Electrode assembly, secondary battery, and electronic device

Abstract

The application discloses an electrode assembly, a secondary battery and an electronic device. One end of a first current collector in a width direction is provided with a plurality of extension pieces. A first surface of the extension piece is provided with a plurality of protruding parts. A second surface of the extension piece is provided with a plurality of recessed parts. The electrode assembly comprises adjacent extension pieces. When viewed in a thickness direction of the electrode assembly, the two adjacent extension pieces at least partially overlap. At least one protruding part of the extension piece is embedded in a recessed part of the adjacent extension piece. The strength of the extension piece is improved. The bending deformation and damage of the extension piece are reduced. The electrical connection of the extension piece is facilitated. The stability of the electrical connection is improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and more particularly to an electrode assembly and a secondary battery. Background Technology

[0002] The electrode components of the battery are mainly manufactured using a stacking process or a winding process. The winding process has been widely adopted due to its simplicity. However, for wound batteries, the contact area between the tabs and the electrode sheets is small, the internal resistance of the battery is high, and it is easy to generate heat during high-current charging and discharging.

[0003] Therefore, wound batteries can employ multiple tabs. The electrode sheet in a multiple tab structure includes a metal current collector and an active material layer disposed on the surface of the current collector. During manufacturing, a section of empty foil is left at the edge in the width direction of the electrode sheet, and this empty foil section is cut to form multiple tabs. After winding, the multiple tabs overlap in the thickness direction of the electrode assembly, and are then bent to connect with an external adapter plate. However, tabs produced by this method have lower strength and are prone to deformation and breakage during manufacturing. Summary of the Invention

[0004] The embodiments of this application aim to provide a motor assembly and a secondary battery that can reduce the technical problems of electrode deformation and damage during battery manufacturing.

[0005] In order to solve its technical problems, the embodiments of this application adopt the following technical solutions:

[0006] In a first aspect, this application proposes an electrode assembly comprising a first electrode, a separator, and a second electrode wound together and stacked. The first electrode includes a first current collector and a first active material layer. Along the thickness direction of the first current collector, the first current collector has a first surface and a second surface disposed opposite to each other. The first active material layer is disposed on the first surface and / or the second surface. A plurality of extensions are provided at one end of the first current collector in the width direction. The first surface of each extension has a plurality of protrusions, and the second surface of each extension has a plurality of recesses. Viewed along the thickness direction of the electrode assembly, adjacent extensions at least partially overlap, and at least one protrusion of an extension is embedded in a recess of an adjacent extension.

[0007] In the above technical solution, by providing protrusions and recesses on the extension, the strength of the extension can be improved and the deformation or tearing damage of the extension can be reduced.

[0008] Furthermore, at least one protrusion of the extension is embedded in the recess of another adjacent extension. After winding, the protrusion of the extension and the recess of the other extension are correspondingly engaged, which can increase the friction between the extensions, reduce the misalignment between the extensions, increase the bonding strength between the extensions, and facilitate the transfer welding of the extensions. At the same time, the embedded arrangement of the protrusion and the recess allows the protrusion to be housed in the recess, which can reduce the space occupied by the protrusion and further improve the overall strength of the extension, reduce bending deformation and damage of the extension, thereby facilitating electrical connection with the adapter.

[0009] In some preferred embodiments, the number of protrusions in a single extension is M, where 20 ≤ M ≤ 60. Reducing the number of protrusions simplifies processing, while increasing the number of protrusions improves strength. Within the above range, processing difficulty can be simplified while increasing the strength of the extension. Furthermore, if the number of individual extensions is too large, excessive frictional resistance between extensions can lead to breakage when the extensions are displaced. Preferably, 33 ≤ M ≤ 40.

[0010] In some preferred embodiments, the first electrode is a negative electrode. The first current collector of the negative electrode can be made of copper foil, and the extension is integrally formed with the first current collector. Its material is also copper. Copper has high strength and good punching performance, which makes it easy to punch recesses and protrusions in the copper extension, thereby improving the strength of the extension.

[0011] 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. This allows for convenient processing and forming of the protrusion while reducing the space occupied by the protrusion and improving the strength of the extension.

[0012] 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 0.16≤S≤0.4. This further reduces the probability of cell failure after a drop.

[0013] In some preferred embodiments, the area of ​​the first surface of the extension is S1 mm. 2 In a single extension, the total coverage area of ​​all protrusions on the first surface is S² mm. 2 The strength of the extension is improved by setting 6% S1 ≤ S2 ≤ 30% S1. Preferably, the strength is 8% S1 ≤ S2 ≤ 20% S1.

[0014] In some preferred embodiments, when viewed along the thickness direction of the electrode assembly, the overlap area of ​​two adjacent extensions is S3 mm. 280%S1≤S3≤100%S1; at least some extensions are located within the overlapping area. Sufficient overlap area increases the friction between adjacent extensions, reduces relative movement between extensions, and improves the bonding strength between extensions, facilitating electrical connection with the adapter and enhancing the stability of the electrical connection. Furthermore, having at least some extensions located within the overlapping area facilitates the insertion of protrusions into recesses of adjacent extensions, and sufficient overlap area further increases the number of protrusions and recesses that can be inserted, increasing the friction between extensions and improving the bonding strength between extensions.

[0015] In some preferred embodiments, a plurality of protrusions are arranged sequentially on the first surface of the extension member along the width direction of the first electrode to form an arrangement group. The extension member includes a plurality of arrangement groups, which are arranged sequentially along the winding direction of the first electrode, with a spacing of L mm between adjacent arrangement groups, where 1.5 ≤ L ≤ 3. The arrangement of multiple extension members forming an arrangement group facilitates the uniform coverage of the protrusions on the extension member, thereby evenly distributing the stress on the extension member, improving the strength of the extension member at various locations, and reducing deformation and breakage of the extension member.

[0016] In some preferred embodiments, the protrusions in adjacent groups are staggered along the winding direction. This arrangement allows the extension to be fully and uniformly covered by the protrusions, further improving the overall strength of the extension and the friction between adjacent extensions.

[0017] In some preferred embodiments, the number of protrusions in a single arrangement is N, where 3 ≤ N ≤ 8, in order to more comprehensively improve the strength of each part of the extension.

[0018] In some preferred embodiments, the protrusion is circular when viewed along the thickness direction of the extension. The circular protrusion better disperses the stress on the extension and can improve the tear resistance of the extension. The radius of the protrusion is R mm, where 1.5 ≤ R ≤ 2.5. Optionally, when viewed along the thickness direction of the extension, the protrusion is at least one of elliptical, square, rhomboid, trapezoidal, or triangular.

[0019] In some preferred embodiments, the first surface of the extension includes a raised area with protrusions and a flat area without protrusions. The protrusion height of the protrusions on the first surface is H1, where 0.02 mm ≤ H1 ≤ 1 mm. The thickness of the flat area is H2, where H2 ≤ H1, which improves the strength of the extension while reducing the space occupied by the extension.

[0020] Secondly, this application also proposes a secondary battery, including a housing, a first electrode tab, a second electrode tab, and an electrode assembly as described in any embodiment of the first aspect above. The electrode assembly is housed within the housing. One end of the first electrode tab is electrically connected within the housing to an extension of a first electrode plate, and the other end extends outside the housing. One end of the second electrode tab is electrically connected within the housing to a second electrode plate, and the other end extends outside the housing.

[0021] Thirdly, this application also proposes an electronic device including an electrochemical device as described in any of the embodiments of the first aspect above. Attached Figure Description

[0022] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0023] Figure 1 This is a schematic diagram of the structure of an electrode assembly according to some embodiments of this application;

[0024] Figure 2 This is a schematic diagram of the stacked structure of the first electrode sheet in some embodiments of this application;

[0025] Figure 3 This is a schematic diagram of the stacked structure of the second electrode sheet in some embodiments of this application;

[0026] Figure 4 This is a schematic diagram of the unfolded structure of the first pole piece in some embodiments of this application;

[0027] Figure 5 This is a schematic diagram of the bending and folding arrangement of the extension in some embodiments of this application;

[0028] Figure 6 This is a schematic diagram of the structure of an extension (showing the first surface) according to some embodiments of this application;

[0029] Figure 7 This is a schematic diagram of the structure of an extension (showing the second surface) according to some embodiments of this application;

[0030] Figure 8 This is a schematic diagram of the structure of an extension of some embodiments of this application;

[0031] Figure 9 This is a schematic diagram of the structure of a secondary battery according to some embodiments of this application.

[0032] Explanation of reference numerals in the attached figures:

[0033] 100. Secondary batteries;

[0034] 10. Electrode assembly; 10a. First turn; 10b. Second turn;

[0035] 11. First electrode; 111. First current collector; 111a. First surface; 111b. Second surface; 112. First active material layer; 1111. Extension; 1112. Protrusion; 1113. Recess; 1114. Arrangement group;

[0036] 12. Second electrode; 121. Second current collector; 121a. Third surface; 121b. Fourth surface; 122. Second active material layer;

[0037] 13. Separating membrane;

[0038] 20. Shell; 21. Receiving cavity;

[0039] 30. First pole ear;

[0040] 40. Second pole ear;

[0041] X, first direction; Y, second direction; Z, third direction; K, fourth direction. Detailed Implementation

[0042] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0043] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "several" and "more than" mean two or more, unless otherwise explicitly defined.

[0044] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0046] In a first aspect, embodiments of this application provide an electrode assembly 10, please refer to... Figure 1 The electrode assembly 10 is formed by winding a first electrode 11, a separator 13 and a second electrode 12 stacked together. The first electrode 11 and the second electrode 12 have opposite polarities, and the separator 13 is disposed between the first electrode 11 and the second electrode 12 to separate them.

[0047] For the first electrode 11 mentioned above, please refer to... Figure 1 and Figure 2 The first electrode 11 includes a first current collector 111 and a first active material layer 112. Taking the first electrode 11 as a negative electrode as an example, the first current collector 111 serves as a conductive substrate and can be a flat, strip-shaped copper foil. In other embodiments, the first current collector 111 can also be a nickel foil or a polymer copper foil (with a polymer such as polyethylene, polypropylene, or polyamide disposed on the surface of the copper foil). The first active material layer 112 can be disposed 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 disposed opposite to each other, and the first active material layer 112 can be disposed 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, etc. The above 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 obtaining 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.

[0048] For the second electrode 12 mentioned above, please refer to... Figure 1 and Figure 3 The second electrode 12 includes a second current collector 121 and a second active material layer 122. Taking the second electrode 12 as a positive electrode as an example, the second current collector 121 can be an aluminum foil with an overall flat and strip-shaped structure. The second active material layer 122 can be disposed 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 disposed opposite each other along a third direction Z, and the second active material layer 122 can be disposed on the third surface 121a and / or the fourth surface 121b. In the embodiments of this application, both the first electrode 11 and the second electrode 12 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.

[0049] The second active material layer 122 includes a positive electrode active material, a conductive agent, and a binder, etc. These materials are mixed, stirred evenly, and coated onto the third surface 121a and / or surface of the second current collector 121, thereby obtaining 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 iron phosphate, and cobalt-free materials. It should be noted that the first electrode 11 can also be a positive electrode, and the second electrode 12 can be a negative electrode; this application does not impose any limitations.

[0050] The aforementioned separator 13 is disposed between the first electrode 11 and the second electrode 12 to provide insulation between them. The separator 13 can be a ceramic-containing PE separator or a PP separator, etc. In some embodiments, an adhesive coating (not shown in the figure) can be provided on both the surface of the separator 13 facing the first electrode 11 and the surface facing the second electrode 12. When the first electrode 11, the separator 13, and the second electrode 12 are stacked and wound, the separator 13 can be directly bonded between the first electrode 11 and the second electrode 12, which can improve the bonding strength between the first electrode 11, the second electrode 12, and the separator 13, thereby improving the overall integrity of the electrode assembly 10.

[0051] Please refer to Figure 4 At one end of the first current collector 111 in the width direction (second direction Y), the first current collector 111 extends with a plurality of extension members 1111. The extension members 1111 can be integrally formed with the first current collector 111. For example, a cutting area is reserved at one end of the first current collector 111 in the width direction, and the extension members 1111 can be cut out by die cutting. In some other embodiments, the extension members 1111 can also be separately formed from the first current collector 111. For example, the extension members 1111 can be electrically connected to the first current collector 111 by welding, bonding or snap-fitting.

[0052] The extension member 1111 can bring out the polarity of the first electrode 11. For example, if the first electrode 11 is a negative electrode, the extension member 1111 can be connected to an external circuit, serving as a bridge between the negative electrode of the electrode assembly 10 and the external circuit. The arrangement of multiple extension members 1111 can improve the overcurrent capacity of the first electrode 11, facilitating the fulfillment of high-rate charge and discharge requirements. For example, please refer to... Figure 5 Multiple extensions 1111 are bent and stacked into a whole. By setting an adapter (not shown in the figure), one end of the adapter is electrically connected to the whole formed by multiple extensions 1111, for example, by welding or bonding with conductive adhesive to connect to an external adapter to concentrate current carrying capacity. The other end of the adapter can be directly connected to an external circuit.

[0053] The inventors of this application discovered during the implementation of this application that when multiple extensions 1111 are bent and stacked, the extensions 1111 are prone to deformation or even tearing and breakage. After being electrically connected to the adapter, this results in unstable electrical connection or even poor electrical contact.

[0054] To improve the above-mentioned problems, please refer further to the embodiments of this application. Figure 6 and Figure 7 The extension member 1111 has a plurality of protrusions 1112 on its first surface 111a and a plurality of recesses 1113 on its second surface 111b. For example, the recesses 1113 can be punched directly on the second surface 111b of the extension member 1111, and the recesses 1113 can protrude 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; or, 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 1112 and the recesses 1113 may not overlap in the thickness direction of the extension member 1111. By providing the protrusions 1112 and the recesses 1113 on the extension member 1111, the strength of the extension member 1111 can be improved and the deformation or breakage of the extension member 1111 can be reduced. It is understood that the extension 1111 is extended or cut from the first current collector 111, and therefore the first surface 111a of the extension 1111 is also extended or cut from the first surface 111a of the first current collector 111, and the second surface 111b is similar.

[0055] In some other embodiments, the first surface 111a may also have a plurality of recesses 1113, and the second surface 111b may also have a plurality of protrusions 1112. Optionally, the first surface 111a may be provided with both recesses 1113 and protrusions 1112, and the second surface 111b may be provided with both recesses 1113 and protrusions 1112, which can further improve the strength of the extension 1111 and reduce deformation or damage to the extension 1111.

[0056] Please refer to Figure 1The two adjacent extensions 1111 can be extensions arranged in two adjacent turns, or extensions arranged after one or more turns. The following explanation uses the example of extensions arranged in two adjacent turns. The first electrode 11, the separator 13, and the second electrode 12, stacked and wound, form a wound electrode assembly 10. Several turns include adjacent first turns 10a and second turns 10b, and the first current collector 111 has extensions 1111 in both the first turns 10a and 10b. The extensions 1111 in each turn can be bent and folded into a single unit for easy electrical connection with the adapter. Due to the aforementioned protrusions 1112 and recesses 1113, the strength of the extensions 1111 is improved, reducing deformation or tearing damage.

[0057] Viewed along the thickness direction of electrode assembly 10 ( Figure 1 In the fourth direction (K), the extension 1111 of the first ring 10a and the extension 1111 of the second ring 10b at least partially overlap, and at least one protrusion 1112 of the first ring 10a extension 1111 is embedded in the recess 1113 of the second ring 10b extension 1111. After winding, the protrusion 1112 of the extension 1111 and the recess 1113 of the other extension 1111 are correspondingly fitted, which can increase the friction between the extensions 1111, reduce the misalignment between the extensions 1111, and increase the bonding strength between the extensions 1111. Furthermore, the embedded arrangement of the protrusion 1112 and the recess 1113, such that the protrusion 1112 is received in the recess 1113, can reduce the space occupied by the protrusion 1112, and can further improve the overall strength of the extension 1111, reduce the bending deformation and damage of the extension 1111, thereby facilitating electrical connection with the adapter. The number of recesses 1113 can be set to be the same as the number of protrusions 1112, so that all protrusions 1112 can be embedded in the corresponding recesses.

[0058] 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 may be made of aluminum foil. Similar to the first current collector 111, the second current collector 121 may also extend into several extensions 1111 in its width direction. The extensions 1111 are provided with recesses 1113 and protrusions 1112 to improve the strength of the extensions 1111 on the second current collector 121. Since aluminum foil is brittle and difficult to process, in some other embodiments, the extensions 1111 on the second current collector 121 may not have recesses 1113 and protrusions 1112. The first current collector 111 may be made of copper foil, nickel foil, or polymer copper foil, etc., which have high strength. For example, the first current collector 111 is made of copper foil, and the extension 1111 is integrally formed with the first current collector 111. Its material is also copper. Copper has high strength and good punching performance, which makes it easy to punch out the recessed part 1113 and the protrusion 1112 in the copper extension 1111, thereby improving the strength of the extension 1111.

[0059] To facilitate the processing and forming of the protrusion 1112, the area of ​​the protrusion 1112 should not be too small. Sufficient area of ​​the protrusion 1112 improves the strength of the extension 1111 and reduces deformation and breakage. If the protrusion 1112 is too large, the improvement in strength of the extension 1111 is not significant, and it occupies a large amount of space. In the embodiments of this application, viewed along the thickness direction of the extension 1111, the projected area of ​​the first surface 111a of a single protrusion 1112 extension 1111 is S mm. 2 With a value of 0.12≤S≤0.5, the protrusion 1112 can be easily processed and formed while reducing the space occupied by the protrusion 1112 and improving the strength of the extension 1111. The recess 1113 corresponds to the protrusion 1112, and its corresponding dimensions can be set with reference to the protrusion 1112.

[0060] In some preferred embodiments, when viewed along the thickness direction of the extension 1111, the projected 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 cell failure after a drop.

[0061] The area of ​​the first surface 111a of the extension 1111 is S1 mm. 2 The total coverage area of ​​all protrusions 1112 on the first surface 111a is S2 mm. 2 In a single extension 1111, the total coverage area of ​​all protrusions 1112 on the first surface 111a is S2mm. 2 6%S1≤S2≤30%S1, preferably 8%S1≤S2≤20%S1.

[0062] For example, the area of ​​the first surface 111a of the extension 1111 can be set to 8 mm. 2 Up to 200mm 2 The total coverage area of ​​all protrusions 1112 on the first surface 111a is 2.4 mm. 2 Up to 12mm 2 To improve the strength of the extension 1111, the number of protrusions 1112 in a single extension 1111 is M, where 20 ≤ M ≤ 60. Reducing the number of protrusions 1112 simplifies processing, while increasing the number of protrusions 1112 improves strength. However, an excessive number of protrusions 1112 increases the friction between the extensions 1111. This can lead to weak cushioning when the battery is dropped and subjected to significant impact, and excessive friction may cause the extension 1111 to shift due to collision with adjacent extensions 1111, resulting in deformation, breakage, or even tearing. Conversely, appropriately reducing friction allows for a buffer space between adjacent extensions 1111, preventing relative displacement. Within the aforementioned range, while simplifying processing, the strength of the extension 1111 can be improved, and the friction between the extensions 1111 can be balanced, reducing deformation, breakage, or tearing of the extensions 1111, thereby reducing the risk of battery production failure and improving the battery's drop and impact resistance. Preferably, 33≤M≤40.

[0063] Please refer to Figure 1 Viewed along the thickness direction of the electrode assembly 10 (fourth direction K), the extension 1111 of the first ring 10a and the extension 1111 of the second ring 10b at least partially overlap. For example, the overlap area of ​​the extension 1111 of the first ring 10a and the extension 1111 of the second ring 10b is S3 mm. 2 80%S1≤S3≤100%S1. Sufficient overlapping area increases the friction between adjacent extensions 1111, reduces relative movement between extensions 1111, and improves the bonding strength between extensions 1111, facilitating electrical connection with the adapter and improving the stability of the electrical connection. At least a portion of the extensions 1111 are located within the overlapping area, for example, 60% to 100% of the protrusions 1112 are located within the overlapping area to facilitate the insertion of the protrusions 1112 of the first ring 10a extension 1111 into the recesses 1113 of the second ring 10b extension 1111. Sufficient overlapping area increases the number of protrusions 1112 and recesses 1113 inserted, increases the friction between the supports of each extension 1111, and improves the bonding strength between extensions 1111.

[0064] Please refer to Figure 6Along the width direction (second direction Y) of the first electrode 11, a plurality of protrusions 1112 are sequentially arranged on the first surface 111a of the extension 1111 to form an arrangement group 1114. The extension 1111 includes a plurality of arrangement groups 1114, which are sequentially arranged along the winding direction (first direction Z) of the first electrode 11, with a spacing of L mm between adjacent arrangement groups 1114, where 1.5 ≤ L ≤ 3. The arrangement of multiple extensions 1111 forming arrangement groups 1114 facilitates the uniform coverage of the protrusions 1112 on the extension 1111, thereby evenly distributing the stress on the extension 1111, improving the strength of the extension 1111 at various locations, and reducing deformation and breakage of the extension 1111.

[0065] Please refer to Figure 6 In two adjacent arrangement groups 1114, the protrusions 1112 are staggered along the winding direction of the first electrode 11. In one arrangement group 1114, two adjacent extensions 1111 are spaced apart to form a gap region. Viewed along the winding direction of the first electrode 11, this gap region overlaps with at least one protrusion 1112 in another arrangement group 1114. This arrangement allows the extensions 1111 to be fully and uniformly covered by the protrusions 1112, which can further improve the overall strength of the extensions 1111 and increase the friction between adjacent extensions 1111.

[0066] In a single arrangement group 1114, the number of protrusions 1112 is N, where 3≤N≤8, and can be set according to the size of the extension 1111, so as to more comprehensively improve the strength of each part of the extension 1111.

[0067] Viewed along the thickness direction of the extension 1111, the protrusion 1112 is circular. The circular protrusion 1112 effectively disperses the stress on the extension 1111, thereby improving the tear resistance of the extension 1111. The radius of the protrusion 1112 is R mm, where 1.5 ≤ R ≤ 2.5. In other embodiments, viewed along the thickness direction of the extension 1111, the protrusion 1112 may also be elliptical, square, rhomboid, trapezoidal, triangular, or polygonal, protruding from the first surface 111a and / or the second surface 111b, and capable of embedding into the recess 1113.

[0068] Please refer to Figure 8The first surface 111a of the extension 1111 includes a raised area with a protrusion 1112 and a flat area without the protrusion 1112. The protrusion height of the protrusion 1112 on the first surface 111a is H1, 0.02mm≤H1≤1mm, which can improve the strength of the extension 1111 while facilitating the insertion of the protrusion 1112 into the recess 1113. The thickness of the flat area is H2, H2≤H1, which improves the strength of the extension 1111 while reducing the space occupied by the extension 1111.

[0069] In the embodiments of this application, by providing a protrusion 1112 and a recess 1113 on the extension 1111, the strength of the extension 1111 can be improved and deformation or tearing damage of the extension 1111 can be reduced. Furthermore, at least one protrusion 1112 of the first ring 10a extension 1111 is embedded in the recess 1113 of the second ring 10b extension 1111. After winding, the protrusion 1112 of the extension 1111 engages with the recess 1113 of another extension 1111, which increases the friction between the extensions 1111, reduces the misalignment between the extensions 1111, and improves the bonding strength between the extensions 1111. At the same time, the embedded arrangement of the protrusion 1112 and the recess 1113 allows the protrusion 1112 to be housed in the recess 1113, which reduces the space occupied by the protrusion 1112 and further improves the overall strength of the extension 1111, reduces bending deformation and damage of the extension 1111, and facilitates electrical connection with the adapter.

[0070] Secondly, embodiments of this application also provide a secondary battery 100, please refer to... Figure 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.

[0071] For the aforementioned housing 20, please refer to Figure 9 The housing 20 encloses a receiving cavity 21, which can accommodate the electrode assembly 10 and the electrolyte. In the embodiments of this application, the housing 20 can be a packaging bag, for example, the housing 20 can be a multi-layer composite film packaging bag containing a metal layer; or, the housing 20 can be directly formed by stamping a single metal layer, for example, by stamping a single steel sheet, to ensure the strength of the housing 20.

[0072] Regarding the first tab 30, one end of the first tab 30 is electrically connected to the extension 1111 of the first electrode 11 inside the housing 20. For example, when the first electrode 11 is stacked and pressed together with the extensions 1111 of each ring, one end of the first tab 30 can be electrically connected to the extension 1111, and the other end extends out of the housing 20 to lead out one polarity of the electrode assembly 10, which can be easily connected to an external circuit. The material of the first tab 30 can be the same as the material of the first current collector 111, such as copper or nickel sheet. Regarding the second tab 40, one end of the second tab 40 is electrically connected to the second electrode 12 inside the housing 20. When the second electrode 12 is also provided with an extension 1111, one end of the second tab 40 can be directly electrically connected to the extension 1111 of the second electrode 12, and the other end extends out of the housing 20 to lead out the other polarity of the electrode assembly 10, which can be easily connected to an external circuit. The material of the second electrode 40 can also be the same as that of the second current collector 121, such as aluminum sheet. In other embodiments, copper sheet or nickel sheet can also be used.

[0073] Thirdly, embodiments of this application also propose an electronic device, including the electrochemical device described in any of the embodiments of the first aspect above. The electronic device in the embodiments of this application is not particularly limited and 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, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., while spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0074] In the embodiments of this application, lithium-ion secondary batteries are used as an example to conduct production failure statistics.

[0075] Example 1

[0076] (1) Preparation of cathode electrode: The cathode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75wt% is prepared and stirred evenly.

[0077] Aluminum foil was selected as the cathode current collector. The slurry was uniformly coated on one surface of the cathode current collector and dried to obtain a cathode electrode sheet with a cathode active material layer coated on one side. The above steps were repeated on the other surface of the aluminum foil to obtain a cathode electrode sheet with a cathode active material layer coated on both sides.

[0078] (2) Preparation of anode sheet: Graphite is used as the negative electrode active material. The negative electrode active material graphite, binder styrene-butadiene rubber (SBR) and thickener sodium carboxymethyl cellulose (CMC) are mixed in a weight ratio of 96:2:2. Deionized water is added as a solvent to prepare a slurry with a solid content of 70wt% and stirred evenly.

[0079] Copper foil is selected as the anode current collector. The slurry is uniformly coated onto one surface of the copper foil, leaving an empty foil area on this surface. After drying, an anode sheet with a single-sided coating of the anode active material layer is obtained. The above steps are repeated on the other surface of the copper foil to obtain an anode sheet with a double-sided coating of the cathode active material layer. The empty foil area is die-cut to form multiple extensions, where the length (dimension in the width direction of the anode sheet) of the extensions is 10 mm, the width (dimension in the winding direction of the anode sheet) is 7 mm, and the area S1 of the extensions is 70 mm². 2 Furthermore, a recess is punched on one surface of the extension, and a protrusion is formed on the other surface of the extension. The number of protrusions M is 35, and the projected area S of a single protrusion on the first surface is 0.1 mm. 2 The sum of the areas of all the protrusions, S2, is 3.5 mm. 2 .

[0080] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are 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) is added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF6 mass concentration of 12.5%.

[0081] (4) Preparation of the separator: A porous polyethylene membrane is used as the substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one side of the substrate layer as a separator (CCS). The mass percentage of alumina ceramic in the ceramic layer is 95%.

[0082] (5) Electrode assembly preparation: The above-mentioned cathode electrode, separator, and anode electrode are stacked and wound together. An extension extends from the anode electrode in each turn. The extensions of each turn are bent and stacked into a single unit, with the protrusions of the extensions embedded in the recesses of the adjacent turns' extensions. Nickel and aluminum sheets with a specification of 12mm × 5mm are selected as electrode tabs. The aluminum tabs are welded to the cathode electrode (the aluminum foil of the cathode electrode), and the nickel tabs are welded to the extensions of the anode electrode to form an electrode assembly for later use.

[0083] (6) Electrode assembly assembly: Place the punched aluminum-plastic film in the assembly fixture with the punched surface facing up, place the electrode assembly in the punch, and set the sealing elements at the two electrode tabs, and apply external force to press it tight. Then cover the electrode assembly with another punched aluminum-plastic film with the punched surface facing down, and heat seal the two aluminum-plastic films around their perimeter by hot pressing to obtain the assembled electrode assembly.

[0084] (7) Liquid injection and encapsulation: Electrolyte is injected into the assembled electrode assembly, and after vacuum encapsulation, standing, hot pressing formation, shaping and other processes, a lithium-ion battery is obtained.

[0085] The relevant parameters for Examples 2 to 16 can be found in Table 1 below;

[0086] Comparative Example 1 differs from Example 1 in that it does not have a protrusion.

[0087] Failure rate statistics during production: The extension parts are inspected with a 10x microscope. Lithium-ion batteries that fail due to deformation, breakage or tearing of the extension parts, or failure during the transfer welding of the electrode tabs (failures include misalignment of each extension part, deformation of the extension part, breakage, tearing, etc.) are counted as P. The total production quantity is 5000. Then the short circuit failure rate during production is P / 5000.

[0088] Table 1

[0089]

[0090]

[0091] According to Table 1 above, and in conjunction with Comparative Example 1 and Examples 1 to 16, it can be seen that when protrusions and recesses are provided on the extension, the production failure rate of the battery can be effectively reduced. This is because the provision of protrusions and recesses increases the strength of the extension and enhances its tear resistance. Therefore, when bending the extension, deformation, breakage, or tearing of the extension can be effectively reduced. Furthermore, the embedded provision of protrusions and recesses increases the friction between each extension, thereby improving the overall integrity of the extension. When transferring the electrode tabs, the risk of welding failure is lower.

[0092] In Example 1, the area of ​​a single protrusion is smaller, resulting in a higher production failure rate than in Examples 2 to 15. This is because the smaller protrusion area weakens the effect on improving the strength of the extension. In Example 16, the area of ​​a single protrusion is larger, and the production failure rate is also higher than in Examples 2 to 16. This may be because the strength of the extension is too high, making it difficult to bend and requiring greater force during bending, thus making the extension prone to deformation. Therefore, in the embodiments 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.

[0093] Referring to Examples 2 to 16, when the area of ​​the protrusion exceeds 0.5 mm 2 At this time, it may lead to an increase in the production failure rate. This may be because the excessively large protrusion makes it easy for the extension to interfere with the electrode tab when it is transferred and welded, resulting in poor welding and welding failure. In addition, the large protrusion will also affect the battery energy density. Therefore, in the embodiments of this application, 0.12≤S≤0.5 is selected.

[0094] Furthermore, when 0.16≤S≤0.4, the drop failure rate is lower and the effect is better.

[0095] In the embodiments of this application, lithium-ion secondary batteries are used as an example to conduct production failure statistics.

[0096] Example 17 differs from Example 1 in that the number of protrusions in a single extension is 15, and the area S of a single protrusion is 0.2 mm. 2 The sum of the areas of all the protrusions, S2, is 3mm. 2 .

[0097] The relevant parameters for Examples 18 to 31 can be found in Table 2 below.

[0098] Drop Test: The lithium-ion battery was charged to 4.45V with a constant current of 0.2C, and then charged to 0.02C with a constant voltage of 4.45V. The OCV (open-circuit voltage, the potential difference between the two terminals when the battery is open and not discharging) and IMP (internal resistance, the battery's static internal resistance) were recorded. At a height of 1.5m, the lithium-ion battery was tested twice, with each of its six sides and four corners facing down. The passing standard was no breakage or leakage, no deformation of extended parts, and no significant voltage drop (a decrease of 20mV).

[0099] Table 2

[0100]

[0101] According to Table 2 above, and in conjunction with Comparative Examples 1 and 17 to 31, when protrusions and recesses are provided on the extension, the strength of the extension can be effectively improved and the risk of drop failure of the extension can be reduced.

[0102] In Example 17, the number of protrusions is relatively small, resulting in a weak improvement in the strength of the extensions and a high failure rate in drop tests. In Example 31, the number of protrusions is large, increasing the friction between the extensions. However, under significant impact during drop tests, the cushioning is weak, and excessive friction may cause the extensions to shift due to collisions with adjacent extensions, leading to deformation, breakage, or even tearing. Therefore, combining Examples 17 to 31, a value of 20 ≤ M ≤ 60 can be selected. Furthermore, combining Examples 23 to 26, preferably 33 ≤ M ≤ 40, can improve strength while balancing the friction between the extensions, reducing deformation, breakage, or tearing, lowering the risk of battery production failure, and improving the battery's drop and impact resistance.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An electrode assembly comprising a first electrode, a separator, and a second electrode stacked and wound together, the first electrode comprising a first current collector and a first active material layer, the first current collector having a first surface and a second surface disposed opposite to each other along the thickness direction of the first current collector, the first active material layer being disposed on the first surface and / or the second surface, characterized in that, The first current collector has a plurality of extension members at one end in the width direction. The first surface of the extension members has a plurality of protrusions, and the second surface of the extension members has a plurality of recesses. Viewed along the thickness direction of the electrode assembly, two adjacent extensions at least partially overlap, and at least one protrusion of the extension is embedded in a recess of the adjacent extension. Along the width direction of the first electrode sheet, a plurality of protrusions are arranged sequentially on the first surface of the extension member to form an arrangement group; the extension member includes a plurality of arrangement groups, the plurality of arrangement groups are arranged sequentially along the winding direction of the first electrode sheet, and the protrusions in two adjacent arrangement groups are staggered along the winding direction.

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

3. The electrode assembly according to claim 2, characterized in that, 33≤M≤40。 4. The electrode assembly according to claim 1, characterized in that, The first electrode is the negative electrode.

5. The electrode assembly according to claim 1, characterized in that, 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.

6. The electrode assembly according to claim 5, characterized in that, Viewed along the thickness direction of the extension, the projected area of ​​a single protrusion on the first surface is S mm², where 0.16 ≤ S ≤ 0.

4.

7. The electrode assembly according to claim 1, characterized in that, The area of ​​the first surface of the extension is S1mm. 2 ; In a single extension, the total area covered by all the protrusions on the first surface is S² mm. 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, Viewed along the thickness direction of the electrode assembly, the overlap area of ​​two adjacent extensions is S3 mm. 2 , 80%S1≤S3≤100%S1.

10. The electrode assembly according to claim 1, characterized in that, The interval between two adjacent arrangement groups is L mm, where 1.5 ≤ L ≤ 3.

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

12. The electrode assembly according to claim 1, characterized in that, Viewed along the thickness direction of the extension, the protrusion is circular, and the radius of the protrusion is R mm, where 1.5 ≤ R ≤ 2.5; or, Viewed along the thickness direction of the extension, the protrusion is at least one of an ellipse, a square, a rhombus, a trapezoid, or a triangle.

13. The electrode assembly according to claim 1, characterized in that, The first surface of the extension includes a raised area with protrusions and a flat area without protrusions. The protrusion height of the protrusion on the first surface is H1, where 0.02mm≤H1≤1mm; The thickness of the flattened area is H2, where H2 ≤ H1.

14. A secondary battery, characterized in that, Includes a housing, a first electrode tab, a second electrode tab, and an electrode assembly as described in any one of claims 1 to 13; The electrode assembly is housed within the housing; One end of the first electrode tab is electrically connected to the extension of the first electrode plate inside the housing, and the other end extends out of the housing; One end of the second electrode tab is electrically connected to the second electrode plate inside the housing, and the other end extends out of the housing.

15. An electronic device, characterized in that, Includes the secondary battery as described in claim 14.

Images