Electrochemical device, preparation method and electric equipment

Abstract

The embodiment of the invention relates to the technical field of batteries, and discloses an electrochemical device, a preparation method and electric equipment, the electrochemical device comprises a shell, an electrode assembly and a first tab, the shell is provided with an accommodating cavity, the electrode assembly is arranged in the accommodating cavity, and one end of the first tab is connected with the electrode assembly. The shell comprises a bottom shell and a top cover which are oppositely arranged, the electrode assembly comprises an electrode main body and an abutting part, the abutting part is arranged at one end, facing the bottom shell, of the electrode main body, the electrode main body is of a winding structure, the electrode main body is provided with a first center hole, and the aperture R of the first center hole is larger than or equal to 0.6 mm and smaller than or equal to 2mm. The first tab is provided with a first connecting part, the first connecting part is located between the bottom shell and the abutting part in the direction from the top cover to the bottom shell, the abutting part abuts against the first connecting part, the first connecting part abuts against the bottom shell, and the first connecting part is welded to the bottom shell. In this way, the energy density of the electrochemical device can be improved.

Description

Technical Field

[0001] Embodiments of the present application relate to the technical field of batteries, and in particular, to an electrochemical device, a preparation method, and an electrical device using the same. Background Art

[0002] With the rapid development of modern technology, the demand for miniaturized and high-performance energy storage devices in the fields of portable electronic devices, smart wearable devices, medical devices, etc. is increasing day by day. As an efficient and compact energy storage device, button batteries have been widely used in many fields due to their small size, high energy density, low self-discharge rate, etc. In the continuous development process of button batteries, the requirement for their energy density is also getting higher and higher. Summary of the Invention

[0003] An object of embodiments of the present application is to provide an electrochemical device, a preparation method, and an electrical device using the same to improve the energy density of the electrochemical device.

[0004] In a first aspect, embodiments of the present application provide an electrochemical device. The electrochemical device includes a housing, an electrode assembly, and a first tab. The housing is provided with a receiving cavity, the electrode assembly is disposed in the receiving cavity, and one end of the first tab is connected to the electrode assembly. The housing includes a bottom case and a top cover disposed opposite to each other. The electrode assembly includes an electrode body and an abutting portion. The abutting portion is disposed at one end of the electrode body facing the bottom case. The electrode body is a wound structure, and the electrode body has a first central hole. The aperture R of the first central hole satisfies: 0.6 mm ≤ R ≤ 2 mm. The first tab has a first connecting portion. Along the direction from the top cover to the bottom case, the first connecting portion is located between the bottom case and the abutting portion. The abutting portion abuts against the first connecting portion, the first connecting portion abuts against the bottom case, and the first connecting portion and the bottom case are welded.

[0005] By providing the abutting portion, the abutting portion and the bottom case jointly abut against the first connecting portion located between the abutting portion and the bottom case, which is beneficial to improving the fitting effect between the surface of the first connecting portion for welding with the bottom case and the bottom case. The abutting portion replaces the metal ejector rod to press the first connecting portion against the bottom case. Compared with the button battery in the related art, the aperture R of the first central hole of the electrode assembly is not limited by the size of the metal ejector rod. After reducing the aperture R of the first central hole of the electrode assembly, it is beneficial to improve the energy density of the electrochemical device, and the step of the ejector rod pressing the first connecting portion is omitted in the processing process, which is beneficial to reducing the production cost and improving the production efficiency. Selecting 0.6 mm ≤ R ≤ 2 mm is beneficial to reducing the problem of the winding needle breaking during the manufacturing process, reducing the production cost, and reducing the space occupied by the central hole, thereby improving the energy density of the electrochemical device.

[0006] In one or more of the above optional embodiments, the aperture R of the first central hole satisfies: 1 mm ≤ R ≤ 1.5 mm.

[0007] Select 1 mm ≤ R ≤ 1.5 mm to further reduce the occurrence of the problem of the winding needle breaking during the manufacturing process, reduce the production cost, and increase the energy density of the electrochemical device.

[0008] In one or more of the above optional embodiments, the electrode assembly includes a first electrode tab, a separator, and a second electrode tab. The separator includes a connected empty winding portion and a stacked portion. The first electrode tab, the stacked portion, and the second electrode tab are stacked and wound to form an electrode body. The empty winding portion is wound by the separator to form a first central hole. One end of the first electrode ear is connected to the first electrode tab.

[0009] In one or more of the above optional embodiments, the abutting portion is formed by the separator of the electrode body extending towards the bottom case.

[0010] The abutting portion is formed by the separator of the electrode body extending towards the bottom case, which is beneficial to reducing additional components and manufacturing processes and lowering the manufacturing cost.

[0011] In one or more of the above optional embodiments, along the direction from the top cover to the bottom case, the abutting portion protrudes from the first electrode tab and the second electrode tab.

[0012] In one or more of the above optional embodiments, the abutting portion is wound to form a second central hole. Along the radial direction of the second central hole, the sum of the thicknesses D of the winding layers of the abutting portion that completely surround the second central hole once satisfies: 30 μm ≤ D ≤ 180 μm.

[0013] Select 30 μm ≤ D ≤ 180 μm, which is beneficial to reducing the problem of the support strength of the abutting portion decreasing due to too small D, thereby reducing the welding defect between the first connecting portion and the bottom case, and is beneficial to reducing the increase in the volume of the abutting portion due to too large D and increasing the energy density of the electrochemical device. Preferably, 80 μm ≤ D ≤ 150 μm, which further reduces the welding defect between the first connecting portion and the bottom case and increases the energy density of the electrochemical device.

[0014] In one or more of the above optional embodiments, along the radial direction of the first central hole, the number of layers N of the separator in the empty winding portion satisfies: N = 14 - 20.

[0015] In one or more of the above optional embodiments, the electrode body includes a first ironing portion. The first ironing portion is provided at one end of the stacked portion facing the bottom case. Along the direction from the top cover to the bottom case, the first ironing portion protrudes from the first electrode tab and the second electrode tab. The first ironing portion is arranged to surround the abutting portion. Along the direction from the top cover to the bottom case, the abutting portion protrudes from the first ironing portion.

[0016] In one or more of the above optional embodiments, along the direction from the top cover to the bottom case, the inner peripheral edge of the projection area of the portion of the abutting portion abutting against the first connecting portion on the bottom case is the first boundary, and the outer peripheral edge of the projection area of the portion of the abutting portion abutting against the first connecting portion on the bottom case is the second boundary. The welding mark formed by welding the first connecting portion to the bottom case is located within the second boundary.

[0017] The periphery of the area within the second boundary is pressed against the bottom case by the abutting portion along the direction from the top cover to the bottom case. The area within the second boundary of the bottom case has a good fitting effect with the first connecting portion. The welding mark formed by welding the first connecting portion to the bottom case is located within the second boundary, which is beneficial to improving the welding effect.

[0018] In one or more of the above optional embodiments, the welding mark formed by welding the abutting portion to the bottom case fills the area between the first boundary and the second boundary.

[0019] Since, along the direction from the top cover to the bottom case, the area between the first boundary and the second boundary is abutted by the abutting portion and has a good fitting effect with the first connecting portion, the welding mark fills the area between the first boundary and the second boundary, which is beneficial to improving the welding effect of welding the first connecting portion to the bottom case.

[0020] In one or more of the above optional embodiments, the electrochemical device includes a second tab. One end of the second tab is connected to the second electrode plate, and the other end of the second tab is connected to the top cover.

[0021] In one or more of the above optional embodiments, the housing further includes a side wall. The side wall is disposed on the bottom case, the top cover covers one end of the side wall away from the bottom case, and the top cover and the side wall are insulated and connected.

[0022] In a second aspect, there is provided an electrical device including the above-mentioned electrochemical device.

[0023] In a third aspect, there is provided a method for manufacturing an electrochemical device, including:

[0024] Providing a housing, an initial electrode assembly, and a first tab. The housing includes a bottom case, the initial electrode assembly includes an electrode body and a protruding portion protruding from the electrode body, and the first tab has a first connecting portion;

[0025] Stacking the first connecting portion and the initial electrode assembly on top of the bottom case in sequence, so that the protruding portion abuts against the first connecting portion, the first connecting portion abuts against the bottom case, the protruding portion deforms to form an abutting portion, and the initial electrode assembly forms an electrode assembly;

[0026] Welding from the outside of the bottom case so that the first connecting portion is welded to the bottom case.

[0027] In one or more of the above alternative embodiments, welding is performed from the outside of the bottom case such that the first connecting portion is welded to the bottom case, including: laser welding the first connecting portion to the bottom case on the side of the bottom case facing away from the first connecting portion.

[0028] Fourthly, a method for preparing an initial electrode assembly is provided, including:

[0029] Providing a first pole piece coil stock, a separator coil stock, and a second pole piece coil stock;

[0030] Stacking and winding the first pole piece coil stock, the separator coil stock, and the second pole piece coil stock to form a wound body. Among them, in the wound body, the first pole piece coil stock forms a first pole piece after winding, and the second pole piece coil stock forms a second pole piece after winding. Along the direction perpendicular to the winding direction of the wound body, the separator coil stock includes opposite first and second ends, and a main body portion connecting between the first and second ends. Along the direction from the second end to the first end, the first end protrudes from the first and second pole pieces. Along the direction from the first end to the second end, the second end protrudes from the first and second pole pieces;

[0031] Along the direction from the first end to the second end, the portion of the first end except for the central region is ironed flat by a heat ironing process to obtain a first ironed portion, and further an protruding portion protruding from the first ironed portion along the direction from the second end to the first end is obtained. Description of the Drawings

[0032] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplary illustrations are not intended to limit the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements.

[0033] Figure 1 A schematic diagram of an electrochemical device provided by an embodiment of the present application;

[0034] Figure 2 An exploded view of an electrochemical device provided by an embodiment of the present application;

[0035] Figure 3 A schematic diagram of an electrode assembly of an electrochemical device provided by an embodiment of the present application;

[0036] Figure 4 is Figure 1 A schematic cross-sectional view taken along line A-A in

[0037] Figure 5 is Figure 4 An enlarged view at B in

[0038] Figure 6 A schematic cross-sectional view of the abutting portion of an electrochemical device provided by an embodiment of the present application along the direction perpendicular to the top cover and towards the bottom case;

[0039] Figure 7 For Figure 6 An enlarged view of location C in

[0040] Figure 8 Schematic diagram of the first boundary and the second boundary of the projection of the abutting portion of an electrochemical device provided by an embodiment of the present application on the bottom case in the direction from the top cover to the bottom case

[0041] Figure 9 Schematic diagram of the stacking between the first electrode sheet coil, the separator coil and the second electrode sheet coil in a method for preparing an initial electrode assembly provided by an embodiment of the present application

[0042] Figure 10 Schematic diagram of the winding body when viewed along a direction perpendicular to direction X' in a method for preparing an initial electrode assembly provided by an embodiment of the present application

[0043] Figure 11 Another schematic diagram of the winding body when viewed along a direction perpendicular to direction X' in a method for preparing an initial electrode assembly provided by an embodiment of the present application

[0044] Explanation of reference numerals:

[0045] 1000, Electrochemical device;

[0046] 1, Housing; 1a, Receiving cavity; 11, Bottom case; 111, First flat portion; 12, Top cover; 121, Terminal post; 13, Side wall;

[0047] 2, Electrode assembly; 21, Electrode body; 21a, First central hole; 211, First electrode sheet; 212, Separator; 2121, Laminated portion; 2121a, First laminated portion; 2121b, Second laminated portion; 2123, First ironed portion; 2124, Second ironed portion; 2125, Third ironed portion; 2122, Empty winding portion; 2122a, First empty winding portion; 2122b, Second empty winding portion; 213, Second electrode sheet; 22, Abutting portion; 221, First abutting portion; 222, Second abutting portion; 22a, Second central hole; 223, Winding layer; b, Dashed line; 223a, Starting end; 223b, Ending end; d, Thickness of the winding layer; 22b, First boundary; 22c, Second boundary;

[0048] 3, First tab; 31, First connecting portion; 311, Second flat portion; 312, Third flat portion; 32, Second connecting portion;

[0049] 4, Second tab;

[0050] 22′, protrusion; a, diaphragm coil; a11, the first end of the first layer of diaphragm coil; a12, the first end of the second layer of diaphragm coil; A, winding structure; a1, the first end; a2, the second end; a3, the main body part; p1, the first pole piece coil; p2, the second pole piece coil;

[0051] X, the direction from the top cover to the bottom case; X′, the direction perpendicular to the winding direction of the winding body; Detailed implementation manners

[0052] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some but not all of the embodiments of this application.

[0053] In this application, referring to "embodiment" means that the specific features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0054] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary and secondary relationship of the indicated technical features.

[0055] It should be noted that when an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element. When an element is considered to be "disposed on" another element, it may be directly disposed on the other element or there may be an intermediate element.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments, and are not intended to limit this application.

[0057] In the related art, for a button battery used in a Bluetooth headset, the electrode assembly is a winding structure, the electrode assembly has a central hole, and the negative electrode tab of the button battery extends to the bottom of the housing and is welded to the bottom case of the housing. To improve the welding effect, it is necessary to ensure that the negative electrode tab fits well with the bottom case, that is, the negative electrode tab needs to be pressed against the bottom case by pressure to ensure a good welding state. To meet the above welding requirements, during the manufacturing process, after the negative electrode tab and the electrode assembly are sequentially stacked on the bottom case, a metal ejector rod is used to pass through the central hole of the electrode assembly and then press against the negative electrode tab for welding.

[0058] The inventors of the present application have found through research that in order for the metal push rod to pass through, a sufficient hollow area needs to be reserved in the central hole of the electrode assembly. For a cylindrical electrode assembly, the diameter of the central hole should be greater than 2 mm. However, when the diameter of the central hole is large, the space occupied by the central hole increases, resulting in a loss of energy density of the button battery. On the other hand, during the manufacturing process, it is necessary to use a push rod to pass through the central hole of the electrode assembly to press the negative electrode tab, which increases the complexity of the processing technology and leads to an increase in production cost.

[0059] Based on this, please refer to Figures 1 - 4 , an electrochemical device 1000 is provided in an embodiment of the present application, including a housing 1, an electrode assembly 2, and a first tab 3. The housing 1 is provided with a receiving cavity 1a, the electrode assembly 2 is disposed in the receiving cavity 1a, and one end of the first tab 3 is connected to the electrode assembly 2. The housing 1 includes a bottom case 11 and a top cover 12 disposed opposite to each other. The electrode assembly 2 includes an electrode body 21 and an abutting portion 22. The abutting portion 22 is disposed at one end of the electrode body 21 facing the bottom case 11. The electrode body 21 is a wound structure, and the electrode body 21 has a first central hole 21a. The first tab 3 has a first connecting portion 31. Along the direction X from the top cover 12 to the bottom case 11, the first connecting portion 31 is located between the bottom case 11 and the abutting portion 22. The abutting portion 22 abuts against the first connecting portion 31, the first connecting portion 31 abuts against the bottom case 11, and the first connecting portion 31 and the bottom case 11 are welded, so that the aperture R of the first central hole 21a can be made within 2 mm. The central hole here is not necessarily strictly at the center. Due to the deviation in the process, it should be at approximately the center position.

[0060] In some embodiments, the aperture R of the first central hole 21a satisfies: 0.6 mm ≤ R ≤ 2 mm. When the aperture of the central hole is too small, the diameter of the winding needle used when winding the electrode body 21 is too small. When the winding needle is pulled out after winding, the winding needle is likely to break, which in turn leads to an increase in production cost; when the aperture of the central hole is too large, the space occupied by the central hole becomes larger, which in turn leads to a decrease in the energy density of the electrochemical device 1000. The embodiment of the present application selects 0.6 mm ≤ R ≤ 2 mm, for example, selects 0.6 mm, 0.8 mm, 1.2 mm, 1.4 mm, 1.6 mm or 2 mm, etc., which is beneficial to reducing the occurrence of the problem of winding needle breakage during the manufacturing process, reducing the production cost, and reducing the space occupied by the central hole, thereby improving the energy density of the electrochemical device 1000.

[0061] The electrochemical device 1000 provided by the present application is configured such that by providing the abutting portion 22 protruding from the electrode body 21, the abutting portion 22 and the bottom case 11 jointly abut against the first connecting portion 31 located between the abutting portion 22 and the bottom case 11, which is conducive to improving the fitting effect between the surface of the first connecting portion 31 for welding with the bottom case 11 and the bottom case 11. The abutting portion 22 presses the first connecting portion 31 against the bottom case 11 in place of the metal ejector rod. Compared with the button battery in the related art, the aperture R of the first central hole 21a of the electrode assembly 2 is not limited by the size of the metal ejector rod. After reducing the aperture R of the first central hole 21a of the electrode assembly 2, it is conducive to improving the energy density of the electrochemical device 1000, and the step of the ejector rod pressing the first connecting portion 31 is omitted during the manufacturing process, which is conducive to reducing production costs and improving production efficiency.

[0062] In some embodiments, the aperture R of the first central hole 21a satisfies: 1 mm ≤ R ≤ 1.5 mm. Selecting 1 mm ≤ R ≤ 1.5 mm further reduces the occurrence of problems such as broken winding needles during the manufacturing process, reduces production costs, and improves the energy density of the electrochemical device 1000.

[0063] In some embodiments, the housing 1 further includes a side wall 13. The side wall 13 is provided on the bottom case 11, and the top cover 12 is disposed on one end of the side wall 13 away from the bottom case 11. The top cover 12 and the side wall 13 are insulated and connected. The top cover 12, the side wall 13, and the bottom case 11 jointly enclose a receiving cavity 1a.

[0064] In some embodiments, the receiving cavity 1a is used to receive an electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 2, thereby causing an electrochemical reaction.

[0065] In some embodiments, the housing 1 is generally in the shape of a flat cylinder, and the bottom case 11 is generally in the shape of a circular sheet.

[0066] Please refer to Figures 2 - 5 , in some embodiments, the electrode assembly 2 includes a first electrode tab 211, a separator 212, and a second electrode tab 213. The separator 212 includes a stacked portion 2121. The first electrode tab 211, the stacked portion 2121, and the second electrode tab 213 are stacked and wound to form the electrode body 21. The stacked portion 2121 is disposed between the first electrode tab 211 and the second electrode tab 213 for insulating and separating the two.

[0067] The stacked portion 2121 here is formed by laminating any one of the separator 212, the first electrode tab 211, and the second electrode tab 213.

[0068] The first electrode tab 211 and the second electrode tab 213 have opposite polarities. For example, the first electrode tab 211 is made of a positive electrode tab, and the second electrode tab 213 is made of a negative electrode tab. Or the first electrode tab 211 is made of a negative electrode tab, and the second electrode tab 213 is made of a positive electrode tab.

[0069] In some embodiments, the first electrode tab 211 is made of a negative electrode tab, and one end of the first pole ear 3 is connected to the first electrode tab 211.

[0070] In some embodiments, the electrochemical device 1000 includes a second pole ear 4. One end of the second pole ear 4 is connected to the second electrode tab 213, and the other end of the second pole ear 4 is connected to the top cover 12.

[0071] In some embodiments, the first electrode tab 211 is made of a negative electrode tab, and the first connection portion 31 is connected to the bottom case 11, such that the bottom case 11 constitutes the negative electrode of the electrochemical device 1000. The top cover 12 is provided with a terminal post 121. The second electrode tab 213 is made of a positive electrode tab, and one end of the second pole ear 4 remote from the second electrode tab 213 is connected to the terminal post 121, such that the top cover 12 constitutes the positive electrode of the electrochemical device 1000.

[0072] In some embodiments, the separator 212 includes an empty winding portion 2122, and the empty winding portion 2122 is formed by winding the separator 212 to form a first central hole 21a.

[0073] In some embodiments, the electrode assembly 2 is generally cylindrical, and the empty winding portion 2122 is generally cylindrical.

[0074] In some embodiments, the abutting portion 22 is obtained by the separator 212 extending toward the bottom case 11. Herein, the abutting portion 22 being obtained by the separator 212 extending means that both the separator 212 of the electrode body 21 and the abutting portion 22 are integrally formed by the same manufacturing process to form a seamless connected integral structure. Compared with separately providing an additional component as the abutting portion 22, the abutting portion 22 being obtained by the separator 212 extending toward the bottom case 11 is beneficial to reducing the additional component and the manufacturing process, and reducing the manufacturing cost. On the other hand, the separator 212 is usually made of a material with a certain flexibility. The abutting portion 22 being obtained by the separator 212 extending is beneficial to reducing the risk that when the abutting portion 22 abuts against the first connection portion 31, the abutting portion 22 squeezes the electrode body 21 and the first connection portion 31, thereby causing damage to the electrode body 21 and the first connection portion 31.

[0075] In some embodiments, the separator 212 includes a base material layer and a coating. The base material layer is used to provide a basic structure and support, while the coating is used to endow the separator 212 with specific functionality and surface characteristics. Correspondingly, the abutting portion 22 obtained by the separator 212 extending also includes a base material layer and a coating.

[0076] In some embodiments, the substrate layer includes at least one of polyethylene, polypropylene, polytetrafluoroethylene, cellulose acetate, or cellulose nanofibers. Each material has good chemical stability and can maintain the stability of its own structure and performance in the electrolyte environment, thereby effectively reducing the failure of the separator 212 caused by chemical reactions with the electrolyte. Moreover, each material has good electrical insulation properties, can effectively isolate the positive and negative electrode sheets of the electrode body 21, and reduce the occurrence of short circuits. At the same time, each material has a certain degree of flexibility and strength, which is beneficial to reducing the damage of the separator 212, and further effectively isolating the positive and negative electrode sheets.

[0077] In some embodiments, the coating includes a ceramic layer, and the ceramic layer includes at least one of boehmite, alumina, or silica. Each material has good insulation and thermal stability. When the internal temperature of the electrochemical device 1000 increases, it can reduce heat dissipation, and further reduce the thermal runaway of the electrochemical device 1000, and can effectively improve the safety performance of the electrochemical device 1000.

[0078] In some embodiments, along the direction X from the top cover 12 to the bottom case 11, the abutting portion 22 protrudes from the first electrode sheet 211 and the second electrode sheet 213.

[0079] In some embodiments, the abutting portion 22 is formed by extending the empty winding portion 2122 towards the bottom case 11.

[0080] In some embodiments, the laminated portion 2121 includes a first laminated portion 2121a and a second laminated portion 2121b. The first electrode sheet 211, the first laminated portion 2121a, the second electrode sheet 213, and the second laminated portion 2121b are laminated and wound. The empty winding portion 2122 includes a first empty winding portion 2122a and a second empty winding portion 2122b. Along the winding direction of the electrode body 21, the first empty winding portion 2122a is connected to one end of the first laminated portion 2121a, and the second empty winding portion 2122b is connected to one end of the second laminated portion 2121b. The first empty winding portion 2122a and the second empty winding portion 2122b are laminated and wound. The abutting portion 22 includes a first abutting portion 221 and a second abutting portion 222. The first abutting portion 221 is formed by extending the first empty winding portion 2122a towards the bottom case 11, and the second abutting portion 222 is formed by extending the second empty winding portion 2122b towards the bottom case 11.

[0081] In some embodiments, the first abutting portion 221 and the second abutting portion 222 are stacked and wound. Compared with the abutting portion 22 including only the first abutting portion 221 or the second abutting portion 222, the abutting portion 22 including the first abutting portion 221 and the second abutting portion 222 which are stacked and wound has a larger thickness dimension in the radial direction along the second central hole 22a. And because the first abutting portion 221 and the second abutting portion 222 are stacked and wound, the gaps between adjacent winding layers of the first abutting portion 221 can be filled by the second abutting portion 222, and vice versa, the gaps between adjacent winding layers of the second abutting portion 222 can be filled by the first abutting portion 221. Thereby, it is beneficial to improve the overall structural strength of the abutting portion 22 and the contact area between the abutting portion 22 and the first connecting portion 31 when the abutting portion 22 abuts against the first connecting portion 31, and further beneficial to improve the fitting effect between the first connecting portion 31 and the bottom shell 11.

[0082] In other embodiments, the abutting portion 22 includes the first abutting portion 221 which extends from the first empty winding portion 2122a towards the bottom shell 11, or the abutting portion 22 includes the second abutting portion 222 which extends from the second empty winding portion 2122b towards the bottom shell 11.

[0083] In other embodiments, the abutting portion 22 includes a central portion and a peripheral portion. The central portion extends from the empty winding portion 2122 towards the bottom shell 11, and the peripheral portion extends from the portion of the lamination portion 2121 adjacent to the empty winding portion 2122 towards the bottom shell 11 in the radial direction along the first central hole 21a.

[0084] In some embodiments, the abutting portion 22 is wound to form a second central hole 22a. Along the radial direction of the second central hole 22a, the sum D of the thicknesses d of the winding layers 223 of the abutting portion 22 that completely surround the second central hole 22a in a circle satisfies: 30 μm ≤ D ≤ 180 μm. When the sum of the thicknesses d of the winding layers 223 of the abutting portion 22 that completely surround the second central hole 22a in a circle is too small, the support strength of the abutting portion 22 is small, and the abutting portion 22 is prone to collapse deformation when abutting against the first connecting portion 31, resulting in the electrode body 21 directly abutting against the first connecting portion 31. Furthermore, one end of the first electrode tab 211 and the second electrode tab 213 close to the bottom case 11 is deformed, and the active material layer of the deformed portions of the first electrode tab 211 and the second electrode tab 213 falls off and enters the welding area between the first connecting portion 31 and the bottom case 11, thereby causing poor welding between the first connecting portion 31 and the bottom case 11. When the sum of the thicknesses d of the winding layers 223 of the abutting portion 22 that completely surround the second central hole 22a in a circle is too large, the overall volume of the abutting portion 22 increases, and the space occupied by the abutting portion 22 increases, resulting in a decrease in the energy density of the electrochemical device 1000. In the embodiments of the present application, 30 μm ≤ D ≤ 180 μm is selected, for example, 30 μm, 50 μm, 100 μm, 150 μm, or 180 μm is selected, which is beneficial to reducing the welding defects between the first connecting portion 31 and the bottom case 11 and improving the energy density of the electrochemical device 1000.

[0085] Among them, the winding layer 223 that completely surrounds the second central hole 22a in a circle is continuously and uninterruptedly wound around the second central hole 22a in the radial direction of the second central hole 22a for one week, and a complete annular structure can be formed in the circumferential direction from the starting end to the ending end. For example, when the inner separator 212 is wound, the starting section is not a complete circle. When the separator 212 is wound more than one circle and exceeds the starting end, it is a complete circle at this time. Specifically, as Figure 7 shown in, taking the point on the dashed line b as the starting point and the ending point, the starting end 223a of the winding layer 223 starts from the starting point at the dashed line b, and after surrounding the second central hole 22a for one week, the ending end 223b reaches the ending point at the dashed line b.

[0086] Exemplarily, the sum of the thicknesses d of the winding layers 223 of the abutting portion 22 that completely surround the second central hole 22a in a circle is related to the thickness d of the winding layer 223 and the number of winding layers 223. For example, when D = 30 μm is selected, the abutting portion 22 can be set to include six winding layers 223 with a thickness d of 5 μm each, where three winding layers 223 are wound by the first abutting portion 221, and the other three winding layers are wound by the second abutting portion 222.

[0087] In some embodiments, 80 μm ≤ D ≤ 150 μm. Selecting 80 μm ≤ D ≤ 150 μm is beneficial to further reducing the welding defects between the first connecting portion 31 and the bottom case 11 and improving the energy density of the electrochemical device 1000.

[0088] In some embodiments, along the radial direction of the first central hole 21a, the number of layers N of the separator 212 in the empty winding portion 2122 satisfies: N = 14 to 20.

[0089] When the empty winding portion 2122 is formed by winding with a winding needle, along the winding direction, when the length of the separator web material for forming the empty winding portion 2122 is fixed, the diameter of the winding needle determines the number of turns of the empty winding portion 2122, and the diameter of the winding needle is related to the diameter of the first central hole 21a after winding. In the present application, the separator web material is a film-like material used for post-winding processing to form the separator 212 during the manufacturing process. In some embodiments, the length of the separator web material reserved for winding to form the empty winding portion 2122 is 30 mm - 40 mm, the separator web materials are stacked in two layers, and a winding method of 7 to 10 turns is selected to obtain N = 14 to 20, so that the aperture of the first central hole 21a formed after winding is less than 2 mm. Compared with the electrochemical device 1000 in the related art where a mandrel is used for welding and the aperture of the first central hole 21a is greater than 2 mm, the volumetric energy density of the electrochemical device 1000 of the present application is greater.

[0090] Please refer to Figure 4 、 Figure 5 and Figure 8 In some embodiments, along the direction X from the top cover 12 to the bottom case 11, the inner peripheral edge of the projection area of the part where the abutting portion 22 abuts against the first connecting portion 31 on the bottom case 11 is the first boundary 22b, and the outer peripheral edge of the projection area of the part where the abutting portion 22 abuts against the first connecting portion 31 on the bottom case 11 is the second boundary 22c. The welding mark formed by welding the first connecting portion 31 to the bottom case 11 is located within the second boundary 22c. The periphery of the area within the second boundary 22c is all pressed against the bottom case 11 by the abutting portion 22 along the direction X from the top cover 12 to the bottom case 11. The area within the second boundary 22c of the bottom case 11 has a good fitting effect with the first connecting portion 31, and the welding mark formed by welding the first connecting portion 31 to the bottom case 11 is located within the second boundary 22c, which is beneficial to improving the welding effect.

[0091] In some embodiments, the bottom case 11 includes a first planar portion 111 facing the top cover 12. The first planar portion 111 is perpendicular to the direction X from the top cover 12 to the bottom case 11, and the first connecting portion 31 is welded to the first planar portion 111.

[0092] In some embodiments, the first pole tab 3 includes a first connecting portion 31 and a second connecting portion 32. The second connecting portion 32 extends along the direction X from the top cover 12 to the bottom case 11, the second connecting portion 32 is connected to the first pole piece 211, and the first connecting portion 31 extends along a direction parallel to the first planar portion 111.

[0093] In some embodiments, the second connecting portion 32 is obtained by bending the first connecting portion 31.

[0094] In some embodiments, the first connecting portion 31 includes a second planar portion 311 and a third planar portion 312 that are arranged opposite to each other in the direction X from the top cover 12 to the bottom case 11. In the direction X from the top cover 12 to the bottom case 11, the end face of the abutting portion 22 facing the bottom case 11 abuts against the second planar portion 311, and the third planar portion 312 abuts against the first planar portion 111.

[0095] In some embodiments, during welding, the first connecting portion 31 and the electrode assembly 2 are sequentially stacked above the first planar portion 111, such that the third planar portion 312 fits against the first planar portion 111. On the side of the bottom case 11 facing away from the accommodating cavity 1a, the third planar portion 312 is welded to the first planar portion 111 by means of laser welding.

[0096] In some embodiments, the welding mark formed by welding the first connecting portion 31 to the bottom case 11 fills the region between the first boundary 22b and the second boundary 22c. Since in the direction from the top cover 12 to the bottom case 11, the region between the first boundary 22b and the second boundary 22c is all abutted by the abutting portion 22 and has a better fitting effect with the first connecting portion 31, the welding mark fills the region between the first boundary 22b and the second boundary 22c, which is beneficial to improving the welding effect of the first connecting portion 31 welded to the bottom case 11.

[0097] Please refer to Figure 4 and Figure 5 , in some embodiments, the electrode body 21 includes a first ironing portion 2123. The first ironing portion 2123 is provided at one end of the stacked portion 2121 facing the bottom case 11. In the direction X from the top cover 12 to the bottom case 11, the first ironing portion 2123 protrudes from the first pole piece 211 and the second pole piece 213. The first ironing portion 2123 is disposed around the abutting portion 22. In the direction X from the top cover 12 to the bottom case 11, the abutting portion 22 protrudes from the first ironing portion 2123.

[0098] In some embodiments, the first ironing portion 2123 is formed by using a thermal ironing process on the portions where the first stacked portion 2121a and the second stacked portion 2121b protrude from the first pole piece 211 and the second pole piece 213 at one end facing the top cover 12.

[0099] In some embodiments, the electrode body 21 includes a second ironing portion 2124. The second ironing portion 2124 is provided at one end of the stacked portion 2121 facing the top cover 12. In the direction from the bottom case 11 to the top cover 12, the second ironing portion 2124 protrudes from the first pole piece 211 and the second pole piece 213.

[0100] In some embodiments, the second ironing portion 2124 is formed by a heat ironing process on a portion of the first stacked portion 2121a and the second stacked portion 2121b that protrudes toward one end of the bottom case 11 beyond the first pole piece 211 and the second pole piece 213.

[0101] In some embodiments, a third ironing portion (not shown in the figure) is provided at one end of the empty winding portion 2122 facing away from the abutting portion 22. Along the direction from the bottom case 11 to the top cover 12, the third ironing portion protrudes beyond the first pole piece 211 and the second pole piece 213.

[0102] In some embodiments, along the direction from the bottom case 11 to the top cover 12, the second ironing portion 2124 is flush with the third ironing portion.

[0103] In some embodiments, the third ironing portion is formed by a heat ironing process on one end of the empty winding portion 2122 facing away from the abutting portion 22.

[0104] In some other embodiments, the abutting portion 22 is adhesively fixed to the electrode body 21.

[0105] In some embodiments, the abutting portion 22 is adhesively fixed to one end of the empty winding portion 2122 facing the bottom case 11.

[0106] In some embodiments, the electrode body 21 includes a first pole piece 211, a separator, and a second pole piece 213. Along the direction X from the top cover 12 to the bottom case 11, the separator includes a relatively arranged fourth ironing portion (not shown in the figure) and a fifth ironing portion (not shown in the figure), and a separator body connected between the fourth ironing portion and the fifth ironing portion. The first pole piece 211, the separator body, and the second pole piece 213 are stacked and wound, and the first pole piece 211 and the second pole piece 213 are arranged between the fourth ironing portion and the fifth ironing portion. The fourth ironing portion faces the bottom case 11, and the abutting portion 22 is adhesively fixed to the fourth ironing portion. Specifically, in some embodiments, the separator body includes a connected stacked portion 2121 and an empty winding portion 2122. The first pole piece 211, the stacked portion 2121, and the second pole piece 213 are stacked and wound. The empty winding portion 2122 is located inside the core of the winding structure formed by the stacking and winding of the first pole piece 211, the stacked portion 2121, and the second pole piece 213. Along the direction X from the top cover 12 to the bottom case 11, the fourth ironing portion includes a first part connected to the empty winding portion 2122 and a second part connected to the stacked portion 2121. The abutting portion 22 is adhesively fixed to the first part and / or the second part.

[0107] In some embodiments, the fourth ironing portion and the fifth ironing portion are obtained by ironing the two ends of the separator web after winding the separator web. The portion of the separator web located between the fourth ironing portion and the fifth ironing portion constitutes the separator body.

[0108] In some embodiments, the abutting portion 22 is generally in the shape of a flat disc or a cylinder.

[0109] In some embodiments, the abutting portion 22 is made of the same material as the base layer of the separator.

[0110] Based on the same inventive concept, the present application also provides an electronic device, including the electrochemical device 1000 in any of the above embodiments. The electronic device in the embodiments of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device includes but is not limited to Bluetooth headsets, mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, ships, spacecraft, etc. Among them, the electric toy can include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc., and the spacecraft can include airplanes, rockets, space shuttles, and spaceships, etc.

[0111] The embodiments of the present application also provide a method for manufacturing an electrochemical device 1000, including:

[0112] Providing a housing 1, an initial electrode assembly, and a first pole ear 3, wherein the housing 1 includes a bottom case 11, the initial electrode assembly includes an electrode body 21 and a protruding portion protruding from the electrode body 21, and the first pole ear 3 has a first connecting portion 31;

[0113] Stacking the first connecting portion 31 and the initial electrode assembly on top of the bottom case 11 in sequence, so that the protruding portion abuts against the first connecting portion 31, the first connecting portion 31 abuts against the bottom case 11, the protruding portion deforms to form an abutting portion 22, and the initial electrode assembly forms an electrode assembly 2;

[0114] When the protruding portion is in an unloaded state, it protrudes from the electrode body 21, so that when the initial electrode assembly is stacked on top of the first connecting portion 31, it first abuts against the first connecting portion 31. The protruding portion is made of a material that can be deformed under pressure, such as the material of the separator 212 in the above embodiments. The protruding portion extends from the separator 212. Under the action of the gravity of the electrode assembly, the protruding portion deforms after abutting against the first connecting portion 31 to form an abutting portion 22, and the initial electrode assembly forms an electrode assembly 2.

[0115] Welding from the outside of the bottom case 11 so that the first connecting portion 31 is welded to the bottom case 11.

[0116] The preparation method of the electrochemical device 1000 provided by the embodiment of the present application, during welding, the weight of the electrode assembly 2 acts on the protruding portion. In a butting manner, the protruding portion presses the first connecting portion 31 against the bottom case 11, and the protruding portion is deformed under pressure to form a butting portion 22, so that the first connecting portion 31 can be better attached to the bottom case 11, thereby improving the welding effect of the welding. And compared with the method in the related art of pressing the first connecting portion 31 by passing a push rod through the central hole of the electrode assembly, the size of the central hole of the electrode assembly 2 is not limited by the size of the push rod, so that the electrode assembly 2 can be provided with a first central hole 21a with a smaller diameter, which is beneficial to improving the energy density of the electrochemical device 1000 and simplifying the processing technology.

[0117] In some embodiments, welding is performed from the outside of the bottom case 11 so that the first connecting portion 31 is welded to the bottom case 11, including: laser welding the first connecting portion 31 to the bottom case 11 on the side of the bottom case 11 facing away from the first connecting portion 31.

[0118] The embodiment of the present application also provides a preparation method of an initial electrode assembly, including:

[0119] Providing a first electrode sheet coil p1, a separator coil a, and a second electrode sheet coil p2.

[0120] Among them, the first electrode sheet coil p1 is a sheet material for winding to form the first electrode sheet 211, the separator coil a is a film-like material for winding to form the separator 212, and the second electrode sheet coil p2 is a sheet material for winding to form the second electrode sheet 213. The number of layers of the separator coil a can be set according to actual needs. As Figure 9 shown, in some embodiments, the number of layers of the separator coil a is two. The first layer of the separator coil a, the first electrode sheet coil p1, the second layer of the separator coil a, and the second electrode sheet coil p2 are alternately stacked. The first ends a11 of the first layer of the separator coil a and a12 of the second layer of the separator coil a both have a preset length L, which is used for forming a central winding structure by winding the first-in coil when winding through a winding needle.

[0121] Stack the first electrode sheet coil p1, the separator coil a, and the second electrode sheet coil p2 and wind them to form a wound body A, as Figure 10As shown, in the winding body A, the first electrode tab stock p1 is wound to form the first electrode tab 211, and the second electrode tab stock p2 is wound to form the second electrode tab 213. Along the direction X' perpendicular to the winding direction of the winding body A, the separator stock a includes opposite first end portion a1 and second end portion a2, and a main body portion a3 connected between the first end portion a1 and the second end portion a2. The main body portion a3 constitutes a stacked portion 2121 that is stacked and wound with the first electrode tab 211 and the second electrode tab 213, and an empty winding portion 2122 at the core of the stacked portion 2121. Along the direction from the second end portion a2 to the first end portion a1, the first end portion a1 protrudes from the first electrode tab 211 and the second electrode tab 213. Along the direction from the first end portion a1 to the second end portion a2, the second end portion a2 protrudes from the first electrode tab 211 and the second electrode tab 213.

[0122] Along the direction from the first end portion a1 to the second end portion a2, the portion of the first end portion a1 except the central region is ironed flat by a hot ironing process to obtain a first ironed portion 2123, and then a protruding portion 22' protruding from the first ironed portion 2123' along the direction from the second end portion a2 to the first end portion a1 is obtained, as Figure 11 shown.

[0123] Among them, the central region of the first end portion a1 is an area that extends a preset distance around with the starting point of the winding of the winding body A as the center point when observed along the direction from the first end portion a1 to the second end portion a2. The area size of the central region can be set according to the size requirements of the abutting portion 22 to be obtained. For example, in some embodiments, the abutting portion 22 is obtained by extending the empty winding portion 2122. The abutting portion 22 and the empty winding portion 2122 are formed by a central winding structure formed by winding the first end a11 of the first layer of separator stock a and the first end a12 of the second layer of separator stock a. The central region is correspondingly set as the region aligned with the central winding structure along the direction from the first end portion a1 to the second end portion a2.

[0124] In some embodiments, the hot ironing head is provided with an avoidance hole for avoiding a part of the first end portion a1 in the central region.

[0125] In some embodiments, the preparation method of the initial electrode assembly further further includes:

[0126] Along the direction from the second end portion a2 to the first end portion a1, the portion of the second end portion a2 except the central region is ironed flat by a hot ironing process to obtain a second ironed portion 2124.

[0127] Among them, the central region of the second end portion a2 is an area that extends a preset distance around the winding starting point of the winding body A as the center point when observed in the direction from the second end portion a2 to the first end portion a1. In some embodiments, in the direction from the second end portion a2 to the first end portion a1, the central region of the second end portion a2 is aligned with the central region of the first end portion a1 and has the same shape. In some embodiments, the second ironing portion 2124 is made of the same hot ironing head as the first ironing portion 2123.

[0128] In some other embodiments, the preparation method of the electrode assembly 2 further includes:

[0129] In the direction from the second end portion a2 to the first end portion a1, the second end portion a2 is ironed by a hot ironing process to obtain a flat second ironing portion 2124 and a third ironing portion.

[0130] Hereinafter, examples and comparative examples are given to further illustrate the implementation manners of the present application.

[0131]

Preparation of the positive electrode sheet

[0132] Lithium cobaltate (LCO, with an average particle size of 8 μm, obtained by screening with a particle size screening tool), PVDF, and conductive carbon black (SP) are mixed in a mass ratio of 97:1.5:1.5, and NMP is added as a solvent to prepare a positive electrode active material layer slurry with a solid content of 75 wt%, and it is stirred evenly. The positive electrode active material layer is uniformly coated on the surface of the positive electrode current collector aluminum foil by a coating process, and then dried at 90 °C to obtain a positive electrode active material layer with a thickness of 120 μm; then the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a positive electrode active material layer coated on both sides; then the obtained positive electrode sheet is cold-pressed, slit, and cut to obtain a positive electrode sheet.

[0133]

Preparation of the negative electrode sheet

[0134] Artificial graphite, conductive carbon black (SP), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 97:1:1:1, and deionized water is added to prepare a slurry with a solid content of 75 wt%, and it is stirred evenly. The slurry is uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 μm, and dried at 85 °C to obtain a negative electrode active material layer with a thickness of 120 μm; then the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a negative electrode active material coated on both sides; then the obtained negative electrode sheet is cold-pressed, slit, and cut to obtain a negative electrode sheet.

[0135]

Preparation of the electrolyte

[0136] Ethylene carbonate, propylene carbonate, diethyl carbonate, propyl propionate and vinylene carbonate were mixed in a mass ratio of 20∶30∶20∶28∶2 to obtain a non-aqueous organic solvent. Then, lithium salt LiPF6 and the non-aqueous organic solvent were formulated in a mass ratio of 8∶92 to obtain an electrolyte.

[0137]

Preparation of diaphragm roll stock

[0138] A diaphragm roll stock with a single-layer thickness of 5 μm was obtained by using a 4-μm-thick polyethylene (PE) and a 1-μm-thick aluminum oxide (Al2O3) coated porous film.

[0139]

Preparation of button battery

[0140] After stacking the positive electrode sheet, diaphragm roll stock, and negative electrode sheet prepared above, a winding body was formed by winding with a winding needle. The part of the first end of the diaphragm roll stock of the winding body except the central region was ironed flat by using a hot ironing probe to obtain a first ironed part and a contact part protruding from the first ironed part in the central region of the first end. The part of the second end of the diaphragm roll stock of the winding body except the central region was ironed flat by using a hot ironing process to obtain a second ironed part, so as to finally obtain an electrode assembly. Among them, the diameter of the winding needle was selected in relation to the first central hole of the cell assembly to be made. The diaphragm roll stock was wound around the winding needle. After the winding needle was withdrawn, a first central hole was formed in the vacant part. The button battery includes a housing, a cell assembly, and an electrolyte. The housing is provided with a receiving cavity. After winding, the negative electrode sheet forms a first electrode sheet. A nickel sheet with a width of 3 mm was used as the first electrode tab. The first electrode tab is a negative electrode tab. After the nickel sheet is bent, one end forms a first connecting part, and the other end forms a second connecting part. The second connecting part is welded to the empty foil area of the first electrode sheet. After winding, the positive electrode sheet forms a second electrode sheet. An aluminum sheet with a width of 3 mm was used as the second electrode tab. The second electrode tab is a positive electrode tab. One end of the second electrode tab is welded to the empty foil area of the second electrode sheet. The electrode assembly was placed in the receiving cavity. The first connecting part and the electrode assembly were sequentially stacked above the bottom case of the housing so that the contact part abuts against the first connecting part, and the first connecting part abuts against the bottom case. The first connecting part was welded to the bottom case by laser welding on the side of the bottom case facing away from the first connecting part. The other end of the second electrode tab was welded to the pole post of the housing top cover. After the cell assembly was dried, the electrolyte was injected, and the button battery was obtained through processes such as vacuum packaging, standing, formation, and degassing.

[0141] The differences between all the comparative examples and the examples were recorded in Table 1, and the remaining preparation methods and specifications were the same. All the comparative examples and the examples were subjected to tests on the pole piece deformation rate, the defective welding rate of the first connecting part, the winding needle fracture rate, and the volume energy density, and the test results were recorded in Table 1 below.

[0142] Among them, the methods for testing the pole piece deformation rate, the defective welding rate of the first connecting part, the winding needle fracture rate, and the volume energy density are as follows.

[0143]

Measurement of the deformation rate of the electrode sheet

[0144] The deformation rate of the electrode sheet = the number of button cells with deformed electrode sheets / the total number of button cells. Among them, the method for judging the deformation of the electrode sheet of the button cell is as follows: Disassemble the battery and observe the part of the first electrode sheet and the second electrode sheet close to the bottom case. If there are obvious wrinkles, film peeling, powder falling and shedding of the active material layer, it is considered that there is a problem with the deformation of the electrode sheet of the button cell.

[0145]

Measurement of the defective soldering rate of the first connection part

[0146] The defective soldering rate of the first connection part = the number of button cells with defective soldering of the first connection part / the total number of button cells. Among them, the method for judging the defective soldering of the first connection part of the button cell is as follows: After disassembling the button cell, use a precision cutting machine to cut along the cross-section of the solder mark to ensure that the cutting surface is flat and perpendicular to the solder mark area. Inlay the cut sample in resin, and use sandpaper and polishing liquid to grind and polish the cutting surface until the surface is smooth and free of scratches. Place the polished sample under a metallurgical microscope, observe the cross-sectional morphology of the solder mark, and use the scale function of the microscope or image analysis software to measure the weld depth. If the weld depth is within the range of 20% - 80% of the sum of the bottom case thickness and the first connection part thickness, it is qualified; otherwise, it is considered that the soldering of the first connection part is defective.

[0147] Observe whether there are explosion points on the solder mark track. If there are explosion points, it is considered that the soldering of the first connection part is defective.

[0148]

Measurement of the breakage rate of the winding needle

[0149] The breakage rate of the winding needle = the number of button cells with broken winding needles / the total number of button cells. Among them, the method for judging the breakage of the winding needle is as follows: During the preparation of the electrode assembly, when the winding needle is withdrawn after the winding body is formed by winding, observe whether the winding needle is broken.

[0150]

Measurement of the volumetric energy density

[0151] Charge the button cell at a constant current of 1C to 4.5V, then charge the button cell at a constant voltage of 4.5V to 0.05C, and discharge the button cell at a constant current of 0.2C to 3V. Record the discharge energy E and the voltage plateau U, and measure the volume V of the button cell. Then the energy density W = E * U / V.

[0152] Table 1

[0153]

[0154] Conclusion:

[0155] (1)Combining Comparative Example 1 and Comparative Example 2, as well as Examples 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, and 1-7, it can be seen that when the aperture of the first central hole is too small, the diameter of the corresponding winding needle used is smaller, and the winding needle is prone to breakage when the winding needle is withdrawn after winding. Moreover, as the aperture of the first central hole decreases, the breakage rate of the winding needle increases, resulting in an increase in processing costs. As the aperture of the first central hole increases, the breakage rate of the winding needle decreases, but the space occupied by the first central hole increases, leading to a decrease in the energy density of the electrochemical device. In the embodiments of the present application, selecting 0.6 mm ≤ R ≤ 2 mm is beneficial to reducing the occurrence of winding needle breakage problems during the manufacturing process, reducing production costs, and reducing the space occupied by the first central hole, thereby improving the energy density of the electrochemical device.

[0156] (2)Compared with Examples 1-1 and 1-2, Examples 1-3, 1-4, and 1-5 have a lower winding needle breakage rate. Compared with Examples 1-6 and 1-7, they have a greater volumetric energy density. In the embodiments of the present application, it is preferably 1 mm ≤ R ≤ 1.5 mm, which further reduces the occurrence of winding needle breakage problems during the manufacturing process, reduces production costs, and improves the energy density of the electrochemical device.

[0157] (3)Combining Examples 1-7, 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-7, and 2-8, it can be seen that when the total thickness of the winding layers where the abutting portion completely surrounds the second central hole is too small, the support strength of the abutting portion is small, which may cause the electrode body to abut against the first connecting portion, resulting in deformation of the first and second pole pieces, and the active material layer falling off into the welding area between the first connecting portion and the bottom case, thereby leading to poor welding between the first connecting portion and the bottom case. When the total thickness of the winding layers where the abutting portion completely surrounds the second central hole is too large, the space occupied by the abutting portion increases significantly, resulting in a decrease in the energy density of the electrochemical device. Therefore, in the embodiments of the present application, selecting 30 μm ≤ D ≤ 180 μm is beneficial to reducing the welding defects between the first connecting portion and the bottom case, and improving the energy density of the electrochemical device.

[0158] (4)Compared with Examples 2-1 and 2-2, Examples 1-7, 2-3, 2-4, 2-5, and 2-6 have a lower pole piece deformation rate and a lower defective rate of welding of the first connecting portion. Compared with Examples 2-7 and 2-8, they have a greater volumetric energy density. In the embodiments of the present application, it is preferably selected that 80 μm ≤ D ≤ 150 μm, which is beneficial to further reducing the welding defects between the first connecting portion and the bottom case, and improving the energy density of the electrochemical device.

[0159] The above disclosure is only for the preferred embodiments of the present application, and of course cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application still fall within the scope covered by the present application.

Claims

1. An electrochemical device, comprising a housing, an electrode assembly, and a first tab. The housing is provided with a receiving cavity, the electrode assembly is disposed in the receiving cavity, and one end of the first tab is connected to the electrode assembly. It is characterized in that, the housing includes a bottom case and a top cover disposed opposite to each other. The electrode assembly includes an electrode body and an abutting portion. The abutting portion is disposed at one end of the electrode body facing the bottom case. The electrode body is a wound structure, and the electrode body has a first central hole. The aperture R of the first central hole satisfies: 0.6 mm ≤ R ≤ 2 mm; the first tab has a first connecting portion. Along the direction from the top cover to the bottom case, the first connecting portion is located between the bottom case and the abutting portion. The abutting portion abuts against the first connecting portion, the first connecting portion abuts against the bottom case, and the first connecting portion and the bottom case are welded.

2. The electrochemical device according to claim 1, wherein, the aperture R of the first central hole satisfies: 1 mm ≤ R ≤ 1.5 mm.

3. The electrochemical device according to claim 2, wherein, the electrode assembly includes a first electrode plate, a separator, and a second electrode plate. The separator includes a connected empty winding portion and a stacked portion. The first electrode plate, the stacked portion, and the second electrode plate are stacked and wound to form the electrode body. The empty winding portion is formed by the separator winding to form the first central hole, and one end of the first tab is connected to the first electrode plate.

4. The electrochemical device according to claim 3, wherein, the abutting portion is obtained by the separator extending towards the bottom case.

5. The electrochemical device according to claim 3, wherein, along the direction from the top cover to the bottom case, the abutting portion protrudes from the first electrode plate and the second electrode plate.

6. The electrochemical device according to claim 4, wherein, the abutting portion winds to form a second central hole. Along the radial direction of the second central hole, the sum D of the thicknesses of the winding layers of the abutting portion completely surrounding the second central hole in one circle satisfies: 30 μm ≤ D ≤ 180 μm.

7. The electrochemical device according to claim 6, wherein D satisfies: 80 μm ≤ D ≤ 150 μm.

8. The electrochemical device according to claim 3, wherein, along the radial direction of the first central hole, the number of layers N of the separator in the empty winding portion satisfies: N = 14 - 20.

9. The electrochemical device according to claim 3, wherein, the electrode body includes a first ironing portion. The first ironing portion is disposed at one end of the stacked portion facing the bottom case. Along the direction from the top cover to the bottom case, the first ironing portion protrudes from the first electrode plate and the second electrode plate. The first ironing portion surrounds the abutting portion, and along the direction from the top cover to the bottom case, the abutting portion protrudes from the first ironing portion.

10. The electrochemical device according to claim 4, wherein, In the direction from the top cover towards the bottom case, the inner peripheral edge of the projection area of the part where the abutting portion abuts against the first connecting portion on the bottom case is the first boundary, and the outer peripheral edge of the projection area of the part where the abutting portion abuts against the first connecting portion on the bottom case is the second boundary. The welding mark formed by welding the first connecting portion to the bottom case is located within the second boundary.

11. The electrochemical device according to claim 10, wherein The welding mark formed by welding the abutting portion to the bottom case fills the area between the first boundary and the second boundary.

12. The electrochemical device according to any one of claims 3 - 11, wherein The electrochemical device includes a second tab. One end of the second tab is connected to the second electrode plate, and the other end of the second tab is connected to the top cover.

13. The electrochemical device according to claim 12, wherein The housing further includes a side wall. The side wall is disposed on the bottom case, the top cover covers one end of the side wall away from the bottom case, and the top cover and the side wall are insulated and connected.

14. An electrical device, characterized in that, Including the electrochemical device according to any one of claims 1 - 13.

15. A method for preparing an electrochemical device, characterized in that, Including: Providing a housing, an initial electrode assembly, and a first tab. The housing includes a bottom case, the initial electrode assembly includes an electrode body and a protruding portion protruding from the electrode body, and the first tab has a first connecting portion; Stacking the first connecting portion and the initial electrode assembly on the bottom case in sequence so that the protruding portion abuts against the first connecting portion, the first connecting portion abuts against the bottom case, the protruding portion deforms to form an abutting portion, and the initial electrode assembly forms an electrode assembly; Welding from the outside of the bottom case so that the first connecting portion is welded to the bottom case.

16. The method according to claim 15, wherein The welding from the outside of the bottom case so that the first connecting portion is welded to the bottom case includes: laser welding the first connecting portion to the bottom case on the side of the bottom case facing away from the first connecting portion.

17. A method for preparing an initial electrode assembly, characterized in that, Including: Providing a first electrode plate coil, a separator coil, and a second electrode plate coil; Stacking and winding the first electrode plate coil, the separator coil, and the second electrode plate coil to form a wound body. In the wound body, the first electrode plate coil forms a first electrode plate after winding, the second electrode plate coil forms a second electrode plate after winding. Along the direction perpendicular to the winding direction of the wound body, the separator coil includes opposite first and second ends and a main body portion connecting the first and second ends. Along the direction from the second end towards the first end, the first end protrudes from the first electrode plate and the second electrode plate. Along the direction from the first end towards the second end, the second end protrudes from the first electrode plate and the second electrode plate; Along the direction from the first end to the second end, the first end except the central area is ironed by a hot ironing process to obtain a first ironed portion, and then a protruding portion protruding from the first ironed portion along the direction from the second end to the first end is obtained.

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