 and the negative electrode active material layer 130, the aqueous negative electrode active material layer 130 and / or the reinforcement layer 190 may produce noticeable bulging due to solute diffusion. Providing a gap G can prevent bulging of the negative electrode active material layer 130 and / or the reinforcement layer 190. In some embodiments, considering process capabilities, the gap G can be in the range of 0.1 mm to 1.1 mm, for example, 0.1 mm to 1 mm, or 0.1 mm to 0.5 mm. If the gap G is too small, miscibility and bulging are likely to occur. If the gap G is too large, wrinkling of the current collector cannot be effectively reduced. In some embodiments, the thickness of the reinforcement layer 190 is 5 μm to 25 μm. If the thickness is less than 5 μm, the reinforcement layer 190 is too thin and may not be effective in reducing wrinkling of the current collector.

[0063] Figure 6 According to other embodiments, Figure 4D A partially enlarged schematic diagram of area A1 in FIG. Figure 6 Many aspects of the illustrated embodiments can be compared with those described above. Figures 4A to 5 Similar to the description, the following mainly describes Figure 6 The differences between the illustrated embodiments. Figure 6As shown, the angle α1° between the first tab side 150b1 and the adjacent first edge 160e can be in the range of 90°≤α1°≤95°. The maximum exposed width of the first edge exposed foil area 110a1 can be specifically d1μm, and the value range of d1 is 1-400. The angle α2° between the second tab side 150b2 and the adjacent first edge 160e can be in the range of 95°<α2°<170°. α2°>α1°. The maximum exposed width of the second edge exposed foil area 110a2 can be specifically d2μm, and the value range of d2 is 100-700, and d2>d1. During the tab cutting process, cutting is performed by moving the negative electrode. When cutting the electrode, the moving speed of the electrode is fixed, so when the inclination angle of α2° is larger, the laser dwell time will be longer, resulting in a larger width d2μm of the second edge exposed foil area 110a2. Therefore, by controlling the moving speed during electrode cutting, the width d2μm of the second edge exposed foil area 110a2 can be controlled within the above-mentioned value range to prevent the width d2μm of the second edge exposed foil area 110a2 on the side with a larger inclination angle from being too large, thereby causing burrs and scratches between the pole ears, thereby improving battery safety.

[0064] Figure 7A Schematic diagram of a negative electrode sheet after the negative electrode tab is cut according to some other embodiments. Figure 7B According to other embodiments, Figure 7A A partially enlarged schematic diagram of area A2 in FIG. Figure 7A and Figure 7B Many aspects of the illustrated embodiments can be compared with those described above. Figures 4A to 5 Similar to the description, the following mainly describes Figure 7A and Figure 7B The differences between the illustrated embodiments. Figure 7A and Figure 7B As shown, in this embodiment, the reinforcement layer 190 is only located on the negative electrode tab 150. A portion of the negative electrode active material layer 130 may extend onto the surface of the negative electrode tab 150 along the direction D1.

[0065] The reinforcement layer 190 is adjacent to at least a portion of the first fillet region 150c1 and the second fillet region 150c2 along direction D2. The bottom edge 190b of the reinforcement layer 190, adjacent to the negative electrode active material layer 130, is adjacent to the first fillet region 150c1 and the second fillet region 150c2 along direction D2. In the negative electrode tab 101 of this structure, because the areas covered by the reinforcement layer 190 and the negative electrode active material layer 130 are both trimmed, the area of the negative electrode active material layer 130 in the tab body 160 can be increased, thereby improving the battery energy density. Furthermore, the negative electrode active material layer 130 and the reinforcement layer 190 on the negative electrode tab 150 can be used together to provide tab support, thereby improving the tab support capability.

[0066] In this embodiment, the reinforcement layer 190 is adjacent to a corresponding portion of the first fillet region 150c1 along direction D2. Specifically, an end e1 of the first fillet region 150c1 is connected to the first tab side 150b1, and a midpoint e2 of the first fillet region 150c1 is aligned with an end of the bottom edge 190b of the reinforcement layer 190 along radial direction F1. The portion between the end e1 and the midpoint e2 constitutes the portion of the first fillet region 150c1 corresponding to the reinforcement layer 190.

[0067] In this embodiment, the exposed width of the first edge exposed foil area 110a1 at the first rounded corner area 150c1 refers to the distance S1 from the edge of the portion of the first rounded corner area 150c1 between the end e1 and the midpoint e2 to the adjacent edge of the reinforcement layer 190 along the radial direction F1. Similarly, the exposed width of the second edge exposed foil area 110a2 at the second rounded corner area 150c2 refers to the distance S2 from the edge of the portion of the second rounded corner area 150c2 corresponding to the reinforcement layer 190 to the adjacent edge of the reinforcement layer 190 along the radial direction F2. In some embodiments, the maximum exposed width dμm of the first edge exposed foil area 110a1 at the first rounded corner area 150c1 and the second edge exposed foil area 110a2 at the second rounded corner area 150c2 ranges from 1μm to 700μm.

[0068] Figure 8A and Figure 8B Schematic diagrams of parts of the negative electrode sheet according to different embodiments. Figure 8A The reinforcement layer 190 in the illustrated embodiment may be configured similarly to the above referenced Figure 5 Similar to what is described, Figure 8B The reinforcement layer 190 in the illustrated embodiment may be configured similarly to the above referenced Figure 7A and Figure 7B Similar to what described.

[0069] See also Figure 8A and Figure 8B As shown, the negative electrode tab 150 may be provided with a reinforcing rib 320. Figure 8A and Figure 8BIn the example, the reinforcing ribs 320 are an array of multiple V-shaped ribs. It should be understood that the reinforcing ribs 320 can be stamped from the tab. The reinforcing ribs 320 can have any other suitable shape, for example, at least one of a dotted, striped, wavy, or zigzag shape. A portion of the reinforcing ribs 320 facing the negative electrode active material layer 130 overlaps the reinforcing layer 190. The maximum width of the overlapping portion of the reinforcing ribs 320 and the reinforcing layer 190 in direction D1 is D mm. The ratio D / W of D mm to the maximum width W mm of the reinforcing layer 190 is in the range of 0.1-1. By disposing a portion of the reinforcing ribs 320 on the reinforcing layer 190 and ensuring that the maximum width D mm of the overlapping portion of the reinforcing ribs 320 and the reinforcing layer 190 is within the above-mentioned suitable range, the strength of the reinforcing layer 190 can be improved, thereby strengthening the tab and reducing tab wrinkling. Furthermore, the width of the empty foil area of the tab can be increased to accommodate more layers of tabs and reduce the DCR (direct current internal resistance) of the battery.

[0070] Figure 9A This is a schematic diagram of the electrode tabs, adapter plates, and electrode posts of two electrode assemblies after welding according to some embodiments. Figure 9B According to some embodiments Figure 9A Schematic diagram of the structure after bonding the insulating tape.

[0071] Combine Figure 9A and Figure 9B As shown, the secondary battery may further include an insulating tape 300, which includes a first adhesive region 301, a second adhesive region 302, and a non-adhesive region 303. In some embodiments, the insulating tape 300 is an adhesive tape. The insulating tape 300 may include a base layer and an adhesive layer. The adhesive layer may be provided on the first adhesive region 301 and the second adhesive region 302 to provide adhesion between the first adhesive region 301 and the second adhesive region 302. The non-adhesive region 303 may only include the base layer without the adhesive layer.

[0072] The first adhesive region 301 covers a portion of the outer circumferential surface of the electrode assembly 120 adjacent to the negative electrode tab 150. The second adhesive region 302 covers the weld mark 107 on the negative electrode tab 150. The weld mark 107 may be a weld mark formed by welding the negative electrode tab 150 to the adapter 226, so as to connect the negative electrode tab 150 to the negative electrode post 223 via the adapter 226. The electrode assembly 120 may include a main body and the above-mentioned active material layer uncoated region 110e. The active material layer uncoated region 110e may include a bent portion 1101 and a connecting portion 1102. The connecting portion 1102 may be welded to the adapter 226 to be fixedly connected to the cap plate assembly 221 via the adapter 226. The bent portion 1101 may be connected between the main body of the electrode assembly 120 and the connecting portion 1102. The non-adhesive region 303 covers the reinforcing layer 190 and may contact the reinforcing layer 190. The insulating tape 300 improves the safety of the negative electrode tab 150, and the non-adhesive area 303 covers the reinforcing layer 190, preventing the reinforcing layer 190 from being adhered to the adhesive layer and falling off. At the same time, the reinforcing layer 190 provides support to prevent the tab from being inserted and torn.

[0073] Similarly, the secondary battery may further include an insulating tape 400 disposed at the positive electrode tab 151. The insulating tape 400 may cover the positive electrode tab 151 (e.g., the weld mark 108 formed by welding the positive electrode tab 151 to the adapter 226) and a portion of the outer circumference of the electrode assembly 120 adjacent to the positive electrode tab 151.

[0074] Figure 10 Schematic diagram showing the electronic device of the embodiment of the present application as a vehicle. Figure 10The present application also provides an electronic device 1000. For ease of explanation, the following embodiments will be described using a vehicle as an example. A battery pack 1002 is provided inside the vehicle. The battery pack 1002 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, the battery pack 1002 can serve as the vehicle's operating power source. The working portion of the electronic device 1000 is electrically connected to the battery pack 1002 to obtain electrical energy. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an augmented-range vehicle, etc., but is not limited thereto. The working portion is the vehicle body. The battery pack 1002 is located at the bottom of the vehicle body 1001 and provides electrical energy to support the vehicle's travel or the operation of the vehicle's electrical components. However, in other embodiments, the electronic device 1000 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part can obtain the electrical energy of the battery pack 1002 and perform corresponding work, such as the fan blade rotation unit of a fan, the dust collection unit of a vacuum cleaner, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship 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. The embodiments of the present application do not impose any special restrictions on the above-mentioned electronic device 1000. The battery pack 1002 may include multiple secondary batteries, such as the secondary battery 100 described above.

[0075] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A secondary battery, characterized in that: An electrode assembly is included, the electrode assembly comprising: 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 comprising a negative electrode current collector, a negative electrode active material layer, and a reinforcing layer, the negative electrode current collector comprising an active material layer coated area covered by the negative electrode active material layer and an active material layer uncoated area not covered by the negative electrode active material layer, adjacently disposed along a first direction, the reinforcing layer covering a portion of the active material layer uncoated area. The negative electrode sheet comprises a sheet body and a tab, the tab extending from a first edge of the sheet body along the first direction, the active material layer uncoated area including the tab, the tab having a tab top edge away from the sheet body, and a tab side edge connected between the tab top edge and the tab body, the tab side edge transitioning to the first edge via a fillet area, the reinforcing layer being adjacent to at least a portion of the fillet area along a second direction, the second direction being perpendicular to the first direction; and The uncoated area of the active material layer has an edge foil leakage area that is not covered by the reinforcing layer and is located between at least a portion of the rounded corner area and the reinforcing layer. The maximum exposed width of the edge foil leakage area along the radial direction of the rounded corner area is d μm, and the value range of d is 1-700.

2. The secondary battery according to claim 1, wherein The tab side includes a first tab side, and the angle between the first tab side and the adjacent first edge is α1°, 90°≤α1°≤95°, The fillet area includes a first fillet area between the first tab side and the first edge, the edge exposed foil area includes a first edge exposed foil area between the first fillet area and the reinforcement layer, the maximum exposed width of the first edge exposed foil area is d1μm, and the value range of d1 is 1-400.

3. The secondary battery according to claim 1 or 2, characterized in that The tab side includes a second tab side, and the angle between the second tab side and the adjacent first edge is α2°, 95°<α2°<170°, The fillet area includes a second fillet area located between the side of the second pole ear and the first edge, the edge exposed foil area includes a second edge exposed foil area located between the second fillet area and the reinforcement layer, the maximum exposed width of the second edge exposed foil area is d2μm, the value range of d2 is 100-700, and d2>d1.

4. The secondary battery according to claim 1, wherein A portion of the negative electrode active material layer is disposed on a portion of the surface of the electrode tab along the first direction.

5. The secondary battery according to claim 1, wherein A transition zone is provided between the tab and the active material layer coating zone, and the reinforcement layer is located on a portion of the transition zone and a portion of the surface of the tab.

6. The secondary battery according to claim 1, wherein The maximum width of the reinforcement layer in the first direction is W mm, wherein the ratio of W mm to d μm ranges from 15 to 60.

7. The secondary battery according to claim 6, characterized in that The tab is provided with a reinforcing rib, and the maximum width of the overlapping portion of the reinforcing rib and the reinforcing layer in the first direction is D mm, wherein the ratio of D mm to W mm is in the range of 0.1-1.

8. The secondary battery according to claim 1, wherein Also includes: The housing comprises a peripheral side wall and an end wall connected to one end of the peripheral side wall, wherein the other end of the peripheral side wall opposite to the end wall is provided with an opening; a cover plate assembly covering the opening to define a receiving cavity together with the shell, wherein the electrode assembly is located in the receiving cavity, the cover plate assembly is provided with a pole, and the pole lug is connected to the pole; and An insulating tape includes a first adhesive area, a second adhesive area, and a non-adhesive area, wherein the first adhesive area covers a portion of the outer peripheral surface of the electrode assembly, the second adhesive area covers the weld mark on the electrode tab for connecting to the electrode column, and the non-adhesive area covers the reinforcement layer.

9. A battery pack, characterized in that: The invention 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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