Electrode assembly, secondary battery and electronic device

Abstract

An electrode assembly (10), a secondary battery (100) and an electronic device. Several extension members (1111) are provided at an end of a first current collector (111) in the direction of width, several protruding portions (1112) are provided on and protrude from a first surface (111a) of each extension member, and several recessed portions (1113) are recessed in a second surface (111b) of each extension member. The electrode assembly (10) comprises adjacent extension members (1111). When observed in the direction of thickness of the electrode assembly (10), two adjacent extension members (1111) at least partially overlap, and at least one protruding portion (1112) of each extension member (1111) is embedded in the recessed portion (1113) of the extension member (1111) adjacent thereto, such that the strength of the extension members (1111) can be improved and the bending deformation and damage to the extension members (1111) can be reduced, thereby facilitating electrical connection of the extension members (1111), and improving the stability of the electrical connection.

Description

Electrode assembly, secondary battery and electronic equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to a Chinese patent application filed with the Patent Office of China on December 14, 2023, with application number 202311725896.5 and entitled “Electrode Assembly, Secondary Battery and Electronic Device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments of the present application relate to the field of electrochemical technology, and in particular to an electrode assembly, a secondary battery, and an electronic device. Background Art

[0004] The electrode assembly of the battery is mainly manufactured using the stacking process or the winding process. The winding process has been widely promoted due to its simple operation. For wound batteries, the contact area between the tabs and the electrodes is small, the internal resistance of the battery is large, and it is easy to generate heat during large current charging and discharging.

[0005] Therefore, wound batteries can use multiple tabs. The pole piece of a multi-tab structure includes a metal current collector and an active material layer disposed on the surface of the current collector. During the manufacturing process, a blank foil area is reserved along the width edge of the pole piece. This blank foil area is cut to form multiple tabs. After winding, the multiple tabs overlap in the thickness direction of the electrode assembly and are bent to connect to the external adapter. However, the tabs produced by this method have lower strength and are prone to deformation and breakage during the manufacturing process. Summary of the Invention

[0006] The embodiments of the present application aim to provide a motor assembly and a secondary battery that can reduce the technical problems of tab deformation and damage during battery manufacturing.

[0007] In order to solve the technical problems, the embodiments of the present application adopt the following technical solutions:

[0008] In the first aspect, the present application proposes an electrode assembly, comprising a first electrode sheet stacked and wound, a separator, and a second electrode sheet wound into shape, wherein the first electrode sheet comprises a first current collector and a first active material layer, and along the thickness direction of the first current collector, the first current collector has a first surface and a second surface arranged opposite to each other, and the first active material layer is arranged on the first surface and / or the second surface. A plurality of extensions are provided at one end in the width direction of the first current collector, wherein a plurality of protrusions are convexly provided on the first surface of the extension, and a plurality of recesses are concavely provided on the second surface of the extension. When viewed along the thickness direction of the electrode assembly, two adjacent extensions at least partially overlap, and at least one protrusion of an extension is embedded in a recess of another adjacent extension.

[0009] In the above technical solution, by providing a protruding portion and a recessed portion on the extension piece, the strength of the extension piece can be improved and deformation or tearing and damage of the extension piece can be reduced.

[0010] Furthermore, at least one protrusion of an extension piece is embedded in a recessed portion of another adjacent extension piece. After winding, the protrusion of the extension piece and the recessed portion of the other extension piece are correspondingly embedded, which can increase the friction between the extension pieces, reduce the mutual misalignment between the extension pieces, improve the bonding strength between the extension pieces, and facilitate the transfer welding of the extension pieces. At the same time, the embedded arrangement of the protrusion and the recessed portion allows the protrusion to be accommodated in the recessed portion, which can reduce the space occupied by the protrusion, further improve the overall strength of the extension piece, reduce the bending deformation and damage of the extension piece, and thus facilitate electrical connection with the adapter piece.

[0011] In some preferred embodiments, the number of protrusions on a single extension is M, with a range of 20 ≤ M ≤ 60. Fewer protrusions can simplify processing, while a greater number can improve strength. Within this range, both processing and strength can be improved. However, if the number of protrusions on a single extension is too large, excessive friction between the extensions can result, leading to breakage when the extensions are displaced. Preferably, 33 ≤ M ≤ 40.

[0012] In some preferred embodiments, the first electrode sheet is a negative electrode sheet. The first current collector of the negative electrode sheet can be made of copper foil. The extension piece is integrally formed with the first current collector and is also made of copper. Copper has high strength and good punching performance, which can facilitate punching out recessed portions and raised portions in the copper extension piece, thereby improving the strength of the extension piece.

[0013] In some preferred embodiments, when viewed along the thickness direction of the extension, the projected area of ​​a single protrusion on the first surface is S mm. 2 , 0.12≤S≤0.5. It can facilitate the processing and forming of the raised part while reducing the space occupied by the raised part and improving the strength of the extension.

[0014] In some preferred embodiments, when viewed along the thickness direction of the extension, the projection area of ​​a single protrusion on the first surface is S mm 2 , 0.16≤S≤0.4. This further reduces the probability of battery cell failure after a drop.

[0015] In some preferred embodiments, the area of ​​the first surface of the extension is S1 mm 2 In a single extension, the coverage area of ​​all protrusions on the first surface is S2 mm 2 , 6% S1≤S2≤30% S1, so as to improve the strength of the extension piece. Preferably, 8% S1≤S2≤20% S1.

[0016] In some preferred embodiments, when viewed along the thickness direction of the electrode assembly, the overlapping area of ​​two adjacent extensions is 53 mm. 2 , 80% S1 ≤ S3 ≤ 100% S1; at least a portion of the extensions are located within the overlapping area. A sufficient overlapping area can increase friction between adjacent extensions, reduce relative motion between the extensions, and improve the bonding strength between the extensions, facilitating electrical connection with the adapter and enhancing the stability of the electrical connection. Furthermore, at least a portion of the extensions are located within the overlapping area, facilitating the insertion of the protrusions of the extensions into the recesses of the adjacent extensions. A sufficient overlapping area further increases the number of insertions between the protrusions and recesses, increasing friction between the extensions and improving the bonding strength between the extensions.

[0017] In some preferred embodiments, a plurality of raised portions are sequentially arranged on the first surface of the extension member along the width of the first pole piece to form an arrangement group. The extension member includes a plurality of arrangement groups, which are sequentially arranged along the winding direction of the first pole piece, with the interval between two adjacent arrangement groups being L mm, with 1.5 ≤ L ≤ 3. The arrangement of multiple extension members forming an arrangement group facilitates uniform coverage of the raised portions on the extension member, thereby evenly distributing the stress on the extension member, improving the strength of each position of the extension member, and reducing deformation and damage of the extension member.

[0018] In some preferred embodiments, the protrusions in two adjacent arrangement groups are staggered along the winding direction. This arrangement allows the extension members to be fully and evenly covered by the protrusions, further improving the overall strength of the extension members and increasing the friction between the two adjacent extension members.

[0019] In some preferred embodiments, in a single arrangement group, the number of protrusions is N, 3≤N≤8, so as to more comprehensively improve the strength of each part of the extension piece.

[0020] In some preferred embodiments, the raised portion is circular when viewed along the thickness of the extension member. A circular raised portion can more easily disperse stress on the extension member, thereby increasing the extension member's tear strength. The raised portion has a radius, R mm, with 1.5 ≤ R ≤ 2.5. Optionally, the raised portion is at least one of an elliptical, square, diamond, trapezoidal, or triangular shape when viewed along the thickness of the extension member.

[0021] In some preferred embodiments, the first surface of the extension member includes a raised region with protrusions and a flat region without protrusions. The protrusions have a height H1 above the first surface, 0.02 mm ≤ H1 ≤ 1 mm. The flat region has a thickness H2, H2 ≤ H1, which increases the strength of the extension member while reducing the space it occupies.

[0022] In a second aspect, the present application further provides a secondary battery comprising a housing, a first tab, a second tab, and an electrode assembly as described in any embodiment of the first aspect. The electrode assembly is housed within the housing. One end of the first tab is electrically connected to an extension of the first electrode sheet within the housing, and the other end extends outside the housing. One end of the second tab is electrically connected to the second electrode sheet within the housing, and the other end extends outside the housing.

[0023] In a third aspect, the present application further proposes an electronic device comprising a secondary battery as described in any embodiment of the first aspect above. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] One or more embodiments are exemplarily illustrated by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0025] FIG1 is a schematic structural diagram of an electrode assembly according to some embodiments of the present application;

[0026] FIG2 is a schematic diagram of the stacked structure of the first pole piece in some embodiments of the present application;

[0027] FIG3 is a schematic diagram of the stacked structure of the second pole piece in some embodiments of the present application;

[0028] FIG4 is a schematic diagram of the expanded structure of the first pole piece in some embodiments of the present application;

[0029] FIG5 is a schematic diagram of a bent and folded extension piece according to some embodiments of the present application;

[0030] FIG6 is a schematic structural diagram of an extension member according to some embodiments of the present application (showing the first surface);

[0031] FIG7 is a schematic structural diagram of an extension member according to some embodiments of the present application (showing the second surface);

[0032] FIG8 is a schematic structural diagram of an extension member according to some embodiments of the present application;

[0033] FIG9 is a schematic structural diagram of a secondary battery according to some embodiments of the present application.

[0034] Explanation of the accompanying drawings: 100, secondary battery; 10, electrode assembly; 10a, first circle; 10b, second circle; 11, first pole piece; 111, first current collector; 111a, first surface; 111b, second surface; 112, first active material layer; 1111, extension piece; 1112, protrusion; 1113, recess; 1114, arrangement group; 12, second pole piece; 121, second current collector; 121a, third surface; 121b, fourth surface; 122, second active material layer; 13, isolation membrane; 20, shell; 21, accommodating cavity; 30, first pole tab; 40, second pole tab; X, first direction; Y, second direction; Z, third direction; K, fourth direction. DETAILED DESCRIPTION

[0035] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0036] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the technical features indicated. In the description of the embodiments of this application, "several" and "plurality" mean more than two, unless otherwise specifically defined.

[0037] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0038] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features described below in the different embodiments of the present application may be combined with each other as long as they do not conflict with each other.

[0039] On the first aspect, an embodiment of the present application proposes an electrode assembly 10. Please refer to Figure 1. The electrode assembly 10 is formed by winding a first electrode sheet 11, an isolation membrane 13 and a second electrode sheet 12 that are stacked. The polarity of the first electrode sheet 11 and the second electrode sheet 12 are opposite. The isolation membrane 13 is arranged between the first electrode sheet 11 and the second electrode sheet 12 to separate the two.

[0040] For the above-mentioned first electrode sheet 11, please refer to Figures 1 and 2. The first electrode sheet 11 includes a first current collector 111 and a first active material layer 112. Taking the first electrode sheet 11 as a negative electrode sheet as an example, the first current collector 111 serves as a conductive substrate, and it can adopt a copper foil that is flat as a whole and has a strip structure. In some other embodiments, the first current collector 111 can also adopt nickel foil or polymer copper foil (the surface of the copper foil is provided with a high molecular polymer such as polyethylene, polypropylene or polyamide). The first active material layer 112 can be provided on at least one surface of the first current collector 111. For example, along the thickness direction (third direction Z) of the first current collector 111, the first current collector 111 includes a first surface 111a and a second surface 111b that are oppositely arranged. The above-mentioned first active material layer 112 can be provided on the first surface 111a and / or the second surface 111b. The first active material layer 112 includes a negative electrode active material, a conductive agent, and a binder. The above-mentioned material components are mixed and stirred evenly and then coated on the first surface 111a and / or the second surface 111b of the first current collector 111, thereby forming the first active material layer 112. The negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, elemental silicon, silicon oxide, or silicon alloy.

[0041] For the above-mentioned second electrode sheet 12, please refer to Figures 1 and 3. The second electrode sheet 12 includes a second current collector 121 and a second active material layer 122. Taking the second electrode sheet 12 as a positive electrode sheet as an example, the second current collector 121 can be made of aluminum foil that is flat and has a strip-shaped structure. The second active material layer 122 can be arranged on at least one surface of the second current collector 121. For example, the second current collector 121 includes a third surface 121a and a fourth surface 121b that are arranged opposite to each other along the third direction Z. The second active material layer 122 can be arranged on the third surface 121a and / or the fourth surface 121b. In the embodiment of the present application, the first electrode sheet 11 and the second electrode sheet 12 both adopt a double-sided coating structure, that is, the first surface 111a and the second surface 111b of the first current collector 111 are both provided with the first active material layer 112, and the third surface 121a and the fourth surface 121b of the second current collector 121 are both provided with the second active material layer 122.

[0042] The second active material layer 122 includes a positive electrode active material, a conductive agent, and a binder. These materials are mixed and stirred evenly and then applied to the third surface 121a and / or the surface of the second current collector 121 to form the second active material layer 122. The positive electrode active material can be selected from one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium iron manganese phosphate, and cobalt-free materials. It should be noted that the first electrode sheet 11 can also be a positive electrode sheet, and the second electrode sheet 12 can be a negative electrode sheet, which is not limited in this application.

[0043] Regarding the above-mentioned isolation membrane 13, the isolation membrane 13 is arranged between the first pole piece 11 and the second pole piece 12, and is used to insulate and separate the first pole piece 11 and the second pole piece 12. The isolation membrane 13 can be a PE isolation membrane or a PP isolation membrane containing ceramics. In some embodiments, an adhesive coating (not shown in the figure) can be provided on the surface of the isolation membrane 13 facing the first pole piece 11 and the surface facing the second pole piece 12. When the first pole piece 11, the isolation membrane 13 and the second pole piece 12 are stacked and wound, the isolation membrane 13 can be directly bonded between the first pole piece 11 and the second pole piece 12, which can improve the bonding strength between the first pole piece 11, the second pole piece 12 and the isolation membrane 13, thereby improving the integrity of the electrode assembly 10.

[0044] Referring to Figure 4 , a plurality of extensions 1111 extend from the first current collector 111 at one end in the width direction (second direction Y) of the first current collector 111. The extensions 1111 can be integrally formed with the first current collector 111. For example, a cutting area is reserved at one end in the width direction of the first current collector 111, and the extensions 1111 can be cut out by die-cutting. In other embodiments, the extensions 1111 can be separate from the first current collector 111. For example, the extensions 1111 can be electrically connected to the first current collector 111 by welding, bonding, or clamping.

[0045] The extension piece 1111 can lead out the polarity of the first electrode piece 11. For example, if the first electrode piece 11 is a negative electrode piece, the extension piece 1111 can be connected to an external circuit to serve as a bridge for the negative electrode of the electrode assembly 10 to be connected to the outside. The provision of multiple extension pieces 1111 can improve the current capacity of the first electrode piece 11, which can facilitate meeting the requirements of high-rate charge and discharge. For example, referring to Figure 5, multiple extension pieces 1111 are bent and stacked into a whole. By providing an adapter (not shown in the figure), one end of the adapter is electrically connected to the whole formed by the multiple extension pieces 1111, for example, by welding or conductive adhesive bonding to an external adapter to concentrate current, and the other end of the adapter can be directly connected to the external circuit.

[0046] During the implementation of the present application, the inventors discovered that when multiple extension pieces 1111 are bent and stacked, the extension pieces 1111 are easily deformed or even torn, which results in unstable electrical connections or even poor electrical contact after being electrically connected to the adapter.

[0047] To alleviate the above-mentioned problem, in the embodiment of the present application, with further reference to Figures 6 and 7, a plurality of protrusions 1112 are convexly formed on the first surface 111a of the extension member 1111, and a plurality of recesses 1113 are concavely formed on the second surface 111b of the extension member 1111. For example, the recesses 1113 can be punched directly on the second surface 111b of the extension member 1111, and the recesses 1113 can be protruded from the first surface 111a to form the protrusions 1112. In this case, the protrusions 1112 and the recesses 1113 overlap in the thickness direction of the extension member 1111. Alternatively, the recesses 1113 can be punched directly on the second surface 111b, and the protrusions can be machined on the first surface 111a. In this case, the protrusions and recesses 1113 do not overlap in the thickness direction of the extension member 1111. By providing the protruding portion 1112 and the recessed portion 1113 on the extension member 1111, the strength of the extension member 1111 can be increased, and deformation or damage of the extension member 1111 can be reduced. It is understood that the extension member 1111 is extended or cut from the first current collector 111, and therefore the first surface 111a of the extension member 1111 is also extended or cut from the first surface 111a of the first current collector 111, and the second surface 111b is similar.

[0048] In other embodiments, the first surface 111a may be provided with a plurality of recessed portions 1113, and the second surface 111b may be provided with a plurality of raised portions 1112. Optionally, the first surface 111a may be provided with both recessed portions 1113 and raised portions 1112, and the second surface 111b may be provided with both recessed portions 1113 and raised portions 1112, to further enhance the strength of the extension member 1111 and reduce deformation or damage of the extension member 1111.

[0049] Referring to Figure 1 , two adjacent extension members 111 can be provided in two adjacent circles, or they can be provided one or more circles apart. The following describes the solution using the arrangement of extension members 111 in two adjacent circles as an example. A first electrode sheet 11, a separator 13, and a second electrode sheet 12 are stacked and wound to form a wound electrode assembly 10. The plurality of circles include an adjacent first circle 10a and a second circle 10b, and the first current collector 111 is provided with extension members 1111 in both the first circle 10a and the second circle 10b. The extension members 1111 of each circle can be bent and folded into a single unit to facilitate electrical connection to the adapter. The provision of the raised portion 1112 and recessed portion 1113 improves the strength of the extension member 1111 and reduces deformation or tearing of the extension member 1111.

[0050] Observed along the thickness direction of the electrode assembly 10 (the fourth direction K in FIG1 ), the extension piece 1111 of the first circle 10a at least partially overlaps with the extension piece 1111 of the second circle 10b, and at least one protrusion 1112 of the extension piece 1111 of the first circle 10a is embedded in the recessed portion 1113 of the extension piece 1111 of the second circle 10b. After winding, the protrusion 1112 of the extension 1111 is correspondingly engaged with the recess 1113 of another extension 1111, which can increase the friction between the extensions 1111, reduce the mutual misalignment between the extensions 1111, and improve the bonding strength between the extensions 1111; and the embedding arrangement of the protrusion 1112 and the recess 1113 allows the protrusion 1112 to be accommodated in the recess 1113, which can reduce the space occupied by the protrusion 1112 and further improve the overall strength of the extension 1111, reduce the bending deformation and damage of the extension 1111, and facilitate electrical connection with the adapter. The number of recesses 1113 can be set to be consistent with the number of protrusions 1112, so that all protrusions 1112 can be embedded in the corresponding recesses.

[0051] In some embodiments, the first electrode 11 is a negative electrode, and the second electrode 12 is a positive electrode. The second current collector 121 can be made of aluminum foil. Similar to the first current collector 111, several extensions 1111 can also extend in the width direction of the second current collector 121. The extensions 1111 are provided with recessed portions 1113 and raised portions 1112 to improve the strength of the extensions 1111 on the second current collector 121. Because aluminum foil is brittle and difficult to process and form, in some other embodiments, the extensions 1111 on the second current collector 121 may not be provided with recessed portions 1113 and raised portions 1112. The first current collector 111 can be made of copper foil, nickel foil, or polymer copper foil, etc., which have higher strength. For example, the first current collector 111 is made of copper foil, and the extension piece 1111 and the first current collector 111 are integrally formed, and the material thereof is also copper. Copper has higher strength and better punching performance, which can facilitate punching out a recessed portion 1113 and a raised portion 1112 in the copper extension piece 1111, thereby improving the strength of the extension piece 1111.

[0052] To facilitate the processing and forming of the protrusion 1112, the area of ​​the protrusion 1112 should not be too small. A sufficient area of ​​the protrusion 1112 improves the strength of the extension 1111 and reduces deformation and damage of the extension 1111. If the protrusion 1112 is too large, the strength of the extension 1111 will not be significantly improved and it will take up a lot of space. In the embodiment of the present application, when viewed along the thickness direction of the extension 1111, the projected area of ​​the first surface 111a of the extension 1111 of a single protrusion 1112 is S mm 2, 0.12≤S≤0.5, which can facilitate the processing and molding of the raised portion 1112 while reducing the space occupied by the raised portion 1112 and improving the strength of the extension 1111. The recessed portion 1113 corresponds to the raised portion 1112, and its corresponding size setting can refer to the raised portion 1112.

[0053] In some preferred embodiments, when viewed along the thickness direction of the extension 111, the projection area of ​​a single protrusion 1112 on the first surface 111a is S mm. 2 , 0.16≤S≤0.4. This further reduces the probability of battery cell failure after a drop.

[0054] The area of ​​the first surface 111a of the extension 1111 is S1 mm 2 The coverage area of ​​all the protrusions 1112 on the first surface 111a is S2 mm 2 In a single extension 1111, the coverage area of ​​all protrusions 1112 on the first surface 111a is S2 mm 2 , 6% S1≤S2≤30% S1, preferably 8% S1≤S2≤20% S1.

[0055] For example, the area of ​​the first surface 111a of the extension piece 1111 can be set to 8mm 2 Up to 200mm 2 , and the coverage area of ​​all the protrusions 1112 on the first surface 111a is 2.4mm 2 Up to 12mm 2 , to improve the strength of the extension 1111. Among them, in a single extension 1111, the number of protrusions 1112 is M, 20≤M≤60. Reducing the number of protrusions 1112 can simplify the processing difficulty, and a large number of protrusions 1112 can better improve the strength. In addition, an excessive number of protrusions 1112 increases the friction between the extensions 1111. However, when the battery falls and is subjected to a large impact force, its buffering performance is weak. Excessive friction may cause the extension 1111 to displace with the adjacent extension 1111 due to collision, resulting in deformation, damage or even tearing of the extension 1111. If the friction is appropriately reduced, a buffer space can be provided between two adjacent extensions 1111 to ensure the relative displacement of adjacent extensions 1111. Within this range, the strength of the extensions 1111 can be increased while simplifying the manufacturing process. This can also balance the friction between the extensions 1111, reduce deformation, breakage, or tearing of the extensions 1111, lower the risk of production failure of the battery, and improve the battery's drop and collision resistance. Preferably, 33 ≤ M ≤ 40.

[0056] 1 , when viewed along the thickness direction of the electrode assembly 10 (fourth direction K), the extension pieces 1111 of the first circle 10a and the extension pieces 1111 of the second circle 10b at least partially overlap. For example, the overlapping area of ​​the extension pieces 1111 of the first circle 10a and the extension pieces 1111 of the second circle 10b is S3 mm. 2 , 80% S1≤S3≤100% S1. A sufficient overlapping area can increase the friction between two adjacent extensions 1111, reduce the relative movement between the extensions 1111, improve the bonding strength between the extensions 1111, facilitate electrical connection with the adapter, and improve the stability of the electrical connection. Among them, at least part of the extensions 1111 are located in the overlapping area, for example, 60% to 100% of the protrusions 1112 are located in the overlapping area, so as to facilitate the protrusions 1112 of the extensions 1111 of the first circle 10a to be embedded in the recesses 1113 of the extensions 1111 of the second circle 10b. In addition, a sufficient overlapping area can increase the number of embeddings of the protrusions 1112 and the recesses 1113, increase the friction between the brackets of the extensions 1111, and improve the bonding strength between the extensions 1111.

[0057] Referring to Figure 6 , along the width direction (second direction Y) of the first pole piece 11, a plurality of protrusions 1112 are sequentially arranged on the first surface 111a of the extension piece 1111 to form an arrangement group 1114. The extension piece 1111 includes a plurality of arrangement groups 1114, which are sequentially arranged along the winding direction (first direction Z) of the first pole piece 11. The interval between two adjacent arrangement groups 1114 is L mm, with 1.5≤L≤3. The arrangement of the arrangement group 1114 formed by multiple extension pieces 1111 facilitates uniform coverage of the protrusions 1112 on the extension piece 1111, thereby evenly distributing the stress on the extension piece 1111, improving the strength of each position of the extension piece 1111, and reducing deformation and damage of the extension piece 1111.

[0058] Referring to Figure 6 , the protrusions 1112 in two adjacent arrangement groups 1114 are staggered along the winding direction of the first pole piece 11. In one arrangement group 1114, two adjacent extension members 1111 are spaced apart to form a spacing region. When viewed along the winding direction of the first pole piece 11, this spacing region overlaps with at least one protrusion 1112 in another arrangement group 1114. This arrangement ensures that the extension members 1111 are fully and evenly covered by the protrusions 1112, further enhancing the overall strength of the extension members 1111 and improving the friction between adjacent extension members 1111.

[0059] In a single arrangement group 1114 , the number of the protrusions 1112 is N, 3≤N≤8, and can be set according to the size of the extension piece 1111 so as to more comprehensively improve the strength of each part of the extension piece 1111 .

[0060] When viewed along the thickness direction of the extension member 1111, the raised portion 1112 is circular. The circular raised portion 1112 disperses the stress on the extension member 1111 and improves the tear resistance of the extension member 1111. The radius of the raised portion 1112 is R mm, and 1.5 ≤ R ≤ 2.5. In other embodiments, when viewed along the thickness direction of the extension member 1111, the raised portion 1112 may also be configured as an ellipse, square, diamond, trapezoid, triangle, or polygon, protruding from the first surface 111a and / or the second surface 111b and being able to fit into the recessed portion 1113.

[0061] Referring to Figure 8 , the first surface 111a of the extension 1111 includes a raised area with raised portions 1112 and a flat area without raised portions 1112. The raised portions 1112 protrude from the first surface 111a with a height H1, 0.02 mm ≤ H1 ≤ 1 mm. This improves the strength of the extension 1111 while facilitating the insertion of the raised portions 1112 into the recessed portion 1113. The flat area has a thickness H2, H2 ≤ H1, which increases the strength of the extension 1111 while reducing the space occupied by the extension 1111.

[0062] In the embodiment of the present application, by providing a raised portion 1112 and a recessed portion 1113 on the extension member 1111, the strength of the extension member 1111 can be improved and deformation or tearing of the extension member 1111 can be reduced. In addition, at least one raised portion 1112 of the extension members 1111 of the first circle 10a is embedded in a recessed portion 1113 of the extension members 1111 of the second circle 10b. After winding, the raised portion 1112 of the extension piece 1111 is correspondingly engaged with the recessed portion 1113 of another extension piece 1111, which can increase the friction between the extension pieces 1111, reduce the mutual misalignment between the extension pieces 1111, and increase the bonding strength between the extension pieces 1111; at the same time, the embedded setting of the raised portion 1112 and the recessed portion 1113 allows the raised portion 1112 to be accommodated in the recessed portion 1113, which can reduce the space occupied by the raised portion 1112, and can further increase the overall strength of the extension piece 1111, reduce the bending deformation and damage of the extension piece 1111, and thus facilitate electrical connection with the adapter.

[0063] In the second aspect, an embodiment of the present application further proposes a secondary battery 100 . Referring to FIG. 9 , the secondary battery 100 includes a housing 20 , a first tab 30 , a second tab 40 , and an electrode assembly 10 as described in any embodiment of the first aspect above.

[0064] Regarding the housing 20, referring to Figure 9 , the housing 20 encloses a chamber 21 that accommodates the electrode assembly 10 and the electrolyte. In the embodiments of the present application, the housing 20 may be a packaging bag, for example, a multi-layer composite film packaging bag including a metal layer; alternatively, the housing 20 may be directly formed by punching a single metal layer, for example, a single steel sheet, to ensure the strength of the housing 20.

[0065] Regarding the first electrode tab 30, one end of the first electrode tab 30 is electrically connected to the extension piece 1111 of the first electrode sheet 11 within the housing 20. For example, after the first electrode sheet 11 is stacked and crimped onto the extension pieces 1111 of each circle, one end of the first electrode tab 30 can be electrically connected to the extension piece 1111, while the other end extends outside the housing 20 to lead one polarity of the electrode assembly 10, facilitating electrical connection to an external circuit. The material of the first electrode tab 30 can be selected to be consistent with the material of the first current collector 111, such as copper or nickel.

[0066] Regarding the second electrode tab 40, one end of the second electrode tab 40 is electrically connected to the second electrode sheet 12 within the housing 20. When the second electrode sheet 12 is also provided with an extension 1111, one end of the second electrode tab 40 can be directly electrically connected to the extension 1111 of the second electrode sheet 12, while the other end directly extends outside the housing 20 to lead the other polarity of the electrode assembly 10, facilitating electrical connection with an external circuit. The material of the second electrode tab 40 can also be the same as that of the second current collector 121, such as aluminum. In other embodiments, copper or nickel sheets can also be used.

[0067] In a third aspect, an embodiment of the present application further proposes an electronic device, comprising a secondary battery as described in any embodiment of the first aspect above. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices include but are not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0068] In the embodiment of the present application, lithium-ion secondary batteries are taken as an example to perform production failure statistics.

[0069] Example 1

[0070] (1) Preparation of cathode electrode: The cathode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and stirred evenly.

[0071] Aluminum foil is used as the cathode current collector. The slurry is evenly coated on one surface of the cathode current collector and dried to obtain a cathode electrode sheet coated with a cathode active material layer on one side. The above steps are repeated on the other surface of the aluminum foil to obtain a cathode electrode sheet coated with a cathode active material layer on both sides.

[0072] (2) Preparation of anode electrode: Graphite was used as the negative electrode active material. The negative electrode active material graphite, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 96:2:2, and deionized water was added as a solvent to prepare a slurry with a solid content of 70 wt%, which was then stirred evenly.

[0073] Copper foil is selected as the anode current collector, the slurry is evenly coated on one surface of the copper foil, and an empty foil area is reserved on the surface, and it is dried to obtain an anode pole piece coated with an anode active material layer on one side. On the other surface of the copper foil, the above steps are repeated to obtain an anode pole piece coated with a cathode active material layer on both sides. The empty foil area is cut by die cutting to form multiple extensions, where the length of the extension (the dimension in the width direction of the anode pole piece) is 10 mm, the width (the dimension in the winding direction of the anode pole piece) is 7 mm, and the area S1 of the extension piece is 70 mm 2 , and a concave portion is punched out on one surface of the extension piece, and a convex portion is formed on the other surface of the extension piece, wherein the number M of the convex portions is 35, and the projection area S of a single convex portion on the first surface is 0.1mm 2 The sum of the areas of all raised parts S2 is 3.5mm 2 .

[0074] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0075] (4) Preparation of isolation membrane: A polyethylene porous membrane is used as a substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one surface of the substrate layer as a separator (CCS), wherein the mass percentage of alumina ceramic in the ceramic layer is 95%.

[0076] (5) Electrode assembly preparation: The cathode electrode sheet, separator, and anode electrode sheet are stacked and wound. The anode electrode sheet has an extension piece extending from each turn. The extension pieces of each turn are bent and stacked into a whole, and the protrusions of the extension pieces are embedded in the recesses of the extension pieces of the adjacent turns. Nickel and aluminum sheets with a specification of 12 mm × 5 mm are selected as tabs. The aluminum tabs are welded to the cathode electrode sheet (the aluminum foil of the cathode electrode sheet), and the nickel tabs are welded to the extension piece of the anode electrode sheet to form an electrode assembly for use.

[0077] (6) Electrode assembly: Place the aluminum-plastic film with the cavities formed in it into an assembly fixture, with the cavities facing upward. Place the electrode assembly in the cavities, and set seals at the two tabs. Apply external force to tighten. Then, place another aluminum-plastic film with the cavities formed in it, with the cavities facing downward, over the electrode assembly. Heat-seal the two aluminum-plastic films around each other using hot pressing to obtain an assembled electrode assembly.

[0078] (7) Liquid injection packaging: The assembled electrode assembly is injected with electrolyte, and after vacuum packaging, static standing, hot pressing, shaping and other processes, the lithium-ion battery is produced.

[0079] The relevant parameters of Examples 2 to 16 can be referred to in Table 1 below;

[0080] Comparative Example 1 is different from Example 1 in that no protrusion is provided.

[0081] Statistics of failure rate during production: Use a 10x microscope to inspect the extension parts, and pick out lithium-ion batteries with deformation, damage or tearing of the extension parts, as well as failure during transfer welding of the tabs (failure includes misalignment of the extension parts, deformation, damage, tearing of the extension parts, etc.). The statistical number is P. The total production quantity is 5000, and the production short-circuit failure rate is P / 5000.

[0082] Table 1

[0083] According to Table 1 above, combined with Comparative Example 1 and Examples 1 to 16, it can be seen that when protrusions and depressions are provided on the extension piece, the production failure rate of the battery can be effectively reduced. This is because the provision of the protrusions and depressions improves the strength of the extension piece and enhances the tear resistance of the extension piece. Therefore, when the extension piece is bent, the deformation, breakage or tearing of the extension piece can be effectively reduced; and the embedded provision of the protrusions and depressions increases the friction between the extension pieces, thereby improving the integrity of the extension piece. When the electrode tabs are transfer welded, the risk of welding failure is lower.

[0084] In Example 1, the area of ​​a single raised portion is small, and its production failure rate is higher than that of Examples 2 to 15. This is because the small area of ​​the raised portion weakens the effect of improving the strength of the extension. In Example 16, the area of ​​a single raised portion is large, and its production failure rate is also higher than that of Examples 2 to 16. This may be because the extension is too strong, making it difficult to bend. When bending, a large force is required, which makes the extension easily deformed. Therefore, in the examples of this application, 6% S1 ≤ S2 ≤ 30% S1 is selected; in Examples 5 to 13, the production failure rate is even lower, preferably 8% S1 ≤ S2 ≤ 20% S1.

[0085] In combination with Examples 2 to 16, when the area of ​​the protrusion exceeds 0.5 mm 2 When the protrusion is too large, the production failure rate may increase. This may be because the extension part is easy to interfere with the pole ear when the pole ear is transferred and welded, resulting in loose welding and even welding failure. The larger protrusion will also affect the battery energy density. Therefore, in the embodiment of the present application, 0.12≤S≤0.5 is selected.

[0086] Furthermore, when 0.16≤S≤0.4, the drop failure rate is lower and the effect is better.

[0087] In the embodiment of the present application, lithium-ion secondary batteries are taken as an example to perform production failure statistics.

[0088] Example 17, different from Example 1, is that in a single extension piece, the number of raised portions is 15, and the area S of a single raised portion is 0.2 mm 2 The sum of the areas of all raised parts S2 is 3mm 2 .

[0089] The relevant parameters of Examples 18 to 31 can be referred to in Table 2 below.

[0090] Drop test: The lithium-ion battery is charged at a constant current of 0.2C to 4.45V, then at a constant voltage of 4.45V to 0.02C. The OCV (open circuit voltage) and IMP (internal resistance) are recorded. The battery is placed at a height of 1.5m, with all six sides and four corners facing downward, for two rounds of testing. Pass criteria include no damage or leakage, no deformation of the extension, and no significant voltage drop (<20mV).

[0091] Table 2

[0092] According to Table 2 above, combined with Comparative Example 1 and Comparative Examples 17 to 31, when protrusions and recesses are provided on the extension piece, the strength of the extension piece can be effectively improved and the risk of failure of the extension piece due to falling can be reduced.

[0093] In Example 17, the number of raised parts is small, and the strength improvement of the extension is weak, so the drop test failure rate is high; in Example 31, the number of raised parts is large, which increases the friction between the extensions. However, when subjected to a large impact force in the drop test, its cushioning is weak. Excessive friction may cause the extension to be displaced from the adjacent extension due to collision, resulting in deformation, damage or even tearing of the extension. Therefore, in combination with the above-mentioned Examples 17 to 31, 20≤M≤60 can be selected; in combination with Examples 23 to 26, preferably, 33≤M≤40 can be selected, which can balance the friction between the extensions while improving the strength, reduce the deformation, damage or tearing of the extensions, reduce the risk of production failure of the battery, and improve the battery's anti-drop and anti-collision performance.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrode assembly, comprising a first pole piece, a separator and a second pole piece stacked and wound, wherein the first pole piece comprises a first current collector and a first active material layer, and along the thickness direction of the first current collector, the first current collector has a first surface and a second surface arranged opposite to each other, and the first active material layer is arranged on the first surface and / or the second surface, characterized in that: A plurality of extension pieces are provided at one end of the first current collector in the width direction, a plurality of protrusions are convexly provided on a first surface of the extension piece, and a plurality of concave portions are concavely provided on a second surface of the extension piece; When viewed along the thickness direction of the electrode assembly, two adjacent extension members at least partially overlap, and at least one protrusion of an extension member is embedded in a recess of the adjacent extension member.

2. The electrode assembly according to claim 1, characterized in that: The number of protrusions of a single extension piece is M, and 20≤M≤60.

3. The electrode assembly according to claim 2, characterized in that: 33≤M≤40。 4. The electrode assembly according to any one of claims 1 to 3, characterized in that: The first pole piece is a negative pole piece.

5. The electrode assembly according to any one of claims 1 to 4, characterized in that: Observed along the thickness direction of the extension piece, the projection area of ​​a single protrusion on the first surface is S mm 2 , 0.12≤S≤0.

5.

6. The electrode assembly according to claim 5, characterized in that: Observed along the thickness direction of the extension piece, the projection area of ​​a single protrusion on the first surface is Smm 2 , 0.16≤S≤0.

4.

7. The electrode assembly according to any one of claims 1 to 6, characterized in that: The area of ​​the first surface of the extension piece is S1mm 2 ; In a single extension piece, the coverage area of ​​all the protrusions on the first surface is S2mm 2 , 6%S1≤S2≤30%S1.

8. The electrode assembly according to claim 7, characterized in that: 8%S1≤S2≤20%S1.

9. The electrode assembly according to claim 7, characterized in that: Observed along the thickness direction of the electrode assembly, the overlapping area of ​​two adjacent extensions is S3mm 2 , 80% S1≤S3≤100% S1.

10. The electrode assembly according to any one of claims 1 to 9, characterized in that: Along the width direction of the first pole piece, a plurality of the protrusions are sequentially arranged on the first surface of the extension member to form an arrangement group; The extension member includes a plurality of arrangement groups, and the plurality of arrangement groups are arranged in sequence along the winding direction of the first pole piece. The interval between two adjacent arrangement groups is L mm, and 1.5≤L≤3.

11. The electrode assembly according to claim 10, characterized in that: The protrusions in two adjacent arrangement groups are staggered along the winding direction.

12. The electrode assembly according to claim 10, characterized in that: In a single arrangement group, the number of the protrusions is N, and 3≤N≤8.

13. The electrode assembly according to any one of claims 1 to 12, characterized in that: When viewed along the thickness direction of the extension piece, the protrusion is circular, and the radius of the protrusion is R mm, 1.5≤R≤2.5; or, When viewed along the thickness direction of the extension piece, the protrusion is at least one of an ellipse, a square, a diamond, a trapezoid or a triangle.

14. The electrode assembly according to any one of claims 1 to 13, characterized in that: The first surface of the extension member includes a raised area provided with a raised portion and a flat area not provided with the raised portion; The protrusion height of the protrusion on the first surface is H1, 0.02mm≤H1≤1mm; The thickness of the flattened area is H2, where H2≤H1.

15. A secondary battery, characterized in that: An electrode assembly comprising a shell, a first electrode tab, a second electrode tab, and any one of claims 1 to 14; The electrode assembly is accommodated in the shell; One end of the first pole lug is electrically connected to the extension piece of the first pole piece in the housing, and the other end extends out of the housing; One end of the second pole lug is electrically connected to the second pole piece in the shell, and the other end extends out of the shell.

16. An electronic device, characterized in that: Comprising the secondary battery as claimed in claim 15.

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