Extrusion structure and extrusion jig

Abstract

The utility model provides an extrusion structure and an extrusion jig so as to relieve the technical problem that the middle part of an electrode assembly is prone to lithium precipitation. The extrusion structure is used for extruding an electrode assembly, the electrode assembly comprises a middle part and an edge part surrounding the middle part, the extrusion structure comprises a middle extrusion part and an edge extrusion part surrounding the edge of the middle extrusion part, and a first extrusion surface used for extruding the edge part is formed on the edge extrusion part. A second extrusion surface used for extruding the middle part is formed on the middle extrusion part, and the second extrusion surface is configured to be capable of forming offset with the first extrusion surface when the extrusion structure extrudes the electrode assembly and be far away from the central axis of the electrode assembly compared with the first extrusion surface.

Description

Technical Field

[0001] This application relates to the field of battery manufacturing technology, specifically to an extrusion structure and an extrusion fixture. Background Technology

[0002] Lithium-ion batteries can be classified into prismatic batteries, cylindrical batteries, and pouch batteries based on their shape. Prismatic batteries, with their flexible size and unique structural features, are widely used in both power and energy storage fields.

[0003] During the manufacturing process of prismatic batteries, the electrode components are typically hot-pressed to facilitate their insertion into a prismatic casing (such as a prismatic aluminum casing). The conventional approach during this hot-pressing process is to hot-press the entire electrode assembly to ensure uniform stress across the entire area. Analysis of the prismatic casing reveals that the areas near the eight edges exhibit stronger resistance to deformation, while the larger surface areas show weaker resistance. During cycling, the SEI film on the negative electrode continuously reconstructs and thickens, causing outward expansion within the electrode assembly, particularly noticeable in the central portion corresponding to the larger surface area of ​​the prismatic casing. Therefore, the central portion of the electrode assembly experiences greater compression than the edges corresponding to the edges of the prismatic casing, making it more susceptible to lithium plating failure during cycling and leading to accelerated battery degradation. Utility Model Content

[0004] The embodiments of this application provide an extrusion structure and an extrusion fixture, which can improve the technical problem that lithium plating easily occurs in the middle part of the electrode assembly.

[0005] In a first aspect, embodiments of this application provide an extrusion structure for extruding an electrode assembly, the electrode assembly including a middle portion and an edge portion surrounding the middle portion, the extrusion structure including a middle extrusion portion and an edge extrusion portion disposed around the edge of the middle extrusion portion, the edge extrusion portion having a first extrusion surface for extruding the edge portion, the middle extrusion portion having a second extrusion surface for extruding the middle portion, the second extrusion surface being configured to form a discontinuity with the first extrusion surface and be farther away from the central axis of the electrode assembly than the first extrusion surface when the extrusion structure extrudes the electrode assembly.

[0006] In one embodiment, the edge extrusion portion is fixedly connected to the middle extrusion portion and together defines a groove, the second extrusion surface is formed as the inner bottom surface of the groove, and the first extrusion surface is located outside the groove and surrounds the opening of the groove.

[0007] In one embodiment, the depth of the groove is 0.005 mm to 0.1 mm.

[0008] In one embodiment, the edge extrusion portion is a rigid portion, the middle extrusion portion is a flexible portion, the rigid portion is connected to the flexible portion, and the flexible portion is used to deform in a direction away from the electrode assembly when the extrusion structure extrudes the electrode assembly.

[0009] In one embodiment, along the thickness direction of the extrusion structure, the intermediate extrusion portion is movably disposed relative to the edge extrusion portion, and the intermediate extrusion portion is used to move toward or away from the electrode assembly when the extrusion structure extrudes the electrode assembly.

[0010] In one embodiment, the edge pressing portion includes a first frame having a first through hole, and the middle pressing portion includes a slider located within the first through hole and slidably connected to the first frame.

[0011] In one embodiment, a groove is formed by a partial recess in the inner wall of the first through hole toward the interior of the first frame. The slider includes a body portion and a boss protruding from the circumferential surface of the body portion. The body portion is located inside the first through hole and is adapted to the first through hole. One end face of the body portion is formed as the second extrusion surface. The boss extends into the groove and slides in cooperation with the groove. In the thickness direction of the first frame, the thickness of the boss is less than the width of the groove, and the distance between the side surface of the boss away from the second extrusion surface and the second extrusion surface is greater than the width of the groove.

[0012] In one embodiment, the ratio of the area of ​​the second extrusion surface to the sum of the areas of the first extrusion surface and the second extrusion surface is 0.1 to 0.4.

[0013] Secondly, embodiments of this application provide an extrusion structure for extruding an electrode assembly, the electrode assembly including a middle portion and an edge portion surrounding the middle portion, the extrusion structure including an edge extrusion portion, the edge extrusion portion being a second frame having a second through hole, the second frame being configured to extrude the edge portion when the extrusion structure extrudes the electrode assembly, and the second through hole corresponding to the middle portion.

[0014] Thirdly, embodiments of this application provide an extrusion fixture, including the extrusion structure described above.

[0015] The beneficial effects of the embodiments of this application are as follows:

[0016] In embodiments of this application, the extrusion structure includes a central extrusion section and an edge extrusion section. The central extrusion section is used to extrude the central region of the electrode assembly, and the edge extrusion section is used to extrude the edge region of the electrode assembly. When the extrusion structure is used to extrude the electrode assembly, during at least a portion of the extrusion process, the extrusion force applied by the central extrusion section to the central region can be less than the extrusion force applied by the edge extrusion section to the edge region. Alternatively, the extrusion structure may only include an edge extrusion section that applies extrusion force to the edge region, thereby making the porosity of the central region of the electrode assembly extruded by the extrusion structure greater than the porosity of the edge region. In this way, when the electrode assembly is applied to a battery cell, the rate at which the central region of the electrode assembly is immersed in the electrolyte is greater than that of the edge region, thereby reducing the risk of lithium plating in the central region. In addition, since the central region of the electrode assembly is more likely to experience volume expansion than the edge region during cycling, extrusion makes the porosity of the central region greater than that of the edge region, which can alleviate the volume expansion of the central region to a certain extent and reduce the risk of lithium plating in the central region. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the front view structure of the electrode assembly provided in an embodiment of this application;

[0019] Figure 2 This is a top view of the electrode assembly provided in an embodiment of this application;

[0020] Figure 3 yes Figure 2 Enlarged view of section A;

[0021] Figure 4 This is a cross-sectional view of the first extrusion structure provided in the embodiments of this application;

[0022] Figure 5 This is a cross-sectional view of the second extrusion structure provided in the embodiments of this application;

[0023] Figure 6 This is a schematic cross-sectional view of the third extrusion structure provided in the embodiments of this application. Figure 1 ;

[0024] Figure 7 This is a schematic cross-sectional view of the third extrusion structure provided in the embodiments of this application. Figure 2 ;

[0025] Figure 8 This is a three-dimensional structural diagram of the fourth extrusion structure provided in the embodiments of this application;

[0026] Figure 9 This is a three-dimensional structural schematic diagram of the first extrusion fixture provided in the embodiments of this application;

[0027] Figure 10 This is a three-dimensional structural diagram of the second type of extrusion fixture provided in the embodiments of this application.

[0028] Figure label:

[0029] 1. Electrode assembly; 101. Middle part; 102. Edge part;

[0030] 10. Extrusion structure;

[0031] 11. Intermediate extrusion section; 110. Second extrusion surface; 111. Flexible section; 112. Plate; 113. Slider; 1131. Boss; 1132. Main body;

[0032] 12. Edge extrusion section; 120. First extrusion surface; 121. Rigid section; 122. First frame; 1221. First through hole; 1222. Slide groove; 124. Second frame; 125. Second through hole;

[0033] 13. Groove; 131. Slot opening;

[0034] 100. Extrusion fixture;

[0035] 20. Substrate. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Furthermore, it should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0038] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0040] The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] In the description of the embodiments of this application, the words "example" or "for example" are used to indicate exemplification, illustration, or description. Any embodiment or design described as "example" or "for example" in the embodiments of this application is not to be construed as being more preferred or having more advantages than another embodiment or design. The use of the words "example" or "for example" is intended to present relative concepts in a clear manner.

[0042] To facilitate understanding of the present application, the spline curves and arrows used in the reference numerals in the accompanying drawings are explained below: spline curves without arrows indicate solid parts, that is, parts with solid structures; spline curves with arrows indicate virtual parts, that is, parts without solid structures.

[0043] Please see Figures 1 to 8 This application provides an extrusion structure 10 for extruding an electrode assembly 1.

[0044] Here, electrode assembly 1, also known as the core package, is the core component constituting the battery cell (also known as a single battery cell). Typically, electrode assembly 1 includes a positive electrode 11, a negative electrode 12, and a separator 13. The separator 13 is located between the positive and negative electrode 11 to separate them, preventing direct contact and short circuits. Electrode assembly 1 can be a stacked structure or a wound structure. The extrusion structure 10 is used to extrude electrode assembly 1, both to shape it for easy insertion into the housing to form a battery cell, and to ensure a tight fit between the separator 13 and the positive and negative electrode 11, shortening the lithium-ion diffusion distance and reducing the internal resistance of electrode assembly 1. Optionally, the extrusion structure 10 is also used to heat the electrode assembly 1, that is, to hot press the electrode assembly 1. Hot pressing can eliminate wrinkles and air in the separator 13, so that the separator 13 is more tightly attached to the positive electrode 11 and the negative electrode 12.

[0045] Typically, please see Figure 1 and Figure 2 Using the dashed line in the figure as a virtual dividing line, the electrode assembly 1 includes an adjacent middle portion 101 and an edge portion 102, wherein the edge portion 102 is disposed around the edge of the middle portion 101. When the electrode assembly 1 is installed in a square housing, the middle portion 101 corresponds to the large surface area of ​​the housing, and the edge portion 102 corresponds to the edge of the housing. As an example, taking the thickness direction of the electrode assembly 1 as the first direction, the orthographic projection of the middle portion 101 is adjacent to the orthographic projection of the edge portion 102 when projected along the first direction, and the ratio of the area of ​​the orthographic projection of the middle portion 101 to the area of ​​the orthographic projection of the electrode assembly 1 is 20% to 80%, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, or 80%. Along the first direction, in the electrode assembly 1, the positive electrode 11, the separator 13, and the negative electrode 12 are stacked.

[0046] Specifically, the extrusion structure 10 includes an intermediate extrusion portion 11 and an edge extrusion portion 12, wherein the edge extrusion portion 12 is disposed around the edge of the intermediate extrusion portion 11.

[0047] When the extrusion structure 10 extrudes the electrode assembly 1, the intermediate extrusion portion 11 corresponds to the intermediate portion 101 of the electrode assembly 1, and the edge extrusion portion 12 corresponds to the edge portion 102 of the electrode assembly 1. Furthermore, when the extrusion structure 10 extrudes the electrode assembly 1, the intermediate extrusion portion 11 applies a first extrusion force F1 to the intermediate portion 101, and the edge extrusion portion 12 applies a second extrusion force F2 to the edge portion 102, wherein F2 ≥ F1, F1 ≥ 0, and F2 > 0. Additionally, during at least a portion of the time period during which the extrusion structure 10 extrudes the electrode assembly 1, F1 < F2.

[0048] Understandably, the edge extrusion portion 12 and the middle extrusion portion 11 can be directly connected together, for example, the edge extrusion portion 12 and the middle extrusion portion 11 can be integrally formed, or they can be indirectly connected together, or they can be independent of each other.

[0049] When the extrusion structure 10 extrudes the electrode assembly 1, the magnitude of the first extrusion force F1 can be fixed or variable, and the magnitude of the second extrusion force F2 can also be fixed or variable. However, regardless of the type, the second extrusion force F2 must be greater than the first extrusion force F1, or the second extrusion force F2 must be equal to the first extrusion force F1, i.e., F2 ≥ F1. Where F2 > 0, this means that when the extrusion structure 10 extrudes the electrode assembly 1, at least the edge extrusion portion 12 applies the second extrusion force F2 to the edge portion 102 of the electrode assembly 1, i.e., the edge extrusion portion 12 always extrudes the electrode assembly 1. F1 ≥ 0, this means that when the extrusion structure 10 extrudes the electrode assembly 1, the intermediate extrusion portion 11 can extrude the middle portion 101 of the electrode assembly 1, or it can not extrude the electrode assembly 1. When the intermediate extrusion portion 11 extrudes the electrode assembly 1, F1 > 0; when the intermediate extrusion portion 11 does not extrude the electrode assembly 1, F1 = 0. Furthermore, F1 < F2 during at least a portion of the time period of the extrusion structure 10 extruding electrode assembly 1, which can be either during the entire time period (i.e. the entire process) of the extrusion structure 10 extruding electrode assembly 1, or during a portion of the time period of the extrusion structure 10 extruding electrode assembly 1.

[0050] As an example, throughout the entire process of the extrusion structure 10 extruding the electrode assembly 1, F2 > F1 > 0, that is, the extrusion force of the edge extrusion part 12 on the edge part 102 of the electrode assembly 1 is always greater than the extrusion force of the middle extrusion part 11 on the middle part 101 of the electrode assembly 1.

[0051] As an example, during the entire process of the extrusion structure 10 extruding the electrode assembly 1, F2 > F1 = 0, that is, only the edge extrusion part 12 extrudes the edge part 102 of the electrode assembly 1, while the middle extrusion part 11 never extrudes the electrode assembly 1.

[0052] The extrusion structure 10 provided in this application embodiment includes a middle extrusion portion 11 and an edge extrusion portion 12, wherein the middle extrusion portion 11 is used to extrude the middle region 101 of the electrode assembly 1, and the edge extrusion portion 12 is used to extrude the edge portion 102 of the electrode assembly 1. When the extrusion structure 10 is used to extrude the electrode assembly 1, during at least a portion of the extrusion process, the intermediate extrusion section 11 does not apply extrusion force to the intermediate section 101 or the extrusion force is less than the extrusion force of the edge extrusion section 12 on the edge section 102. This results in the porosity of the intermediate section 101 of the electrode assembly 1 after extrusion by the extrusion structure 10 being greater than the porosity of the edge section 102. Thus, when the electrode assembly 1 is applied to the battery cell, the rate at which the intermediate section 101 of the electrode assembly 1 is immersed in the electrolyte is greater than that of the edge section 102, thereby reducing the risk of lithium plating in the intermediate section 101. In addition, since the intermediate section 101 is at greater risk of volume expansion than the edge section 102 during the cycling process, extrusion makes the porosity of the intermediate section 101 greater than that of the edge section 102, which can alleviate the volume expansion of the intermediate section 101 to a certain extent and reduce the risk of lithium plating in the intermediate section 101.

[0053] In some implementations, please refer to Figures 4 to 8 The extrusion structure 10 includes a central extrusion portion 11 and an edge extrusion portion 12, with the edge extrusion portion 12 surrounding the edge of the central extrusion portion 11. A first extrusion surface 120 is formed on the edge extrusion portion 12 for extruding the edge portion 102; a second extrusion surface 110 is formed on the central extrusion portion 11 for extruding the central portion 101. Furthermore, when the extrusion structure 10 extrudes the electrode assembly 1, the second extrusion surface 110 is configured to form a discontinuity with the first extrusion surface 120, and the second extrusion surface 110 is located further away from the central axis of the electrode assembly 1 than the first extrusion surface 120.

[0054] Understandably, since the edge extrusion portion 12 has a first extrusion surface 120 and the middle extrusion portion 11 has a second extrusion surface 110, both the edge extrusion portion 12 and the middle extrusion portion 11 are solid structures.

[0055] It should be noted that the first extrusion surface 120 can be independently planar or curved, and the second extrusion surface 110 can be independently planar or curved. Optionally, the first extrusion surface 120 is adapted to the outer surface of the edge portion 102 of the electrode assembly 1 to better extrude the edge portion 102; the first extrusion surface 120 is adapted to the outer surface of the middle portion 101 of the electrode assembly 1 to better extrude the middle portion 101. As an example, the electrode assembly 1 has a wound structure, the outer surface of the middle portion 101 is planar, the second extrusion surface 110 is also planar, the outer surface of the edge portion 102 is curved, and the first extrusion surface 120 is also curved; or the electrode assembly 1 has a wound structure, the outer surfaces of the middle portion 101 and the edge portion 102 are both planar, and the first extrusion surface 120 and the second extrusion surface 110 are both planar.

[0056] During at least a portion of the time period of the extrusion structure 10 extruding electrode assembly 1, the second extrusion surface 110 and the first extrusion surface 120 form a discontinuity. This discontinuity means that the second extrusion surface 110 and the first extrusion surface 120 are not coplanar. This discontinuity can be maintained throughout the entire time period (i.e., the entire process) of the extrusion structure 10 extruding electrode assembly 1, or it can exist only for a portion of the time period during the extrusion process.

[0057] Furthermore, when the second extrusion surface 110 and the first extrusion surface 120 are not coplanar, the second extrusion surface 110 is farther away from the central axis of the electrode assembly 1 compared to the first extrusion surface 120. In other words, the distance between the second extrusion surface 110 and the central axis of the electrode assembly 1 is greater than the distance between the first extrusion surface 120 and the central axis of the electrode assembly 1. When the distance between the second extrusion surface 110 and the central axis of the electrode assembly 1 increases, the force between the intermediate extrusion part 11 and the electrode assembly 1 (i.e., the first extrusion force F1) decreases, and the following different situations may occur: the intermediate extrusion part 11 continues to extrude force on the intermediate part 101 of the electrode assembly 1, but the first extrusion force F1 decreases; or the second extrusion surface 110 separates from the electrode assembly 1, and the first extrusion force F1 becomes zero. Here, the central axis of the electrode assembly 1 is perpendicular to the first direction.

[0058] During the extrusion process of the extrusion structure 10 extruding the electrode assembly 1, at least one of the second extrusion surface 110 and the first extrusion surface 120 remains in contact with the electrode assembly 1. It can be understood that during the extrusion process of the extrusion structure 10 extruding the electrode assembly 1, the first extrusion surface 120 always remains in contact with the edge portion 102 of the electrode assembly 1, while the second extrusion surface 11 may come into contact with or separate from the middle portion 101 of the electrode assembly 1. In this case, the first extrusion force F1 exerted by the middle extrusion portion 11 on the middle portion 101 of the electrode assembly 1 decreases or disappears.

[0059] To more clearly illustrate the compression of the electrode assembly 1 by the first extrusion surface 120 and the second extrusion surface 110 during the extrusion process of the extrusion structure 10, the following example is provided. The extrusion process of the electrode assembly 1 by the extrusion structure 10 is divided into three time periods, namely, the first time period t1, the second time period t2, and the third time period t3, from beginning to end. During the period from t1 to t3, the force applied by the first extrusion surface 120 to the edge portion 102 of the electrode assembly 1 is the second extrusion force F2, which remains constant and its magnitude is always F20. During the period from t1 to t3, the force applied by the second extrusion surface 110 to the middle portion 101 of the electrode assembly 1 is the first extrusion force F1. During the period from t1 to t3, the magnitude of F1 is F11, during the period from t2 to t3, the magnitude of F1 is F12, and during the period from t3 to t3, the magnitude of F1 is F13.

[0060] As an example, during the process from t1 to t3, the step difference between the second extrusion surface 110 and the first extrusion surface 120 remains at D1, then 0 < F11 = F12 = F13 < F20. That is to say, the extrusion time of the second extrusion surface 110 on the middle part 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge part 102 of the electrode assembly 1, but the extrusion force is smaller.

[0061] As an example, during processes t1 and t2, the second extrusion surface 110 is coplanar with the first extrusion surface 120. However, during process t3, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is D3, so 0 < F13 < F12 = F11 = F20. That is, the extrusion time of the second extrusion surface 110 on the middle part 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge part 102 of the electrode assembly 1, but the extrusion force decreases in the third time period t3.

[0062] As an example, during processes t1 and t3, the second extrusion surface 110 is coplanar with the first extrusion surface 120. However, during process t2, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is D2, so 0 < F12 < F13 = F11 = F20. That is, the extrusion time of the second extrusion surface 110 on the middle part 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge part 102 of the electrode assembly 1, but the extrusion force decreases in the second time period t2.

[0063] As an example, during processes t2 and t3, the second extrusion surface 110 is coplanar with the first extrusion surface 120, while during process t1, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is D1, then 0 < F11 < F12 = F13 = F20. That is to say, the extrusion time of the second extrusion surface 110 on the middle part 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge part 102 of the electrode assembly 1, but the extrusion force decreases in the first time period t1.

[0064] As an example, during process t1, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is D1; ​​during process t2, the step difference is D2; and during process t3, the step difference is D3. Since D1 < D2 < D3, then 0 < F13 < F12 < F11 < F20. That is, the extrusion time of the second extrusion surface 110 on the middle portion 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge portion 102 of the electrode assembly 1, but the extrusion pressure decreases sequentially in each time period.

[0065] As an example, during processes t1 and t2, the second extrusion surface 110 is coplanar with the first extrusion surface 120. However, during process t3, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is D4, and the second extrusion surface 110 separates from the electrode assembly 1. Therefore, 0 = F13 < F12 = F11 = F20. In other words, the extrusion time of the second extrusion surface 110 on the middle portion 101 of the electrode assembly 1 is the same as the extrusion time of the first extrusion surface 120 on the edge portion 102 of the electrode assembly 1, but the extrusion force decreases to zero in the third time period t3. Alternatively, the extrusion force of the second extrusion surface 110 on the middle portion 101 of the electrode assembly 1 is the same as the extrusion force of the first extrusion surface 120 on the edge portion 102 of the electrode assembly 1, but the extrusion time is shorter.

[0066] In summary, the extrusion structure 10 provided in this application embodiment includes a middle extrusion portion 11 and an edge extrusion portion 12. The edge extrusion portion 12 has a first extrusion surface 120 for extruding the edge portion 102 of the electrode assembly 1, and the middle extrusion portion 11 has a second extrusion surface 110 for extruding the middle portion 101 of the electrode assembly 1. When the extrusion structure 10 extrudes the electrode assembly 1, a discontinuity is formed between the second extrusion surface 110 and the first extrusion surface 120, and the second extrusion surface 110 is farther away from the central axis of the electrode assembly 1 than the first extrusion surface 120. Thus, during the process of the extrusion structure 10 extruding the electrode assembly 1, for at least a part of the time period, the extrusion force of the middle extrusion portion 11 on the middle portion 101 (i.e., the first extrusion force F1) is less than the extrusion force of the edge extrusion portion 12 on the edge portion 102 (i.e., the second extrusion force F2), thereby making the porosity of the middle portion 101 of the electrode assembly 1 after being extruded by the extrusion structure 10 greater than the porosity of the edge portion 102. Thus, when electrode assembly 1 is applied to the battery cell, the rate at which the middle portion 101 of electrode assembly 1 is immersed in the electrolyte is greater than that of the edge portion 102 of electrode assembly 1, thereby reducing the risk of lithium plating in the middle portion 101. In addition, since the middle portion 101 is at greater risk of volume expansion than the edge portion 102 during the cycling process, the porosity of the middle portion 101 is made greater than that of the edge portion 102 by compression, which can alleviate the volume expansion of the middle portion 101 to a certain extent and reduce the risk of lithium plating in the middle portion 101.

[0067] In some implementations, please refer to Figure 4 The edge extrusion portion 12 is fixedly connected to the middle extrusion portion 11 and together defines the groove 13. The second extrusion surface 110 is formed as the inner bottom surface of the groove 13, and the first extrusion surface 120 is located outside the groove 13 and surrounds the opening 131 of the groove 13. In this case, the step difference between the second extrusion surface 110 and the first extrusion surface 120 is a fixed value and is equal to the depth of the groove 13.

[0068] As an example, the edge extrusion part 12 is a first frame 122, which has a first through hole 1221. The middle extrusion part 11 is a plate 112, which is located on one side of the first frame 122 and blocks one end opening of the first through hole 1221, thereby forming a groove 13. The other opening of the first through hole 1221 is formed as the slot 131 of the groove 13. The plate 112 is fixedly connected to the first frame 122 to form an extrusion structure 10.

[0069] When using the extrusion structure 10 to extrude the electrode assembly 1, the second extrusion force F2 can always be kept greater than the first extrusion force F1, thereby making the porosity of the middle part 101 greater than the porosity of the edge part 102.

[0070] In some embodiments, the depth of the groove 13 is 0.005 mm to 0.1 mm. The depth of the groove 13 represents the step difference between the second extrusion surface 110 and the first extrusion surface 120. The greater the depth of the groove 13, the greater the porosity difference between the edge portion 102 and the middle portion 101. However, if the depth of the groove 13 is too large, the second extrusion surface 110 will not be able to extrude the middle portion 101 of the electrode assembly 1, resulting in poor shaping effect of the electrode assembly 1, affecting the assembly of the electrode assembly 1 with the housing and the internal resistance of the electrode assembly 1. As an example, the depth of the groove 13 is any one of 0.005 mm, 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, and 0.1 mm, or a range between any two.

[0071] In some implementations, please refer to Figure 5 The edge extrusion portion 12 is a rigid portion 121, and the middle extrusion portion 11 is a flexible portion 111. The rigid portion 121 is connected to the flexible portion 111, and the flexible portion 111 is used to deform in a direction away from the electrode assembly 1 when the extrusion structure 10 extrudes the electrode assembly 1. In this case, since the flexible portion 111 is a flexible portion 111, the characteristic that the flexible portion 111 will undergo elastic deformation when subjected to force is utilized to form a step difference between the second extrusion surface 110 and the first extrusion surface 120, thereby making the first extrusion force F1 of the middle extrusion portion 11 on the middle portion 101 less than the second extrusion force F2 of the edge extrusion portion 12 on the edge portion 102.

[0072] As an example, the flexible part 111 is made of a flexible resin. The flexible resin includes, but is not limited to, at least one of silicone and rubber. The rigid part 121 is a metal component, such as a stainless steel sheet.

[0073] As an example, the flexible part 111 is a capsule filled with a fluid medium. The deformation of the capsule can be adjusted by regulating the amount of fluid medium inside the capsule. Furthermore, the timing of the fluid medium filling the capsule can be adjusted to improve the formation time of the step difference.

[0074] In some implementations, please refer to Figure 6 and Figure 7Along the thickness direction of the extrusion structure 10, the intermediate extrusion section 11 is movably disposed relative to the edge extrusion section 12. The intermediate extrusion section 11 is used to move towards or away from the electrode assembly 1 when the extrusion structure 10 extrudes the electrode assembly 1. Since the intermediate extrusion section 11 can move relative to the edge extrusion section 12 along the thickness direction of the extrusion structure 10, the distance between the second extrusion surface 110 on the intermediate extrusion section 11 and the first extrusion surface 120 on the edge extrusion section 12 can be adjusted when the extrusion structure 10 extrudes the electrode assembly 1. This allows a step difference to be formed between the second extrusion surface 110 and the first extrusion surface 120 during at least a portion of the time period when the extrusion structure 10 extrudes the electrode assembly 1. As a result, the first extrusion force F1 of the intermediate extrusion section 11 on the intermediate part 101 is less than the second extrusion force F2 of the edge extrusion section 12 on the edge part 102.

[0075] As an example, the process of the extrusion structure 10 extruding the electrode assembly 1 is divided into three time periods, which are divided into the first time period t1, the second time period t2 and the third time period t3 from the beginning to the end. During the first time period t1 and the second time period t2, the second extrusion surface 110 and the first extrusion surface 120 are kept coplanar. Then, the intermediate extrusion part 11 is moved away from the electrode assembly 1, so that a step difference is formed between the second extrusion surface 110 and the first extrusion surface 120 during the third time period t3.

[0076] As an example, the process of the extrusion structure 10 extruding the electrode assembly 1 is divided into three time periods, which are divided into the first time period t1, the second time period t2 and the third time period t3 from the beginning to the end. During the first time period t1 and the second time period t2, a step difference is maintained between the second extrusion surface 110 and the first extrusion surface 120. Then, the intermediate extrusion part 11 is moved towards the electrode assembly 1 so that the second extrusion surface 110 and the first extrusion surface 120 are coplanar during the third time period t3.

[0077] As an example, the process of the extrusion structure 10 extruding the electrode assembly 1 is divided into three time periods, which are divided into the first time period t1, the second time period t2, and the third time period t3 from the beginning to the end. During the first time period t1, a step difference is maintained between the second extrusion surface 110 and the first extrusion surface 120. Then, the middle extrusion part 11 is moved towards the electrode assembly 1 so that the second extrusion surface 110 and the first extrusion surface 120 are coplanar during the second time period t2. Then, the middle extrusion part 11 is moved away from the electrode assembly 1 so that a step difference is formed between the second extrusion surface 110 and the first extrusion surface 120 during the third time period t3.

[0078] In some embodiments, the extrusion structure 10 further includes a drive member (not shown) connected to the intermediate extrusion section 11 and used to drive the intermediate extrusion section 11 to move. As an example, the drive member is a push rod motor.

[0079] In some implementations, please refer to Figure 6 and Figure 7 The edge extrusion part 12 includes a first frame 122 having a first through hole 1221, and the middle extrusion part 11 includes a slider 113, which is located inside the through hole 1221 and slidably connected to the first frame 122. The distance between the second extrusion surface 110 and the first extrusion surface 120 can be adjusted by sliding the first frame 122 and the slider 113.

[0080] In some implementations, please refer to Figure 6 and Figure 7 A groove 1222 is formed by a partial recess in the inner wall of the first through hole 1221 into the interior of the first frame 122. The slider 113 includes a boss 1131 and a body portion 1132. The boss 1131 protrudes from the circumferential surface of the body portion 1132. The body portion 1132 is located within and fits into the first through hole 1221, and one end face of the body portion 1132 is formed as a second pressing surface 110. The boss 1131 extends into the groove 1222 and slides within it. Please continue reading... Figure 7 When the boss 1131 slides to one end of the groove 1222, as shown in the figure, the second extrusion surface 110 is flush with the first extrusion surface 120, i.e., they are coplanar; please continue reading. Figure 6 When the boss 1131 slides to the other end of the groove 1222, as shown at the bottom end, there is a step difference between the second extrusion surface 110 and the first extrusion surface 120. Optionally, the length of the groove 1222 is less than the thickness of the first frame 122.

[0081] In some implementations, please refer to Figure 6 and Figure 7 In the thickness direction of the first frame 122, the thickness of the boss 1131 is less than the width of the groove 1222, and the distance between the side surface of the boss 1131 facing away from the second pressing surface 110 and the second pressing surface 110 is greater than the width of the groove 1222. Thus, when the side surface of the boss 1131 facing away from the second pressing surface 110 abuts against the side wall of the groove 1222, the body portion 1132 can seal the opening of the groove 1222, reducing the risk of foreign objects entering the groove 1222.

[0082] In some implementations, please refer to Figure 6 and Figure 7 The distance between the side surface of the boss 1131 near the second extrusion surface 110 and the end face of the body portion 1132 opposite to the second extrusion surface 110 is greater than the width of the groove 1222. Thus, when the side surface of the boss 1131 near the second extrusion surface 110 abuts against the side wall of the groove 1222, the body portion 1132 can seal the opening of the groove 1222, reducing the risk of foreign objects entering the groove 1222.

[0083] In some embodiments, the ratio of the area of ​​the second extrusion surface 110 to the sum of the areas of the first extrusion surface 120 and the second extrusion surface 110 is 0.1 to 0.4. As an example, the ratio of the area of ​​the second extrusion surface 110 to the sum of the areas of the first extrusion surface 120 and the second extrusion surface 110 is 0.1, 0.2, 0.3 or 0.4.

[0084] In some implementations, please refer to Figure 8 The extrusion structure 10 includes only the edge extrusion portion 12, eliminating the middle extrusion portion 11. Specifically, the edge extrusion portion 12 is a second frame 124 with a second through hole 125. The second frame 124 is configured to extrude the edge portion 102 when the extrusion structure 10 extrudes the electrode assembly 1. The second through hole 125 corresponds to the middle portion 101, i.e., the second through hole 125 is used to avoid the middle portion 101. In this case, when the extrusion structure 10 extrudes the electrode assembly 1, only the second frame 124 extrudes the edge portion 102 of the electrode assembly 1, while the extrusion force on the middle portion 101 of the electrode assembly 1 is zero, thereby making the porosity of the middle portion 101 greater than that of the edge portion 102. Thus, when electrode assembly 1 is applied to the battery cell, the rate at which the middle portion 101 of electrode assembly 1 is immersed in the electrolyte is greater than that of the edge portion 102 of electrode assembly 1, thereby reducing the risk of lithium plating in the middle portion 101. In addition, since the middle portion 101 is at greater risk of volume expansion than the edge portion 102 during the cycling process, the porosity of the middle portion 101 is made greater than that of the edge portion 102 by compression, which can alleviate the volume expansion of the middle portion 101 to a certain extent and reduce the risk of lithium plating in the middle portion 101.

[0085] Additionally, please see Figures 9 to 10 This application embodiment also provides an extrusion fixture 100, including any of the extrusion structures 10 described above.

[0086] In some implementations, please refer to Figure 9 The extrusion fixture 100 has two extrusion structures 10, which are arranged facing each other. When using the extrusion fixture 100 to extrude the electrode assembly 1, the electrode assembly 1 is located between the two opposing extrusion structures 10.

[0087] In some implementations, please refer to Figure 10 The extrusion fixture 100 includes one extrusion structure 10. The extrusion fixture 100 also includes a substrate 20, which is optionally a flat plate. The extrusion structure 10 and the substrate 20 are arranged face-to-face. When using the extrusion fixture 100 to extrude the electrode assembly 1, the electrode assembly 1 is located between the extrusion structure 10 and the substrate 20.

[0088] In some embodiments, the extrusion fixture 100 is a hot press fixture, and during the extrusion of the electrode assembly 1, at least one of the extrusion structure 10 and the substrate 20 can also heat the electrode assembly 1.

[0089] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An extrusion structure for extruding an electrode assembly, the electrode assembly comprising a central portion and an edge portion surrounding the central portion, characterized in that, The extrusion structure includes a central extrusion section and an edge extrusion section disposed around the edge of the central extrusion section. A first extrusion surface for extruding the edge section is formed on the edge extrusion section, and a second extrusion surface for extruding the central section is formed on the central extrusion section. The second extrusion surface is configured to form a discontinuity with the first extrusion surface and be farther away from the central axis of the electrode assembly than the first extrusion surface when the extrusion structure extrudes the electrode assembly.

2. The extrusion structure according to claim 1, characterized in that, The edge extrusion part is fixedly connected to the middle extrusion part and together defines the groove. The second extrusion surface is formed as the inner bottom surface of the groove, and the first extrusion surface is located outside the groove and surrounds the opening of the groove.

3. The extrusion structure according to claim 2, characterized in that, The depth of the groove is 0.005mm to 0.1mm.

4. The extrusion structure according to claim 1, characterized in that, The edge extrusion part is a rigid part, the middle extrusion part is a flexible part, the rigid part is connected to the flexible part, and the flexible part is used to deform in a direction away from the electrode assembly when the extrusion structure extrudes the electrode assembly.

5. The extrusion structure according to claim 1, characterized in that, Along the thickness direction of the extrusion structure, the intermediate extrusion portion is movably disposed relative to the edge extrusion portion, and the intermediate extrusion portion is used to move toward or away from the electrode assembly when the extrusion structure extrudes the electrode assembly.

6. The extrusion structure according to claim 5, characterized in that, The edge extrusion part includes a first frame having a first through hole, and the middle extrusion part includes a slider located in the first through hole and slidably connected to the first frame.

7. The extrusion structure according to claim 6, characterized in that, A groove is formed by a partial recess in the inner wall of the first through hole into the interior of the first frame. The slider includes a body and a boss protruding from the circumferential surface of the body. The body is located inside the first through hole and is adapted to the first through hole. One end face of the body is formed as the second extrusion surface. The boss extends into the groove and slides in cooperation with the groove. In the thickness direction of the first frame, the thickness of the boss is less than the width of the groove, and the distance between the side surface of the boss away from the second extrusion surface and the second extrusion surface is greater than the width of the groove.

8. The extrusion structure according to any one of claims 1 to 7, characterized in that, The ratio of the area of ​​the second extrusion surface to the sum of the areas of the first extrusion surface and the second extrusion surface is 0.1 to 0.

4.

9. An extrusion structure for extruding an electrode assembly, the electrode assembly comprising a central portion and an edge portion surrounding the central portion, characterized in that, The extrusion structure includes an edge extrusion portion, which is a second frame having a second through hole. The second frame is configured to extrude the edge portion when the extrusion structure extrudes the electrode assembly, and the second through hole corresponds to the middle portion.

10. An extrusion fixture, characterized in that, Includes the extrusion structure according to any one of claims 1 to 9.

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