Secondary battery, battery pack, and electronic device

Abstract

This application provides a secondary battery, a battery pack, and an electronic device. The secondary battery includes an electrode assembly. At least one side of the negative electrode current collector of the negative electrode assembly includes an active material layer coated area covered by a negative active material layer and an uncoated active material layer area not covered by the negative active material layer. The direction from the coated active material layer area to the uncoated active material layer area is a first direction. A reinforcing layer covers a portion of the uncoated active material layer area. The uncoated active material layer area includes a tab, and the tab has reinforcing ribs, a portion of which overlaps with the reinforcing layer. The above technical solution of this application can at least prevent wrinkling of the uncoated active material layer area of ​​the negative electrode current collector, improving the support for the tab.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a secondary battery, battery pack, and electronic device. Background Technology

[0002] In the field of new energy power batteries, the application of rechargeable batteries is becoming increasingly widespread. These batteries (such as lithium-ion batteries) can be used in vehicles, energy storage, mobile phones, tablets, wearable devices, power banks, e-cigarettes, digital products, power tools, power units, and energy storage devices. One type of rechargeable battery is the prismatic battery, which includes a casing and an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator between the positive and negative electrodes. These are stacked sequentially and wound into a flat rectangular shape before being encapsulated within the casing.

[0003] The existing negative electrode sheet only has a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer is directly adjacent to the uncoated area of ​​the negative electrode active material layer of the negative electrode current collector, which causes the uncoated area of ​​the active material layer to wrinkle easily, and this problem urgently needs to be solved. Utility Model Content

[0004] In view of the problems existing in the related technologies, the purpose of this application is to provide a secondary battery, battery pack and electronic device that can at least prevent wrinkling of the uncoated area of ​​the active material layer of the negative electrode current collector and improve the support for the electrode tab.

[0005] To achieve the above objectives, embodiments of this application provide a secondary battery comprising an electrode assembly, the electrode assembly including: a negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode. At least one side of the negative current collector of the negative electrode includes an active material layer coated area covered by the negative active material layer and an active material layer uncoated area not covered by the negative active material layer, the direction from the active material layer coated area to the active material layer uncoated area being a first direction; and a reinforcing layer covering a portion of the active material layer uncoated area, wherein the active material layer uncoated area includes a tab, the tab being provided with a reinforcing rib, a portion of the reinforcing rib overlapping the reinforcing layer.

[0006] In some embodiments, in the first direction, the maximum width of the overlapping area of ​​the reinforcing rib and the reinforcing layer is D, the maximum width of the reinforcing layer is d, and the value of D / d ranges from 0.1 to 1.

[0007] In some embodiments, a plurality of reinforcing ribs form a reinforcing rib array, wherein, along a first direction, the minimum spacing between any two adjacent reinforcing ribs is a, and the value of a / d ranges from 0.3 to 3.

[0008] In some embodiments, the tab extends from the electrode body of the negative electrode sheet along a first direction, the maximum height of the tab along the first direction is h, and the value of a / h ranges from 0.08 to 0.5.

[0009] In some embodiments, the reinforcing ribs are provided in at least one of the following forms: dotted, striped, wavy, or zigzag.

[0010] In some embodiments, the tab has a top edge of the electrode body that is away from the negative electrode sheet, and a side edge of the tab connecting the top edge of the tab and the electrode body. The angle between the side edge of the tab and the edge of the adjacent electrode body is α°, 95° < α° < 170°. The uncoated area of ​​the active material layer has an edge exposed foil area that is not covered by the reinforcing layer. The edge exposed foil area is transitioned to the edge of the electrode body through a rounded corner area. The edge exposed foil area is located at least along a second direction perpendicular to the first direction between the rounded corner area and the reinforcing layer. The maximum exposed width of the edge exposed foil area along the radial direction of the rounded corner area is m, and the value of m ranges from 1 μm to 700 μm.

[0011] In some embodiments, the reinforcing layer is spaced apart from the negative electrode active material layer in a first direction by a spacing G, wherein the value of G / m ranges from 0.14 to 1100.

[0012] In some embodiments, the maximum width of the reinforcing layer in the first direction is d, and the value of d / m ranges from 15 to 20.

[0013] In some embodiments, a negative electrode, a positive electrode, and a separator are sequentially stacked and wound to form an electrode assembly. The number of turns of the negative electrode is n, the number of tabs is N, and the value of N / n ranges from 1.1 to 2.

[0014] In some embodiments, the grayscale value of the reinforcement layer is 0-110.

[0015] In some embodiments, the secondary battery is a prismatic battery, and the secondary battery further includes: a housing having an opening, an electrode assembly disposed within the housing; a cover plate assembly sealing the opening of the housing; an electrode post passing through the cover plate assembly and electrically isolated from the cover plate assembly; and an adapter piece disposed on the side of the cover plate assembly facing the electrode assembly and electrically connecting the electrode post to the electrode assembly, wherein the uncoated area of ​​the active material layer includes a bent portion and a connecting portion, the bent portion connecting between the electrode body of the negative electrode sheet and the connecting portion, and the adapter piece being welded to the bent connecting portion.

[0016] Embodiments of this application also provide a battery pack comprising the aforementioned secondary battery.

[0017] Embodiments of this application also provide an electronic device that includes the battery pack described above.

[0018] The technical solution of this application effectively prevents wrinkling in the uncoated areas of the active material layer of the negative electrode current collector by providing an insulating layer. Furthermore, by extending the reinforcing ribs onto the reinforcing layer and making them overlap with the reinforcing layer, the support for the tabs can be further improved, providing enhanced bending strength to the tabs. This increases the height of the empty foil area of ​​the tabs, allowing for more layers of tabs to be accommodated, reducing the DC resistance of the battery, and improving the battery's fast charging capability. Attached Figure Description

[0019] 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.

[0020] Figure 1 A perspective view of a secondary battery according to an embodiment of this application is shown.

[0021] Figure 2A A cross-sectional schematic diagram of a secondary battery according to an embodiment of this application is shown.

[0022] Figure 2B This is a schematic diagram of the tabs, adapters, and posts of two electrode assemblies welded together according to some embodiments.

[0023] Figure 3 yes Figure 2A A cross-sectional schematic diagram of the electrode assembly of the secondary battery.

[0024] Figures 4A to 4F This is a schematic diagram illustrating different manufacturing stages of a negative electrode sheet according to an embodiment of this application.

[0025] Figure 5 According to some embodiments Figure 4F A magnified view of region A1 in the diagram.

[0026] Figure 6A and Figure 6B Schematic diagrams of the reinforcing rib structures according to different embodiments are shown.

[0027] Figure 7 This is a schematic diagram of the negative electrode sheet after the negative electrode tab has been cut, according to some other embodiments.

[0028] Figure 8 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle. Detailed Implementation

[0029] To better understand the spirit of the embodiments of this application, the following description is based on some preferred embodiments of this application.

[0030] 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.

[0031] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and indicate minor variations. When used in conjunction with an event or situation, these 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.

[0032] 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.

[0033] For ease of description, "first," "second," "third," etc., can be used in this article to distinguish different components of a figure or a series of figures. "First," "second," "third," etc., are not intended to describe the corresponding components.

[0034] Currently, the negative electrode current collector of the negative electrode sheet only has a layer of negative active material. This layer is directly adjacent to the uncoated area of ​​the active material layer of the negative electrode current collector, which leads to the problem that the uncoated area of ​​the active material layer is prone to wrinkling. For example, to match high-capacity cells, more layers of tabs are needed. When laser welding multiple layers of tabs to the adapter plate, the outer tabs need to be bent due to the multiple layers, resulting in a longer tab path. This leads to a higher required height for the tabs and the uncoated area of ​​the active material layer (for example, the current standard tab height is usually 30mm-32mm, but now it needs to be 35mm-38mm). This multi-layer tab structure makes the uncoated area of ​​the active material layer more prone to wrinkling.

[0035] Figure 1 A perspective view of a secondary battery according to an embodiment of this application is shown. Figure 2AA cross-sectional schematic diagram of a secondary battery according to an embodiment of this application is shown. Figure 2B This is a schematic diagram of the tabs, adapters, and posts of two electrode assemblies welded together according to some embodiments. Figure 3 yes Figure 2A A cross-sectional schematic diagram of the electrode assembly of the secondary battery.

[0036] Combination Figures 1 to 2B 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. An opening 205 is provided at the other end of the peripheral sidewall 109 opposite to the end wall 111. A cover assembly 221 covers the opening 205 of the housing 200 to define a receiving cavity together with the housing 200, in which the electrode assembly 120 is located.

[0037] The direction from end wall 111 to cover assembly 221 is the height direction Z of secondary battery 100. Height direction Z may correspond to direction D1 described below. In this embodiment, two electrode assemblies 120 are stacked in housing 200 along the thickness direction of electrode assembly 120. In other embodiments, more than two electrode assemblies 120 may be provided in housing 200.

[0038] In some embodiments, see Figure 3 As shown, the electrode assembly 120 is a wound body formed by winding a negative electrode 101, a positive electrode 102, and a separator 204 located between the negative electrode 101 and the positive electrode 102. In other embodiments, the electrode assembly 120 may also be a stacked body formed by sequentially stacking the negative electrode 101, the positive electrode 102, and the separator 204 located between the negative electrode 101 and the positive electrode 102. The electrode assembly 120 may be flat. Correspondingly, the housing 200 may be flat and have a cuboid shape. The plurality of negative electrode tabs 150 of the negative electrode 101 and the plurality of positive electrode tabs 151 of the positive electrode 102 may be stacked in the thickness direction of the electrode assembly 120, respectively.

[0039] The positive electrode may include a positive current collector and a positive active material layer, the positive active material layer being coated on a portion of the surface of the positive current collector. The negative electrode may include a negative current collector and a negative active material layer, the negative active material layer being coated on a portion of the surface of the negative current collector. In some embodiments, such as in a lithium-ion battery, the material of the positive current collector may be aluminum. The positive active material layer may include a positive active material, such as lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. For high-nickel ternary lithium batteries, the positive active material may be a ternary material composed of nickel, cobalt, and manganese (or aluminum). The material of the negative current collector may be copper. The negative active material layer may include a negative active material, such as carbon or silicon. The separator material may be, for example, PP (polypropylene) or PE (polyethylene).

[0040] Combination Figures 1 to 3 As shown, the negative electrode post 223 and the positive electrode post 224 can pass through the cover plate assembly 221 and are insulated from the cover plate assembly 221. An electrode tab is provided at one end of the electrode assembly 120 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. An adapter piece 226 is provided on the side of the cover plate assembly 221 facing the electrode assembly 120 and electrically connects the positive electrode post 224 and the negative electrode post 223 to the positive electrode tab 151 and the negative electrode tab 150 of the electrode assembly 120. In some embodiments, the negative electrode tab 150 and the negative electrode post 223, and the positive electrode tab 151 and the positive electrode post 224, can be connected via corresponding adapter pieces 226, thereby forming solder marks 107 and 108 on the negative electrode tab 150 and the positive electrode tab 151, respectively. The negative electrode tab 150 and the positive electrode tab 151 can be soldered to the adapter piece 226 after (e.g.) Figure 2B (As shown), then fold the two electrode assemblies 120 toward each other, and then insert them into the housing 200 (as shown). Figure 2A (As shown).

[0041] The negative electrode tab 150 includes an uncoated area of ​​the active material layer of the negative electrode current collector (uncoated area 110e of the active material layer described below). The uncoated area of ​​the active material layer may include a bent portion 1501 and a connecting portion 1502. The connecting portion 1502 can be fixedly connected to the cover plate assembly 221 via an adapter piece 226. The bent portion 1501 is connected between the electrode body of the negative electrode sheet 101 and the connecting portion 1502. The adapter piece 226 is welded to the bent connecting portion 1502.

[0042] It should be understood that Figures 1 to 3The example used here is a prismatic battery. The secondary battery described in this application can also be any other suitable type, such as a pouch battery or a cylindrical battery.

[0043] Figures 4A to 4F This is a schematic diagram illustrating different manufacturing stages of a negative electrode sheet according to an embodiment of this application. First, see... Figure 4A As shown, a negative electrode active material layer 130 is coated on both opposite surfaces of the negative electrode current collector 110 along its thickness direction. The negative electrode active material layer 130 can be applied to the negative electrode current collector 110 using 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 can be, for example, copper.

[0044] See Figure 4B As shown, a reinforcing layer 190 is applied, which covers a portion of the uncoated area 110e of the active material layer. In some embodiments, the negative electrode active material layer 130 and the reinforcing layer 190 may be applied simultaneously.

[0045] After applying the negative electrode active material layer 130 and the reinforcing layer 190, the negative electrode current collector 110 and the negative electrode active material layer 130 can be cut along the dotted line L1 to obtain... Figure 4C The diagram shows a single negative electrode 101 for forming a single electrode assembly. The uncoated area 110e of the active material layer of the negative current collector 110 of the negative electrode 101 can then be cut; this cutting process can be referred to as tab cutting. In some embodiments, a laser can be used to perform the tab cutting process.

[0046] After cutting, see Figure 4D and Figure 4E As shown, where Figure 4E yes Figure 4D A cross-sectional schematic diagram shows 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 can be referred to as the electrode body 160. The negative electrode tabs 150 extend from the first edge 160e of the electrode body 160 along direction D1 (which can be referred to as the first direction). Direction D1 can correspond to the aforementioned height direction Z of the secondary battery 100. (See 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 covers two opposing surfaces of the negative electrode current collector 110 along its thickness direction. A reinforcing layer 190 is disposed on the two opposing surfaces of the negative electrode current collector 110 and covers a portion of the uncoated area 110e of the active material layer. In other embodiments, the negative electrode active material layer 130 and the reinforcing layer 190 may be located on either surface of the negative electrode current collector 110. Furthermore, a thinning region 130e is formed at the edge of the negative electrode active material layer 130 along direction D1, and the thinning region 130e is connected to a uniformly coated straight region 130b of the negative electrode active material layer 130. The thickness of the thinning region 130e gradually decreases along direction D1. A negative electrode tab 150 is connected to a first edge 160e of the electrode body 160, which extends along a direction D2 (which may be referred to as the second direction) perpendicular to direction D1. Direction D2 can be the width direction of the negative electrode tab 150, and the width of each negative electrode tab 150 can decrease as the distance from the electrode body 160 increases. The area of ​​the negative electrode tab 150 where the negative electrode active material layer 130 and the reinforcing layer 190 are not provided can be called the tab empty foil area.

[0047] This application uses the example of forming an electrode tab after the current collector is coated with an active material and cut. The electrode tab involved in this application can also be connected to the electrode body 160 by other means such as welding.

[0048] To address the issue of wrinkling in the uncoated area 110e of the active material layer, a reinforcing layer 190 is provided there. This reinforcing layer 190 provides support to the uncoated area 110e, effectively preventing wrinkling and allowing for the creation of more tabs. Furthermore, the reinforcing layer 190 prevents unwanted short circuits, thus enhancing battery safety.

[0049] See Figure 4F As shown, at least one reinforcing rib 320 is provided on the surface of each negative electrode tab 150. In some embodiments, the reinforcing rib can be formed before or after the tab is cut. Preferably, the reinforcing rib is formed on the tab before cutting. In some embodiments, the tab is rolled using an embossing roller before cutting to form the reinforcing rib; this method of forming the reinforcing rib using an embossing roller can also be called embossing. In some embodiments, the reinforcing rib 320 can be formed by stamping the negative electrode tab 150. Forming the reinforcing rib 320 on the negative electrode tab 150 can provide the tab with a bending resistance effect.

[0050] Figure 5 According to some embodiments Figure 4F A magnified view of region A1 in the diagram. (Combined with...) Figure 5As shown, in this embodiment, the reinforcing rib 320 extends to the reinforcing layer 190, but not to the electrode body 160. By extending the reinforcing rib 320 to the reinforcing layer 190, the bending strength provided by the reinforcing rib to the electrode tab can be increased.

[0051] Furthermore, a portion of the reinforcing rib 320 overlaps with the reinforcing layer 190. By setting the reinforcing rib 320 to overlap with the reinforcing layer 190, the support for the tabs can be further improved, thereby increasing the width of the tab foil area in direction D1, accommodating more layers of tabs, reducing the battery's DCR (DC resistance), and improving the battery's fast charging capability.

[0052] In some embodiments, the thickness of the negative electrode current collector 110 is less than or equal to 5.5 μm. A negative electrode current collector 110 with a thickness of less than or equal to 5.5 μm can improve energy density to meet requirements such as fast charging. However, such a thin current collector makes the uncoated area 110e of the active material layer thinner and more prone to wrinkling. By providing a reinforcing layer 190 at the uncoated area 110e of the active material layer, and with a portion of the reinforcing rib 320 overlapping the reinforcing layer 190, the tab can be provided with enhanced bending strength, increasing the width of the empty foil area of ​​the tab, thereby accommodating more layers of tabs, reducing the DC resistance of the battery, and improving the battery's fast charging capability.

[0053] More specifically, in direction D1, the maximum width of the overlapping area between the reinforcing rib 320 and the reinforcing layer 190 is D, and the maximum width of the reinforcing layer 190 is d. The value of D / d ranges from 0.1 to 1. Here, D is measured at the position of the nearest negative electrode active material layer 130 in the area where the multiple reinforcing ribs 320 on the tab are located. In some embodiments, the maximum width d of the insulating layer 190 is 4mm-6mm, for example, 6mm. By setting this range of D / d, the maximum width of the overlapping area can be reasonably configured as D to reduce tab wrinkles, improve the strength of the insulating layer 190, and further increase the width of the tab empty foil area, thereby accommodating more layers of tabs and reducing the battery's DCR.

[0054] In this embodiment, each reinforcing rib 320 is a continuous wavy reinforcing rib. Multiple reinforcing ribs 320 on the negative electrode tab 150 can form a reinforcing rib array. Along direction D1, every two adjacent reinforcing ribs 320 are spaced apart. Along direction D1, the minimum spacing between every two adjacent reinforcing ribs 320 is 'a'. The minimum spacing 'a' is the minimum spacing between the ends of two adjacent reinforcing ribs 320 facing the negative electrode active material layer 130. In some embodiments, the value of a / d ranges from 0.3 to 3. In some embodiments, the value of 'd' can range from 2 mm to 5 mm. This range of values ​​for the ratio a / d can optimize the number of reinforcing ribs 320 in the insulating layer 190 region.

[0055] The maximum height of the negative electrode tab 150 along direction D1 is h. In some embodiments, the value of a / h ranges from 0.08 to 0.5. If the value of a / h is too large, the array of reinforcing ribs 320 will be too sparse, reducing the reinforcing effect; if the value of a / h is too small, the array of reinforcing ribs 320 will be too dense, easily causing excessive stress and damaging the tab during roll forming. Preferably, the value of a / h ranges from 0.15 to 0.35 to better balance the tab reinforcement effect and reduce stress during roll forming.

[0056] In some embodiments, the maximum height h of the negative electrode tab 150 along direction D1 is 35mm-38mm, which is higher than the conventional height of existing tabs (typically 30mm-32mm), thus providing a longer tab path. However, the height of the uncoated area 110e of the active material layer corresponding to the higher tab is also higher, making it more prone to wrinkling. By providing a reinforcing layer 190 on the negative electrode tab 150 and setting the reinforcing rib 320 to overlap with the reinforcing layer 190, more layers of tabs can be accommodated, while preventing wrinkling of the uncoated area 110e of the active material layer in the multi-layer tabs.

[0057] The negative electrode tab 150 has a top edge 150a away from the electrode body 160 and a side edge 150b connecting the top edge 150a and the electrode body 160. In some embodiments, the section of the side edge 150b connected to the first edge 160e of the electrode body 160 is a rounded corner region 150c. The angle between each side edge 150b and the top edge 150a is α°. In some embodiments, 95° < α° < 170°. The uncoated area 110e of the active material layer has an exposed edge foil area 110a not covered by the reinforcing layer 190, which is located along direction D2 between a portion of the side edge 110b (e.g., at least a portion of the rounded corner region 150c) and the reinforcing layer 190. The maximum exposed width of the exposed edge foil area 110a along the radial direction of the corresponding rounded corner region 150c is m, where m ranges from 1 μm to 700 μm. Wherein, the exposed width m of the exposed foil area 110a at the edge of the rounded corner area 150c refers to the distance from the edge of the rounded corner area 150c along the radial direction of the rounded corner area 150c to the edge of the adjacent reinforcing layer 190.

[0058] The exposed foil area 110a at the edge can be formed due to the cutting of the electrode tabs, for example, by the ablation of heat from the laser used in the cutting process. Burrs may be present in the uncoated area 110e of the active material layer of the negative electrode current collector 110 at the rounded corner area 150c. If the width of the exposed foil area 110a at the edge is too large, the negative electrode tabs may tear along the burrs. Furthermore, the negative electrode tabs of the wound or stacked electrode assembly 120 need to be aligned and welded together; when the negative electrode tabs are aligned, the exposed foil area 110a at the edge can cause scratches on the bottom of the corresponding tab. By appropriately configuring the maximum exposed width m of the exposed foil area 110a to a range of 1μm-700μm, the problems of tearing of the negative electrode tabs and scratches on the bottom can be avoided, thereby improving battery performance.

[0059] In this embodiment, the insulating 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 exposed foil area 110a at the edge can also extend along the first edge 160e.

[0060] The reinforcing layer 190 is spaced apart from the negative electrode active material layer 130 by a spacing G in direction D1. The spacing G can be a preset spacing. By setting the spacing G, bulging of the negative electrode active material layer 130 and / or the insulating layer 190 can be avoided. In some embodiments, considering process capability, the value of the spacing G ranges from 0.1mm to 1.1mm, for example, it can be 0.1mm to 1mm, or 0.1mm to 0.5mm. If the size of the spacing G is too small, mutual dissolution and bulging are likely to occur; if the size of the spacing G is too large, it cannot provide sufficient support for the tabs and cannot effectively prevent wrinkling of the uncoated area 110e of the active material layer. In some embodiments, the value of G / m ranges from 0.14 to 1100. It should be understood that the ratio G / m is the ratio when G and m are in the same unit. For example, it is the ratio of m within the range of 1μm-700μm to the spacing G within the range of 100μm-1100μm (i.e., 0.1mm-1.1mm). Within this range of values ​​for G and m, the dimensions of the spacing G and the maximum exposed width m of the edge exposed foil area 110a can be controlled within a suitable range, thereby simultaneously ensuring the support of the tab and preventing the tab from tearing.

[0061] In some embodiments, the value of d / m ranges from 15 to 20. When the maximum width d of the insulating layer 190 is fixed, the value of m can be reasonably optimized by using the range of this ratio to balance support and, on the other hand, to avoid the width of the coated insulating layer 190 being too wide, thereby avoiding an excessively large exposed foil area 110a at the edge that would affect safety.

[0062] In some embodiments, the grayscale value of the insulating layer 190 is 0-110. In some embodiments, the material of the insulating layer 190 may include a color developer, such that the grayscale value of the insulating layer 190 is 0-100. In some embodiments, the color developer may be carbon black. If the insulating layer 190 does not contain a color developer, the insulating layer 190 will be a light color (e.g., white) with a high grayscale value. This will result in a small color difference between the color of the negative current collector 110 (e.g., copper) and the white of the insulating layer 190, making it difficult for image recognition devices (e.g., CCD cameras) to recognize, thus causing problems such as image recognition issues. In embodiments where the insulating layer 190 contains a color developer, the grayscale value of the insulating layer 190 is 0-100, thereby solving the problem of difficulty in recognition by image recognition devices and facilitating the recognition of the size and position of the insulating layer 190 by CCD cameras. In addition, compared to a white insulating layer 190, by selecting an insulating layer 190 containing a color developer (e.g., carbon black), the insulating layer 190 can absorb more energy, thus reducing the power of the laser used in the tab cutting process. In the process of cutting tabs using variable power lasers, the power of the laser can also be reduced.

[0063] In some embodiments, the material of the insulating layer 190 may include ceramic (boehmite), an aqueous binder, and a colorant. The aqueous binder may be, for example, a water-soluble polymer PAA (polyarylacetylene). If an oil-based binder is used in the insulating layer 190, an organic gas recovery system is required in the negative electrode production line. By using an aqueous binder, the negative electrode production line does not require an organic gas recovery system. In some embodiments, the peel force between the insulating layer 190 using an aqueous binder and the negative current collector 110 is >300 N / m. Furthermore, the ceramic design can also provide support for the insulating layer 190. In some embodiments, the volume percentage of ceramic (boehmite) in the insulating layer 190 is, for example, 10%-20%, the volume percentage of the aqueous binder is, for example, 75%-90%, and the volume percentage of the colorant (such as carbon black) is, for example, 0.5%-5%.

[0064] In an embodiment where a negative electrode, a positive electrode, and a separator are sequentially stacked and wound to form a wound electrode assembly 120, the ratio N / n, which is the number of negative electrode tabs (N) to the number of winding turns of the negative electrode (n), ranges from 1.1 to 2. The number of winding turns of the negative electrode is counted one turn at a time from the starting end of the negative electrode outwards along the winding direction. To increase the current-carrying area and reduce the DC resistance (DCR), when the number of tabs increases, for multi-tab electrode assemblies, a longer length is required when the outer tabs are bent and directly welded to the adapter or electrode post. Therefore, the technical solution of this application can improve problems such as wrinkling in the uncoated area of ​​the active material layer, tab insertion, and edge turning in multi-tab electrode assemblies.

[0065] It should be understood that Figure 4F and Figure 5 The reinforcing rib structure shown is merely an example. In some embodiments, the reinforcing rib 320 may be arranged in at least one of the following forms: dotted, striped, wavy, or zigzag. Figure 6A and Figure 6B Schematic diagrams of the reinforcing rib structures according to different embodiments are shown. See also Figure 6A As shown, each reinforcing rib 320 has a V-shaped structure, and multiple reinforcing ribs 320 are arranged in a multi-row and multi-column array on the negative electrode tab 150. See also Figure 6B As shown, the reinforcing rib 320 includes strip reinforcing ribs extending along direction D1, and a plurality of point reinforcing ribs arranged at intervals along direction D1 between adjacent strip reinforcing ribs.

[0066] See also Figure 6A and Figure 6B As shown, in direction D1, the maximum width of the overlapping area between the reinforcing rib 320 and the reinforcing layer 190 is D, and the maximum width of the reinforcing layer 190 is d. The value range of D / d is 0.1-1.

[0067] Figure 7 This is a schematic diagram of the negative electrode sheet after the negative electrode tab has been cut, according to some other embodiments. Figure 7 Several aspects of the illustrated embodiments are related to the above references. Figures 4A to 5 Similar to the descriptions below, the main focus is on... Figure 7 The differences between the illustrated embodiments are as follows. See also: Figure 7 As shown, in this embodiment, the insulating layer 190 is located only on the negative electrode tab 150. A portion of the negative electrode active material layer 130 extends onto the negative electrode tab 150. The bottom edge of the insulating layer 190 adjacent to the negative electrode active material layer 130 is located on the negative electrode tab 150. In this structure of the negative electrode sheet 101, since the areas covered by both the insulating layer 190 and the negative electrode active material layer 130 are cut, the area of ​​the negative electrode active material layer 130 in the electrode body 160 can be increased, thereby increasing the battery energy density. Furthermore, the negative electrode active material layer 130 on the negative electrode tab 150 and the negative electrode active material layer 130 can work together to provide tab support, thus improving the tab support capability.

[0068] Figure 8 A schematic diagram is shown when the electronic device according to an embodiment of this application is a vehicle. See also Figure 8This application also provides an electronic device 1000. For ease of explanation, the following embodiments use a vehicle as an example. A battery pack 1002 is installed 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, 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 other embodiments, the electronic device 1000 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working unit can obtain electrical energy from the battery pack 1002 and perform corresponding work, such as the fan blade rotation unit of a fan, the vacuuming unit of a vacuum cleaner, etc. Electric toys include stationary 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. This application embodiment does not impose any special limitations on the above-described electronic device 1000. The battery pack 1002 may include multiple secondary batteries, such as the secondary battery 100 described above.

[0069] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A secondary battery, characterized in that, Includes an electrode assembly, the electrode assembly comprising: A negative electrode, a positive electrode, and a separator disposed between the negative electrode and the positive electrode; at least one side of the negative current collector of the negative electrode includes an active material layer coated area covered by the negative active material layer and an uncoated active material layer area not covered by the negative active material layer; the direction from the coated active material layer area to the uncoated active material layer area is a first direction; and A reinforcing layer covers a portion of the uncoated area of ​​the active material layer. The uncoated area of ​​the active material layer includes tabs, and the tabs are provided with reinforcing ribs, a portion of which overlaps with the reinforcing layer.

2. The secondary battery according to claim 1, characterized in that, In the first direction, the maximum width of the overlapping area of ​​the reinforcing rib and the reinforcing layer is D, the maximum width of the reinforcing layer is d, and the value of D / d ranges from 0.1 to 1.

3. The secondary battery according to claim 2, characterized in that, The plurality of the reinforcing ribs form a reinforcing rib array, wherein, along the first direction, the minimum spacing between any two adjacent reinforcing ribs is a, and the value of a / d ranges from 0.3 to 3.

4. The secondary battery according to claim 3, characterized in that, The tab extends from the electrode body of the negative electrode sheet along the first direction, and the maximum height of the tab along the first direction is h, with a / h ranging from 0.08 to 0.

5.

5. The secondary battery according to claim 1, characterized in that, The reinforcing ribs are arranged in at least one of the following forms: dotted, striped, wavy, or zigzag.

6. The secondary battery according to claim 1, characterized in that, The electrode tab has a top edge of the electrode body that is away from the negative electrode plate, and a side edge of the electrode tab connecting the top edge of the electrode tab and the electrode body. The angle between the side edge of the electrode tab and the edge of the adjacent electrode body is α°, where 95° < α° < 170°. The uncoated area of ​​the active material layer has an exposed foil edge area not covered by the reinforcing layer. The tab side and the edge of the electrode body are transitioned by a rounded corner area. The exposed foil edge area is located between the rounded corner area and the reinforcing layer at least along a second direction perpendicular to the first direction. The maximum exposed width of the exposed foil edge area along the radial direction of the rounded corner area is m, and the value of m ranges from 1 μm to 700 μm.

7. The secondary battery according to claim 6, characterized in that, The reinforcing layer is spaced apart from the negative electrode active material layer in the first direction by a distance G, where the value of G / m ranges from 0.14 to 1100.

8. The secondary battery according to claim 6, characterized in that, The maximum width of the reinforcing layer in the first direction is d, and the value of d / m ranges from 15 to 20.

9. The secondary battery according to claim 1, characterized in that, The negative electrode, the positive electrode, and the diaphragm are sequentially stacked and wound to form the electrode assembly. The number of turns of the negative electrode is n, the number of tabs is N, and the value of N / n ranges from 1.1 to 2.

10. The secondary battery according to claim 1, characterized in that, The grayscale value of the reinforcing layer is 0-110.

11. The secondary battery according to claim 1, characterized in that, The secondary battery is a prismatic battery, and the secondary battery further includes: A housing having an opening, the electrode assembly being disposed within the housing; A cover assembly that seals the opening of the housing. The electrode post passes through the cover plate assembly and is electrically isolated from the cover plate assembly. An adapter piece is disposed on the side of the cover plate assembly facing the electrode assembly and electrically connects the electrode post to the electrode assembly. The uncoated area of ​​the active material layer includes a bent portion and a connecting portion. The bent portion connects the electrode body of the negative electrode sheet and the connecting portion, and the adapter piece is welded to the bent connecting portion.

12. A battery pack, characterized in that, Includes the secondary battery as described in any one of claims 1-11.

13. An electronic device, characterized in that, Includes the battery pack as described in claim 12.

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